The Clinical Guide to Supportive and Palliative Care for HIV/AIDS

A Clinical Guide to Supportive and Palliative Care for HIV/AIDS • Chapter 27: Pharmacologic Interactions of Clinical SignificanceOTHER DRUG INTERACTIONSDrug Interactions with Herbal ProductsUse of herbal remedies, multiple vitamins, and mineral and dietary supplements is extremelycommon among all patient populations surveyed. In one U.S. survey of adults who regularly takeprescription medications, 18.4% reported concurrent use of at least one herbal product or highdose vitamin. In another study, 61.5% of patients who used conventional therapies did not discloseuse of other remedies to their health care provider. 11Anecdotal experience from questions asked of people with HIV at our busy outpatient clinicsuggests that the use of such remedies is reasonably high among this population, particularly aspatients advance in their illness and shift into palliative care. In a survey of 515 users of herbalremedies in the U.K., 26% of patients would consult their general practitioner for a seriousadverse reaction associated with a conventional over-the-counter medicine, but not for a similarreaction from an herbal remedy. It seems that most patients still do not quite regard herbalremedies as medications.Another reason patients may not disclose their use of herbal remedies, even if the remediescause severe adverse effects, is that patients are afraid of censure. 12 Health providers must thereforeask patients about their use of herbs in a relaxed manner that is nonjudgmental; it has beenshown in several studies that disapproval will ensure that patients conceal any such use in thefuture. Such patients should be involved in a partnership in which providers share whateverinformation is available about the herbal product, including the lack of information on druginteractions and the need for open communication on both sides about the use of all such remedies.All such formulations, the reasons for their use, dosages, brand and manufacturer shouldbe documented in patient charts and updated from time to time.Interactions with St. John’s WortThis commonly used, over-the-counter antidepressant herbal product induces cytochromeP450 3A enzymes and as a result has been shown in several studies to decrease significantlylevels of all of the protease inhibitors and, most probably also, the NNRTIs currently available inthe market. In one study, indinavir trough levels decreased 81% when concomitantly given withSt. John’s wort. 13 The DHHS guidelines of February 2002 recommend that St. John’s wort not betaken by patients on PI antiretroviral medications. 1An increased risk of serotonin syndrome has also been reported in patients who mix St. John’swort with certain SSRIs, namely trazodone (Desyrel), paroxetine (Paxil), sertraline (Zoloft)and nefazodone (Serzone). 4,14Reports also have been made of decreased serum concentrations of drugs such as digoxin, theophylline,cyclosporine and phenprocoumon when combined with St. John’s wort. 11 At the presenttime, many reports of herb-drug interactions are sketchy and lack proper pharmacokineticstudies to substantiate them; nonetheless, health care providers should counsel patients on theneed always to form a partnership in the use of these remedies and if possible to avoid unnecessaryherbal and unproven remedies that can lead to undesirable drug-herb interactions.566U.S. Department of Health and Human Services • Health Resources and Services Administration • HIV/AIDS Bureau