Design-assisted HPLC-UV method for therapeutic drug monitoring of pholcodine, ephedrine, and guaifenesin in biological fluids

Abstract

Drug-drug interactions may amplify or diminish their intended effects, or even produce entirely new effects. Multicomponent mixture HPLC analysis offers a thorough and effective method for comprehending the makeup and behavior of complicated materials, advancing research and development across a range of scientific and industrial domains. A novel experimental design-assisted HPLC methodology for the concurrent investigation of the drug-drug interaction of pholcodine, ephedrine, and guaifenesin in biological fluids has been established. Rather than the routine methodology, the application of the factorial design-HPLC method offers a powerful and efficient tool for the analysis of these compounds. Both mixed and full factorial designs were employed to assess the impact of variable factors on chromatographic results. Utilizing an isocratic elution mode on a C₁₈ column, the chromatographic separation was carried out. 15% Methanol, 5% acetonitrile, and 80% phosphate buffer with 0.1%(v/v) triethylamine set to pH 3 make up the mobile phase flowing at rate 1.0 mL/min. The calibration curves of the drugs show excellent linearity over a concentration ranges: 0.20-13.0 µg/mL for PHO, 0.50-20.0 µg/mL for EPH and 0.70-20.0 µg/mL for GUA with LOQ values of 0.18, 0.38 and 0.50. The fast separation and quantitation in less than 6 min is an advantage. Also, the method includes a robust sample preparation protocol for the analysis of complex biological samples, ensuring high selectivity and precision. The ease, speed and cost-effectiveness of the method are ideal for supporting in vitro studies, including drug-drug interaction investigations, especially in bioanalytical labs.

Keywords: Drug interactions; Ephedrine; Experimental design; Guaifenesin; Pholcodine.

Fig. 1

The structural formulae of the studied drugs. (A) pholcodine (B) ephedrine (C) guaifenesin.

Fig. 2

Absorption spectra of the three drugs where (a) is EPH, (b) PHO and (c) is GUA (5 µg/mL each).

Fig. 3

a Optimization plot showing the optimum ratio of the mobile phase using the mixture design. b 2³ FFD Optimization plot showing optimum chromatographic conditions using full factorial design.

Fig. 4

a mobile phase. b Typical chromatogram under the specified chromatographic conditions (1): PHO (10.0 µg/mL). (2): EPH (10.0 µg/mL) (3): GUA (10.0 µg/mL).

Fig. 5

a Blank plasma. b Typical drug chromatogram in spiked human plasma at the specified chromatographic conditions: (1): plasma peak (2): PHO (0.5 µg/mL). (3): EPH(1.0 µg/mL) (4): GUA (1.0 µg/mL).