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Principles of analgesic use can be found in the American Pain Society publication1, they include some of the following guidelines for practitioners.
Analgesic medications are available to be given by several routes. The oral route is preferred for the treatment of chronic pain, especially chronic cancer pain. For patients who are unable to swallow pills or tablets, some medications are available in a liquid. Most opioids peak in 1.5-2 hours after oral administration. This allows the drug to be repeated in 2 hours if side effects are not excessive. If you treat every 4 hours you create peaks and valleys in the pain control, that are unnecessary.2
The intramuscular route is common in the acute care setting, but should be avoided when possible, especially when managing chronic pain. Intramuscular injections are painful and absorption is unpredictable. Absorption varies from person to person and from muscle to muscle. The peak effect for intramuscular opioids is anywhere from 30-60 minutes. The analgesic effect falls quickly compared to the oral route. Repeated injections cause damage to the muscles and soft tissue and further alters absorption patterns.
Analgesics may be given by intermittent intravenous bolus which provides a rapid onset for quick pain relief. The peak effect may vary from 1-15 minutes. The duration of the analgesic effect is shorter than when given intramuscular or by the oral route. If pain persists, the bolus may be repeated at the expected peak time. A continuous intravenous infusion of opioids will provide a consistent blood level and prevent the peaks and valleys that often accompany the intermittent regimens. This method has been shown to provide more effective pain relief with less side effects than intermittent or pm dosing. Intravenous infusions are preceded by an intravenous bolus. After the infusion begins, the patient may require intravenous bolus several more times until a steady blood level is reached.
Another route available is transdermal. Currently Fentanyl is available as a transdermal patch. It has been useful to control chronic pain associated with cancer. The patch is replaced every 72 hours. Transdermal absorption is slow. It may take 12-16 hours to achieve a therapeutic effect, and 2 days to establish adequate blood levels. Keep this in mind when switching a patient from the intramuscular or intravenous routes to a transdermal route. Short acting opioids are usually needed to manage pain during this time of transition.
Guidelines for Opioid Analgesic Administration
1. Individualize the route, dosage and schedule.
2. Administer analgesics regularly (not pm) if pain is present most of the day.
3. Become familiar with the dose and the time-course of several strong opioids.
4. Give infants and children adequate opioid doses.
5. Follow patients closely, particularly when beginning or changing analgesic regimens.
6. When changing to a new opioid or a different route, first use the equianalgesic doses in the accompanying table to estimate the new dose. Then, modify the estimate based on the clinical situation and specific drugs.
7. Recognize and treat side effects.
8. Be aware of the potential hazards of meperidine (Demerol, pethidine) and mixed agonist-antagonists, particularly pentazocine (Talwin).
9. Do not use placebos to assess th& nature of pain.
10. Watch for development of tolerance and treat appropriately.
11. Be aware of the development of physical dependence and prevent withdrawal.
12. Do not label a patient "addicted" (psychologically dependent), ii you merely mean physically dependent on or tolerant to opioids.
13. Be alert to the psychological state of the patient.
How often should opioid analgesics be given? The most common orders are pm (as needed). This requires that the patient becomes uncomfortable, calls the nurse and identifies to the nurse that they need something for pain, the nurse must then obtain the drug and administer it. Those of us who work in the acute care setting know that there may be a considerable time lag between the onset of the patients pain and the nurses availability to relieve the pain. As a rule, pm is acceptable for pain control that may or may not be needed. For example; Tyienol pm for headaches is reasonable. We don't know if the patient will have a headache or need the medication, but it is available if he/she does need it. However, patients with chronic pain or post-operative patients with acute pain will need pain management. For these patients it is not advisable to give pain relief only after it has been requested. Analgesic relief for these patients needs to be continuous to avoid peaks and valleys in the blood level. Analgesia should be given around-the-clock. Yes, that means patients should be awakened at night for their pain medication. I am not saying that no analgesia should be ordered pm, there are times when patients receiving around-the-clock dosing may require an additional dose. This order should be available if needed.
In actuality, it requires less medication, in lower doses, and with fewer side effects when you administer the medication around-the-clock than when it is given intermittently, only upon request. Of particular concern, are patients who are unable to communicate. For these patients it is essential that the nurse identify their need and administer pain relief around the clock. Since they cannot tell the nurse when they hurt, the nurse would have to rely on other physiological signs, by the time the nurse identifies these signs the pain is already out of control.3
When selecting a drug for pain management, several things should be kept in mind. Ask if the patient has responded well to any particular drug in the past. People respond differently to different drugs. A good drug history can help to narrow down the drug selection.
Determine the preferred duration of action. There are immediate release and sustained release preparations available for some drugs, such as morphine. Since it may take 4 hours for sustained release morphine to peak, it is not recommended for prn use. When a patient is started on a sustained release analgesic, a short-acting opioid should precede it.
When administering an analgesic as premedication for a procedure, consider the onset of action of the drug. Meperidine and Fentanyl have rapid onsets, while Morphine and Hyromorphone are slower. You want the medication to peak during the procedure, not before or after it. Timing the administration is important.
