SODIUM P.A.S.
Clinical safety rating
cautionComprehensive clinical and safety monograph for SODIUM P.A.S. (SODIUM P.A.S.).
Comprehensive clinical and safety monograph for SODIUM P.A.S. (SODIUM P.A.S.).
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
Sodium P.A.S. (para-aminosalicylate) inhibits folic acid synthesis in Mycobacterium tuberculosis by competing with para-aminobenzoic acid, thereby suppressing bacterial growth.
| Metabolism | Hepatic acetylation via N-acetyltransferase (NAT2); undergoes conjugation with glycine and glucuronic acid. |
| Excretion | Primarily renal (80-90% as unchanged drug) via glomerular filtration and tubular secretion; biliary/fecal ≤10%. |
| Half-life | 0.5–1 hour (normal renal function); prolonged to ≥10 hours in renal impairment (requires dose adjustment). |
| Protein binding | 50–60% bound to serum albumin. |
| Volume of Distribution | 0.2–0.4 L/kg (suggests low tissue penetration, primarily extracellular). |
| Bioavailability | Oral: ~80–90%. IV: 100%. |
| Onset of Action | Oral: ~1–2 hours. IV: Immediate. Rectal: 2–4 hours. |
| Duration of Action | 6–12 hours (oral); sustained with impaired renal function. |
| Molecular Weight | 153.14 |
4 g orally three times daily (total 12 g/day). For intravenous administration, 4 g (10 mL of 40% solution) diluted in 250 mL of 5% dextrose or normal saline infused over 2-3 hours three times daily.
| Dosage form | TABLET |
| Renal impairment | GFR 30-50 mL/min: administer every 12 hours. GFR 10-30 mL/min: administer every 24 hours. GFR <10 mL/min: administer every 48 hours or avoid use. |
| Liver 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. |
| Pediatric use | 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. |
| Geriatric use | 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. |
| 1st trimester | Aminosalicylic acid is generally avoided in the first trimester unless benefit clearly outweighs risk; animal studies suggest no teratogenicity but human data limited. |
| 2nd trimester | May be used if necessary; no consistent evidence of fetal harm in second trimester. |
| 3rd trimester | Use with caution near term due to possible risk of kernicterus in newborn (displaces bilirubin from albumin). |
Clinical note
Comprehensive clinical and safety monograph for SODIUM P.A.S. (SODIUM P.A.S.).
| Placental transfer | Aminosalicylic acid crosses the placenta; concentrations in fetal serum are approximately 10-20% of maternal levels. |
| Breastfeeding | Sodium P.A.S. is excreted into breast milk in small amounts; no adverse effects reported in infants, but caution is advised due to potential for gastrointestinal intolerance or hypersensitivity. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | 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. |
| Fetal Monitoring | Baseline and periodic liver function tests, renal function, CBC with differential, and serum electrolytes. Monitor for signs of hemolysis in G6PD-deficient mothers. Fetal growth ultrasound if used in pregnancy. |
| Fertility Effects | No evidence of impaired fertility in animal studies or human reports. PAS does not affect gonadal function or spermatogenesis. |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
Hypersensitivity to aminosalicylic acid or any componentSevere renal impairment (creatinine clearance <30 mL/min)Active peptic ulcer disease
| Precautions | 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 |
| Food/Dietary | 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. |
| Clinical Pearls | 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 (CrCl <30 mL/min). |
| Patient Advice | 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. |
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