Validated liquid chromatographic ultraviolet method for the quantitation of Etoricoxib in human plasma using liquid-liquid extraction.

A simple, sensitive and specific HPLC method with UV detection (284 nm) was developed and validated for quantitation of Etoricoxib in human plasma, the newest addition to the group of nonsteroidal anti-inflammatory drugs-a highly selective cyclooxygenase-2 inhibitor. Following a single-step liquid-liquid extraction with diethyl ether/dichloromethane (70/30, v/v), the analyte and internal standard (Zaleplon) were separated using an isocratic mobile phase of water/acetonitrile (58/42, v/v) on reverse phase Waters symmetry C(18) column. The lower limit of quantitation was 5 ng/mL, with a relative standard deviation of less than 20%. A linear range of 5-2500 ng/mL was established. This HPLC method was validated with between- and within-batch precision of 4.1-5.1% and 1.1-2.4%, respectively. The between- and within-batch bias was -3.8-4.7% and -0.6-9.4%, respectively. Frequently coadministered drugs did not interfere with the described methodology. Stability of Etoricoxib in plasma was >90%, with no evidence of degradation during sample processing (autosampler) and 30 days storage in a freezer. This validated method is sensitive and simple with between-batch precision of <6% and was used in pharmacokinetic studies.