Pharmacokinetics of intranasal alfentanil.

STUDY OBJECTIVE

To determine the pharmacokinetics of intranasal and intravenous (IV) administrations of alfentanil in 10 healthy volunteers.

DESIGN

Randomized, prospective, double-blind, placebo-controlled, cross-over trial with at least one week between the two modes of administration.

SETTING

Healthy volunteers at a university medical center.

SUBJECTS

10 healthy, nondrug-dependent volunteers.

INTERVENTIONS

Alfentanil 0.54 mg was administered either intranasally [with 12 ml of sodium chloride (NaCl) 0.9% IV] or IV (with 12 sprays of NaCl 0.9% intranasally). Each subject was assigned once to the intranasal and once to the IV group. To guarantee a complete elimination of alfentanil, there was a time period of at least one week between the different modes of administration.

MEASUREMENTS AND MAIN RESULTS

Venous blood was sampled from a cubital vein at 3, 6, 9, 12, 15, 20, 30, 60, and 120 minutes after administration. Alfentanil plasma concentrations were determined by radioimmunoassay. Maximal plasma concentrations were 20.1 ng/ml +/- 7.3 ng/ml after 9 minutes in the intranasal group. At this measurement point, the intranasal alfentanil concentrations were 64.7% (18.7 ng/ml +/- 6.8 ng/ml) of the IV concentrations (28.9 ng/ml +/- 7.9 ng/ml). The calculated bioavailability after intranasal administration was 64.96% +/- 26.3%.

CONCLUSIONS

This pharmacokinetic study demonstrates a rapid rise in plasma concentrations, as well as a high bioavailability, following the intranasal administration of alfentanil.