Mefenamic acid

Mefenamic acid

Systematic (IUPAC) name
2-(2,3-dimethylphenyl)aminobenzoic acid
Clinical data
Trade names	Ponstel
AHFS/Drugs.com	monograph
MedlinePlus	a681028
Pregnancy cat.	C (Australia, United States)
Legal status	℞-only (U.S.), POM in UK
Routes	Oral
Pharmacokinetic data
Bioavailability	90%
Protein binding	90%
Metabolism	Hepatic (CYP2C9)
Half-life	2 hours
Excretion	Renal and fecal
Identifiers
CAS number	61-68-7 Y
ATC code	M01AG01
PubChem	CID 4044
DrugBank	APRD0073
ChemSpider	3904 Y
UNII	367589PJ2C Y
KEGG	D00151 Y
ChEMBL	CHEMBL686 Y
Chemical data
Formula	C15H15NO2
Mol. mass	241.285 g/mol
SMILES	eMolecules & PubChem
InChI InChI=1S/C15H15NO2/c1-10-6-5-9-13(11(10)2)16-14-8-4-3-7-12(14)15(17)18/h3-9,16H,1-2H3,(H,17,18) Y Key:HYYBABOKPJLUIN-UHFFFAOYSA-N Y
N(what is this?)  (verify)

Mefenamic acid is a non-steroidal anti-inflammatory drug used to treat pain, including menstrual pain. It is typically prescribed for oral administration. Mefenamic acid is marketed in the USA as Ponstel.

Mefenamic acid decreases inflammation (swelling) and uterine contractions by a still unknown mechanism. However it is thought to be related to the inhibition of prostaglandin synthesis. There is also evidence that supports the use of mefenamic acid for perimenstrual migraine headache prophylaxis, with treatment starting 2 days prior to the onset of flow or 1 day prior to the expected onset of the headache and continuing for the duration of menstruation.

Since hepatic metabolism plays a significant role in mefenamic acid elimination, patients with known liver deficiency may be prescribed lower doses. Kidney deficiency may also cause accumulation of the drug and its metabolites in the excretory system. Therefore patients suffering from renal conditions should not be prescribed mefenamic acid.

Brand Names
Mefalth, Mefalth T, Ponstel, Ponstan, Ponstal, Parkemed, Mafepain, Mefamed, Mephadolor, Meftal, Dyfenamic, Potarlon, Dolfenal, Meyerdonal, Alfoxan, Fenagesic, Spiralgin.

Side effects

Known mild side effects of mefenamic acid include headaches, nervousness and vomiting. Serious side effects may include diarrhea, hematemesis (vomiting blood), haematuria (blood in urine), blurred vision, skin rash, itching and swelling, sore throat and fever. It is advised to consult a doctor immediately if these symptoms appear while taking this medication.

Non-steroidal anti-inflammatory drugs (NSAIDs) may worsen hypertension. Persons with hypertension, left ventricular dysfunction, and heart failure may wish to avoid NSAIDs.

Mefenamic acid is recommended to be taken with food.

Mefenamic acid usage has been discontinued in Germany in 2007 because no study to date could prove any advantage over other NSAIDs, but some severe side-effects have been observed.

Overdose

Overdose can lead to a range of symptoms including convulsions, nausea, vomiting, vomiting blood, shallow breathing, coma. Onset of symptoms is usually between 30 minutes and 4 hours, but signs of renal failure may appear several days after an overdose. Seek medical attention immediately in the case of overdose. The lethal dose can be as low as 2.5g.

Synthesis

Analogous to fenamic acid, this compound may be synthesized from 2-chlorobenzoic acid and 2,3-dimethylaniline.

Sources

• MedlinePlus Drug Information: Mefenamic Acid. Last accessed September 28, 2005.
• Ponstel Pharmacology, Pharmacokinetics, Studies, Metabolism - Mefenamic Acid - RxList Monographs. Last accessed September 28, 2005.
• Consumption of NSAIDs and the Development of Congestive Heart Failure in Elderly Patients
• NSAIDs May Increase Risk for Worsening Heart Failure