Pharmacokinetics of butorphanol tartrate administered from single-dose intranasal sprayer

Purpose. The Pharmacokinetics and tolerability of single and multiple doses of intranasal butorphanol tartrate using a single-dose, metered sprayer were studied. Methods. In this randomized, open-label, two-way crossover study, 24 healthy subjects received either 1 or 2 mg of intranasal butorphanol as a single dose (treatment A) and 1 or 2 mg of intranasal butorphanol every six hours for seven doses (treatment B). During phase 1, 12 subjects selected at random received a single 1-mg dose and the other 12 a single 2-mg dose. During phase 2, those who received the 1-mg single dose received 1 mg every six hours for seven doses. During phase 3, those who received the 2-mg single dose received 2 mg every six hours for seven doses. Serial blood samples were collected over 12 hours. Pharmacokinetic parameters were determined using noncompartmental methods. Results. Mean (coefficient of variation) values for the area under the concentration-versus-time curve (AUC) from time zero to infinity (AUC _0-∞) were 4.15 (26.4%) and 10.42 (19.6%) ng·hr/mL after single doses of 1 and 2 mg of butorphanol, respectively. At steady state, mean values for the AUC from time zero to the dosing interval (AUC_0-τ) were 4.82 (40.2%) and 10.60 (22.3%) ngε·hr/mL, respectively. The accumulation indices were around 2 for both the 1- and 2-mg doses. Median time to maximum concentration values ranged from 15 to 30 minutes for each treatment. Dose-normalized parameters AUC_0-∞ AUC_0-τ and maximum concentration (C_max) were significantly larger after a single 2-mg versus 1-mg dose (p < 0.05). Conclusion. Intranasal butorphanol has rapid absorption predictable accumulation after multiple closes administered with single-dose metered sprayers. Intranasal administration of butorphanol was well tolerated and adverse events were generally mild to moderate in severity and as expected for this drug.