The effect of cephalexin in influencing the pharmacokinetics of a novel drug – 5′-valyl-cytarabine hydrochloride

The aim of this study is to investigate the pharmacokinetics of 5′-valyl-cytarabine hydrochloride (OPC) when co-administered with cephalexin, which are both the substrates of PepT1. The drugs were administered orally by gavage. Blood samples were collected from the orbital plexus of the rats after oral administration of drug solutions. A new high-performance liquid chromatographic method was validated and used for determination of the two drugs. Pharmacokinetic parameters were calculated using DAS 2.1.1 software with noncompartmental analysis. After oral administration of OPC and co-administration of OPC and cephalexin, there were significant differences in the main pharmacokinetic parameters. The main pharmacokinetic parameters for the OPC group and the co-administrative group were as follows: AUC(0-10) (18,168.7 ± 2561.4) ng⋅h/ml and (13,448.5 ± 2544.73) ng⋅h/ml, AUC(0-∞) (18,683.1 ± 3066.5) ng⋅h/ml and (13,721.1 ± 2683.0) ng⋅h/ml, C(max) (6654.8 ± 481.3) ng/ml and (4765.1 ± 928.9) ng/ml, respectively. The results showed that the bioavailability of OPC could be reduced when co-administered with cephalexin, suggesting that the efficacy of a novel drug might be reduced when it came to combination use of β-lactam antibiotics.