Action

Inhibits RNA synthesis by blocking RNA transcription in susceptible organisms (mycobacteria and some gram-positive and gram-negative bacteria)

Availability

Capsules: 150 mg

Indications and dosages

➣ To prevent disseminated Mycobacterium avium intracellulare complex in patients with advanced human immunodeficiency virus (HIV) infection

Adults: 300 mg P.O. daily as a single dose or in two divided doses

Off-label uses

• Tuberculosis

• Prophylaxis and treatment of M. avium intracellulare in children

Contraindications

• Hypersensitivity to drug

• Active tuberculosis

Precautions

Use cautiously in:

• severe hepatic disease

• pregnant or breastfeeding patients.

Administration

• Give in divided doses twice daily with food to reduce GI upset.

Adverse reactions

CNS: headache, asthenia, weakness

CV: pressure sensation in chest

EENT: uveitis; discolored tears, saliva, or sputum

GI: nausea, vomiting, diarrhea, dyspepsia, abdominal pain, eructation, flatulence, discolored feces, anorexia

GU: discolored urine

Hematologic: eosinophilia, neutropenia, leukopenia, thrombocytopenia Musculoskeletal: joint pain, myalgia

Respiratory: dyspnea

Skin: rash, discolored skin or sweat

Other: abnormal taste, fever, flulike symptoms

Interactions

Drug-drug. Clarithromycin, itraconazole, saquinavir: reduced blood levels and efficacy of these drugs

Delavirdine: decreased delavirdine blood level, increased rifabutin blood level

Drugs metabolized by liver (such as zidovudine): altered blood levels of these drugs

Hormonal contraceptives: decreased contraceptive efficacy

Indinavir, nelfinavir, ritonavir: increased rifabutin blood level

Drug-diagnostic tests. Alanine aminotransferase, aspartate aminotransferase, eosinophils: increased levels

Neutrophils, platelets, white blood cells: decreased counts

Drug-food. High-fat foods: delayed drug absorption

Patient monitoring

• Monitor CBC with white cell differential. Watch for signs and symptoms of blood dyscrasias.

• Assess nutritional status.

• Closely monitor vital signs and temperature. Stay alert for dyspnea and flulike symptoms.

Patient teaching

• Advise patient to take twice daily with food (but not high-fat food) if GI upset occurs. To further minimize GI upset, teach him to eat small, frequent servings of healthy food and drink plenty of fluids.

• Instruct patient to take exactly as prescribed, even after symptoms subside.

See Tell patient to immediately report easy bruising or bleeding.

• Tell patient drug may turn tears, urine, and other body fluids reddish or brownish orange. Instruct him not to wear contact lenses during therapy because drug may stain them permanently.

• Inform patient that drug occasionally causes eye inflammation. Instruct him to report symptoms promptly.

• Caution patient to avoid driving and other hazardous activities until effects of drug are known.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, and foods mentioned above.