Pyrazinamide

INTRODUCTION

Indications

Used in combination with other agents in the treatment of active tuberculosis.

Action

Mechanism not known. Therapeutic Effects: Bacteriostatic action against susceptible mycobacteria. Spectrum: Active against mycobacteria only.

Adverse Reactions/Side Effects

GI: HEPATOTOXICITY, anorexia, diarrhea, nausea, vomiting. GU: dysuria. Derm: acne, itching, photosensitivity, skin rash. Hemat: anemia, thrombocytopenia. Metab: hyperuricemia. MS: arthralgia, gouty arthritis.

PHYSICAL THERAPY IMPLICATIONS

Examination and Evaluation

• Be alert for signs of hepatotoxicity, including anorexia, abdominal pain, severe nausea and vomiting, yellow skin or eyes, fever, sore throat, malaise, weakness, facial edema, lethargy, and unusual bleeding or bruising. Report these signs immediately to the physician.

• Assess any joint pain or arthritic symptoms to rule out musculoskeletal pathology; that is, try to determine if pain is drug induced rather than caused by anatomic or biomechanical problems.

• Monitor signs of blood dyscrasias such as thrombocytopenia (bruising, nose bleeds, and bleeding gums), or unusual weakness and fatigue that might be due to anemia. Report these signs to the physician.

Interventions

• Always wash hands thoroughly and disinfect equipment (whirlpools, electrotherapeutic devices, treatment tables, and so forth) to help prevent the spread of infection. Use universal precautions or isolation procedures as indicated for specific patients.

• Causes photosensitivity; use care if administering UV treatments.

Patient/Client-Related Instruction

• Advise patient about photosensitivity and to use sunscreens, protective clothing, and avoid prolonged sun exposure. Advise patient to also report any rashes or other skin reactions.

• Instruct patient and family/caregivers to report other troublesome side effects such as severe or prolonged skin problems (rash, acne, itching), GI problems (diarrhea, nausea, vomiting, loss of appetite), or difficult/painful urination.

Pharmacokinetics

Absorption: Well absorbed after oral administration.

Distribution: Widely distributed. Reaches high concentrations in the CNS (same as plasma). Excreted in breast milk.

Metabolism and Excretion: Mostly metabolized by the liver. Metabolite (pyrazinoic acid) has antimy-cobacterial activity; 3–4% excreted unchanged by the kidneys.

Half-life: Pyrazinamide—9.5 hr. Pyrazinoic acid—12 hr. Both are prolonged in renal impairment.

Contraindications/Precautions

Contraindicated in: Hypersensitivity; Cross-sensitivity with ethionamide, isoniazid, niacin, or nicotinic acid may exist; Severe liver impairment; Concurrent use with rifampin.

Use Cautiously in: Gout; Diabetes mellitus; Acute intermittent porphyria; Pregnancy (safety not established).

Interactions