Rifamycins
GENERAL PRINCIPLES
Rifamycins exert bactericidal activity on susceptible mycobacteria by inhibiting DNA-dependent RNA polymerase, thereby halting transcription.
TREATMENT
• Rifampin (rifampicin; 600 mg PO q24h or twice a week) is an integral component of most TB treatment regimens.
It is also active against many gram-positive and gram-negative bacteria. Rifampin is used as adjunctive therapy in staphylococcal prosthetic valve endocarditis (300 mg PO q8h) and prosthetic bone and joint infections (450 mg PO q12h) and for prophylaxis of close contacts of patients with Neisseria meningitidis infection (5 mg/kg PO q12h ? 4 doses). The drug is well absorbed orally and is widely distributed throughout the body including the cerebrospinal fluid (CSF).• Rifabutin (300 mg PO q24h) is primarily used to treat TB and MAC infections in HIV-positive patients on antiretroviral therapy because it has fewer drug-drug interactions and less deleterious effects on protease inhibitor metabolism than rifampin (see Chapter 16, Sexually Transmitted Infections, Human Immunodeficiency Virus, and Acquired Immunodeficiency Syndrome).
• Rifapentine (600-900 mg PO one to two times weekly) is primarily used in combination with isoniazid for 12-week once-weekly treatment of latent TB infection, but can also be used for the treatment of active TB. Doses are adjusted based on body weight and active versus latent infection.
SPECIAL CONSIDERATIONS
Adverse events include rash, GI disturbances, hematologic disturbances, hepatitis, and interstitial nephritis. Patients should also be warned about reddish-orange discoloration of body fluids, including contact lenses. Uveitis has also been associated with rifabutin. This class of antibiotics has major drug interactions based on CYP enzyme inhibition. Concomitant medications should be screened for drug interactions prior to starting therapy with a rifamycin.