Pharmacokinetic and clinical evaluation of ketamine administered by i.v. and epidural routes

The evolution of the plasma levels of ketamine and its two biotransformation products, norketamine (metabolite I) and dehydronorketamine (metabolite II) was studied after i.v. and epidural administration at doses of 2 and 5 mg/kg, respectively. The results show a good access capacity of ketamine from the epidural space to the systemic circulation as reflected in the high value of its apparent incorporation constant (ka = 5.54 +/- 2.33 h-1) and its good bioavailability (F = 0.77 +/- 0.22). The evaluation of clinical parameters points to a more attenuated cardiovascular and respiratory response after administration of the anesthetic by the epidural route.