When changing from one drug to another, or from one route to another, refer to an equianalgesic chart. All drugs and doses are not equal. The equianalgesic chart uses 10mg of Morphine IM as the standard. All drugs are then compared to this standard. Intravenous bolus doses are based on 1/2 the IM dose. For continuous intravenous infusion, IM and IV doses over a 24-hour period are equal.
Let's practice using one of these charts (this chart is from the American Pain Society)4.[See p. 144.]
Mr. Jones has been receiving Demerol 75 mg every 3 hours for the past 24 hours. He is now able to take fluids by mouth. If the drug of choice is Hydromorphone, calculate the amount needed to provide the same analgesic coverage as the Demerol provided.
| Step One: | Determine how much Demerol was given in the previous 24 hours |
| Step Two: | Find the equianalgesic dose for demerol on the chart. |
| Step Three: | Divide this number into the 24 hour total. This will give you the number of equianalgesic doses in 24 hours. |
| Step Four: | Estimate the equivalent oral dose of Hydromorphone by multiplying the number of equianalgesic doses by the equianalgesic dose of oral Hydromorphone. |
Let's see how you did.
| Step One: | Determine how much Demerol was given in the previous 24
hours? 24 hours divided by 3 = 8 doses |
| Step Two: | Find the equianalgesic dose for demerol on the chart. The equianalgesic dose of Demerol is 75 mg. |
| Step Three: | Divide this number into the 24 hour total. 600 mg divided by 75 mg = 8 equianalgesic doses |
| Step Four: | Estimate the equivalent oral dose of Hydromorphone by multiplying the number of equianalgesic doses by the equianalgesic dose of oral Hydromorphone. 8 equianalgesic doses times 7.5 mg of Hydromorphone = 60 mg-of Hydromorphone every 24 hours |
Mr. Johnson has been receiving Morphine 2.5 mg per hour by continuous infusion. He is going to be changed to oral Morphine.
| Step One: | Determine how many mg of Morphine he received in 24 hours? |
| Step Two: | What is the equianalgesic dose of continuous IV Morphine? |
| Step Three: | Divide this number into the 24 hour total. This will give you the number of equianalgesic doses in 24 hours. |
| Step Four: | Estimate the equivalent dose of oral morphine by multiplying the number of equianalgesic doses by the equianalgesic dose of oral Morphine to estimate the required 24 hour oral dose. |
Solution to Problem Number Two
| Step One: | Determine how many mg of Morphine he received in 24 hours. Multiple 2.5 mg times 24 hours = 60 mg |
| Step Two: | What is the equianalgesic dose of continuous IV Morphine? Continuous IV medication is equivalent to the IM dose. Therefore, the equianalgesic dose of IV Morphine is 10 mg. If the morphine had been given via intermittent bolus, the dose would have been 1/2 of the IM dose. |
| Step Three: | Divide this number into the 24 hour total. This will give you the number
of equianalgesic doses in 24 hours. 60mg divided by 10=6 equianalgesic doses |
| Step Four: | Estimate the equivalent dose of oral morphine by multiplying the number
of equianalgesic doses by the equianalgesic dose of oral Morphine to
estimate the required 24 hour oral dose. 6 equianalgesic doses times 30 mg =180 mg over 24 hours |
Mrs. Rosewater has been getting 100mg of Demerol IM for pain relief prior to her therapy, and it is preferable to give it IV Calculate the correct IV equivalent.
Solution to Problem Three
Problem Three: Mrs. Rosewater is getting 100 mg of Demerol IM prior to her therapy. To calculate an equivalent IV bolus dose divide the IM dose by 2. The IV dose is 1/2 of the IM dose. Answer: 50 mg IV Bolus
Using the equianalgesic chart, calculate the following single dose equivalents.
1. 10 mg of Morphine IM is equal to ___mg of Demerol IM
2. 150 mg of Demerol IM is equal to ___mg of Hydromorphone IM
3. 0.1 mg of Fentanyl is equal to ____mg of oral Morphine
4. 10 mg of Nalbuphine IM is equal to ___mg of Demerol IM
5. 10 mg of Morphine IV bolus is equal to __mg of oral Morphine
6. 75 mg of Demerol IM is equal to ___mg of Oxycodone orally
7. 3 mg of Dilaudid IM is equal to __mg of Morphine IV bolus
Solution to Problem Four
1. 10 mg Morphine IM is equal to 75 mg of Demerol IM.
2. 150 mg of Demerol IM is 2 equianalgesic doses. One equianalgesic dose of Hydromorphone IM is 1.5 mg. 1.5 mg times 2=3 mg.
3. 0.1 mg of Fentanyl is equal to 30 mg of oral Morphine.
4. 10 mg ofNalbuphine IM is equal to 75 mg of Demerol IM.
5. 10 mg of Morphine IV bolus is equal to twice the IM equivalent. The oral dose would be equal to 2 equianalgesic doses of oral morphine or 60 mg.
6. 75 mg of Demerol IM is equal to 30 mg of Oxycodone orally.
