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Rabeprazole analysis in human plasma by fully validatedHPLCassay

Rajaa Farhan Hussein, Muhammad M.Hammami

Asimple, rapid, and precise high performance liquid chromatography (HPLC) assay for rabeprazole measurement in human plasma was developed, validated, and used to study the stability of rabeprazole under various laboratory conditions.After extractionwith the tert. butylmethyl ether, rabeprazole and lansoprazole (internal standard, IS) were separated at 4.8 and 8.7 minutes, respectively, on a Nova-Pak C18 cartridge at room temperature (RT), and detected by a photodiode array detector set at 284nm. The mobile phase consisted of 0.05% dibasic sodium phosphate, acetonitrile, and triethylamine (65:35:0.005, v: v: v) and the run time was 10min. The response was linear over the range of 0.01-1.60 µg/ml. Extraction recovery and intraand inter-run bias were  90% (mean 92%), ï‚£9% and <10%, respectively. Rabeprazole was stable in plasma for 24 h at RT ( 92%), 10weeks at -20ï‚°C ( 95%), and after 3 cycles of freeze at -20ï‚°C and thaw at RT (100%). In extracted samples, rabeprazole was stable for 24 h at RT ( 93%) and 48 h at -20ï‚°C ( 92%). Rabeprazole stock solution (1mg/ml inmethanol) was stable for 48 h at RT (100%) and 10 weeks at -20ï‚°C (98%). Rabeprazole levelwas 0.26µg/ml five hours after the ingestion of a single 20mg dose. The data indicate that the described assay is suitable for therapeutic drug monitoring and bioequivalence studies in humans.