Development and validation of an analytical method for the dosage of clonidine capsule by HPLC-UV

Introduction
Clonidine, a central antihypertensive, is used for the diagnostic of growth hormone deficiency in child but there is not any commercially available oral dosage forms allowing to perform adequate dosing in this population (0.15 mg/m²). Consequently, our unit compounds clonidine capsules from powder. According to the European Pharmacopeia, several assays must be performed to assess quality and security of these preparations. The objective of this work was to develop an analytical method to perform uniformity of content assay on compounded clonidine capsules.

Materials and methods
An analytical method, using HPLC-UV analysis, has been developed to determine clonidine strength in our preparation. Parameters of the method are described as follows: the mobile phase was composed of a mixture of acetonitrile and ultrapure water (25/75; v/v) with 0.1% trifluoroacetic acid and the flow rate was settled at 1 mL/min. The column was a Purospher® STAR RP-18 endcapped (5µm) 150x4.6 mm and the wavelength of the detector was settled at 210 nm. Calibration range of the method varies from 3.125 to 50 µg/mL. Three levels quality controls were realized (3.125; 12.5 and 50µg/mL respectively low, medium and high level). Validation of the method was carried out in accordance with ICH Q2 R(1) international guideline using the following criteria : linearity, accuracy (precision and trueness) and specificity.
The analytical method was applied on a batch of clonidine capsules according to the European Pharmacopeia (2.9.40).

Results/discussion
The retention time of clonidine was found to be 3,30 min.
Calibration curves provided adequate linearity over the calibration range with correlations coefficients greater than 0,9994 and residual value lower than 8.35% The mean equation of the linear regression line was y= 386566(±10851)x + 63579 (± 52891).
Coefficients of variation obtained during repeatability and intermediate precision studies were lower than 3.22 and 4.65% respectively, whatever the quality control assessed. The mean percent recoveries obtained during the trueness study remained close to 100% of the expected value.
Application of the analytical method showed that our batch did not meet the criteria of the EP, demonstrating the interest in developing this analytical method to avoid dosing errors.

Conclusion
The analytical method showed adequate linearity and accuracy, allowing the determination of clonidine content in capsules. The method was successfully applied to the estimation of clonidine due to its simplicity, rapidness (analysis time less than 5min), and high precision. This will allow to perform control on our clonidine capsules and improve the quality of our preparations.

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