BIOAVAILABILITY OF INTRANASAL SCOPOLAMINE IN NORMAL SUBJECTS

The bioavailability of scopolamine in three dosage forms was compared in 12 healthy nonsmoking male volunteers. Subjects received 0.4-mg dos es of scopolamine bromide in intravenous (IV), intranasal (IN), or ora l (PO) dosage forms on three occasions, with at least 2 weeks separati ng the doses. Scopolamine concentrations in plasma were determined wit h a combined reverse-phase liquid chromatographic-radioreceptor bindin g assay. Saliva volume and flow rate and percent suppression of contro l flow rate were determined from each sample. Absorption after IN and PO scopolamine administration was rapid; plasma concentrations [1680 ( IN) and 164 pg/mL (PO)] peaked within 1 h of dosing [0.37 (IN) and 0.7 8 h (PO)], respectively. IN and IV scopolamine suppressed salivary flo w rate to similar extents (95% and 99.7%), respectively. Times to reac h maximum effect were 1.05 and 0.27 h after IN and IV dosage, respecti vely. Absolute intranasal bioavailability, calculated from the area un der the drug concentration vs time curve, was found to be significantl y greater than that of PO scopolamine (83% vs 3.7%, p < 0.05). The IN route may provide a noninvasive, reliable, fast, and effective route f or administering scopolamine.