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Ponstel (Mefenamic Acid) - Drug Interactions, Contraindications, Overdosage, etc



Drug Interactions

A number of compounds are inhibitors of CYP2C9. Drug interactions studies of mefenamic acid and these compounds have not been conducted. The possibility of altered safety and efficacy should be considered when PONSTEL is used concomitantly with these drugs.


Symptoms following acute NSAIDs overdoses are usually limited to lethargy, drowsiness, nausea, vomiting, and epigastric pain, which are generally reversible with supportive care. Gastrointestinal bleeding can occur. Hypertension, acute renal failure, respiratory depression and coma may occur, but are rare. Anaphylactoid reactions have been reported with therapeutic ingestion of NSAIDs, and may occur following an overdose.

Patients should be managed by symptomatic and supportive care following an NSAID overdose. There are no specific antidotes. Emesis and/or activated charcoal (60 to 100 g in adults, 1 to 2 g/kg in children) and/or osmotic cathartic may be indicated in patients seen within 4 hours of ingestion with symptoms or following a large overdose (5 to 10 times the usual dose). Forced diuresis, alkalinization of urine, hemodialysis, or hemoperfusion may not be useful due to high protein binding.


PONSTEL is contraindicated in patients with known hypersensitivity to mefenamic acid.

PONSTEL should not be given to patients who have experienced asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs. Severe, rarely fatal, anaphylactic-like reactions to NSAIDs have been reported in such patients (see WARNINGS - Anaphylactoid Reactions, and PRECAUTIONS - Preexisting Asthma).

PONSTEL is contraindicated for the treatment of peri-operative pain in the setting of coronary artery bypass graft (CABG) surgery (see WARNINGS).

PONSTEL is contraindicated in patients with acute active ulceration or chronic inflammation of either the upper or lower gastrointestinal tract.

PONSTEL should not be used in patients with preexisting renal disease.


  1. Neuvonen PJ, Kivisto KT: Enhancement of drug absorption by antacids. An unrecognized drug interaction. Clin Pharmacokinet.27:120-8, Aug 1994.
  2. Tall AR, Mistilits SP: Studies on Ponstan (mefenamic acid): I. Gastro-intestinal blood loss; II. Absorption and excretion of a new formulation.  J Int Med Res (UK). 1975, 3 (3) p176-82.
  3. Winder CV, Kaump DH, Glazko et al: Experimental observations of flufenamic, mefenamic, and meclofenamic acids. AnnPhys Med (Eng), Suppl p7-49.1967.
  4. Glazko AJ: Experimental observations of flufenamic, mefenamic, and meclofenamic acids. Part III. Metabolic disposition, in Fenamates in Medicine. A Symposium, London, 1966. Annals of Physical Medicine, Supplement, pp 23-36, 1967.
  5. Data on file, First Horizon (Protocol 356).
  6. Budoff PW: Use of mefenamic acid in the treatment of primary dysmenorrhea. JAMA.  241: 2713-2716, 1979.
  7. Buchanan RA, et al. The breast milk excretion of mefenamic acid. Curr Ther Res. 10:592, 1968.
  8. Corby DG, Decker WJ: Management of acute poisoning with activated charcoal. Pediatrics. 54:324,1974.
  9. Champion GD, Graham GG: Pharmacokinetics of non-steroidal anti-inflammatory agents. Aust NZ J Med. 8 (Supp 1): 94-100, Jun 1978.
  10. McGurk KA, Remmel RP, Hosagrahara VP, Tosh D, Burchell B: Reactivity of mefenamic acid 1-o- acyl glucuronide  with proteins in vitro and ex vivo. Drug Metab Dispos. Aug 1996, 24 (8) p842-9.
  11. Ito K, Niida Y, Sato J et al: Pharmacokinetics of mefenamic acid in preterm infants with patent ductus arteriosus. Acta Paediatr JPN. 36 (4): 387-91, 1994 

Manufactured for:
Shionogi Inc.
Florham Park, NJ 07932

Manufactured by:
Halo Pharmaceutical Inc
Whippanny, NJ 07981

Rev. 05/2013

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