A validated HPLC method for the determination of thiazinamium methylsulphate in pharmaceutical preparations

The phenothiazine derivative thiazinamium methylsulphate is a drug with ant ihistaminic and anticholinergic properties, often used in some types of obs tructive lung diseases. Because there is a lack of chromatographic data ava ilable for its determination, the objective of the present investigation wa s to develop a sensitive and rapid HPLC method for the quantitative estimat ion of thiazinamium methylsulphate in a pharmaceutical dosage form, applica ble to routine analysis. The drug was chromatographed on a C18-reversed pha se system applying a Licrocart column (LiChrospher 100 RP 18, 125 x 4 mm) w ith a mobile phase consisting of acetonitrile-water (3:7, v/v), employing a s ion-pairing agent octanesulphonic acid sodium salt (20 mM) together with N,N-dimethyloctylamine (20 mM), adjusted to pH 3. Detection occurred at 254 nm. Propylparaben was used as an internal standard. The method was applied to solutions for intramuscular injection containing thiazinamium methylsul phate (65 mg/2 ml). Since little sample preparation is required, most analy ses can be carried out within 15 min. The optimized method was validated an d provided acceptable results with respect to linearity (r = 0.9999), preci sion and accuracy in the concentration range of 26-78 mu g/ml. The proposed method is presently employed to investigate the stability of thiazinamium methylsulphate in solutions for intramuscular injection in the presence of anti-oxidizing agents. (C) 2000 Elsevier Science B.V. All rights reserved.