Determination of therapeutic serum concentrations of oral and parenteral meperidine by liquid chromatography

Abstract

A sensitive and specific method for estimation of serum meperidine by gas-liquid chromatography and its application in a clinical study are described. Patients were given, under double-blind conditions, either oral (75 or 150 mg) or intramuscular (50 or 100 mg) doses of meperidine for postoperative analgesia. Serum meperidine levels were measured 0.5, 1, 2, 3, and 4 hours post-dose. Although wide variations of serum meperidine levels were observed among individuals within each group for each time period, the intramuscular route produced and sustained significantly higher serum levels than did the oral route. The mean concentration of meperidine (mug/100 ml +/- S.E.) for 100 mg i.m. was 37.7 +/- 3.8 at one hour and 23.4 +/-5.7 at three hours; for 150 mg orally it was 11.9 +/- 1.6 at one hour and 11.8 +/- 3.2 at three hours. A correlation observed between the intramuscular dose (in mg/kg body weight) and serum meperidine concentration attained at one hour indicated that 1 mg/kg meperidine i.m. will achieve a one-hour serum level of approximately 20 mug/100 ml, an apparent minimally effective level for analesia in most patients.