A patient with gout has been prescribed Allopurinol. Which of the following instructions should the nurse emphasize to the patient?

A. Oral tablet: Oral medications must pass through the gastrointestinal tract and undergo first-pass metabolism in the liver before entering systemic circulation, significantly delaying the onset of action compared to parenteral routes.
B. Intramuscular injection: IM injections are absorbed faster than oral or subcutaneous routes due to the rich blood supply in muscle tissue. The rate of absorption depends on factors such as blood flow to the muscle, the solubility of the drug, and the injection site. While faster than oral administration, it is still slower than IV.
C. Intravenous injection: IV administration delivers the drug directly into the bloodstream, resulting in immediate systemic availability and the fastest onset of action. This route bypasses absorption barriers entirely.
D. Subcutaneous injection: SC injections are absorbed more slowly than IM and IV routes because of the lower vascularity of subcutaneous tissue. Onset of action is delayed relative to other parenteral methods.

A. Increased risk of arrhythmias due to drug interactions: While both drugs affect cardiovascular function, the primary risk with concurrent use is not arrhythmias. Nitroglycerin and PDE-5 inhibitors mainly influence vascular tone, not cardiac electrical activity directly.
B. Potential for life-threatening hypotension due to excessive vasodilation: Both nitroglycerin and PDE-5 inhibitors are potent vasodilators. When used together, they can cause profound hypotension due to synergistic effects on the vascular system, which may lead to syncope, myocardial infarction, or even death.
C. Increased risk of severe headache due to overlapping side effects: Headache is a known side effect of both drugs due to vasodilation, but it is not the most dangerous interaction. While uncomfortable, headaches are not life-threatening compared to the risk of severe hypotension.
D. Decreased effectiveness of nitroglycerin in relieving angina: There is no evidence that PDE-5 inhibitors reduce the efficacy of nitroglycerin. The concern is not about reduced therapeutic benefit but rather the risk of severe, potentially fatal cardiovascular side effects.