Pyrazinamide

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PYRAZINAMIDE

Chemical formula of PYRAZINAMIDE. Copyright ITM

1.       TYPE OF DRUG – PYRAZINAMIDE
Antitubercular Agent

 

2.       INDICATIONS (USE) – PYRAZINAMIDE
For the initial treatment of active tuberculosis in adults and children when combined with other antituberculous agents.

 

3.       MECHANISM OF ACTION (MOA) – PYRAZINAMIDE
Pyrazinamide diffuses into M. tuberculosis, where the enzyme pyrazinamidase converts pyrazinamide to the active form pyrazinoic acid. Under acidic conditions, the pyrazinoic acid that slowly leaks out converts to the protonated conjugate acid, which is thought to diffuse easily back into the bacilli and accumulate. The net effect is that more pyrazinoic acid accumulates inside the bacillus at acid pH than at neutral pH. Pyrazinoic acid was thought to inhibit the enzyme fatty acid synthase (FAS) I, which is required by the bacterium to synthesise fatty acids.

 

4.       ROUTES OF ADMINISTRATION – PYRAZINAMIDE
Tablet.

 

5.       ONSET OF EFFECT OR ACTION – PYRAZINAMIDE
Within 30-60 mins.

 

6.      DOSAGE (DOSING INFORMATION) – PYRAZINAMIDE
Oral

Tuberculosis

Adult: As part of a mulitdrug regimen, 20-25 mg/kg (max: 2 g) daily or 1.5-3 g 3 times weekly.

Child: As part of a mulitdrug regimen, 35 mg/kg daily or 50 mg/kg 3 times weekly or 75 mg/kg twice weekly. Max dose: 3 g daily.

Renal impairment: May need dose reduction.

 

7.       HALF LIFE (DURATION OF ACTION) – PYRAZINAMIDE
9-10 hours (normal conditions)

 

8.       ADVERSE EFFECTS OR SIDE EFFECTS – PYRAZINAMIDE
9.       CONTRAINDICATIONS – PYRAZINAMIDE
Hypersensitivity; existing liver disease; acute gout or hyperuricaemia. Porphyria. Pregnancy and lactation.

 

10.   DRUG INTERACTIONS – PYRAZINAMIDE
Excretion may be blocked by probenecid

 

11.   EXCRETION – PYRAZINAMIDE
Approximately 70% of an oral dose is excreted in the urine, mainly by glomerular filtration within 24 hours

 

Pyrazinamide 2

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