Simultaneous determination of amfenac sodium and its metabolite (7-benzoyl-2-oxindole) in human plasma by high-performance liquid chromatography.
A simple, selective, sensitive and rapid high-performance liquid chromatographic method for the simultaneous determination of amfenac sodium (AMF) and its metabolite (7-benzoyl-2-oxindole, S1) in plasma was established. To 100 microliters of plasma, purified water (100 microliters), ammonium sulphate (0.2 g) and ethanol (100 microliters) containing fenbufen (100 micrograms/ml, internal standard) were added. After centrifugation the ethanol layer was directly injected into a reversed-phase ODS column. AMF and S1 were eluted using a gradient buffer system of 20-80% acetonitrile-phosphate buffer (pH 7.0), and detected at 245 nm. The analytical recoveries of AMF at concentrations of 0.5, 2 and 10 micrograms/ml in plasma were ca. 92.1, 95.4 and 94.6%, respectively. The coefficients of variation of the AMF recoveries were below 4.6%. The S1 recoveries at the concentrations of 40, 200 and 400.ng/ml were ca. 93.4, 98.7 and 95.3%, and the coefficients of variation were below 6.0%. The coefficients of variation for intra- and inter-day variation of AMF (5 micrograms/ml) and S1 (100 ng/ml) were 4.5 and 3.6% and 4.2 and 4.2%, respectively. The detection limits of AMF and S1 in plasma were as low as 0.1 microgram/ml and 20 ng/ml, and the coefficients of variation were 4.0 and 4.4%, respectively. The method was applied to determine the plasma concentrations of AMF and S1 after oral administration of AMF capsules (100 mg of AMF) to human volunteers.
Department of Pharmacy, National Medical Center Hospital, Tokyo, Japan.
Y
Y
Kato
M
M
Shimokawa
T
T
Yokoyama
K
K
Mohri
D000284:Administration, Oral; D000328:Adult; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000008:administration & dosage / Q000097:blood* / Q000493:pharmacokinetics; D002214:Capsules; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D007202:Indicators and Reagents; D007211:Indoles / Q000097:blood* / Q000493:pharmacokinetics; D008297:Male; D000078183:Oxindoles; D010648:Phenylacetates / Q000008:administration & dosage / Q000097:blood* / Q000493:pharmacokinetics; D012015:Reference Standards; D013056:Spectrophotometry, Ultraviolet
D000894:Anti-Inflammatory Agents, Non-Steroidal; D002214:Capsules; D007202:Indicators and Reagents; D007211:Indoles; D000078183:Oxindoles; D010648:Phenylacetates; C014285:amfenac; C083310:7-benzoyl-2-oxindole