Nasal absorption of testosterone in rats

Testosterone levels in the blood were determined in rats following nasal, intravenous, and intraduodenal administration of 25-micrograms and 50-micrograms doses. The results indicated that the drug levels after nasal and intravenous administration were similar, whereas intraduodenal administration resulted in considerably lower levels. The bioavailability of the nasally administered drug was calculated to be 99% and 90% at the 25-micrograms and 50-micrograms doses, respectively. The intraduodenal bioavailability was only 1% at the dose studied.