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 MYAMBUTOL
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 arabinosyl transferase, an enzyme involved in cell wall synthesis of mycobacteria, leading to inhibition of cell growth.
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 pulmonary tuberculosis in combination with other antituberculosis agents,Treatment of extrapulmonary tuberculosis
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.
15-25 mg/kg orally once daily (max 2.5 g/day); usual dose 20 mg/kg/day.
0.5–1 hour (normal renal function); prolonged to ≥10 hours in renal impairment (requires dose adjustment).
Terminal elimination half-life: 3-4 hours in normal renal function; prolonged to 7-15 hours in renal impairment.
Hepatic acetylation via N-acetyltransferase (NAT2); undergoes conjugation with glycine and glucuronic acid.
Partially metabolized in the liver via dealkylation to an aldehyde intermediate, which is further oxidized to a dicarboxylic acid. Approximately 50% of the drug is excreted unchanged in urine.
Primarily renal (80-90% as unchanged drug) via glomerular filtration and tubular secretion; biliary/fecal ≤10%.
Renal: 50% unchanged drug; 20% as metabolite (ethambutol carboxylic acid); 15% as aldehyde intermediate; 15% unknown; fecal: <10%.
50–60% bound to serum albumin.
20-30% bound to albumin.
0.2–0.4 L/kg (suggests low tissue penetration, primarily extracellular).
1.6 L/kg; distributes widely into tissues, including erythrocytes and cerebrospinal fluid (with inflamed meninges).
Oral: ~80–90%. IV: 100%.
Oral: approximately 80% absorbed.
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.
Cr Cl 30-60 m L/min: 15-20 mg/kg daily; Cr Cl 10-29 m L/min: 15 mg/kg every 24-36 hours; Cr Cl <10 m L/min: 15 mg/kg every 48 hours.
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 Child-Pugh based adjustments; use with caution in severe hepatic impairment.
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.
15-25 mg/kg orally once daily (max 1 g/day for children weighing <20 kg, otherwise 2.5 g/day).
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.
Consider reduced initial dose based on renal function; monitor for optic neuritis.
No FDA black box warning.
MYAMBUTOL may cause optic neuritis and decreased visual acuity, which may be dose-related and reversible upon discontinuation. Not recommended for use in children under 13 years of age.
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
Optic neuritis (monitor visual acuity and color discrimination); hepatic toxicity; renal impairment (dose adjustment required); interaction with aluminum-containing antacids (decreased absorption).
Hypersensitivity to para-aminosalicylate or any component,Severe hepatic impairment,Severe renal impairment (Cr Cl < 30 m L/min)
Hypersensitivity to ethambutol; optic neuritis (unless benefit outweighs risk); children under 13 years of age (relative contraindication).
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.
No significant food interactions. However, administration with food may reduce gastrointestinal upset. Concurrent use with aluminum-containing antacids may decrease absorption; separate by at least 2 hours.
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.
Ethambutol (Myambutol) is classified as FDA Pregnancy Category B. Animal studies have not demonstrated teratogenic effects. Human data are limited but do not suggest a significant increase in major malformations. However, due to the risk of optic neuritis in the mother, use during pregnancy should be cautious and 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.
Ethambutol is excreted into human breast milk in low concentrations; the estimated infant dose is approximately 2-4% of the maternal weight-adjusted dose. The milk-to-plasma ratio is approximately 0.57. The American Academy of Pediatrics considers ethambutol compatible with breastfeeding. Monitor the infant for signs of optic neuritis or gastrointestinal effects.
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 specific dose adjustments are routinely recommended during pregnancy. However, pharmacokinetic changes in pregnancy (increased volume of distribution, enhanced renal clearance) may reduce serum concentrations; therapeutic drug monitoring is not standard but may be considered. Adjust dose based on renal function; usual dose is 15-25 mg/kg/day, not to exceed 2.5 g/day.
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).
MYAMBUTOL (ethambutol) is a bacteriostatic agent used primarily in combination therapy for tuberculosis. Monitor for optic neuritis, which can cause decreased visual acuity, color blindness, and visual field defects; baseline and monthly visual acuity and color discrimination tests are mandatory. Dose adjustments required in renal impairment (Cr Cl <30 m L/min). Avoid in children <13 years old due to inability to monitor vision. May cause hyperuricemia; monitor uric acid levels in patients with gout.
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 exactly as prescribed, usually once daily, with or without food.,Report any changes in vision immediately, such as blurred vision, difficulty seeing colors, or blind spots.,Avoid consuming alcohol; may increase risk of liver toxicity.,Do not stop taking this medication even if you feel better; complete full course to prevent resistance.,This drug may cause numbness or tingling in hands or feet; report these symptoms.,Inform your doctor if you have kidney disease, gout, or eye problems before starting treatment.
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 MYAMBUTOL, 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.. MYAMBUTOL is a Antitubercular Agent that works by Inhibits arabinosyl transferase, an enzyme involved in cell wall synthesis of mycobacteria, leading to inhibition of cell growth.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between SODIUM P.A.S. and MYAMBUTOL 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 MYAMBUTOL is: 15-25 mg/kg orally once daily (max 2.5 g/day); usual dose 20 mg/kg/day.. 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 MYAMBUTOL 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 . MYAMBUTOL is classified as Category C. Ethambutol (Myambutol) is classified as FDA Pregnancy Category B. Animal studies have not demonstrated teratogenic effects. Human data are limited but do not suggest a significant . Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.