Validation of a simplified method for determination of cimetidine in human plasma and urine by liquid chromatography with ultraviolet detection

A HPLC method was developed for determination of cimetidine in human plasma and urine. Plasma samples were alkalinized followed by liquid extraction with water-saturated ethyl acetate then evaporated under nitrogen. The extracts were reconstituted in mobile phase and injected onto a C18 reversed-phase column; UV detection was set at 228 nm. Urine samples were diluted with an internal standard/mobile phase mixture (1:9) prior to injection. The lower limit of quantification in plasma and urine were 100 ng/ml and 10 μg/ml, respectively; intra- and inter-day coefficients of variation were ≤4.2%. Advantages of this validated assay include a readily available internal standard, simplified plasma extraction and urine dilution methods, and applicability to clinical studies investigating the renal handling of cimetidine.