Rapid-onset intranasal delivery of anticonvulsants: pharmacokinetic and pharmacodynamic evaluation in rabbits.

Intranasal (IN) administration is a promising approach for rapid-onset delivery of medications. In order to assess the feasibility of this approach for the emergency treatment of status epilepticus, three anticovulsants, i.e. diazepam (DZ), clonazepam (CZ), and a monocarbamate-based new compound (MCA) were studied in rabbits for the pharmacokinetics (PK) and pharmacodynamic (PD) response following intravenous (IV) and IN administrations. The animals were intranasally dosed with DZ (1 mg/kg), CZ (0.2 mg/kg), and MCA (5 mg/kg), dissolved in 200 microl of vehicle consisting of propylene glycol (PG), ethanol (EtOH), and water in the presence or absence of 1% sodium glycocholate (SGC) using single and repeated dosing schedules. Both DZ and CZ were absorbed very rapidly from 1% SGC/60% PG-30% EtOH-10% Water after IN single application; the T(max)'s were less than 2 min. The absorption rate of MCA was relatively slower with the peak time of 13-32 min. The bioavailability of single IN administration for DZ, CZ, and MCA determined over the first 2 or 4 h was found to be 77, 45, and 79%, respectively. The peak plasma level of DZ increased linearly with increasing the volume fraction of EtOH in the ternary cosolvent (20% to 60%). A repeated IN application of DZ, 5 min after the first dose, doubled the C(max) and AUC(0-2 h) values of the first one, whereas those of CZ and MCA resulted in an increase of 73-94% of the first dose. A single IN application of DZ- and CZ-containing formulations produced a PD response within 1.5 min, which was comparable to that of an IV injection. These results suggest that single or repeated IN applications of DZ, CZ, and MCA in a hydroalcohol-glycolic formulation might represent a viable approach to achieving a rapid systemic absorption of these anticonvulsants during the emergency treatment of status epilepticus and other types of seizures.