Effect of catechin and commercial preparation of green tea essence on the pharmacokinetics of l-dopa in rabbits.

The aim of this study was to investigate drug interactions of L-dopa/carbidopa with catechin and green tea essence in rabbits following the simultaneous administration via an intramuscular injection of catechin or via an intragastric route for green tea essence with L-dopa/carbidopa. The results indicated that catechin at doses of 10, 20 and 50 mg/kg increased the area under the plasma concentration-time curve from time zero to the time of the last quantifiable concentration (AUC0-t ) of L-dopa by about 69, 78 and 42%, respectively. The metabolic ratios of the AUC0-t for 3-O-methyldopa (3-OMD)/L-dopa significantly decreased by about 56, 68 and 76% (P < 0.05), respectively. In addition, a single dose of 5/1.25 mg/kg L-dopa/carbidopa was co-administrated with 150 mg/kg green tea essence via an intragastric route with an oral-gastric tube. Comparing the related pharmacokinetic parameters of L-dopa, the clearance and metabolic ratio of L-dopa decreased by 20 and 19% (P < 0.05), respectively. In conclusion, catechin and green tea essence can significantly affect the metabolism of L-dopa by the catechol-O-methyltransferase (COMT) metabolic pathway. Catechin can enhance L-dopa bioavailability, and both catechin and green tea essence decreased 3-OMD formation. Therefore, catechin and green tea essence may increase L-dopa efficacy for Parkinson's disease treatment.

Pharmacokinetics of dinalbuphine sebacate and nalbuphine in human after intramuscular injection of dinalbuphine sebacate in an extended-release formulation.

Nalbuphine is a semi-synthetic opioid indicated for the relief of moderate to severe pain. Its short half-life requires frequent injections in clinical practice, resulting in a greater incidence of adverse events. A prodrug of nalbuphine has been developed, dinalbuphine sebacate (DNS), dissolved in a simple oil-based injectable formulation, which could deliver and maintain an effective blood level of nalbuphine. An open-label, prospective, two-period study was performed in healthy volunteers to verify the extended blood concentration profile of nalbuphine. Twelve healthy Taiwanese were randomized to receive an intramuscular injection of 20 mg nalbuphine HCl and 150 mg DNS sequentially with a washout period of 5 days. To prevent DNS hydrolysis during sample analysis, the effect of four esterase inhibitors was evaluated in the quantitation of DNS in human whole blood and thenoyltrifluoroacetone was chosen. The bioavailability of nalbuphine from intramuscularly injected DNS relative to that from nalbuphine HCl was 85.4%. The mean absorption time of nalbuphine from DNS was 145.2 h. It took approximately 6 days for the complete release of DNS into the blood stream where DNS was rapidly hydrolysed to nalbuphine; suggesting a single injection of 150 mg DNS in our extended-release formulation could provide long-lasting pain relief.