SOURCES: Elaine Mackowiak, PhD, registered pharmacist; professor of pharmacy practice, Temple University School of Pharmacy. WebMD Medical News: 'What Could Possibly Be Bad About Grapefruit?' WebMD Public Information from the FDA: 'Over-the-Counter Drug Know-How'. Medicines and Healthcare products Regulatory Agency (MHRA). Current problems in Pharmacovigilance (MHRA). Pharmacokinetic interaction of digoxin with an herbal extract from St John's wort Institute of Clinical Pharmacology, University Medical Center Charité, Humboldt University, Berlin, Germany.Pharmacology Weekly How does St. John's wort (Hypericum perforatum L.) decrease drug concentrations of antiretroviral medications thereby causing a loss of viral control in HIV patients?

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