para-aminosalicylic acid: prescribing and clinical use
Focused clinical detail for use alongside current product information, local policy and patient-specific assessment.
para-aminosalicylic acid: clinical details
Prescribing considerations
- Reserve for an appropriate multidrug-resistant tuberculosis combination when resistance or tolerability prevents construction of another effective regimen.
- Assess renal and hepatic function, peptic-ulcer history, HIV status, concurrent treatments and potential vitamin B12 deficiency.
- Monitor closely for hypersensitivity and hepatotoxicity, especially early in treatment.
- Paediatric use is licensed from 28 days of age, but the optimal paediatric regimen is uncertain.
Contraindications and cautions
- Hypersensitivity to para-aminosalicylic acid or a formulation excipient
- Severe renal disease because the inactive acetyl metabolite accumulates
Monitoring
- Clinical signs of rash, fever, intolerance and hepatitis
- Renal and hepatic function according to clinical risk
- Thyroid function in people living with HIV, particularly with ethionamide or prothionamide
- Serum digoxin when co-administered
- Vitamin B12 status or supplementation requirements during extended treatment
Clinical pharmacology
A bacteriostatic antimycobacterial agent active against Mycobacterium tuberculosis. It interferes with bacterial folate metabolism, is acetylated in the liver and is eliminated mainly through the kidneys as unchanged compound and metabolites.
Formulation and product differences
- The selected product contains gastro-resistant granules rather than an immediate-release preparation.
- The acid-resistant coating limits degradation in the stomach and formation of the hepatotoxic breakdown product meta-aminophenol.
- Granules must remain intact and be administered in a supported acidic drink or soft food.
- A calibrated measuring spoon is supplied for prescribed quantities smaller than a complete sachet.
para-aminosalicylic acid interactions
Tell the tuberculosis team about all prescribed, non-prescribed and complementary treatments. Relevant interactions include:
Vitamin B12
Para-aminosalicylic acid can reduce absorption, potentially causing clinically important deficiency during extended treatment.
Digoxin
Absorption may be reduced, so serum digoxin concentrations should be monitored.
Ethionamide
The combination may worsen gastrointestinal and liver-related adverse effects; the regimen requires specialist review if these become significant.
Diphenhydramine
It reduces gastrointestinal absorption of para-aminosalicylic acid and should not be used at the same time.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.