Combined effect of rifampicin-induced P-glycoprotein expression and lipopolysaccharide-induced intestinal sepsis on the effective permeability and pharmacokinetics of an anti-malarial candidate CDRI 97/78 in rats.

1. The study aimed to investigate the influences on the pharmacokinetics (PK) of an anti-malarial drug 97/78 in rats pretreated with orally administered rifampicin and bacterial endotoxin lipopolysaccharide (LPS). 2. In-situ intestinal absorption studies were conducted on rats pretreated with rifampicin and LPS or both to estimate effective permeability (Peff) of 97/78. In-vivo studies were then conducted to explore 97/78 PK profile under these conditions. In-situ studies revealed that Peff value decreased to 64% (2.7 ± 0.6) × 10(-4 )cm/s in rats pretreated with rifampicin. This decrease was further enhanced very significantly to 4.5% (0.19 ± 0.03) × 10(-4 )cm/s in rats pretreated both with rifampicin and LPS (p<0.05). For PK studies, it was found that relative bioavailability (RB) was decreased to 22.56% in rifampicin-pretreated rats and to 8.02% in rats pretreated both with rifampicin and LPS. About five-fold decrease was observed in systemic exposure (AUC) of 97/78 in rifampicin-pretreated rats. This decrease was further augmented to 12-fold upon rifampicin and LPS pretreatment. 3. Orally administered rifampicin decreased the concentration of 97/78 in circulation. This decrease was further enhanced significantly to a very low level by LPS-induced intestinal sepsis.

Determination of metabolic profile of novel triethylamine containing thiophene S006-830 in rat, rabbit, dog and human liver microsomes.

CDRI S006-830 is a potent triethylamine containing thiophene antitubercular compound of the Central Drug Research Institute, India. The present study aimed to conduct comprehensive metabolic investigations of CDRI S006-830 to corroborate its preclinical investigations. Preliminary metabolic investigations were performed to assess the metabolic stability, enzyme kinetics, reaction phenotyping, and metabolite identification of CDRI S006-830 in rat, rabbit, dog, and human liver microsomes using liquid chromatography with mass spectrometry. The observed in vitro t1/2 and Clint values were 9.9 ± 1.29, 4.5 ± 0.52, 4.5 ± 0.86, 17 ± 5.21 min and 69.60 ± 8.37, 152.0 ± 17.26, 152.34 ± 27.63, 33.62 ± 21.04 µL/min/mg in rat, rabbit, dog and human liver microsomes respectively. These observations suggested that CDRI S006-830 rapidly metabolized in the presence of NADPH in liver microsomes of rat, rabbit and dog while moderately metabolized in human liver microsomes. It was observed that CDRI S006-830 exhibited monophasic Michaelis-Menten kinetics. The metabolism of CDRI S006-830 was primarily mediated by CYP3A4 and was deduced by CYP reaction phenotyping with known potent inhibitors. CYP3A4 involvement was also confirmed by cDNA-expressed recombinant human isozyme activity with different CYPs. Four major phase-I metabolites of S006-830, (M-1 to M-4) were detected in rat, rabbit, dog (except M4) and human liver microsomes.

Rifabutin reduces systemic exposure of an antimalarial drug 97/78 upon co-administration in rats: An in-vivo &in-vitro analysis.

OBJECTIVE: To determine the potential drug-drug interactions between anti-malarial candidate 97/78 and anti-tubercular drug rifabutin in-vivo in rats followed by in-vitro investigation of the underlying mechanisms of drug interaction. METHODS: Single oral dose study was conducted in male and female rats at 40 mg/kg and 70 mg/kg for 97/78 and rifabutin respectively. RESULTS: It was reported that rifabutin co-administration altered pharmacokinetics of 97/63 (active metabolite of 97/78). A significant decrease was reported in the systemic exposure of 97/63 by a factor of 3-4. The AUC0-last values were (4.03 ± 0.60) and (5.44 ± 1.15) µg h mL(-1) upon 97/78 administration alone, while the values were decreased to (1.13 ± 0.10) and (1.23 ± 1.13) µg h mL(-1) upon rifabutin co-administration in male and female rats respectively. Statistically significant differences were also reported in Cmax and Tmax values upon rifabutin co-administration. In-vitro drug metabolism study in rat liver microsomes has shown that the metabolism of 97/63 was increased by 10%-12% upon rifabutin co-incubation. The extent of plasma protein binding of 97/63 was found to be decreased from 54%-55% to 6%-8% upon rifabutin addition. CONCLUSIONS: It was concluded that rifabutin co-administration altered PK parameters of 97/63 in SD rats. However, no intersex influences were reported in the interaction pattern. The results obtained in the in-vivo study were well correlated with the in-vitro findings and can further be applied to explore other aspects of potential drug interactions between these two drugs.

UFLC method development and validation of a novel triethylamine containing thiophene S006-830 - an antitubercular molecule and its application to pharmacokinetic and bioavailability studies in SD rats.

A sensitive and selective ultra fast liquid chromatography (UFLC) method has been developed and validated for the determination of a potent and novel antitubercular compound S006-830 in Sprague Dawley (SD) rat plasma. Samples were extracted and processed by protein precipitation method using acetonitrile. Chromatographic separation was achieved on a Phenomenex, Luna C-18 column (3µm, 100mm x 2mm i.d.) under isocratic condition. Detection was performed on UFLC-NEXERA system (LC-30AD, Shimadzu, Kyoto, Japan) with a degasser (DGU-20A), auto-injector (SIL-30AC), fixed with a 100-µL loop. Method was found sensitive and reproducible over a linearity range of 15.6-2000 ng/mL. Recovery of S006-830 and internal standard was found >90% for spiked matrix control and standard quality control plasma samples. This validated method was successfully applied to generate pharmacokinetic profile of S006-830 in SD rats. Oral dose proportionality studies were conducted at 100, 50, 25 mg/Kg dose levels, while an IV study was conducted at 25 mg/Kg dose. There was dose dependent increase in AUC and Cmax indicating S006-830 to exhibit linear pharmacokinetics. S006-830 exhibited favorable bioavailability in the range of 45-55%.

Time Course of the Changes in Novel Trioxane Antimalarial 99/411 Pharmacokinetics upon Antiepileptic Drugs Co-Administration in SD Rats.

Objective. The study aimed to evaluate the influences of coadministration of antiepileptic drugs (AEDs) on an antimalarial candidate 99/411 pharmacokinetic (PK) profile. Method. For this, single oral dose PK drug interaction studies were conducted between 99/411 and FDA approved AEDs, namely, Phenytoin (PHT), Carbamazepine (CBZ), and Gabapentin (GB) in both male and female SD rats, to assess the coadministered and intersexual influences on 99/411 PK profile. Results. Studies revealed that there were no significant alterations in the PK profile of 99/411 upon PHT and CBZ coadministration in both male and female rats, while systemic exposure of 99/411 was significantly increased by about 80% in female rats upon GB coadministration. In terms of AUC, there was an increase from 2471 ± 586 to 4560 ± 1396 ng·h/mL. Overall, it was concluded that simultaneous administration of AEDs with 99/411 excludes the requirements for dose adjustment, additional therapeutic monitoring, contraindication to concomitant use, and/or other measures to mitigate risk, except for GB coadministration in females. These findings are further helpful to predict such interactions in humans, when potentially applied through proper allometric scaling to extrapolate the data.