Determination of abacavir in human plasma by high-performance liquid chromatography with ultraviolet detection and the analytical error function

Stress Degradation Behavior of Abacavir Sulfate and Development of a Suitable Stability-Indicating UHPLC Method for the Determination of Abacavir, its Related Substances, and Degradation Products

A novel, stability-indicating UHPLC method was developed for the quantitative determination of Abacavir sulfate, its related substances, and forced degradation impurities in bulk drugs. The chromatographic separation was achieved on a Waters Acquity BEH C₈, 50 mm × 2.1 mm, 1.7 μm particle size column with a mobile containing a gradient mixture of solution A (0.10 % v/v o-phosphoric acid in water) and solution B (0.10% v/v o-phosphoric acid in methanol). The flow rate was set at 0.40 mL/min and the run time was 6.0 min. The drug substance was subjected to the stress studies of hydrolysis, oxidation, photolysis, and thermal degradation. Abacavir sulfate was found to degrade significantly under acidic hydrolysis and oxidative stress conditions. The formed degradation products were reported and were well-resolved from Abacavir and its related substances. The mass balance was found to be satisfactory in all of the stress conditions, thus proving the stability-indicating capability of the method. The developed UHPLC method was validated to be in agreement with ICH requirements and found to be rapid, accurate, precise, linear, specific, and suitable for the quantitative determination of related substances and degradants in the bulk drug samples of Abacavir sulfate.

[Development and validation of laboratory methods for antiretroviral quantitation using HPLC]

OBJECTIVE

Development, validation and error characterization of three analytical methods, by high performance liquid chromatography (HPLC), for the quantitative analysis of ritonavir, saquinavir and abacavir in human plasma.

METHOD

Reagents and instrumentation used, preparation of different standards, sample extraction procedure from biologic matrix, and analytical conditions assayed were detailed to set up three analytical methods. In addition, the validation and the determination of analytical error were also described.

RESULTS

The analytical methods developed for ritonavir, saquinavir and abacavir in human plasma were selective, linear (r2>0.99), precise (coefficients of variation<15%) and accurate (relative errors<15%) over the concentration range selected. The recovery was more than 95% in all methods. Antiretroviral drugs were stable in the storage conditions assayed according to the routine laboratory. The error function discriminated for each analytical method validated was linear in saquinavir (SD=4.84+7.14.10(-2)C) and abacavir (SD=-1.072+3.70.10(-2)C), and non-linear in ritonavir (SD=39.98+2.40.10(-5)C2).

CONCLUSIONS

Three analytical methods were developed and subsequently validated, with validation parameters being within the specifications and attributes of quality established. The error function characterized for each validated method can be used as a heteroscedastic weighting method in the parameter estimation by non-linear regression analysis in clinical pharmacokinetic studies of antiretroviral drugs assayed.

Development and validation of a reverse-phase liquid chromatographic method for assay and related substances of abacavir sulfate

A simple isocratic liquid chromatographic method was developed for the determination of abacavir from its related substances and assay for the first time. This method involves the usage of C18 (Intertsil octadecyl silane-3V, 150 mm x 4.6 mm, 5 microm) column. The method was validated over the range of 0.002-0.1 mg/mL for chloro impurity, 0.005-0.1 mg/mL for amino impurity and pyrimidine impurity, and 0.005-0.2 mg/mL for abacavir. The mobile phase consists of a mixture of 10 mM ammonium acetate buffer and ACN in the ratio of 90:10. The flow rate was set at 1.0 mL/min with UV detection monitored at 214 nm. The drug substance was subjected to stress conditions of hydrolysis, oxidation, photolysis, and thermal degradation. The developed method was validated for linearity, range, precision, accuracy, and specificity. This method can be conveniently used in a quality control laboratory for routine analysis of both related substances and assay.