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 NYDRAZID
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 bacterial cell wall synthesis by blocking the incorporation of mycolic acid into the arabinogalactan layer, specific to mycobacteria.
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 active tuberculosis (in combination with other antituberculous agents),Prophylaxis of tuberculosis in high-risk individuals
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.
300 mg orally once daily; alternatively, 5 mg/kg (max 300 mg) orally once daily for 6-9 months for latent tuberculosis; for active tuberculosis, 5 mg/kg (max 300 mg) orally once daily for 2 months followed by 3 times weekly dosing (15 mg/kg, max 900 mg) for 4-7 months.
0.5–1 hour (normal renal function); prolonged to ≥10 hours in renal impairment (requires dose adjustment).
Terminal elimination half-life: 1-4 hours (fast acetylators), 2-8 hours (slow acetylators). Half-life prolonged in hepatic impairment; adjust dose.
Hepatic acetylation via N-acetyltransferase (NAT2); undergoes conjugation with glycine and glucuronic acid.
Hepatic metabolism primarily via N-acetyltransferase 2 (NAT2) to acetylisoniazid, which is further metabolized to hepatotoxic metabolites.
Primarily renal (80-90% as unchanged drug) via glomerular filtration and tubular secretion; biliary/fecal ≤10%.
Renal excretion of unchanged drug and metabolites; 50-70% excreted in urine within 24 hours, mainly as acetylisoniazid and isonicotinic acid. Biliary/fecal: <10%.
50–60% bound to serum albumin.
10-20% bound primarily to albumin; binding is low and clinically insignificant.
0.2–0.4 L/kg (suggests low tissue penetration, primarily extracellular).
Vd: 0.6-0.8 L/kg; distributes into total body water, including CSF, pleural fluid, and caseous granulomas.
Oral: ~80–90%. IV: 100%.
Oral: 90-100% (fasting). Food may decrease absorption by 20-50%; take on empty stomach.
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.
If GFR < 30 m L/min: administer 200 mg once daily or 300 mg three times weekly. For severe renal impairment (GFR < 10 m L/min) or hemodialysis: 200 mg daily or 300 mg three times weekly, given after dialysis.
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.
Child-Pugh Class A: no adjustment needed. Child-Pugh Class B: reduce dose by 50% (e.g., 150 mg daily). Child-Pugh Class C: reduce dose by 50-75% (e.g., 100-150 mg daily) or consider alternative therapy; monitor liver function closely.
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.
For latent tuberculosis: 10-15 mg/kg (max 300 mg) orally once daily for 6-9 months. For active tuberculosis: 10-15 mg/kg (max 300 mg) orally once daily for 2 months, then 15 mg/kg (max 900 mg) orally three times weekly for 4-7 months.
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.
Start at lower end of dosing range (e.g., 200-300 mg daily) due to potential renal impairment; monitor liver function and signs of hepatotoxicity; adjust dose based on creatinine clearance if GFR < 30 m L/min.
No FDA black box warning.
Severe and sometimes fatal hepatitis has been reported, even after months of treatment. Risk increases with age, daily alcohol use, and pre-existing liver disease. Monitor liver function tests closely.
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
Peripheral neuropathy (prevent with pyridoxine), hepatotoxicity, hypersensitivity reactions (e.g., fever, rash), lupus-like syndrome, seizures, optic neuritis, drug interactions (e.g., phenytoin, carbamazepine, disulfiram).
Hypersensitivity to para-aminosalicylate or any component,Severe hepatic impairment,Severe renal impairment (Cr Cl < 30 m L/min)
Severe hepatic disease, acute liver disease, or previous isoniazid-associated hepatitis; hypersensitivity to isoniazid or any component.
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.
Isoniazid inhibits monoamine oxidase (MAO) and reduces metabolism of tyramine, leading to hypertensive crisis. Avoid tyramine-rich foods: aged cheeses (cheddar, blue cheese), cured or fermented meats (salami, pepperoni, pickled herring), soy products (tofu, miso, tempeh), sauerkraut, fava beans, tap beers, and red wines. Also avoid foods containing histamine (tuna, mackerel, sauerkraut). Concomitant alcohol consumption increases risk of hepatotoxicity and should be strictly avoided. High-protein meals or dairy may interfere with absorption; maintain consistent timing relative to meals. There is no restriction on carbohydrates or fats.
