Charlie has been prescribed itraconazole. Which of his medications might show interaction with itraconazole?

• A. Aspirin 325 mg one daily.
• B. Calcium carbonate 400 mg 4 tablets every 8 hours as needed.
• C. Hydrochlorothiazide 25 mg one daily.
• D. All of the above.

Answer: (D)

Itraconazole is an antifungal medication that can interact with various other drugs and substances, primarily due to its effect on metabolic pathways, especially those involving the cytochrome P450 enzyme system, particularly CYP3A4.

In the case of aspirin, while there is no direct interaction with itraconazole, the potential for increased toxicity cannot be completely ruled out, especially in patients with underlying health conditions.

Calcium carbonate is often used as an antacid and can impact the absorption of itraconazole. Itraconazole requires an acidic environment for optimal absorption; therefore, taking it with calcium carbonate may reduce its efficacy due to changes in gastric pH.

Hydrochlorothiazide is a diuretic that can also be affected indirectly by itraconazole due to its potential to alter electrolyte levels and influence the effectiveness of other medications due to changes in fluid status or renal function.

Thus, itraconazole has the potential to interact with all medications listed, leading to reduced effectiveness or increased side effects. This understanding makes the option that indicates all medications might show interaction the most appropriate.