A potential interaction was shown between statins metabolized by CYP3A4 (atorvastatin, lovastatin, simvastatin)—where vitamin D supplementation (800 IU/d) caused a significant decrease in drug sera concentration, HAART drugs—again strongly affecting CYP3A4, with reporting of statistically lower serum levels of 25(OH)D, and of rifampin and isoniazid, anti-tuberculosis (TB) drugs, a CYP3A4 inducer and inhibitor respectively, with an unclear effect depending on the study. The gene discussed is CYP3A4; the disease is tuberculosis.