7. 3mg of DilaudidIM is 2 equianalgesic doses. Since Morphine IV bolus is equal to 1/2 the IM dose, the correct IV bolus dose would be 10 mg.
Using the equianalgesic chart, calculate the following 24 hour dose equivalents:
Solutions to Problem Number Five
Since the purpose of pain management is to provide optimal pain control, the amount of analgesia needs to be titrated to the patients self-report of pain, as well as to the control of undesirable side effects. The side effects that we will discuss include excessive sedation and respiratory depression, constipation, nausea, vomiting, and urticaria.
There are several options available for the treatment of side effects. The selection of options should be individualized to each patient. One option is to switch from intermittent to continuous infusion of analgesic. Often this provides the same or better control of pain at lower doses.5
Another option is to select another opioid, which has less of the undesirable side effects. The practitioner could also add a medication that counteracts the undesirable side effects. Stool softeners can help prevent constipation. Caffeine can decrease sedation. Anti-emetics can be used to treat the nausea associated with some opioids. Itching can be relieved with an antihistamine.6
Treating sedation and respiratory depression requires discussion. Earlier we discussed using a sedation assessment scale to prevent respiratory depression. This is effective as sedation precedes respiratory depression.
When administering opioids, remember that they are all capable of producing respiratory depression. It is often a mistake for a nurse to assume that respiratory depression only occurs in patients receiving large opioid doses. In fact, in my experience, the patients who have had respiratory depression and excessive sedation received a small or normal dose of opioid. However, it was usually their first dose.
The signs to watch for are drowsiness, inability to carry on a conversation, or limited response to stimuli. These signs precede respiratory depression. Be sure to count respirations for a full minute. Respirations of 10 a minute or less are a warning flag and need to be addressed quickly.
Two actions are immediately required by the nurse. First, stop the drug, then administer Naloxone (Narcan), to reverse the effects of the opioid. When should you assess the patient for signs and symptoms of sedation and respiratory depression? It is important that nurses are aware of the peak analgesic times of all drugs they administer. If the peak effect occurs in 30 minutes, assessing the patient after one hour is inappropriate. When we discuss individual opioids we will discuss their peak times. Become familiar with those that you give most often, and always look up those you are not familiar with. Plan your assessment based on this information.
Since Naloxone (Narcan) is the drug used to counter-act the sedative effect of opioids, it would be helpful to discuss this drug in depth at this time. Naloxone (Narcan) is an opiate antagonist. The idea is to treat the excessive sedation or respiratory sedation without eliminating all of the opioid, which would leave the patient in pain again. Naloxone comes in several doses; 1mg/ml, 0.4mg/ml, and 0.02mg/ml. The preferred route is IV Push. If an IV route is not available, Naloxone can be given IM or SQ. However, its action is delayed when administered via these routes.
Naloxone should be kept at 15-30 degrees centigrade and protected from light. Narcan is thought to act by competing with opioids at various receptor sites. It has a rapid onset of action when given IV (usually 1-2 minutes). When given IM or SQ it acts within 2-5 minutes. The duration varies by route, the IV duration is the shortest.7
The following guidelines for the administration of Naloxone to reverse respiratory depression secondary to opioid administration comes from Pasero and McCaffery.8 As we discussed earlier, once sedation and respiratory depression have been assessed, the nurse should stop the drug. The nurse should stay with the patient, so getting assistance from another nurse is required. The patient will need Naloxone (Narcan), preferably IV The dose selected for an adult is 0.4mg/ml ampule or preloaded syringe. Unlike the treatment for overdoses, this drug should be further diluted and titrated to effect. Mix 0.4 mg of Narcan in 10 cc of normal saline and begin injecting 0.5 cc over 2 minutes. Observe the patient closely. The patient should begin to respond in 1-2 minutes. If not, continue giving the Narcan up to 0.8 mg. If the patient is not responding to this dose, it is suggested that another cause of respiratory depression should be considered. The initial dose of Narcan can be stopped when the patient is able to follow simple commands and responds to physical stimulation.
Since the duration of Narcan is shorter than the duration of the opioid, it may be necessary to repeat the Narcan in 30 minutes. Someone must monitor the patient continuously until the patient is alert. When the crisis is past, the opioid can be restarted at half the original dose. Continue to monitor the patient closely. Be sure to document all assessment data as well as nursing interventions.
The first group of drugs we will discuss are the opiate agonists. They relieve pain without causing loss of consciousness. The main effect of opiate agonists is on the central nervous system and the intestines. They interact at opiate receptor sites. The highest concentration of these of these sites are in the limbic system, the thalamus, the midbrain, and the spinal cord.
There are several types of receptor sites. The mu receptors are located in the central nervous system. The kappa sites are within the deep layers of the cerebral cortex, and the sigma receptor sites are located within the limbic system. Agonist activity at mu and kappa sites cause analgesia, miosis and decreased body temperature.
These drugs do not alter the transmission of pain impulses, but do alter pain perception at the spinal cord and higher central nervous system levels. In this way it alters the patient's perception of pain, as well as the patient's response to the pain.
