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In patients taking Ponstel (mefenamic acid) or other NSAIDs, the most frequently reported adverse experiences occurring in approximately 1-10% of patients are:
Gastrointestinal experiences including - abdominal pain, constipation, diarrhea, dyspepsia, flatulence, gross bleeding/perforation, heartburn, nausea, GI ulcers (gastric/duodenal), vomiting, abnormal renal function, anemia, dizziness, edema, elevated liver enzymes, headaches, increased bleeding time, pruritus, rashes, tinnitus
Additional adverse experiences reported occasionally and listed here by body system include:
Metabolic and nutritional - weight changes
Special senses - blurred vision
Other adverse reactions, which occur rarely are:
Body as a whole - anaphylactoid reactions, appetite changes, death
Metabolic and nutritional - hyperglycemia
Respiratory- respiratory depression, pneumonia
Special senses - conjunctivitis, hearing impairment
Read the Ponstel (mefenamic acid) Side Effects Center for a complete guide to possible side effects
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 (mefenamic acid) is used concomitantly with these drugs.
When PONSTEL (mefenamic acid) is administered with aspirin, its protein binding is reduced, although the clearance of free PONSTEL (mefenamic acid) is not altered. The clinical significance of this interaction is not known; however, as with other NSAIDs, concomitant administration of MEFENAMIC ACID and aspirin is not generally recommended because of the potential of increased adverse effects.
Clinical studies, as well as post marketing observations, have shown that PONSTEL (mefenamic acid) can reduce the natriuretic effect-of furosemide and thiazides in some patients. This response has been attributed to inhibition of renal prostaglandin synthesis. During concomitant therapy of NSAIDs, the patient should be observed closely for signs of renal failure (see PRECAUTIONS, Renal Effects), as well as to assure diuretic efficacy.
NSAIDs have produced an elevation of plasma lithium levels and a reduction in renal lithium clearance. The mean minimum lithium concentration increased 15% and the renal clearance decreased by approximately 20%. These effects have been attributed to inhibition of renal prostaglandin synthesis by the NSAID. Thus, when NSAIDs and lithium are administered concurrently, subjects should be observed carefully for signs of lithium toxicity.
NSAIDs have been reported to competitively inhibit methotrexate accumulation in rabbit kidney slices. This may indicate that they could enhance the toxicity of methotrexate. Caution should be used when NSAIDs are administered concomitantly with methotrexate.
The effects of warfarin and NSAIDs on GI bleeding are synergistic, such that users of both drugs together have a risk of serious GI bleeding higher than users of either drug alone.
In a single dose study (n=6), ingestion of an antacid containing 1.7-gram of magnesium hydroxide with 500-mg of mefenamic acid increased the Cmax and AUC of mefenamic acid by 125% and 36%, respectively.1
Drug/Laboratory Test Interactions
A false-positive reaction for urinary bile, using the diazo tablet test, may result after mefenamic acid administration. If biliuria is suspected, other diagnostic procedures, such as the Harrison spot test, should be performed.
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.
Read the Ponstel Drug Interactions Center for a complete guide to possible interactions
Last reviewed on RxList: 3/25/2008
This monograph has been modified to include the generic and brand name in many instances.
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