Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
SODIUM AMINOSALICYLATE vs P.A.S. SODIUM
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Sodium aminosalicylate inhibits folic acid synthesis in Mycobacterium tuberculosis by competing with para-aminobenzoic acid (PABA) for the enzyme dihydropteroate synthase, thereby blocking bacterial growth.
P. A. S. (p-aminosalicylic acid) sodium is a bacteriostatic agent that competitively inhibits the synthesis of folic acid in Mycobacterium tuberculosis by antagonizing the incorporation of p-aminobenzoic acid (PABA) into dihydrofolate. It is selective for mycobacterial folate synthase.
Tuberculosis (second-line therapy, in combination with other antituberculous agents)
Treatment of tuberculosis (TB) in combination with other antituberculosis agents, particularly in multidrug-resistant TB (FDA-approved).,Off-label: Used as a second-line agent in atypical mycobacterial infections and in Crohn's disease (though not FDA-approved for these indications).
4 g orally three times daily (total daily dose 12 g) for tuberculosis treatment. Also available as 10 g in 250 m L for intravenous infusion over 5-6 hours, typically once daily.
Oral: 4 g three times daily (total daily dose 12 g); IV: 12 g daily in 2-4 divided doses.
0.75-1.5 hours (parent drug); prolongs to 4-6 hours in renal impairment or with probenecid coadministration. Rapid acetylation phenotype reduces half-life by ~30%.
1 hour (normal renal function); prolonged to 5-7 hours in anuria or severe renal impairment; clinical context: requires frequent dosing or renal dose adjustment
Hepatic acetylation (N-acetyltransferase) and renal excretion of metabolites.
Primarily metabolized by hepatic acetylation via N-acetyltransferase (NAT); minor pathways include glycine conjugation and renal excretion of unchanged drug.
Renal: >80% as metabolites (acetylated and free), with 50-60% as N-acetyl-4-aminosalicylic acid; biliary/fecal: <1%.
Renal (80% as active drug and metabolites, primarily acetylated form); fecal (minor; <10%)
50-60% bound to albumin; binding is saturable at high concentrations.
50-60% (primarily to albumin)
0.2-0.3 L/kg (distributes into total body water; low tissue penetration except inflamed pleural fluid and caseous granulomas).
0.5-0.6 L/kg (indicates distribution into total body water, with some tissue binding)
Oral: 90-100% (rapidly absorbed from GI tract); no parenteral formulation available.
Oral: approximately 90% (well absorbed from GI tract)
For GFR <30 m L/min: reduce dose to 4 g orally twice daily (total 8 g/day). For GFR <10 m L/min: administer 4 g orally once daily. No adjustment for GFR ≥30 m L/min.
Cr Cl <50 m L/min: reduce dose by 50%; Cr Cl <10 m L/min: avoid use or reduce to 25% of normal dose.
Child-Pugh Class A: no adjustment. Child-Pugh Class B: consider 50% dose reduction. Child-Pugh Class C: use with caution; consider further reduction or alternative therapy as pharmacokinetics are not well studied.
Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid use.
Children: 150-300 mg/kg/day orally divided into 3-4 doses, not to exceed 12 g/day. Intravenous: 150-200 mg/kg/day as a continuous infusion or in divided doses.
Oral: 200-300 mg/kg/day in 3-4 divided doses, maximum 12 g/day.
Start at lower end of dosing range (e.g., 4 g orally twice daily) due to age-related decline in renal function. Monitor renal function and adjust per GFR-based guidelines. Caution with hepatic impairment.
Start at lower end of dosing range; monitor renal function and adjust based on Cr Cl; typical initial dose 4 g twice daily.
None.
None explicitly stated in current FDA labeling; however, caution is advised in hepatic impairment due to risk of hepatitis.
May cause hepatotoxicity, hypersensitivity reactions (fever, rash, eosinophilia), gastrointestinal intolerance, and crystalluria. Monitor liver function tests and renal function periodically.
May cause severe hypersensitivity reactions (e.g., fever, rash, lymphadenopathy).,Hepatic toxicity: risk of hepatitis, especially with prolonged use; monitor liver function.,Renal impairment: dose adjustment required in severe renal disease.,Gastrointestinal intolerance: nausea, vomiting, diarrhea common.,Development of resistance if used as monotherapy.,May induce hemolytic anemia in G6PD deficiency.
Hypersensitivity to aminosalicylic acid or any component; severe renal impairment (Cr Cl < 10 m L/min).
Hypersensitivity to p-aminosalicylic acid or any component.,Severe hepatic impairment.,Severe renal failure (unless dose-adjusted).,Contraindicated in patients with active peptic ulcer disease.
Take with or after meals to minimize gastrointestinal irritation. Avoid alcohol due to increased risk of hepatotoxicity and GI upset. No specific food interactions; but a low-fat diet may help reduce GI side effects.
Take with food, especially acidic foods (e.g., applesauce, yogurt) to improve taste and reduce gastrointestinal irritation. Avoid alkaline foods (e.g., milk, antacids) as they may decrease absorption. Avoid alcohol due to increased risk of hepatotoxicity.