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.
Isoniazid (INH) is not associated with major congenital malformations in humans. However, in vivo animal studies have shown embryocidal effects at high doses. The drug is considered safe during all trimesters; however, due to the risk of hepatotoxicity, monitoring of liver function is recommended, especially in the third trimester. Perinatal exposure increases the risk of neonatal hemorrhage due to vitamin K deficiency, which can be prevented by prophylactic vitamin K administration to the mother.
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.
Isoniazid is excreted into breast milk in concentrations similar to maternal plasma. The milk-to-plasma (M/P) ratio is approximately 1.0. The American Academy of Pediatrics considers it compatible with breastfeeding. However, due to the theoretical risk of hepatotoxicity and peripheral neuropathy in the infant, monitoring of the infant for signs of jaundice, hepatitis, or neuropathy is recommended. The dose to the infant is subtherapeutic (about 0.5-2% of the maternal dose) and is unlikely to cause adverse 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.
Standard dosing of isoniazid (300 mg daily or 900 mg twice weekly) is generally recommended during pregnancy. No dose adjustment is required as pregnancy does not significantly alter the pharmacokinetics of isoniazid. However, due to increased hepatic metabolism in pregnancy, some experts recommend monitoring serum drug levels to ensure therapeutic concentrations, though routine monitoring is not standard. Pyridoxine (25-50 mg daily) should be co-administered to prevent peripheral neuropathy in the mother and fetus.
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).
NYDRAZID (isoniazid) is a first-line antitubercular agent. Always prescribe pyridoxine (vitamin B6) 25-50 mg daily to prevent peripheral neuropathy, especially in patients with risk factors like diabetes, alcoholism, malnutrition, or HIV. Monitor liver function tests closely; hepatotoxicity risk increases with age >35, concurrent use of acetaminophen or other hepatotoxic drugs, and pre-existing liver disease. Slow acetylators (genetic) have higher risk of toxicity. Isoniazid can cause bilateral optic neuritis; monitor for visual symptoms. Drug interactions: increases levels of phenytoin, carbamazepine, and theophylline; reduce doses accordingly. Administer on empty stomach (1 hour before or 2 hours after meals) for optimal absorption. In case of overdose, high-dose pyridoxine is antidote (1 g per gram of isoniazid ingested).
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 isoniazid on an empty stomach with a full glass of water, at least 1 hour before or 2 hours after meals.,Do not drink alcohol while taking this medication; combined with alcohol increases risk of severe liver damage.,Take vitamin B6 (pyridoxine) exactly as prescribed to prevent nerve damage.,Report immediately: dark urine, pale stools, yellowing of skin or eyes, nausea/vomiting, abdominal pain, unusual fatigue (liver toxicity signs).,Report numbness, tingling, or burning in hands/feet; vision changes; rash; or fever.,Avoid foods high in tyramine (aged cheese, cured meats, soy products, tap beer) while taking isoniazid; may cause hypertensive crisis.,Take all doses on schedule; do not skip or stop without consulting provider.,Keep all follow-up appointments for blood tests to monitor liver function.
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 NYDRAZID, 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.. NYDRAZID is a Antitubercular Agent that works by Inhibits bacterial cell wall synthesis by blocking the incorporation of mycolic acid into the arabinogalactan layer, specific to mycobacteria.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between SODIUM P.A.S. and NYDRAZID 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 NYDRAZID is: 300 mg orally once daily; alternatively, 5 mg/kg (max 300 mg) orally once daily for 6-9 months for latent tuberculosis; for active tuberculosis, 5 mg/kg (max 300 mg) orally once daily for 2 months followed by 3 times weekly dosing (15 mg/kg, max 900 mg) for 4-7 months.. 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 NYDRAZID 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 . NYDRAZID is classified as Category C. Isoniazid (INH) is not associated with major congenital malformations in humans. However, in vivo animal studies have shown embryocidal effects at high doses. The drug is considere. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.