Prescribing Guides
Pyrazinamide Prescribing Guide for Indian Clinical Practice
Pyrazinamide prescribing guide for Indian clinicians covering its sterilising activity, hyperuricaemia, hepatotoxicity monitoring and NEET PG pharmacology.
MedNext Editorial Team | 2026-08-01 | 8 min read
Pyrazinamide Prescribing Guide for Indian Clinical Practice
Pyrazinamide prescribing guide for Indian clinicians covering its sterilising activity, hyperuricaemia, hepatotoxicity monitoring and NEET PG pharmacology.
Pyrazinamide is a unique sterilising drug in the TB treatment arsenal, essential for shortening treatment from 9 to 6 months. Its activity in acidic intracellular environments complements the action of rifampicin and isoniazid.
Clinical Pharmacology Overview
Pyrazinamide is a prodrug that is converted to pyrazinoic acid (POA) by the mycobacterial enzyme pyrazinamidase (encoded by the pncA gene). Pyrazinoic acid disrupts mycobacterial membrane energy metabolism, specifically targeting the membrane-bound fatty acid synthase I (FAS-I) and disrupting transmembrane proton motive force. The drug is uniquely effective against semi-dormant bacilli in acidic environments within macrophage phagolysosomes.
Pharmacokinetics: Well absorbed orally (bioavailability nearly 100%). Low protein binding (10-20%). Excellent distribution to all tissues including CSF (CSF levels equal to plasma). Metabolised in the liver to pyrazinoic acid (active) and then to 5-hydroxypyrazinoic acid. Half-life is 9-10 hours. Renally excreted (70%).
Indian Brand Names
- Pyrazinamide IP (generic, NTEP supply)
- P-Zide (Lupin)
- Pyzina (Macleods)
- Available predominantly as part of FDC formulations under NTEP
Approved Indications in Indian Clinical Practice
- Drug-sensitive tuberculosis (intensive phase only -- first 2 months)
- Some MDR-TB regimens (if susceptible)
- TB meningitis (excellent CSF penetration -- used in intensive phase)
Dosing in Adults
NTEP daily regimen: weight-based dosing as part of FDC.
30-39 kg: 750 mg daily 40-54 kg: 1000 mg daily 55-69 kg: 1500 mg daily 70 kg and above: 2000 mg daily
Alternatively: 25-35 mg/kg/day (maximum 2000 mg).
Duration: first 2 months only (intensive phase). NOT continued in the continuation phase.
Can be taken with or without food (absorption not significantly affected).
Important Drug Interactions
- Allopurinol: both affect uric acid handling -- combination does not reliably prevent PZA-induced hyperuricaemia
- Probenecid: antagonised by pyrazinamide's uric acid retention effect
- Rifampicin and isoniazid: additive hepatotoxicity -- the triple combination has the highest liver risk
- Cyclosporine: pyrazinamide may reduce cyclosporine levels
Side Effects and Monitoring
Common: hyperuricaemia (very common, usually asymptomatic), arthralgia, nausea, anorexia.
Serious: hepatotoxicity (most hepatotoxic of first-line anti-TB drugs -- dose-related), clinical gout (treat symptomatically without stopping PZA unless severe), photosensitive dermatitis, sideroblastic anaemia.
Hyperuricaemia management: asymptomatic elevation of uric acid does NOT require treatment or drug discontinuation. Symptomatic gout: manage with colchicine or NSAIDs. Do not start allopurinol during the 2-month PZA course.
Monitoring: LFTs at baseline and monthly (or earlier if symptomatic). Serum uric acid at baseline. Stop PZA if ALT exceeds 5x ULN (asymptomatic) or 3x ULN with symptoms. In hepatic reactions requiring rechallenge, PZA is often the first drug NOT reintroduced.
Special Populations
Pregnancy: Category C. Included in the NTEP standard regimen for TB in pregnancy. WHO recommends standard HRZE in pregnancy (benefit outweighs risk). Some international guidelines previously excluded PZA in pregnancy, extending treatment to 9 months.
Renal impairment: Dose reduction recommended in severe renal impairment (GFR < 30 mL/min). 25 mg/kg thrice weekly in dialysis patients (give after dialysis).
Hepatic impairment: Use with extreme caution. Omit pyrazinamide in patients with severe pre-existing liver disease (use extended 9-month regimen without PZA).
Gout: Pre-existing gout is a relative contraindication. If PZA is essential, manage gout symptoms prophylactically.
NEET PG High-Yield Points
- Prodrug activated by pyrazinamidase (pncA gene) to pyrazinoic acid
- Active ONLY in acidic pH (pH 5.0-5.5) -- targets intracellular bacilli in macrophages
- Sterilising drug that enables 6-month short-course TB therapy
- Most hepatotoxic first-line anti-TB drug
- Causes hyperuricaemia by inhibiting renal uric acid excretion (URAT1 inhibition by POA)
- pncA mutation = most common mechanism of PZA resistance
- Used ONLY in the intensive phase (first 2 months)
- Excellent CSF penetration -- used in TB meningitis
- Not reintroduced first in hepatic drug reaction rechallenge
Indian Regulatory Status
Pyrazinamide is a Schedule H drug under the Drugs and Cosmetics Act. It is included in the NLEM of India. Under the NTEP, it is supplied as part of the 4-drug FDC (HRZE) and is not typically dispensed as a single-drug formulation to the public, to prevent monotherapy. Weight-banded FDC kits are the standard of care in India's TB programme.
Frequently Asked Questions
Why is pyrazinamide only used in the intensive phase?
Pyrazinamide is most effective in the first 2 months of TB treatment because it targets semi-dormant bacilli in acidic intracellular environments (within macrophages). After the intensive phase, the bacillary load is reduced and the remaining organisms are in different metabolic states where pyrazinamide adds less benefit. Its hepatotoxicity risk also favours shorter duration.
Why does pyrazinamide cause hyperuricaemia?
Pyrazinoic acid (the active metabolite) inhibits uric acid excretion in the renal tubule by blocking the URAT1 transporter. This causes asymptomatic hyperuricaemia in most patients and clinical gout in some. Asymptomatic hyperuricaemia alone is not a reason to stop pyrazinamide.
Is pyrazinamide the most hepatotoxic first-line anti-TB drug?
Yes. Pyrazinamide has the highest rate of hepatotoxicity among first-line anti-TB drugs when used at standard doses. Hepatotoxicity is dose-related and is a major reason for the drug's restriction to the 2-month intensive phase. In hepatic TB drug reactions, pyrazinamide is often the first drug not reintroduced.
Does pyrazinamide work at neutral pH?
No. Pyrazinamide requires an acidic environment (pH 5.0-5.5) for activation and activity. It is most effective against intracellular bacilli within acidified macrophage phagolysosomes. At neutral pH (as in cavitary lesions), it has minimal activity. This pH-dependent mechanism is a high-yield exam concept.
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