Sensitive LC‐MS/MS‐ESI method for simultaneous determination of nifedipine and atenolol in human plasma and its application to a human pharmacokinetic study

A rapid, simple, sensitive and selective LC-MS/MS method has been developed and validated for quantification of nifedipine (NF) and atenolol (AT) in human plasma (250 μL). The analytical procedure involves a one-step liquid-liquid extraction method using carbamazepine as an internal standard (IS). The chromatographic resolution was achieved on a Hypurity Advance C(18) column using an isocratic mobile phase consisting of 5 mm ammonium acetate-acetonitrile (15:85, v/v) at flow rate of 1.0 mL/min. The LC-MS/MS was operated under the multiple-reaction monitoring mode using electrospray ionization. The total run time of analysis was 2 min and elution of NF, AT and IS occurred at 0.79, 1.04 and 0.76 min, respectively. A detailed method validation was performed as per the FDA guidelines and the standard curves found to be linear in the range of 1.02-101 ng/mL for NF and 5.05-503 ng/mL for AT, with a coefficient of correlation of ≥ 0.99 for both the drugs. NF and AT were found to be stable in a battery of stability studies, viz. bench-top, auto-sampler and repeated freeze-thaw cycles. The validated assay method was successfully applied to a pharmacokinetic study in humans.