Opiate agonists also suppress the cough reflex, cause respiratory depression, drowsiness, sedation, euphoria, dysphoria, nausea, and vomiting. Gastrointestinal secretions are decreased by opiate agonists, which slows digestion. Since these drugs also slow gastric and intestinal motility, they lead to constipation. Another common side effect is orthostatic hypotension. It is important to assess for and anticipate this side effect when getting the patient up. Side effects of respiratory depression may lead to respiratory arrest. Hypotension may lead to cardiac arrest, especially in patients who are already fluid-depleted due to hemorrhage or dehydration.
Opiate agonists are well absorbed. They are used for the treatment of moderate to severe pain that is acute or chronic. They are also useful as pre-operative sedatives.
Patient teaching is important if these drugs are to be self-administered at home. Since they affect the central nervous system, the patient should be told not to drive, drink alcohol, or operate any machinery while on this medication.
Opiate agonists can potentiate the effect of any other central nervous system depressant. Of particular concern is the use of Demerol and Fentanyl for a patient who is also receiving an MAO inhibitor. In general this combination is contraindicated.
Opiate agonists are available in oral, rectal, and parenteral forms. The dose and route of administration is dependent on the patient's individual needs and should be titrated to effect.9
One of the first drugs we will consider is Codeine. Codeine is available alone, but is also used with other products in combination drugs. Codeine is often combined with aspirin, caffeine, and acetaminophen.
Codeine is an opiate agonist. It is useful as a mild analgesic. It also has antitussive properties. Codeine may be given orally, intramuscular or subcutaneously. The usual adult dose range is 15-60 mg every 4 hours.10
Codeine is not as effective or potent an analgesic as Morphine and it would take 130 mg orally to equal 30 mg of Morphine orally.11 When using combination drugs, be sure to calculate the non-opioid dose before increasing the dose or the frequency of administration, as this is often the limiting factor. The usual onset of action following oral or subcutaneous administration is 15-30 minutes. It peaks after 30 minutes and lasts from 4-6 hours.
Fentanyl is available as both a parenteral and a transdermal preparation. It should be protected from light. When given parenterally, Fentanyl has a faster onset of action than Morphine or Demerol but the duration is shorter. The respiratory effects of Fentanyl may persist longer than the analgesic effect. So monitor sedation levels appropriately in patients receiving this drug and keep in mind when giving the next dose, as residual effects of the previous dose may potentiate the effects of subsequent doses.
Fentanyl has strong analgesic properties. It is used parenterally both pre and post operatively. The transdermal route is especially useful for the treatment of chronic pain that requires opioid analgesia. Fentanyl has similar side effects as other opiate agonists. However, it has a lower incidence of nausea and vomiting. When giving Fentanyl IV it may cause severe muscle rigidity and may affect respiratory compliance. Bradycardia may also occur and Atropine should be immediately available. Fentanyl needs to be used with caution in patients with a history of bradydysrhythmias.
When Fentanyl is used transdermally, it is important to monitor the patient's temperature. Increased temperatures increase the rate of absorption. Patients with fever need to be observed carefully for opioid toxicity. Another precaution when using transdermal Fentanyl is related to its long half-life. If a patient has an adverse effect that requires discontinuation of the drug, it is important to continue to monitor the patient carefully for at least 12-24 hours after removal.
When applying a transdermal patch, select a site without obvious signs of irritation. Hair at the site should not be shaved, but may be clipped short. Wash the area with clear water only. Soaps and lotions should not be used. When applying the next patch, select a new site.
Fentanyl is not recommended as the first opiate agonist. It should be given after other opiate agonists have been used. The correct dose should then be calculated based on the equianalgesic charts. Transdermal release is approximately 25 micrograms per hour per 10cm2.
When given transdermally the drug is absorbed slowly. It peaks in 12-24 hours and the analgesic effect persists for 72 hours. When given IV it begins to work in 1-2 minutes, peaks in 3-5 minutes and lasts for 30-60 minutes. The onset of action when given IM is 7-15 minutes with a duration of 1-2 hours.13
Dilaudid is available for oral, rectal, or parenteral use. It has a more rapid onset than Morphine but a shorter duration of action. Dilaudid has strong analgesic properties and is recommended for the relief of moderate to severe pain. Side effects are similar to those of morphine with less nausea, vomiting, constipation, and euphoria.
Dilaudid comes in a highly concentrated dose of 10 mg per ml. This concentration is contraindicated for patients who have not had previous treatment with opiate agonists. For those individuals who are not tolerant to opiate agonists the less concentrated preparations are advised. Dilaudid is also available in the following preparations; Img/ml, 2mg/ml, 3mg/ml, and 4mg/ml. The usual oral adult dose is 2mg every 4-6 hours. The IM dose ranges from 2-4 mg every 4-6 hours. High doses of 10 mg may be given to patients with chronic severe cancer pain who are tolerant to opiate agonists.14
Demerol is a popular opiate agonist. It is used to treat moderate to severe pain. Side effects are similar to Morphine. However, as Demerol breaks down, Normeperidine (a metabolite) is released. This metabolite causes anxiety, tremors, and seizures. Patients with renal problems are most at risk. Narcan is not effective in reversing these symptoms and is contraindicated as it may increase the likelihood of seizures. Demerol is not recommended for long term pain management nor for the management of acute pain that lasts for more than 48 hours. Dosage should not exceed 600mg in 24 hours.
