Rifampin is a potent inducer of cytochrome P-450 oxidative enzymes. A few examples of well-documented clinically significant interactions include interactions with warfarin, oral contraceptives, cyclosporine, glucocorticoids, ketoconazole or itraconazole, theophylline, quinidine sulfate, digitoxin or digoxin, verapamil hydrochloride, human immunodeficiency virus-related protease inhibitors, zidovudine, delavirdine mesylate, nifedipine, and midazolam. Recent reports have demonstrated clinically relevant interactions with numerous other drugs, such as buspirone hydrochloride, zolpidem tartrate, simvastatin, propafenone hydrochloride, tacrolimus, ondansetron hydrochloride, and opiates. Rifabutin reduces serum concentrations of antiretroviral agents, but less so than rifampin. To avoid a reduced therapeutic response, therapeutic failure, or toxic reactions when rifampin is added to or discontinued from medication regimens, clinicians need to be cognizant of these interactions. Enhanced knowledge of known interactions will continue to develop, including research on the induction of specific cytochrome P-450 isoenzymes and on the importance of the P-glycoprotein transport system. New rifampin and rifabutin interactions will be discovered with further investigations.

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To avoid a reduced therapeutic response, therapeutic failure, or toxic reactions when rifampin, rifabutin, or rifapentine are added to or discontinued from medication regimens, clinicians need to be aware of these interactions. Recent studies have indicated that other transporter systems play a role in these drug interactions. As reports of rifampin drug interactions continue to grow, this review is a reminder to clinicians to be vigilant.

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Minority populations in the United States continue to experience a disproportionate share of emergency department (ED) visits and hospitalizations due to asthma. This review examines programs that have attempted to reduce these acute care visits in African American and Hispanic patients. We performed a PubMed search of the English literature for studies published from March 1990 to March 2005, aimed at reducing ED visits and hospitalizations in patients with asthma. Decreased acute care visits in African American and Hispanic patients with asthma have been demonstrated in several studies over the past 15 years, including collaboration by physicians, nurses, and clinical pharmacists in achieving this goal. These studies have shown that reduced acute care visits are associated with optimal drug therapy per national guidelines, concurrent with patient education, environmental control, and objective monitoring of this inflammatory airway disease. Early intensive patient education was a key feature of these successful programs. Written action plans, including early use of oral corticosteroids at home, and rapport with patients are other key components of programs that have resulted in a decrease in ED visits and hospitalizations.

Isoniazid inhibits the metabolism of several drugs, resulting in clinically significant interactions in some patients. Clinical trials and case reports have documented that isoniazid can cause increased phenytoin and carbamazepine serum concentrations and toxicity. In relatively high doses, isoniazid can also cause increased effect of theophylline and warfarin. Isoniazid inhibits metabolism of selected benzodiazepines and vitamin D. Inhibition of monoamine oxidase and histaminase by isoniazid can cause significant drug-food interactions. Food greatly decreases isoniazid bioavailability. Although probably best recognized as an inhibitor of drug metabolism, isoniazid has a biphasic effect of inhibition-induction on one cytochrome P450 isozyme, CYP2E1, which partially explains the interaction with acetaminophen and increased risk of hepatotoxicity. Continued investigations will likely result in discovery of new isoniazid interactions.

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Despite evidence of reduced ED visits and hospitalizations and the recommendations of national and international guidelines, the home use of OCS in managing asthma exacerbations remains unacceptably low. New strategies are needed to ensure home use of OCS as part of written action plans to prevent ED visits and hospitalizations for asthma exacerbations.