Which drug should be avoided in patients taking MAOIs?

The correct choice is phenylephrine, which should be avoided in patients taking monoamine oxidase inhibitors (MAOIs) due to the potential for severe hypertension. Phenylephrine is a selective α1 adrenergic agonist that leads to vasoconstriction and increased blood pressure. When administered to patients who are on MAOIs, which impede the breakdown of norepinephrine and other neurotransmitters, the combined effect can result in a significant increase in blood pressure. This could precipitate a hypertensive crisis, a serious and potentially life-threatening condition.

Understanding the interactions between drugs and their mechanisms is crucial in ocular pharmacology, especially for ensuring patient safety. MAOIs can increase the levels of norepinephrine, and the addition of phenylephrine can exacerbate this elevation, leading to dangerously high blood pressure levels. Therefore, clinicians must be cautious in prescribing medications that can interact adversely with MAOIs, such as phenylephrine.