Stereoselective pharmacokinetics and tissue distribution of levodropropizine after administration of pure levodropropizine and the rac-dropropizine to Sprague-Dawley rats.

Levodropropizine (LDP) is a non-opioid anti-tussive. The stereoselective pharmacokinetics and tissue distribution (TD) of LDP vs. dextrodropropizine (DDP) have been characterized after oral and intravenous (IV) administration of LDP and rac-dropropozine in rats.Oral/IV doses of 50/5.0 mg/kg and 25/2.5 rac-dropropizine and LDP were employed. TD study focused on tissues such as liver, lung and kidney. Blood samples were collected for pharmacokinetic and TD evaluation. Validated methods were used to quantitate LDP, DDP and rac-dropropizine.No stereoselectivity in pharmacokinetics was observed between LDP vs. DDP following rac-dropropizine. However, LDP pharmacokinetics after LDP administration (oral/IV) appeared to be different compared to LDP derived from rac-dropropizine.TD data were similar between the two enantiomers regardless of oral/IV rac-dropropizine administration. When LDP alone was administered, levels were comparable to those derived for LDP from rac-dropropizine after oral/IV. However, in the lung and kidney tissues, the exposure after oral dosing was higher for LDP alone as compared to LDP from rac-dropropizine.In summary, complete characterization of stereoselective pharmacokinetics and TD of rac-dropropizine has been reported after oral/IV routes. It was evident that the presence of DDP, increased the plasma/tissue exposure of LDP which was evident after oral rac-dropropizine dosing.