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 SignificanceIllicit substances most commonly abused include cocaine, marijuana, methamphetamine, ecstacy(MDMA, or methylenedioxymethamphetamine), heroin, methadone, ketamine, crystal andGHB (gamma hydroxy butyrate). As a result of the myriad side effects that can follow use ofthese substances (see Table 27-10), combining any of these substances with PIs especially increasesthe likelihood of an overdose due to one of these agents, particularly ecstasy.Cocaine has been reported to increase the speed at which HIV replicates, while combination ofthe protease inhibitors with marijuana increases levels of tetrahydrocannabinoids in the blood.Because combination of methamphetamine with ritonavir (Norvir) causes an increase in thepotency of ritonavir, two-fold or three-fold, the likelihood of overdose with methamphetamine isincreased. Concomitant use of ketamine in the presence of the protease inhibitors causes hepatitis.Ritonavir decreases plasma levels of heroin by 50%.The potency of methadone is decreased in the presence of ritonavir, indinavir (Crixivan) andnevirapine (Viramune), while methadone increases the potency of ritonavir by 50%. Nevirapinewas demonstrated to reduce plasma methadone levels and to precipitate opiate withdrawal inpatients who were maintained on methadone for narcotics addiction. 28 More recent studies havereported decreases in the amount of stavudine (Zerit) and didanosine (Videx) absorbed fromthe digestive tract into the bloodstream in the presence of methadone. Table 27-10 provideshighlights of the side effects that may be exacerbated by the use of ecstasy (MDMA), a powerfulstreet drug recently associated with fatal drug interactions when administered concomitantlywith ritonavir. 29Table 27-10: Side Effects of Ecstasy (MDMA) That May Be ExacerbatedWhen Used with Conventional Drugs with Similar Side Effects• Bradycardia• Decreased libido• Drowsiness• Dysphoria• Euphoria• Faintness• Headache• Insomnia• Nausea and vomiting• Pruritus• Rash• Respiratory depression• Physical and psychological dependence• Urinary retention• Visual disturbancesSources: Adapted from multiple sources, mainly Pham JV, Puzantian T. Ecstasy: Dangers and controversies. Pharmacotherapy 21:1561-5, 2001.570U.S. Department of Health and Human Services • Health Resources and Services Administration • HIV/AIDS Bureau