Demerol is used to treat pain associated with myocardial infarction, but is less effective than Morphine. It is also useful as pre-operative sedation. Side effects are similar to other opiate agonists at normal doses, however, it may increase heart rate and should be used with caution in patients with tachydysrhythmias such as atrial fibrillation or atrial flutter. Demerol is also not recommended for the management of pain related to Sickle Cell Anemia, bums, or cancer pain. Demerol interacts with Isoniazid and MAO inhibitors.
The oral dose of Demerol is less effective than parenteral administration. When giving oral Demerol it should be followed by a full glass of water. When giving Demerol IM it should be given into a large muscle mass. Demerol can be given subcutaeously but should be avoided as it is extremely irritating to the tissues.
The usual intermittent adult dose of Demerol is 50-150 mg every 3-4 hours. However, for some people the analgesic effect may only last 2-3 hours. This leads to under medication in many people, and should be considered when selecting this drug. The continuous IV dose is 15-35 mg per hour. Peak action, when given orally is one hour, with a duration of 2-4 hours. When given IM, demerol peaks in 30-50 minutes and lasts from 2-4 hours.
When assessing patients receiving Demerol be sure to monitor for toxic side effects secondary to metabolites as well as the usual side effects of opiate agonists.15
Methadone has similar side effects when compared to Morphine. Repeated doses cause a cumulative effect that may increase sedation and the duration of analgesic effect. Methadone is indicated for the management of severe chronic pain in terminally ill patients. It is available for oral, intramuscular, and subcutaneous administration.
For pain management the usual dose is 2.5-10 mg every 3-4 hours. For relief of severe chronic pain 5-20 mg orally every 6-8 hours is commonly ordered. Higher doses have been used when patients become tolerant to opiate agonists.16
Morphine is the opiate agonist that all others are compared to. Morphine can be given orally, rectal, subcutaneously, intramuscular, IV bolus, continuous IV drip, or via epidural catheter. Morphine is indicated for the management of severe acute or chronic pain. It is also useful as a pre-operative sedative. Morphine is the drug of choice for pain associated with myocardial infarction because of its effect on the cardiovascular system. It decreases systemic vascular resistance which decreases the workload of the heart. This may cause a drop in blood pressure. Respiratory depression is a common side effect. Monitoring sedation levels closely is essential. Since each route has a different peak effect the nurse needs to be aware-of the approximate timing of adverse effects. When given orally, Morphine peaks in about 60 minutes. Rectal doses peak in 20-60 minutes. Intramuscular administration peaks in 30-60 minutes. The IV route peaks in 7-20 minutes. Nurses should plan their assessment based on this information.
Orthostatic hypotension is another common side effect, especially when the patient has a low circulating volume secondary to hemorrhage or dehydration, or in patients with impaired cardiac function. Urinary retention, constipation, nausea and vomiting are also associated with Morphine and should be treated as necessary.
When giving Morphine IV for the first time, resuscitation equipment should be readily available. Morphine IV should be injected slowly with the patient lying down. Rapid injection increases the incidence of side effects.
Morphine can be administered as a continuous epidural or intrathecal infusion, but should only be given by persons knowledgeable about these routes. Morphine is also available as an extended release tablet. This tablet should never be broken or crushed. This could cause absorption of an excessively large dose with severe adverse side effects.
The usual dose varies by route and should be titrated to the patients response. The usual oral dose is 10-30 mg every 4 hours. Rectally, the normal dose is 10-20 mg every 4 hours. Intramuscular doses range from 5-20 mg every 4 hours. When giving Morphine by IV bolus 2.5-15 mg can be given over 4-5 minutes. Higher doses are given to patients who have developed tolerance to Morphine.17
Oxycodone is available alone, with Acetaminophen (Tyiox, Percocet), or with Aspirin (Percodan). Oxycodone is a mild analgesic and is used to treat moderate pain. It is useful for patients with bursitis and orthopedic injuries. It is more useful for the management of acute pain than chronic pain. Oxycodone is given orally. The usual dose is 5 mg every 6 hours. It begins to provide relief after 10-15 minutes, peaks in 30-60 minutes and lasts from 3-6 hours.18
Oxymorphone is available in both parenteral and rectal forms. It is a strong analgesic and is indicated for the relief of moderate to severe pain. The usual dose is 1-1.5 mg every 4-6 hours IM or
0.5 mg IV The rectal dose is 5 mg every 4-6 hours. The onset of action varies slightly by route. IV administration produces an effect in 5-10 minutes, IM onset is 10-15 minutes, and the onset for rectal administration is 15-30 minutes. All routes have a similar duration of anywhere from 3 to 6 hours.19
Another type of opioid analgesic is the partial opiate agonists. These produce less analgesic response than full opiate agonists, regardless of their concentration. Unlike full opiate agonists, partial agonists have a ceiling effect with regard to both side effects and analgesia.20
The most common of the partial agonists is Buprenorphine Hydrochloride (Buprenex). It acts as a partial agonist at mu receptor sites. It seems to have a longer duration of analgesic effect and less physical dependence than full opiate agonists. This is thought to be due to its slow binding and diassociation at the receptor sites. The analgesic effect appears to be dose related. Excessive doses can cause antagonist activity rather than agonist activity. This is important to know when considering increasing the dose or frequency to increase pain control. Unlike full agonist, the ceiling effect prevents titrating doses upward to achieve optimal pain relief.
