Symptomatic orthostasis with extended-release nifedipine and protease inhibitors

Human immunodeficiency virus (HIV) protease inhibitors are prone to drug interactions with other agents. As individuals with HIV infection live longer, the clinical significance of many interactions is becoming recognized. A 51-year-old man with HIV infection who was receiving extended-release nifedipine developed symptomatic orthostasis and heart block after starting antiretroviral therapy that included nelfinavir. He experienced dizziness, fatigue, and hypotension and developed complete heart block with a junctional escape rhythm. Electrocardiogram abnormalities abated within 24 hours of discontinuing antiretroviral therapy. The patient developed orthostatic symptoms after restarting nelfinavir. He was switched successfully to an efavirenz-based regimen. Subsequent administration of antiretroviral therapy containing ritonavir and indinavir with extended-release nifedipine resulted in recurrence of his orthostatic symptoms. Discontinuation of atenolol, and nifedipine dosage reduction by 50% were effective in managing his orthostatic changes. Careful monitoring by clinicians is necessary when concomitant administration of HIV protease inhibitors are prescribed with other agents that are metabolized through the cytochrome P450 system.