Mefenamic acid.txt

CLINICAL USE

NSAID:Mild to moderate rheumatic pain Dysmenorrhoea and menorrhagia

DOSE IN NORMAL RENAL FUNCTION

500 mg 3 times a day

PHARMACOKINETICS

Molecular weight &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp :241.3

%Protein binding &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp :99

%Excreted unchanged in urine &nbsp &nbsp : 6

Volume of distribution (L/kg) &nbsp &nbsp &nbsp :1.06

half-life – normal/ESRD (hrs)&nbsp &nbsp &nbsp : 2–4/Unchanged

DOSE IN RENAL IMPAIRMENT

GFR (mL/MIN)

20 to 50 &nbsp &nbsp : Dose as in normal renal function, but avoid if possible

10 to 20 &nbsp &nbsp : Dose as in normal renal function, but avoid if possible

<10 &nbsp &nbsp &nbsp &nbsp &nbsp : Dose as in normal renal function, but only use if on dialysis

DOSE IN PATIENTS UNDERGOING RENAL REPLACEMENT THERAPIES

CAPD &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp:Unlikely to be dialysed. Dose as in normal renal function.

HD &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp :Not dialysed. Dose as in normal renal function.

HDF/high flux &nbsp :Unknown dialysability. Dose as in normal renal function.

CAV/VVHD &nbsp &nbsp &nbsp:Unlikely to be dialysed. Dose as in GFR 10 to 20 mL/min

IMPORTANT DRUG INTERACTIONS

Potentially hazardous interactions with other drugsACE inhibitors and angiotensin-II antagonists: antagonism of hypotensive effect; increased risk of nephrotoxicity and hyperkalaemia

Analgesics: avoid concomitant use of 2 or more NSAIDs, including aspirin (increased side effects); avoid with ketorolac (increased risk of side effects and haemorrhage)

Antibacterials: possibly increased risk of convulsions with quinolones

Anticoagulants: effects of coumarins enhanced; possibly increased risk of bleeding with heparins and coumarins

Antidepressants: increased risk of bleeding with SSRIs and venlafaxineAntidiabetic agents: effects of sulphonylureas enhanced

Anti-epileptics: possibly increased phenytoin concentration

Antivirals: increased risk of haematological toxicity with zidovudine; concentration possibly increased by ritonavir

Ciclosporin: may potentiate nephrotoxicity Cytotoxic agents: reduced excretion of methotrexate; increased risk of bleeding with erlotinib

Diuretics: increased risk of nephrotoxicity; antagonism of diuretic effect; hyperkalaemia with potassium-sparing diuretics

Lithium: excretion decreased Pentoxifylline: increased risk of bleeding

Tacrolimus: increased risk of nephrotoxicity

ADMINISTRATION

Reconstition

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Route

Oral

Rate of Administration

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Comments

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OTHER INFORMATION

As with other prostaglandin inhibitors, allergic glomerulonephritis has occurred occasionally. There have also been reports of acute interstitial nephritis with haematuria and proteinuria and occasionally nephrotic syndromeInhibition of renal prostaglandin synthesis by NSAIDs may interfere with renal function, especially in the presence of existing renal disease – avoid use if possible; if not, check serum creatinine 48–72 hours after starting NSAID – if raised, discontinue NSAID therapyUse with caution in renal transplant recipients (can reduce intrarenal autocoid synthesis)Use normal doses in patients with CKD 5 on dialysis if they do not pass any urine.

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