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.
Kato
Y
Y
Department of Pharmacy, National Medical Center Hospital, Tokyo, Japan.
Shimokawa
M
M
Yokoyama
T
T
Mohri
K
K
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