Pharmacokinetic study of neostigmine after intranasal and intravenous administration in the guinea pig.

It is well known that the nasal route may be an effective alternative to the administration of drugs poorly absorbed via oral administration. Thus an investigation of neostigmine bioavailability after nasal administration was undertaken. The neostigmine kinetic profiles after nasal and intravenous administration in the guinea pig have been compared, and results indicate good nasal absorption of neostigmine. At the same dose, no significant differences have been noticed between the two administration routes, as the area under the curve and the bioavailability index is close to 100%. Moreover nasal administration shows a longer plasmatic elimination compared with the i.v. route (t1/2 beta e.n. = 160.04 min; t1/2 beta i.v. = 23.35 min). Nasal absorption is observed to be dose-related. The present results suggest that nasal administration of neostigmine may be an effective clinical means in Myasthenia gravis therapy.