Development and application of a high-performance liquid chromatographic method for the determination of in vitro drug release of levodopa, carbidopa, and entacapone from a tablet formulation.

A simple, precise, and accurate high-performance liquid chromatographic method was developed and validated to determine percent drug release of levodopa (LEV), carbidopa (CAR), and entacapone (ENT) from its combination dosage form. A mixture of acetonitrile and buffer was used as the mobile phase for reversed-phase liquid chromatographic separation for determination of the in vitro drug release of LEV, CAR, and ENT. A dissolution test was conducted at 75 rpm with United States Pharmacopeia (USP) apparatus-II (paddle) by using pH 5.5 phosphate buffer as a dissolution medium. Three formulations, differing in strength, were evaluated. The developed method was validated for specificity, linearity, precision, accuracy, and solution stability. The specificity of the method was determined in the presence of placebo interference. The method was linear over the drug concentration ranges of 4-210 microg/mL for LEV, 1-52 microg/mL for CAR, and 6-280 microg/mL for ENT. Precision was established by determination of system precision, method precision, and intermediate precision. Accuracy values for the method ranged from 96.8 to 104.3% for LEV, from 97.2 to 101.3% for CAR, and from 99.5 to 102.8% for ENT. The developed method was suitable for estimating percent drug release of LEV, CAR, and ENT in terms of the dissolution test.