Pharmacology
Permanent URI for this community
Browse
Browsing Pharmacology by Author "Binyane, Moleboheng Emily"
Now showing 1 - 1 of 1
Results Per Page
Sort Options
Item Open Access The effect of the traditional medicine phela on p-glycoprotein and multidrug resistance-associated protein 2 drug transporters in the gastrointestinal tract of a rat model(University of the Free State, 2015-11) Binyane, Moleboheng Emily; Walubo, A.English: Phela is the herbal preparation of four African traditional medicinal plants, and is under the development by the Medical Research Council (MRC) as an immune stimulant for immune compromised individuals. Patients might use Phela with other medicines; therefore, the herb-drug interactions profiling of Phela is important. Membrane drug-transporters such as P-glycoprotein (P-gp) and multidrug resistance-associated protein 2 (MRP2) are considered important factors in determining the pharmacokinetic parameters of drugs such as paclitaxel (PTX) and methotrexate (MTX), respectively. Inhibition or induction of transport might result in drug interactions with other drugs transported by these respective transporters. Moreover, significant herb-drug interactions involving P-gp and MRP2 have been described. Therefore, the effect of Phela on P-gp and MRP2 in the gastrointestinal tract of a rat model was investigated here. First, a high performance liquid chromatography (HPLC) method for determination of PTX in plasma was developed. It involved liquid-liquid extraction of 100 μl plasma, spiked with PTX, extracted with diethyl ether: dichloromethane (2:1), followed by centrifugation. The supernatant was evaporated to dryness under a stream of nitrogen, reconstituted, and 100 μl was injected into the HPLC. The sample was eluted with a mobile phase of sodium phosphate buffer (pH 2): acetonitrile (60:40, v/v) over a C8 (1) (4.6 X 250 mm) 5 μ analytic column at 1 ml/min. PTX was detected by UV at 230 nm. Docetaxel (DTX) was used as the internal standard. Under these conditions, DTX and PTX eluted at retention times of 6.595 and 6.038 minutes, respectively. The average calibration curve (0-15 μg/ml) was linear with a regression equation of y = 0.1931x + 0.0705, and correlation coefficient (r) of 0.9973. The method was used successfully in animal experiments to measure PTX in the plasma of treated rats. Thereafter, a preliminary experiment was conducted in vitro to establish whether Phela has a direct/ physical effect on PTX, using a direct drug interaction testing experiment in buffer, as well as Slide-A-Lyzer® dialysis. During the direct drug interaction experiment, buffer was spiked with 10 μg/ml of PTX with or without 3.85 mg/ml Phela, and PTX concentrations were determined by HPLC. Then, using a Slide-A-Lyzer® dialysis cassette, the time of equilibrium of PTX was determined by monitoring the changes in PTX concentrations over 12 hours, in plasma containing 230 μg/ml PTX and buffer. Thereafter, the potential of an interaction was tested by adding 88.55 mg/ml Phela to the same experiment after 8 hours of incubation, and monitoring PTX concentrations after 10 and 12 hours by HPLC. In the first experiment, Phela had no direct effect on PTX concentrations, while in the second experiment the time of equilibrium of PTX was estimated at 8 hours. After Phela was added, PTX concentrations and its free fraction (fu) remained unchanged. Therefore, it was concluded that there is no interaction between Phela and PTX in vitro. This final part of the study was undertaken to investigate the effect of Phela on P-gp and MRP2 transporters. PTX and cyclosporin A (CyA) were used as the respective substrate and inhibitor of P-gp, while MTX and probenecid (PRO) were those of MRP2. Ethical approval was obtained and male Sprague-Dawley (SD) rats (200-250 g) were used. The animal experiment was divided into two parts. In Part I, three groups of 40 rats each received a one-off oral dose of PTX-only (10 mg/kg); PTX & CyA (10 mg/kg); or PTX & Phela (15.4 mg/kg), while in Part II, three groups of 40 rats each received a one-off oral dose of MTX-only (10 mg/kg); MTX & PRO (20 mg/kg); or MTX & Phela (15.4 mg/kg). For each group, 5 rats were sacrificed after 0.5, 1, 2, 4, 6, 8, 10, and 12 hours. Blood was analysed for full blood count, liver function, and PTX and MTX concentrations. CyA and PRO increased the area under the plasma concentration-time curve (AUC) of PTX and MTX, respectively, whereas Phela had no effect on the AUC of PTX or MTX. Overall, no direct interaction between PTX and Phela was observed both in vitro and in vivo, and there were also no interactions between MTX and Phela in vivo. Phela did not inhibit P-gp or MRP2. This implies that Phela will most probably not be involved in herb- drug interactions of membrane transporter origin. Therefore, the doses of drugs that are transported by P-gp and MRP2 need not be adjusted when co-administered with Phela.