Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
POTASSIUM 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
Exact mechanism unknown; may competitively inhibit folic acid synthesis and/or disrupt mycobacterial cell wall metabolism via inhibition of salicylate hydroxylation.
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.
Adjunctive treatment of tuberculosis (as second-line agent),Off-label: treatment of ulcerative colitis (as mesalamine prodrug)
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).
Adults: 4 g (as granules or powder) orally twice daily, equivalent to 8 g/day of aminosalicylic acid base.
Oral: 4 g three times daily (total daily dose 12 g); IV: 12 g daily in 2-4 divided doses.
0.5-1.5 hours for parent drug; acetylated metabolite half-life 2-3 hours; accumulation occurs in renal impairment.
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 to N-acetyl-4-aminosalicylic acid and other metabolites); also undergoes intestinal metabolism by gut bacteria.
Primarily metabolized by hepatic acetylation via N-acetyltransferase (NAT); minor pathways include glycine conjugation and renal excretion of unchanged drug.
Renal: >80% as metabolites (acetyl, glycolyl conjugates) and unchanged drug; fecal: <5%.
Renal (80% as active drug and metabolites, primarily acetylated form); fecal (minor; <10%)
50-60% bound to albumin.
50-60% (primarily to albumin)
0.2-0.4 L/kg; reflects distribution into total body water with limited tissue penetration.
0.5-0.6 L/kg (indicates distribution into total body water, with some tissue binding)
Oral: ~90% absorbed; food may delay absorption.
Oral: approximately 90% (well absorbed from GI tract)
GFR <50 m L/min: not recommended due to risk of accumulation; if unavoidable, reduce dose to 4 g once daily. GFR <30 m L/min: avoid use.
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: reduce dose by 50% (to 2 g twice daily). Child-Pugh Class C: avoid use.
Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid use.
Children: 200-300 mg aminosalicylic acid base per kg body weight per day, divided into 2 doses. Maximum 8 g/day.
Oral: 200-300 mg/kg/day in 3-4 divided doses, maximum 12 g/day.
Start at lower end of dosing (4 g once daily) due to potential decreased renal function and increased risk of gastrointestinal intolerance.
Start at lower end of dosing range; monitor renal function and adjust based on Cr Cl; typical initial dose 4 g twice daily.
No FDA black box warning.
None explicitly stated in current FDA labeling; however, caution is advised in hepatic impairment due to risk of hepatitis.
Hypersensitivity reactions including fever and rash,Hepatotoxicity (discontinue if jaundice or liver enzyme elevation occurs),Renal impairment may require dose adjustment,Gastrointestinal intolerance,May cause hypocalcemia and hypokalemia,Interference with thyroid function tests
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 any salicylate component,Severe hepatic disease,Severe renal impairment (e GFR < 30 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.
Avoid alcohol. Take with food or milk to reduce gastrointestinal irritation. Avoid large amounts of high-potassium foods (e.g., bananas, oranges, potatoes) unless directed by a physician, as this drug may alter potassium levels. No specific food restrictions beyond these.
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.
First trimester: Insufficient data; no known human teratogenicity but animal studies inconclusive. Second/third trimester: No documented fetal harm; use only if clearly needed.
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.
Excreted in breast milk; M/P ratio unknown. Caution due to potential for infant methemoglobinemia or gastrointestinal disturbances.
Excreted into breast milk in low amounts; M/P ratio not determined. Considered compatible with breastfeeding; monitor infant for diarrhea or rash.
No specific dose adjustment recommended; standard doses may be used, but monitor for potassium disturbances due to pregnancy-induced hypervolemia.
No pharmacokinetic changes requiring dose adjustment in pregnancy; use standard dosing but monitor for hepatotoxicity, which may be increased.
Monitor for hepatotoxicity, including elevated liver enzymes and bilirubin, especially in the first 3 months of therapy. Administer with food to reduce GI upset. Concurrent use with rifampin may decrease rifampin levels; separate doses by 8-12 hours. Contraindicated in severe renal impairment (Cr Cl < 30 m L/min) due to risk of hypokalemia and salicylate toxicity. Hypersensitivity reactions including fever, rash, and eosinophilia may occur; discontinue if severe.
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 food or milk to prevent stomach upset.,Do not take antacids containing aluminum or magnesium within 3 hours of this medication.,Avoid alcohol while taking this medication due to increased risk of liver damage.,Report any signs of liver problems (yellowing skin or eyes, dark urine, abdominal pain) to your doctor immediately.,Use effective contraception during treatment as this drug may harm an unborn baby.,Do not stop taking this medication without consulting your doctor, even if you feel better.,Keep all appointments for blood tests to monitor liver function and potassium levels.
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 POTASSIUM AMINOSALICYLATE vs P.A.S. SODIUM, answered by our medical review team.
POTASSIUM AMINOSALICYLATE is a Antitubercular Agent that works by Exact mechanism unknown; may competitively inhibit folic acid synthesis and/or disrupt mycobacterial cell wall metabolism via inhibition of salicylate hydroxylation.. 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 POTASSIUM 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 POTASSIUM AMINOSALICYLATE is: Adults: 4 g (as granules or powder) orally twice daily, equivalent to 8 g/day of aminosalicylic acid base.. 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 POTASSIUM 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. POTASSIUM AMINOSALICYLATE is classified as Category C. First trimester: Insufficient data; no known human teratogenicity but animal studies inconclusive. Second/third trimester: No documented fetal harm; use only if clearly needed.. 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.