FDA Pregnancy Category C. First trimester: Limited data; animal studies show some teratogenicity at high doses; no adequate human studies; use only if clearly needed. Second and third trimesters: No specific known fetal risks; however, theoretical risk of kernicterus due to bilirubin displacement from albumin binding, though not confirmed with aminosalicylic acid.
First trimester: No evidence of teratogenicity in human studies; limited animal data show no adverse effects. Second trimester: No specific risks identified. Third trimester: No known adverse fetal effects; use only if clearly needed.
Excretion into breast milk is unknown; due to potential for serious adverse reactions in nursing infants (e.g., hypersensitivity, gastrointestinal disturbance), decision should be made to discontinue nursing or the drug, taking into account importance of drug to mother.
Excreted into breast milk in low amounts; M/P ratio not determined. Considered compatible with breastfeeding; monitor infant for diarrhea or rash.
No established dose adjustment guidelines for pregnancy; pharmacokinetic changes (increased volume of distribution, increased renal clearance) may theoretically reduce serum concentrations; therapeutic drug monitoring is not routinely recommended but may be considered if efficacy is in question.
No pharmacokinetic changes requiring dose adjustment in pregnancy; use standard dosing but monitor for hepatotoxicity, which may be increased.
Sodium aminosalicylate (PAS) is a bacteriostatic agent used in combination therapy for multidrug-resistant tuberculosis. Administer with or after meals to reduce gastrointestinal upset. Monitor liver function tests and renal function periodically. Watch for hypersensitivity reactions, including fever, rash, and eosinophilia. Use with caution in patients with glucose-6-phosphate dehydrogenase deficiency due to risk of hemolytic anemia.
Sodium aminosalicylate (PAS sodium) is a second-line antituberculosis agent used in multidrug-resistant TB (MDR-TB). It is bacteriostatic against Mycobacterium tuberculosis by inhibiting folate synthesis. Must be administered with other antitubercular drugs to prevent resistance. Monitor for hepatotoxicity, hypersensitivity reactions (fever, rash, eosinophilia), and gastrointestinal intolerance. Can cause hypothyroidism; monitor thyroid function. Drug interactions: may increase phenytoin levels; avoid concurrent probenecid (increases PAS levels). PAS granules should be sprinkled on soft acidic food to reduce GI upset.
Take this medication with or after food to reduce stomach upset.,Do not skip doses or stop taking this medication without consulting your doctor.,Report any signs of allergic reaction such as rash, fever, or swelling.,Avoid alcohol while taking this medication.,Keep all appointments for blood tests to monitor liver and kidney function.,Contact your doctor if you experience nausea, vomiting, abdominal pain, or yellowing of skin or eyes.
Take this medication exactly as prescribed, usually twice daily with food to reduce stomach upset.,Do not skip doses; complete the full course to prevent drug resistance.,Report any signs of liver problems: yellowing of skin/eyes, dark urine, severe abdominal pain.,Notify your doctor if you develop fever, rash, or unusual tiredness.,You may need regular blood tests to monitor thyroid and liver function.,Avoid alcohol while taking this medication.,Keep all appointments for TB treatment monitoring.
No interactions on record
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about SODIUM AMINOSALICYLATE vs P.A.S. SODIUM, answered by our medical review team.
SODIUM AMINOSALICYLATE is a Antitubercular Agent that works by Sodium aminosalicylate inhibits folic acid synthesis in Mycobacterium tuberculosis by competing with para-aminobenzoic acid (PABA) for the enzyme dihydropteroate synthase, thereby blocking bacterial growth.. P.A.S. SODIUM is a Antitubercular Agent that works by P. A. S. (p-aminosalicylic acid) sodium is a bacteriostatic agent that competitively inhibits the synthesis of folic acid in Mycobacterium tuberculosis by antagonizing the incorporation of p-aminobenzoic acid (PABA) into dihydrofolate. It is selective for mycobacterial folate synthase.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between SODIUM AMINOSALICYLATE and P.A.S. SODIUM depend on the specific clinical indication. These are both Antitubercular Agent agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of SODIUM AMINOSALICYLATE is: 4 g orally three times daily (total daily dose 12 g) for tuberculosis treatment. Also available as 10 g in 250 m L for intravenous infusion over 5-6 hours, typically once daily.. The standard adult dose of P.A.S. SODIUM is: Oral: 4 g three times daily (total daily dose 12 g); IV: 12 g daily in 2-4 divided doses.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between SODIUM AMINOSALICYLATE and P.A.S. SODIUM in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. SODIUM AMINOSALICYLATE is classified as Category C. FDA Pregnancy Category C. First trimester: Limited data; animal studies show some teratogenicity at high doses; no adequate human studies; use only if clearly needed. Second and th. P.A.S. SODIUM is classified as Category C. First trimester: No evidence of teratogenicity in human studies; limited animal data show no adverse effects. Second trimester: No specific risks identified. Third trimester: No kn. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.