Action

Unknown. Thought to exert bacteriostatic activity.

Availability

Tablets: 500 mg

Indications and dosages

➣ Tuberculosis

Adults and children: 15 to 30 mg/kg/day P.O., not to exceed 2 g/day; or 50 to 70 mg/kg P.O. twice weekly, up to a maximum of 4 g/dose; or 50 to 70 mg/kg/dose P.O. three times weekly, up to a maximum of 3 g/dose

Dosage adjustment

• Renal impairment

Contraindications

• Hypersensitivity to drug

• Severe hepatic disease

• Acute gout

Precautions

Use cautiously in:

• renal failure, diabetes mellitus, porphyria, chronic gout, history of gout

• pregnant or breastfeeding patients

• children younger than age 13.

Administration

• Give with other antituberculars, as prescribed, to reduce risk of resistant organisms.

• Be aware that drug therapy may last 6 months or longer.

Adverse reactions

CNS: headache

GI: nausea, vomiting, diarrhea, peptic ulcer, abdominal cramps, anorexia

GU: dysuria, increased uric acid secretion

Hematologic: hemolytic anemia

Hepatic: hepatotoxicity

Metabolic: hyperuricemia, gout

Musculoskeletal: joint pain

Skin: urticaria, photosensitivity

Interactions

Drug-drug. Ethionamide: increased risk of hepatotoxicity

Probenecid: decreased probenecid efficacy (possibly precipitating gout)

Drug-diagnostic tests. Acetest or Ketostix urine test: false interpretation

Liver function tests: abnormal results

Uric acid: increased level

Patient monitoring

• Monitor CBC, uric acid level, and liver and kidney function tests.

• Assess for signs and symptoms of gout, hepatic failure, and hemolytic anemia.

See Discontinue at first sign of hepatic impairment or hyperuricemia accompanied by acute gouty arthritis.

Patient teaching

• Advise patient to take regularly with other antituberculars, as prescribed.

See Teach patient to recognize and immediately report signs and symptoms of gout and liver impairment.

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