Intranasal absorption of melatonin in vivo bioavailability study

The bioavailability of melatonin in rabbits after nasal administration of two formulations has been studied. In each case, a total amount of 1.5 mg melatonin in 50 μl was administered and compared with 1.5 mg i.v. The test solutions were formulated with 40% polyethylene glycol 300 (PEG 300), one with 1% sodium glycocholate (+GC) and one without (−GC). The bioavailability for +GC was 94% (S.D.±29%, n=4), whereas the bioavailability for −GC was 55% (S.D.±17%, n=6). These results indicate that GC has an enhancer effect ( P