Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
SODIUM P.A.S. vs PASER
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Sodium P. A. S. (para-aminosalicylate) inhibits folic acid synthesis in Mycobacterium tuberculosis by competing with para-aminobenzoic acid, thereby suppressing bacterial growth.
Inhibits cell wall synthesis in Mycobacterium tuberculosis by blocking mycolic acid synthesis. Also acts as a competitive inhibitor of folate synthesis.
Treatment of tuberculosis as part of a multi-drug regimen (FDA-approved),Off-label: treatment of inflammatory bowel disease (ulcerative colitis, Crohn's disease) and other mycobacterial infections
Treatment of tuberculosis in combination with other antituberculosis drugs,Off-label: None
4 g orally three times daily (total 12 g/day). For intravenous administration, 4 g (10 m L of 40% solution) diluted in 250 m L of 5% dextrose or normal saline infused over 2-3 hours three times daily.
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.
0.5–1 hour (normal renal function); prolonged to ≥10 hours in renal impairment (requires 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.
Hepatic acetylation via N-acetyltransferase (NAT2); undergoes conjugation with glycine and glucuronic acid.
Hepatic via N-acetyltransferase (polymorphic acetylation); major metabolite is acetyl-PAS.
Primarily renal (80-90% as unchanged drug) via glomerular filtration and tubular secretion; biliary/fecal ≤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% bound to serum albumin.
Protein binding is approximately 10-15%, primarily to albumin. Binding is low, nonlinear, and saturable at high concentrations.
0.2–0.4 L/kg (suggests low tissue penetration, primarily extracellular).
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: ~80–90%. IV: 100%.
Oral bioavailability is approximately 70-80% (range 60-90%). Food decreases the rate and extent of absorption, with AUC reduction of about 20-40%.
GFR 30-50 m L/min: administer every 12 hours. GFR 10-30 m L/min: administer every 24 hours. GFR <10 m L/min: administer every 48 hours or avoid use.
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 Class A: no adjustment. Child-Pugh Class B: reduce dose by 50%. Child-Pugh Class C: avoid use due to risk of hepatotoxicity.
No specific dose adjustment guidelines for Child-Pugh classification. Use with caution in severe hepatic impairment due to potential hepatotoxicity; monitor liver function tests.
Children: 150-300 mg/kg/day orally in 3-4 divided doses, maximum 12 g/day. Intravenous: 150-300 mg/kg/day in divided doses every 6-8 hours.
Not recommended for children (safety and efficacy not established).
Start at lower end of dosing range (e.g., 4 g orally twice daily) and titrate based on renal function. Monitor for electrolyte disturbances and hepatotoxicity.
Lower initial doses may be considered due to age-related decline in renal function. Monitor renal function and serum concentrations closely.
No FDA black box warning.
None
Hepatotoxicity, including hepatic necrosis and jaundice,Hypersensitivity reactions (drug rash, fever, eosinophilia),Gastrointestinal intolerance (nausea, vomiting, diarrhea),Renal impairment may require dose adjustment,Monitor liver function tests, blood counts, and renal function
May cause hypothyroidism, hepatitis, and crystalluria. Use with caution in patients with renal impairment or glucose-6-phosphate dehydrogenase deficiency.
Hypersensitivity to para-aminosalicylate or any component,Severe hepatic impairment,Severe renal impairment (Cr Cl < 30 m L/min)
Hypersensitivity to para-aminosalicylic acid or any component; severe renal impairment.
Take with food to minimize gastrointestinal irritation. Avoid alcohol due to hepatotoxicity risk. No significant food-drug interactions except for potential interference with vitamin B12 absorption; consider monitoring B12 levels with prolonged use.
Take with food to reduce gastrointestinal irritation. Avoid high-fat meals as they may delay absorption. Avoid alcohol.
PAS is not associated with major congenital malformations. First trimester: no significant increase in defect risk. Second/third trimester: may increase risk of maternal hemolysis in G6PD deficiency; no direct fetal toxicity reported. Limited human data.
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.
PAS enters breast milk in low concentrations; M/P ratio unknown. Considered compatible with breastfeeding by American Academy of Pediatrics, but monitor infant for gastrointestinal disturbances or allergic reactions.
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.
Pregnancy may decrease serum concentrations due to increased renal clearance. Monitor therapeutic levels if available; consider increasing dose if subtherapeutic. No standard dose adjustment, but individual titration based on clinical response and serum levels recommended.
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 P. A. S. (para-aminosalicylic acid) is a second-line antitubercular agent used in combination therapy for multidrug-resistant tuberculosis (MDR-TB). Administer with food to reduce gastrointestinal irritation. Monitor liver function tests due to hepatotoxicity risk. May cause hypothyroidism; monitor thyroid function. Avoid in patients with severe renal impairment (Cr Cl <30 m L/min).
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 with food to reduce stomach upset.,Complete full course of therapy as prescribed, even if you feel better.,Report any signs of liver problems: yellowing of skin/eyes, dark urine, severe nausea/vomiting.,May cause hypothyroidism; report fatigue, weight gain, or cold intolerance.,Avoid alcohol due to increased risk of liver damage.
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 SODIUM P.A.S. vs PASER, answered by our medical review team.
SODIUM P.A.S. is a Antitubercular Agent that works by Sodium P. A. S. (para-aminosalicylate) inhibits folic acid synthesis in Mycobacterium tuberculosis by competing with para-aminobenzoic acid, thereby suppressing bacterial growth.. 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 SODIUM P.A.S. 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 SODIUM P.A.S. is: 4 g orally three times daily (total 12 g/day). For intravenous administration, 4 g (10 m L of 40% solution) diluted in 250 m L of 5% dextrose or normal saline infused over 2-3 hours three times daily.. 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 SODIUM P.A.S. 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. SODIUM P.A.S. is classified as Category C. PAS is not associated with major congenital malformations. First trimester: no significant increase in defect risk. Second/third trimester: may increase risk of maternal hemolysis . 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.