Rifampin
Rifampin (Rifadin)
Rifampin
(rih- FAM-pin)
Pregnancy Category: C Rifadin Rimactane Rofact (Rx)

Classification: Primary antitubercular agent

Action/Kinetics: Semisynthetic antibiotic derived from Streptomyces mediterranei. Suppresses RNA synthesis by binding to the beta subunit of DNA-dependent RNA polymerase. This prevents attachment of the enzyme to DNA and blockade of RNA transcription. Both bacteriostatic and bactericidal; most active against rapidly replicating organisms. Well absorbed from the GI tract; widely distributed in body tissues. Peak plasma concentration: 4-32 mcg/mL after 2-4 hr. t 1/2: 1.5-5 hr (higher in clients with hepatic impairment). In normal clients t 1/2 decreases with usage. Metabolized in liver; 60% is excreted in feces.

Uses: All types of tuberculosis. Must be used in conjunction with at least one other tuberculostatic drug (such as isoniazid, ethambutol, pyrazinamide) but is the drug of choice for retreatment. Also for treatment of asymptomatic meningococcal carriers to eliminate Neisseria meningitidis. Investigational: Used in combination for infections due to Staphylococcus aureus and S. epidermidis (endocarditis, osteomyelitis, prostatitis); Legionnaire's disease; in combination with dapsone for leprosy; prophylaxis of meningitis due to Haemophilus influenzae and gram-negative bacteremia in infants.

Contraindications: Hypersensitivity; not recommended for intermittent therapy.

Special Concerns: Safe use during lactation has not been established. Safety and effectiveness not determined in children less than 5 years of age. Use with extreme caution in clients with hepatic dysfunction.

Side Effects: GI: N&V, diarrhea, anorexia, gas, pseudomembranous colitis, pancreatitis, sore mouth and tongue, cramps, heartburn, flatulence. CNS: Headache, drowsiness, fatigue, ataxia, dizziness, confusion, generalized numbness, fever, difficulty in concentrating. Hepatic: Jaundice, hepatitis. Increases in AST, ALT, bilirubin, alkaline phosphatase. Hematologic: Thrombocytopenia, eosinophilia, hemolysis, leukopenia, hemolytic anemia. Allergic: Flu-like symptoms, dyspnea, wheezing, SOB, purpura, pruritus, urticaria, skin rashes, sore mouth and tongue, conjunctivitis. Renal: Hematuria, hemoglobinuria, renal insufficiency, acute renal failure. Miscellaneous: Visual disturbances, muscle weakness or pain, arthralgia, decreased BP, osteomalacia, menstrual disturbances, edema of face and extremities, adrenocortical insufficiency, increases in BUN and serum uric acid. NOTE: Body fluids and feces may be red-orange.

Laboratory Test Alterations: AST, ALT, alkaline phosphatase, BUN, bilirubin, uric acid, BSP retention values. False + Coombs' test.

Overdose Management: Symptoms: Shortly after ingestion, N&V, and lethargy will occur. Followed by severe hepatic involvement (liver enlargement with tenderness, increased direct and total bilirubin, change in hepatic enzymes) with unconsciousness. Also, brownish red or orange discoloration of urine, saliva, tears, sweat, skin, and feces. Treatment: Gastric lavage followed by activated charcoal slurry introduced into the stomach. Antiemetics to control N&V. Forced diuresis to enhance excretion. If hepatic function is seriously impaired, bile drainage may be required. Extracorporeal hemodialysis may be necessary.

Drug Interactions: Acetaminophen / Acetaminophen effects R/T liver breakdown Aminophylline / Aminophylline effects R/T liver breakdown Amiodarone / Amiodarone serum levels R/T liver breakdown Anticoagulants, oral / Anticoagulant effects R/T liver breakdown Antidiabetics, oral / Antidiabetic effects R/T liver breakdown Barbiturates / Barbiturate effects R/T liver breakdown Benzodiazepines / Benzodiazepine effects R/T liver breakdown Beta-adrenergic blocking agents / Beta-blocking effects R/T liver breakdown Chloramphenicol / Chloramphenicol effects R/T liver breakdown Clofibrate / Clofibrate effects R/T liver breakdown Contraceptives, oral / OC effects R/T liver breakdown Corticosteroids / Corticosteroid effects R/T liver breakdown Cyclosporine / Cyclosporine effects R/T liver breakdown Digitoxin / Digitoxin effects R/T liver breakdown Digoxin / Digoxin serum levels Disopyramide / Disopyramide effects R/T liver breakdown Estrogens / Estrogen effects R/T liver breakdown Halothane / Risk of hepatotoxicity and hepatic encephalopathy Hydantoins / Hydantoin effects R/T liver breakdown Isoniazid / Risk of hepatotoxicity Ketoconazole / Effect of either ketoconazole or rifampin Methadone / Methadone effects R/T liver breakdown Mexiletine / Mexiletine effects R/T liver breakdown Morphine / Morphine analgesia Ondansetron / Ondansetron plasma levels R/T liver breakdown Quinidine / Quinidine effects R/T liver breakdown Sulfones / Sulfone effects R/T liver breakdown Theophylline / Theophylline effects R/T liver breakdown Tocainide / Tocainide effects R/T liver breakdown Verapamil / Verapamil effects R/T liver breakdown

How Supplied: Capsule: 150 mg, 300 mg; Powder for injection: 600 mg

Dosage
?Capsules, IV Pulmonary tuberculosis.
Adults: Single dose of 600 mg/day; children over 5 years: 10-20 mg/kg/day, not to exceed 600 mg/day.
Meningococcal carriers.
Adults: 600 mg b.i.d. for 2 days; children: 10-20 mg/kg q 12 hr for four doses, not to exceed 600 mg/day.