Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
ACULAR PRESERVATIVE FREE 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
Ketorolac tromethamine is a nonsteroidal anti-inflammatory drug (NSAID) that inhibits cyclooxygenase (COX-1 and COX-2) enzymes, thereby reducing prostaglandin synthesis. It produces anti-inflammatory and analgesic effects.
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.
FDA-approved: Treatment of ocular inflammation and pain following cataract surgery and corneal refractive surgery.,Off-label: Relief of seasonal allergic conjunctivitis symptoms, management of cystoid macular edema, and treatment of postoperative inflammation in other ocular procedures.
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).
1 drop into affected eye(s) four times daily (every 6 hours). Instill into conjunctival sac. Shake well before use.
Oral: 4 g three times daily (total daily dose 12 g); IV: 12 g daily in 2-4 divided doses.
Terminal elimination half-life is approximately 5-6 hours in adults, but can be prolonged in elderly patients (up to 8-9 hours) and in patients with renal impairment (up to 13-19 hours).
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
Ketorolac undergoes hepatic metabolism via hydroxylation and conjugation (glucuronidation) to inactive metabolites. It is primarily metabolized by CYP2D6 and CYP3A4 isoenzymes, with renal excretion of metabolites and unchanged drug.
Primarily metabolized by hepatic acetylation via N-acetyltransferase (NAT); minor pathways include glycine conjugation and renal excretion of unchanged drug.
Primarily renal excretion of metabolites and unchanged drug; approximately 80% of a dose is excreted in urine as ketorolac and its hydroxy metabolites, with about 6% excreted in feces.
Renal (80% as active drug and metabolites, primarily acetylated form); fecal (minor; <10%)
99% bound to plasma proteins, primarily albumin.
50-60% (primarily to albumin)
0.15-0.25 L/kg after oral administration; for ophthalmic use, systemic absorption is minimal, so Vd is not clinically meaningful.
0.5-0.6 L/kg (indicates distribution into total body water, with some tissue binding)
Ophthalmic administration: Systemic bioavailability is approximately 0.5-1% after ocular instillation due to low corneal penetration and rapid clearance; oral bioavailability is 100%.
Oral: approximately 90% (well absorbed from GI tract)
No dosage adjustment required for renal impairment. Drug is minimally absorbed systemically.
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.
No dosage adjustment required for hepatic impairment. Drug is minimally absorbed systemically.
Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid use.
Children ≥3 years: 1 drop into affected eye(s) four times daily. Safety and efficacy in children <3 years not established.
Oral: 200-300 mg/kg/day in 3-4 divided doses, maximum 12 g/day.
No specific dosage adjustment required. Use same dose as adults; monitor for tolerability.
Start at lower end of dosing range; monitor renal function and adjust based on Cr Cl; typical initial dose 4 g twice daily.
NSAIDs may increase the risk of serious cardiovascular events (e.g., myocardial infarction, stroke) and gastrointestinal events (e.g., bleeding, ulceration, perforation). However, due to low systemic absorption with ophthalmic use, this boxed warning is less clinically relevant but still applies.
None explicitly stated in current FDA labeling; however, caution is advised in hepatic impairment due to risk of hepatitis.
Use with caution in patients with compromised ocular surface, history of herpes simplex keratitis, bleeding tendencies, or those on anticoagulants. Prolonged use may delay wound healing. Monitor for signs of corneal epithelial breakdown or infection.
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.
Hypersensitivity to ketorolac or any component of the formulation; patients with active ocular infection or advanced dry eye; history of asthma, urticaria, or allergic-type reactions to aspirin or other NSAIDs.
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.
No known food interactions. No dietary restrictions required.
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.
FDA Pregnancy Category C. No adequate studies in pregnant women. In animal studies, ketorolac tromethamine (active ingredient) was not teratogenic in rats or rabbits at doses up to 1.5-3 times the human exposure. However, because NSAIDs can cause premature closure of the ductus arteriosus and oligohydramnios in the third trimester, use is contraindicated after 30 weeks gestation. In first and second trimesters, use only if potential benefit justifies potential fetal risk.
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.
Ketorolac is excreted in human milk following oral administration. After a single intramuscular dose of 10 mg, the milk-to-plasma (M/P) ratio was 0.037. Low levels are expected in breastmilk; however, due to potential adverse effects of NSAIDs on neonates, caution is advised. Use is generally avoided in nursing mothers, especially with premature infants or those with thrombocytopenia or renal impairment.
Excreted into breast milk in low amounts; M/P ratio not determined. Considered compatible with breastfeeding; monitor infant for diarrhea or rash.
No specific pharmacokinetic studies in pregnancy. Dosing should be at the lowest effective dose for the shortest duration. Avoid use after 30 weeks gestation. No adjustment for first or second trimester unless renal function changes.
No pharmacokinetic changes requiring dose adjustment in pregnancy; use standard dosing but monitor for hepatotoxicity, which may be increased.
ACULAR (ketorolac tromethamine ophthalmic solution) is an NSAID for ocular use. Preservative-free formulation is indicated for single-use to avoid corneal toxicity. Apply with caution in patients with bleeding disorders or those on anticoagulants due to risk of ocular bleeding. Prolonged use may delay corneal healing. Monitor for signs of keratitis or conjunctival hyperemia.
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.
Use exactly as prescribed; do not touch the dropper tip to any surface to avoid contamination.,Each single-use vial is for one dose only; discard after use to prevent infection.,Remove contact lenses before instillation and wait 10 minutes before reinserting.,Do not drive or operate machinery if vision is blurry after application.,Report eye pain, increased redness, or vision changes to your doctor immediately.
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 ACULAR PRESERVATIVE FREE vs P.A.S. SODIUM, answered by our medical review team.
ACULAR PRESERVATIVE FREE is a NSAID Ophthalmic that works by Ketorolac tromethamine is a nonsteroidal anti-inflammatory drug (NSAID) that inhibits cyclooxygenase (COX-1 and COX-2) enzymes, thereby reducing prostaglandin synthesis. It produces anti-inflammatory and analgesic effects.. 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 ACULAR PRESERVATIVE FREE and P.A.S. SODIUM depend on the specific clinical indication. These are agents from distinct pharmacological classes and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of ACULAR PRESERVATIVE FREE is: 1 drop into affected eye(s) four times daily (every 6 hours). Instill into conjunctival sac. Shake well before use.. 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 ACULAR PRESERVATIVE FREE 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. ACULAR PRESERVATIVE FREE is classified as Category C. FDA Pregnancy Category C. No adequate studies in pregnant women. In animal studies, ketorolac tromethamine (active ingredient) was not teratogenic in rats or rabbits at doses up to. 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.