Spectrophotometric determination of mefenamic acid excreted as free drug in urine of human beings

Urinary excretion of free mefenamic acid was investigated in 16 healthy human volunteers, eight males and eight females, following the oral administration of 500 mg tablet of mefenamic acid. Urine samples were collected at pre-determined schedule and drug concentration was determined by spectrophotometric method. The total recovery of free mefenamic acid was 1.526 +- 0.128 and 1.193 +- 0.112% in male and female volunteers respectively. The average +- S.E values for diuresis, pH and rate of excretion of mefenamic acid was 0.0160 +- 0.004 mL/min./kg of body weight, 6.22 +- 0.167, 0.077 +- 0.016 micro g min/sup -1/kg/sup -1/in male while 0.0084 +- 0.0023mL min/sup -1/kg-1 of body weight, 6.35 +- 0.164, 0.054 +- 0.008 micro g min/sup -1/kg/sup -1/respectively in female volunteers. The results obtained are different from the earlier studies due to variability in dose, gender variation, fluctuation in urine pH, environmental conditions and nutritional ingredients. (author)