The use of polymeric solid phase extraction and HPLC analysis for the determination of ranitidine in routine plasma samples obtained from paediatric patients

A sensitive HPLC method for the determination of ranitidine in small‐volume (0.5 mL) paediatric plasma samples is described. Plasma samples were extracted using a simple, rapid solid phase extraction (SPE) technique developed using disposable copolymer packed SPE cartridges. Chromatographic separation was achieved by reverse‐phase HPLC with isocratic elution using a μBondapak C18 column and a phosphate buffer (10 mm, pH 3.75)‐acetonitrile (87:13 v/v) mobile phase with UV detection at 313 nm. The HPLC system exhibited linearity in the range 8–800 ng mL−1. Intraday % CV and % bias values were in the range 1.28–8.09% (% bias %‐4.33 to %‐0.87) and interday % CV and % bias values were in the range 0.73–15.28% (% bias %‐1.80 to +1.65). The limits of detection and quantitation obtained were 2 ng mL−1 and 8 ng mL−1, respectively, and ranitidine extraction recoveries from plasma ranged from 92.30 to 103.88%. In this study, the developed HPLC and SPE methodologies have been successfully applied to the determination of ranitidine concentrations in 68 paediatric plasma samples. The sampled population was drawn from patients already receiving the study drug therapeutically. Patients recruited had received ranitidine by two main routes ‐ oral and intravenous. The plasma concentrations of ranitidine encountered in paediatric samples following oral or intravenous administration of a range of prescribed doses are presented graphically. These profiles are based on analysis of the first 68 plasma samples obtained from the first 35 patients recruited to the study receiving ranitidine by the oral or intravenous route.