PONSTEL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PONSTEL (PONSTEL).
Nonsteroidal anti-inflammatory drug (NSAID) that inhibits cyclooxygenase (COX-1 and COX-2), reducing prostaglandin synthesis, thereby decreasing inflammation, pain, and fever.
| Metabolism | Primarily hepatic via glucuronidation and oxidation; CYP450 (CYP2C9) minor role. |
| Excretion | Primarily renal (70-80% as glucuronide conjugates and unchanged drug); biliary/fecal (20-30%) |
| Half-life | 2-4 hours (terminal elimination half-life); clinical context: duration of analgesia 4-6 hours; accumulates with renal impairment |
| Protein binding | >99% bound to albumin |
| Volume of Distribution | 0.2 L/kg; relatively low Vd consistent with high protein binding and limited tissue distribution |
| Bioavailability | Oral: near 100% (almost completely absorbed) with first-pass metabolism minimal |
| Onset of Action | Oral: 15-30 minutes; peak effect 1-2 hours |
| Duration of Action | 4-6 hours; longer duration may occur with hepatic impairment or higher doses |
250 mg orally every 6 hours as needed, not to exceed 1 g per day, for no longer than 7 days.
| Dosage form | CAPSULE |
| Renal impairment | GFR 30-89 mL/min: No adjustment needed. GFR <30 mL/min: Contraindicated. Hemodialysis: Not recommended. |
| Liver impairment | Child-Pugh A: No adjustment. Child-Pugh B: Use with caution, reduce dose by 50%. Child-Pugh C: Contraindicated. |
| Pediatric use | Children ≥14 years: 250 mg orally every 6 hours as needed, not to exceed 1 g per day. Children <14 years: Safety and efficacy not established. |
| Geriatric use | Initiate at lower dose (250 mg every 8-12 hours) due to increased risk of GI bleeding and renal impairment; limit duration to 3 days. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PONSTEL (PONSTEL).
| Breastfeeding | Mefenamic acid is excreted into breast milk at low levels; M/P ratio reported as approximately 0.18. Based on limited data, it is considered compatible with breastfeeding. Due to potential adverse effects in infants (e.g., gastrointestinal or renal effects), use lowest effective dose for shortest duration. |
| Teratogenic Risk | Ponstel (mefenamic acid) is a nonsteroidal anti-inflammatory drug (NSAID). Avoid use after 30 weeks gestation due to risk of premature closure of the ductus arteriosus and oligohydramnios. Use in first and second trimesters is associated with increased risk of miscarriage and congenital malformations, particularly cardiac defects. Risk summary: avoid throughout pregnancy unless absolutely necessary. |
■ FDA Black Box Warning
Increased risk of serious cardiovascular thrombotic events, including myocardial infarction and stroke, with use of NSAIDs, especially in patients with cardiovascular risk factors or following CABG surgery.
| Serious Effects |
History of allergic reaction to mefenamic acid or other NSAIDs; active peptic ulcer; severe renal impairment; perioperative pain in CABG surgery; pregnancy (third trimester).
| Precautions | Risk of GI bleeding, ulceration, and perforation; hypertension; fluid retention; renal toxicity; anaphylactoid reactions; exacerbation of asthma; avoid in late pregnancy. |
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| Fetal Monitoring | Monitor maternal renal function, blood pressure, and signs of gastrointestinal bleeding. Fetal monitoring includes ultrasound for amniotic fluid volume and ductus arteriosus patency if used beyond 20 weeks gestation. |
| Fertility Effects | NSAIDs including mefenamic acid may impair female fertility by interfering with ovulation via inhibition of prostaglandin synthesis. Effects are reversible upon discontinuation. |