GoodRx for Healthcare Professionals7 Vitamin D Interactions to Watch For

Recent clinical findings highlight important drug interactions between vitamin D supplements and common medications that warrant careful consideration in clinical practice. The article examines seven specific drug interactions with vitamin D that can affect medication efficacy, absorption rates, and patient safety, particularly involving statins, anticonvulsants, and cardiovascular medications.

Key Points:

• Statin medications metabolized by CYP3A4 (atorvastatin, lovastatin, simvastatin) may show decreased blood levels when taken with vitamin D due to enhanced enzyme activity, potentially reducing their effectiveness in managing cholesterol levels
• Bile acid sequestrants, particularly cholestyramine, require specific timing considerations – vitamin D supplements should be administered at least 1 hour before or 4 hours after cholestyramine to ensure proper absorption
• Tuberculosis medications (rifampin, isoniazid) affect CYP3A4 activity differently, necessitating vitamin D level monitoring and potential dosage adjustments during treatment
• Anticonvulsants (phenobarbital, phenytoin, carbamazepine) accelerate vitamin D metabolism, often requiring higher supplementation doses to maintain therapeutic levels
• Concurrent use of vitamin D with thiazide diuretics increases hypercalcemia risk, particularly in patients over 65, those with kidney problems, or individuals with hyperparathyroidism

HCN Medical Memo
Clinical vigilance regarding vitamin D interactions is essential, particularly for patients on multiple medications. Consider medication timing adjustments and monitoring protocols rather than discontinuing either agent when managing these interactions.

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