RESUMEN
A high-pressure liquid chromatographic procedure was developed to determine the D and L isomers of moxalactam in human plasma and urine. After protein precipitation with hydrochloric acid the sample was extracted with ethyl acetate. It was then back extracted into tromethamine buffer (pH 8.0) and washed with octanol. Extraction recovery from plasma ranged from 73-81%. An aliquot of the tromethamine buffer was then injected onto a C18-muBondapak column. The mobile phase was 3% acetonitrile in 0.05 M ammonium acetate pH 6.5 buffer. Samples were quantitated by UV detection at 275 nm and 0.01 aufs. The lower limit of detection was 0.5 microgram/ml for each isomer. Preliminary stability studies were performed to assess proper sample handling and storage conditions. The procedure was evaluated in a clinical setting to demonstrate its applicability to the study of moxalactam pharmacokinetics in critically ill patients.
Asunto(s)
Cefalosporinas/metabolismo , Cefamicinas/metabolismo , Cromatografía Líquida de Alta Presión/métodos , Estabilidad de Medicamentos , Humanos , Cinética , Moxalactam , Estereoisomerismo , Factores de TiempoRESUMEN
We describe a liquid-chromatographic procedure for determination of cimetidine, its hydroxymethyl-, sulfoxide-, and guanyl urea metabolites, and creatinine in patients serum and urine. SKF 92374 is used as the internal standard. Protein in 0.5 mL of serum or diluted urine is precipitated with 2 mL of acetonitrile, the organic and aqueous phases are separated by adding 0.3-0.5 g of anhydrous K2HPO4. The organic phase is evaporated, and 0.5 mL of 50 mmol/L HCl is added. This solution is washed with 3 mL of water-saturated isoamyl alcohol, the aqueous phase is extracted with 3 mL of methylene chloride and enough K2HPO4 to saturate the solution. The methylene chloride is evaporated, the residue reconstituted with 100 microL of mobile phase, and a 25-microL aliquot injected onto the chromatographic column (Dupont Sil). The mobile phase is acetonitrile/methanol/water/ammonium hydroxide (1000/50/50/2, by vol). The column effluent is monitored at 228 nm. Lower limits of detection ranged from 0.05 mg/L for cimetidine to 0.2 mg/L for guanyl urea. We determined cimetidine and its principal metabolites in the serum of a patient receiving cimetidine for the treatment of Zollinger-Ellison syndrome, and have assessed use of the assay in a clinical setting.