The nurse is obtaining a medication history of a 48-year-old patient with an ear infection who is to receive penicillin therapy.
The patient reports taking a beta-adrenergic blocker for his hypertension.
The nurse would identify that this patient is at increased risk for which of the following if penicillin is administered?

Choice A rationale: Tetracycline can increase the levels of digoxin (Lanoxin) in the blood, leading to an increased risk of digoxin toxicity. This interaction occurs because tetracycline can interfere with the metabolism and excretion of digoxin, causing higher concentrations of the drug in the bloodstream1. Symptoms of digoxin toxicity include nausea, vomiting, dizziness, and cardiac arrhythmias. Therefore, patients taking both medications should be closely monitored for signs of toxicity and may require dosage adjustments.

Choice B rationale: Phenytoin (Dilantin) does not have a significant interaction with tetracycline that increases the risk of toxicity. While both medications can be used together, they do not significantly affect each other's metabolism or excretion1.

Choice C rationale: Vancomycin (Vancocin) does not have a significant interaction with tetracycline that increases the risk of toxicity. Both medications can be used together without causing significant changes in their metabolism or excretion1.

Choice D rationale: Carbamazepine (Tegretol) does not have a significant interaction with tetracycline that increases the risk of toxicity. While both medications can be used together, they do not significantly affect each other's metabolism or excretion