Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
P.A.S. SODIUM vs PASER
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
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.
Inhibits cell wall synthesis in Mycobacterium tuberculosis by blocking mycolic acid synthesis. Also acts as a competitive inhibitor of folate synthesis.
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).
Treatment of tuberculosis in combination with other antituberculosis drugs,Off-label: None
Oral: 4 g three times daily (total daily dose 12 g); IV: 12 g daily in 2-4 divided doses.
4 g (8 capsules of 500 mg) orally every 8 hours, taken with food or an acidic beverage (e.g., orange juice) to enhance absorption.
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
Terminal elimination half-life is 1.5 to 2.5 hours in patients with normal renal function. In anuria or severe renal impairment (Cr Cl <10 m L/min), half-life may extend to 8-12 hours. Clinical context: Accumulation occurs with renal failure, requiring dose adjustment.
Primarily metabolized by hepatic acetylation via N-acetyltransferase (NAT); minor pathways include glycine conjugation and renal excretion of unchanged drug.
Hepatic via N-acetyltransferase (polymorphic acetylation); major metabolite is acetyl-PAS.
Renal (80% as active drug and metabolites, primarily acetylated form); fecal (minor; <10%)
Renal excretion accounts for approximately 80% of the administered dose, with about 60-70% as unchanged drug and 10-20% as metabolites (primarily acetylated). The remainder is excreted via feces (approximately 10-15%) and minor biliary elimination. Renal clearance is highly dependent on glomerular filtration rate.
50-60% (primarily to albumin)
Protein binding is approximately 10-15%, primarily to albumin. Binding is low, nonlinear, and saturable at high concentrations.
0.5-0.6 L/kg (indicates distribution into total body water, with some tissue binding)
Volume of distribution is 0.5-0.7 L/kg, indicating distribution into total body water. Clinical meaning: Moderate distribution suggests penetration into well-perfused tissues but limited CNS penetration unless inflamed.
Oral: approximately 90% (well absorbed from GI tract)
Oral bioavailability is approximately 70-80% (range 60-90%). Food decreases the rate and extent of absorption, with AUC reduction of about 20-40%.
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.
Contraindicated in severe renal impairment (Cr Cl <30 m L/min). For Cr Cl 30-50 m L/min: reduce dose to 4 g orally every 12 hours; monitor serum concentrations. Use with caution in moderate impairment.
Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid use.
No specific dose adjustment guidelines for Child-Pugh classification. Use with caution in severe hepatic impairment due to potential hepatotoxicity; monitor liver function tests.
Oral: 200-300 mg/kg/day in 3-4 divided doses, maximum 12 g/day.
Not recommended for children (safety and efficacy not established).
Start at lower end of dosing range; monitor renal function and adjust based on Cr Cl; typical initial dose 4 g twice daily.
Lower initial doses may be considered due to age-related decline in renal function. Monitor renal function and serum concentrations closely.
None explicitly stated in current FDA labeling; however, caution is advised in hepatic impairment due to risk of hepatitis.
None
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.
May cause hypothyroidism, hepatitis, and crystalluria. Use with caution in patients with renal impairment or glucose-6-phosphate dehydrogenase deficiency.
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.
Hypersensitivity to para-aminosalicylic acid or any component; severe renal impairment.
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.
Take with food to reduce gastrointestinal irritation. Avoid high-fat meals as they may delay absorption. Avoid alcohol.
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.
PASER (aminosalicylic acid) is classified FDA pregnancy category C. First trimester: Limited human data; animal studies show no teratogenicity but some fetal toxicity at high doses. Second and third trimesters: No known major malformations; risks may include gastrointestinal intolerance in mother. Advised use only if clearly needed.
Excreted into breast milk in low amounts; M/P ratio not determined. Considered compatible with breastfeeding; monitor infant for diarrhea or rash.
Excreted into breast milk in small amounts. M/P ratio unknown. Considered compatible with breastfeeding by American Academy of Pediatrics; monitor infant for diarrhea or rash.
No pharmacokinetic changes requiring dose adjustment in pregnancy; use standard dosing but monitor for hepatotoxicity, which may be increased.
No dosing adjustment required for pregnancy. Pharmacokinetic changes in pregnancy (increased clearance) not significant for PASER; standard adult dose of 4 g twice daily is recommended.
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.
PASER (aminosalicylic acid) is a second-line antitubercular agent that inhibits folic acid synthesis. Administer with food to reduce GI upset; avoid concurrent use with salicylates due to additive GI irritation. Monitor for hepatotoxicity and hypersensitivity reactions. Drug levels should be monitored in patients with renal impairment.
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.
Take this medication with food to minimize stomach upset.,Do not crush or chew the tablets; swallow them whole.,Complete the full course of therapy even if you feel better.,Report any signs of liver problems (yellowing of skin/eyes, dark urine) or allergic reactions (rash, fever) immediately.,Avoid alcohol during treatment.,Store at room temperature away from moisture and heat.
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 P.A.S. SODIUM vs PASER, answered by our medical review team.
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.. PASER is a Antitubercular Agent that works by Inhibits cell wall synthesis in Mycobacterium tuberculosis by blocking mycolic acid synthesis. Also acts as a competitive inhibitor of folate synthesis.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between P.A.S. SODIUM and PASER 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 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.. The standard adult dose of PASER is: 4 g (8 capsules of 500 mg) orally every 8 hours, taken with food or an acidic beverage (e.g., orange juice) to enhance absorption.. 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 P.A.S. SODIUM and PASER 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. 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. PASER is classified as Category C. PASER (aminosalicylic acid) is classified FDA pregnancy category C. First trimester: Limited human data; animal studies show no teratogenicity but some fetal toxicity at high doses. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.