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A patient receiving a liquid antacid containing magnesium and aluminum hydroxides (Maalox) developed a urinary tract infection. Her doctor ordered 500 mg of tetracycline every 6 hours.
The pharmacist dispensed a supply of 500-mg capsules of tetracyline to the unit. When the patient's nurse brought her the first capsule, the patient said she couldn't swallow capsules. So the nurse opened it, emptied the contents into 15 ml of Maalox, mixed the suspension, and gave it to the patient to drink.
The nurse administered several doses of tetracyline in this manner before another nurse stopped her. The second nurse explained that aluminum, magnesium, or calcium in any drug or food will chelate (bind) with tetracyline, preventing most of it from being absorbed. Because the tetracycline had been 'mixed with Maalox, 'the patient had received very little of it.
This type of error is easy to prevent. Whenever a patient can't swallow a solid oral dosage form, ask the pharmacist if an alternate form is available. Many drugs are available in liquid form or can be prepared as a suspension.