Pharmacokinetic and pharmacodynamic response after intranasal administration of diazepam to rabbits

Nasal application of drugs might be an alternative to intravenous administration in acute situations such as epileptic or fever seizures. In the search for a nasal formulation leading to a peak plasma concentration of diazepam at a t(max) less than or equal to 5 min bioavailability in rabbits has been studied after intranasal administration of the drug in ten vehicles of different polarity. The animals were dosed with 3 mg diazepam, dissolved in 100 mu L vehicle, the solution being administered into both nostrils. The bioavailability, measured during the first 30 min, because periods after this are not relevant for acute treatment, was found to be between 49 and 62% for the four most promising vehicles, pure glycofurol 75, tetraethyleneglycol, poly(ethylene glycol) 200 and 30% glycofurol in tetraethyleneglycol. The t(max) for these vehicles was achieved after 5 min, and they induced a very rapid pharmacodynamic response after 1.5 to 3.5 min. The bioavailability was reduced when more polar liquids such as ethanol and tween 20, or lipid oils, e.g. vegetable oil and miglyol 840 were added to the glycofurol. There was a good correlation between t(max) and the induction of pharmacodynamic response. These results suggest that nasal application of diazepam in a water-free low-molecular-weight glycol might be of clinical importance as an alternative to intravenous injection, especially in acute situations.