Buprenex acts as an antagonist when given to patients receiving full opiate agonists. This blocks the analgesic effect of the opiate agonist and may lead to withdrawal in patients who have developed a tolerance to opioids.
Buprenex produces side effects that are similar to Morphine. The onset of sedation is slower due to its slow binding at receptor sites. Respiratory depression is less common than with Morphine and larger doses do not necessarily produce more respiratory depression than normal doses. Narcan is used to reverse life-threatening respiratory depression, however it is not as effective an antagonist for Buprenex as it is for Morphine.
The onset of action and peak effect of Buprenex is similar to that of Morphine. The duration of action is around 6 hours. Buprenex is used for the treatment of moderate to severe pain. It is used in the management of post-operative pain, and because of its limited cardiovascular side effects may be preferable to Morphine in patients with compromised cardiovascular function. Buprenex is effective for the management of pain associated with trigeminal-neuralgia, ureteral calculi, and trauma.
Buprenex is given IM or slow IV push. For pain management, the usual dose IM or IV is 0.3-0.6 mg every 4-6 hours. Buprenex can also be given by continuous infusion at a rate of 25-250 micrograms per hour.21 Buprenex is listed as one of the drugs not recommended for the treatment of chronic cancer pain because of its ceiling effect as well as its potential for causing withdrawal symptoms.22
The last class of opioids are the mixed agonist-antagonists. Mixed agonist-antagonists activate some receptor sites and block others. Patients who are on full agonists such as Hydromorphone or Morphine should not be switched to mixed agonist-antagonists. This could cause severe withdrawal symptoms and can increase the pain.23 Mixed agonist-antagonists, like partial agonists, have a ceiling effect. Mixed agonist-antagonists may cause dysphoria and hallucinations in addition to other side effects commonly associated with other opioids. The three we will discuss are Stadol, Nubain, and Talwin.24
Stadol has both analgesic and opiate antagonist effects. The analgesic effect is thought to occur at receptor sites in the limbic system. Like opiate agonists, Stadol may cause sedation and respiratory depression. Narcan effectively reverses the respiratory depression.
Peak effects are route dependent. The peak concentration from the oral route occurs in 1-1.5 hours. Peak plasma levels after IM injection occurs in 30-60 minutes. The peak effect after intravenous injection is 2-4 minutes. The duration of analgesia is 3-6 hours.
Stadol is effective in the treatment of moderate to severe pain. It has been used with both acute and chronic pain. However, it is not recommended for the treatment of chronic cancer pain.25 It is useful for the management of pain related to orthopedic injuries, bums, renal colic and post-operative discomfort.
Sedation is the most common side effect. It occurs more frequently with Stadol than with Morphine. However, respiratory depression occurs less frequently than equivalent doses of Morphine. Narcan can be used to reverse the respiratory depression. Other unpleasant side effects include nausea, vertigo, dizziness, confusion, unusual dreams, agitation, euphoria, and hallucinations.
Stadol has an additive effect when used with other central nervous system depressants. Stadol is available for IM or IV administration. The usual dose is 1-4 mg IM or 0.5-2 mg IV every 3-4 hours.26
Nubain has both agonist and antagonist actions. Its action is similar to Stadol and it probably acts in the limbic system. Respiratory depression is a potential side-effect and can be effectively treated with Narcan. The peak effect when given IM or IV occurs in about 30 minutes. The onset of action is 2-3 minutes when given IV, and 15 minutes when given IM. Duration varies among individuals and ranges from 3-6 hours.
Nubain is used to treat moderate to severe pain that is acute or chronic. It is not recommended for the treatment of chronic cancer pain.27 It is useful for the treatment of pain related to orthopedic injuries, renal colic, migraine headaches, or post-operative pain. This drug is also used for obstetric pain.
Side effects are similar to those of Morphine. It causes some unpleasant side effects such as dizziness, vertigo, restlessness, euphoria, confusion, fainting, nausea, and vomiting. Nubain has an additive effects when given with other central nervous system depressants. Nubain can be given subcutaneously, intramuscular, or intravenous. The usual dose is 10-20 mg every 3-6 hours.28
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Note: Published tables vary in the suggested doses that are equianalgesic to morphine. Clinical response is the criterion that must be applied for each patient; titration to clinical response is necessary. Because there is not complete cross-tolerance among these drugs, it is usually necessary to use a lower than equianalgesic dose when changing drugs and to reiterate to response.
Caution: Recommended doses do not apply to patients with renal or hepatic insufficiency or other conditions affecting drug metabolism and kinetics.
