Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
NYDRAZID vs P.A.S. SODIUM
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Inhibits bacterial cell wall synthesis by blocking the incorporation of mycolic acid into the arabinogalactan layer, specific to mycobacteria.
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.
Treatment of active tuberculosis (in combination with other antituberculous agents),Prophylaxis of tuberculosis in high-risk individuals
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).
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.
Oral: 4 g three times daily (total daily dose 12 g); IV: 12 g daily in 2-4 divided doses.
Terminal elimination half-life: 1-4 hours (fast acetylators), 2-8 hours (slow acetylators). Half-life prolonged in hepatic impairment; adjust dose.
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
Hepatic metabolism primarily via N-acetyltransferase 2 (NAT2) to acetylisoniazid, which is further metabolized to hepatotoxic metabolites.
Primarily metabolized by hepatic acetylation via N-acetyltransferase (NAT); minor pathways include glycine conjugation and renal excretion of unchanged drug.
Renal excretion of unchanged drug and metabolites; 50-70% excreted in urine within 24 hours, mainly as acetylisoniazid and isonicotinic acid. Biliary/fecal: <10%.
Renal (80% as active drug and metabolites, primarily acetylated form); fecal (minor; <10%)
10-20% bound primarily to albumin; binding is low and clinically insignificant.
50-60% (primarily to albumin)
Vd: 0.6-0.8 L/kg; distributes into total body water, including CSF, pleural fluid, and caseous granulomas.
0.5-0.6 L/kg (indicates distribution into total body water, with some tissue binding)
Oral: 90-100% (fasting). Food may decrease absorption by 20-50%; take on empty stomach.
Oral: approximately 90% (well absorbed from GI tract)
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.
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.
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.
Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid use.
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.
Oral: 200-300 mg/kg/day in 3-4 divided doses, maximum 12 g/day.
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.
Start at lower end of dosing range; monitor renal function and adjust based on Cr Cl; typical initial dose 4 g twice daily.
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.
None explicitly stated in current FDA labeling; however, caution is advised in hepatic impairment due to risk of hepatitis.
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).
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.
Severe hepatic disease, acute liver disease, or previous isoniazid-associated hepatitis; hypersensitivity to isoniazid or any component.
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.
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.
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.
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.
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.
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.
Excreted into breast milk in low amounts; M/P ratio not determined. Considered compatible with breastfeeding; monitor infant for diarrhea or rash.
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.
No pharmacokinetic changes requiring dose adjustment in pregnancy; use standard dosing but monitor for hepatotoxicity, which may be increased.
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).
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.
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.
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.
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 NYDRAZID vs P.A.S. SODIUM, answered by our medical review team.
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.. 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.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between NYDRAZID and P.A.S. SODIUM 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 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.. 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.. 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 NYDRAZID and P.A.S. SODIUM 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. 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. 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. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.