EFFECT OF GREEN TEA (CAMELLIA SINENSIS) ON THE PHARMACOKINETIC PROFILE OF CEPHALEXIN IN HEALTHY HUMAN VOLUNTEERS

EFFECT OF GREEN TEA (CAMELLIA SINENSIS) ON THE PHARMACOKINETIC PROFILE OF CEPHALEXIN IN HEALTHY HUMAN VOLUNTEERS

ABSTRACT

Tea is a herb commonly consumed globally. Herbs are often taken concurrently with conventional medicines which results in increased potential of drug-herb interactions, and this may have important clinical significance based on an increasing number of reports of such interactions. This research work, determines the effects of green tea (Camellia sinensis) on the pharmacokinetic profile of cephalexin in healthy human volunteers. Quality control studies were conducted on a sample of cephalexin (500 mg) capsule to establish identity, weight uniformity, disintegration time, dissolution, and as well as assay using the methods of BP 1993 and BP 2013.A UV spectrophotometric method for determining cephalexin in plasma using water as a solvent at pH 4 was developed and validated based on international conference on harmonization (ICH) guidelines. For the in vivo study, six apparently healthy human volunteers were used throughout the study. The study involved four phases with one week washout period between the phases; phase I (administration of cephalexin alone), phase II (concurrent administration of cephalexin with aqueous extract of green tea), phase III (administration of cephalexin one hour after ingestion of aqueous extract of green tea) and phase IV (administration of cephalexin one hour before ingestion of aqueous extract of green tea). Blood samples (2 mL) were collected in a heparinized sample bottles from each of the six volunteers at 0, 0.5, 1, 2, 3, 4 and 6 hours. Plasma proteins were precipitated using 20 µL of 40 % perchloric acid, followed by centrifugation and buffering of the supernatant with 1 ml phosphate buffer pH 4, and subsequently volumes were adjusted to 5 ml with distilled water. Samples were analysed for cephalexin content using the developed UV method and pharmacokinetic parameters generated for each of these phases. The results of quality control studies revealed that the cephalexin 500 mg capsule passed the test. It was found to contain the labeled active pharmaceutical ingredient and results for uniformity of weight, dissolution, and desintegration time were within the accepted range of 92.5 - 110 % , ˂ 7.5 %, ≥ 90 % and ˂ 15 minutes respectively. The calibration curve was found to be linear within the range of 5 - 150 µg/mL as its coefficient of determination (r2 = 0.9994) close to unity with a regression equation of y = 0.0045 - 0.0178. UV spectral analysis revealed 261 nm as the wavelength of maximum absorption of cephalexin in water at pH 4. Percentage recovery was found to be 84.5 - 85.5 % which is outside the accepted range of 98 - 102 %. The mean plasma concentration of cephalexin in phase I were found to be 13.50, 69.00, 58.60, 48.00, 42.60 and 12.40 (µg/mL) at time 0.5, 1, 2, 3, 4 and 6 (hours) respectively. The Cmax (µg/mL) for phases I, II, III and IV were found to be 69.00, 79.95, 68.00 and 87.07 (µg/mL) respectively at time 1 hour (Tmax) except for phase III with Tmax of 2 hours. Their AUCs were found to be 235172, 302982, 354333 and 244449 µg/L*h respectively. With the exception of Tmax of phase II and IV, Cmax of phase III, and also the clearance (Cl) of phase IV, all other pharmacokinetic parameters of phases II, III and IV determined were found to be significantly different (p ˂ 0.05) from those of phase I (control) . Therefore, it can be concluded that Camellia sinensis (green tea) aqueous extract was found to significantly (p ˂ 0.05) enhance the extent and the rate of absorption, decreased elimination rate of cephalexin as well as increase in its volume of distribution to the peripheral compartments.

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