1 Caution: Doses listed for patients with body weight less than 50 kg cannot be used as initial starting doses in babies less than 6 months of age. Consult the Clinical Practice Guideline for Acute Pain Management: Operative or Medical Procedures and Trauma section on management of pain in neonates for recommendations.
2 For morphine, hydromorphone, and oxymorphone, rectal administration is an alternate route for patients unable to take oral medications, but cqiiianalgesic doses may differ from oral and parenteral doses because ofphannacokinetic differences.
3 Caution: Codeine doses above 65 mg often are not appropriate due to diminishing incremental analgesia with increasing doses but continually increasing constipation and other side effects.
4 Caution: Doses of aspirin and acetaminophen in combination with opioid/NSAID preparations must also be adjusted to the patient's body weight
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Talwin has analgesic actions and weak antagonist effects. As with the other medications we have discussed sedation and respiratory depression are common side effects. Narcan is effective to reverse sedative effects of Talwin.
Onset of action is route dependent. When given orally the analgesic action begins in 15-30 minutes, with a peak action in 1-3 hours, and a duration of 3 hours. IM administration has an onset of 15-20 minutes, it peaks in about 1 hour and lasts up to 2 hours. After IV administration the analgesic effect appears in 2-3 minutes, it peaks in 15 minutes and lasts about 1 hour.
Talwin has been used to treat moderate to severe pain. It is useful for the treatment of post-operative pain, pain associated with dental surgery, or orthopedic injuries. As with other mixed agonist-antagonists it is not recommended for the management of chronic cancer pain.29
Side effects include dizziness, euphoria, sedation, nausea, hallucinations, and confusion. It may be associated with seizures in patients with a history of seizure disorders. Talwin is not recommended in patients with decreased cardiac function. It may cause increased heart rate, hypotension, circulatory depression, and shock. IM injections are painful and may cause tissue irritation. Ulceration may occur with repeated injections. Talwin has an additive effect when given with other central nervous system depressants. It is available for injection or oral administration. It is also available as a combination drug with Aspirin or Acetaminophen. The usual oral adult dose is 50-100 mg every 3-4 hours. The dose should not exceed 600 mg in 24 hours. When given IM or IV the usual adult dose is 30 mg every 3-4 hours and should not exceed 360 mg in 24 hours.30
| Class | Drug | Rationale for not recommending |
| Opioids | Meperidine | Short (2-3 hour) duration. Repeated administration may lead to CNS toxicity (tremor, confusion, or seizures). High oral doses required to relieve severe pain, and these increase the risk of CNS toxicity. |
| Miscellaneous | Caimabinoids | Side effects ofdysphoria, drowsiness. hypotension, and bradycardia preclude its routine use as an analgesic. |
| Cocaine | Has demonstrated no efficacy as an analgesic or coanalgesic in combination with opioids. | |
| Opioid agonist-antagonists | Pentazocine Butorphanol Naibuphine |
Risk of precipitating withdrawal in opioid-dependent patients. Analgesic ceiling. Possible production of unpleasant psycho-mimetic effects (e.g., dysphoria, hallucinations). |
| Partial agonist | Buprenorphine | Analgesic ceiling. Can precipitate withdrawal. |
| Antagonist | Naloxone Naltrexone |
May precipitate withdrawal. Limit use to treatment of life-threatening respiratory depression. |
| Combination preparations | Brompton's cocktail | No evidence of analgesic benefit to using Brompton's cocktail over single opioid analgesics. |
|
DPT (Meperidine, Promethazine, and Chlorpromazine) |
Efficacy is poor compared with that of other analgesics. High incidence of adverse effects. | |
| Antiolytlcs alone | Benzodiazepine (e.g., alprazolam) | Analgesic properties not demonstrated except for some instances ofneuropathic pain. Added sedation from anxiolytics may limit opioid dosing. |
| Sedative/hypnotic drugs alone | Barbiturates Benzodiazepine | Analgesic properties not demonstrated. Added sedation from sedative/hypnotic drugs limits opioid dosing. |
| Routes of administration | Rationale for not recommending | |
| Intramuscular (IM) | Painful. Absorption unreliable. Should not be used for children or parents prone to develop dependent edema or in patients with thrombocytopenia. | |
| Transnasal | The only drug approved by the FDA for transnasal administration at this time is butorphanol, an agonist-antagonist drug, which generally is not recommended. (See opioid agonist-antagonists above.) | |
Source: Management of Cancer Pain: Adults Quick Reference Guide for Clinicians, No. 9. AHCPR Pub No. 95-0593 (1994)
Over the past twenty years, because of the research done in the area of pain management, several new techniques for pain management have been developed. They include intraspinal analgesic infusions, continuous subcutaneous analgesic infusions, and continuous intravenous infusions (with or without patient control).
Intraspinal Analgesic Infusion of opioids or local anesthetics can be used to control post-operative pain as well as chronic pain that has not been successfully relieved by other methods. An intrathecal or epidural catheter is placed in the spinal column for analgesic infusion. Analgesics can be given via bolus or continuous infusion. Since smaller doses of opioids are required to produce pain control, less side effects are experienced by patients.31
Intraspinal opioid administration delivers the drug close to the site of its action (spinal cord). This both enhances and prolongs the analgesic effect. Because it is an invasive procedure it is not suggested as a first time treatment option. Intraspinal analgesic infusion is more successful when used to treat somatic pain rather than visceral pain and is more useful for the management of chronic pain than acute pain.
When switching patients to intraspinal opioids, the initial dose is calculated based on the previous 24-hour requirements.32
Step 1 Calculate 24-hour IV Opioid Requirement
Step 2 a) Epidural dose = 0.25-0.33 of the IV requirement
b) Intrathecal dose = 0.025-0.050 of the IV requirement
There are several options available for catheter insertion. It can be placed intrathecal or epidural. Cervical, thoracic, or lumbar areas have been used. The catheter can be externalized, or internalized with an external pump, or an internal pump can be employed (Infusaid Pump). Often a port system is chosen. It has a small subcutaneous injection port that can be easily accessed using a Huber needle.
This system provides options for the patient. Analgesia can be administered via bolus or continuous infusion. Continuous infusion has advantages over bolus injections. It provides more consistent pain control in lower doses. This decreases tolerance as well as side effects.
Morphine is the usual opioid selected. Duramorph is a preservative-free morphine concentration developed for intraspinal use. If other drugs are selected, it is important that they contain no neurotoxic preservatives, such as Phenol or Formaldehyde. Hydromorphone, Fentanyl, and Methadone have also been used for intraspinal analgesia.33
Intraspinal opioids bind to opiate receptor sites in the spinal cord to block the pain gates and control pain. Local anesthetics, such as Marcaine, have also been used via this route. They block conduction of pain impulses to control pain. It is possible to increase pain control, without increasing the dose of opioids by adding local anesthetic agents.
The side effects of opioids when given via the intraspinal route are nausea, itching, urinary retention, and respiratory depression. Patients should be carefully monitored (at least every hour) for the first 24 hours of administration. Side effects can be managed by slowing the rate of infusion. If further analgesia is needed an NSAID can be added orally.
Epidural local anesthetics can cause hypotension, weakness in legs, paralysis or parathesia of lower extremities. This is usually dose related.34 Persons not familiar with this route should not use it. It requires special training. A special problem that the nurse should be aware of includes the development of an abscess of the nerve route at the insertion site.35
Subcutaneous analgesic infusion has been used to treat chronic pain in patients who cannot tolerate the oral or IM routes, but who are not candidates for intraspinal infusion. The analgesia is infused via butterfly needle placed in the subcutaneous layer of the skin. The site must be changed weekly.36 This method does not involve a lot of training and may permit patients to remain in their homes, managing their own care for long periods of time.
While this may should like a new technique, hypodermoclysis was used in the 50's and 60's for hydration. This is simply a new treatment using an old technique.
Morphine and Hydromorphone are the drugs preferred because their short half-life creates a quick blood level that can be maintained and evaluated. Methadone and Levorphanol which have slightly longer half-lives, have also been used.
The infusion is given via a small pump that is loaded with 30-100 cc of the analgesic preparation. Concentrated preparations are required. When starting the subcutaneous infusion the patient should be monitored closely for the first 4 hours. The site should also be assessed for erythema or pain. This would indicate the need for a site change. The usual sites for needle insertion are the anterior chest, anterior abdomen, or arm.
Since this method of pain management allows patients to remain at home, patient and family teaching is essential. Patients and families also need a resource person to call in case of problems or questions. One major drawback to this method of pain management is the cost. A preloaded syringe may cost up to $15.00 per day.37
Continuous IV infusion of opioids has several advantages. It requires less opioid than intermittent dosing and therefore produces less side effects. It can be managed at home. It can be patient controlled or given by consistent rate infusion. Both systems use a computerized pump to control and monitor the rate of infusion.
The patient controlled system (PCA) requires the use of an infusion pump that is preprogrammed to prevent accidential overdoses. It allows the patient to control the amount and frequency of pain medication administration. The infusion pumps keep a detailed record of analgesic use that can be accessed by the nurse and must be documented on the patient's record.
The usual medications used are Morphine or Demerol. Demerol is used for short-term post-operative pain but is not suggested for use with chronic pain. Morphine and Demerol are available in pre-loaded syringes that fit directly into the PCA pump. Care should be taken when changing the syringe that the patient does not receive an accidental bolus of the analgesia.
As with other routes of administration, the nurse must carefully monitor the patient for adverse effects of opioid therapy. Assessment of sedation level and respiratory rate should be documented at regular intervals.38
When patients are unable to control their own analgesia or when intermittent IV bolus systems do not provide sufficient pain control, the opioid can be delivered via continuous drip. An infusion pump must always be used to prevent accidental overdoses. The same precautions exist for this method of delivery as for the other we discussed.
Review of Opioid Pharmacology
Answers:
1. c
2. a
3. c
4. a
5. b
6. a
7. d
8. c
9. b
10. a
11.b
12. a
13. c
14. a
15. d
16. c
17. b
18. c
19. a
20. a
21.b
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