Testosterone undecanoate – increase of oral bioavailability by nanostructured lipid carriers (NLC)

Testosterone undecanoate (TU) has a low oral bioavailability of about 3 % in beagle dogs and 7 % in men. To avoid administration of a single dose in two oral units and to increase lymphatic absorption to minimise side effects in the liver, TU was incorporated into nanostructured lipid carriers (NLC) and formulated as drug nanocrystals. Testosterone (T) was run as nanocrystal formulation for reasons of comparison. NLC and drug nanocrystals were produced by high pressure homogenisation. The in vivo studies were performed in male Wistar rats. The drug absorbed was quantified as testosterone analysed by EIA assay. The nanocarriers were compared with the commercial product Andriol Testocaps®. The drug nanocrystals reached about half the AUC of Andriol Testocaps® (testosterone) or were just below (testosterone undecanoate). The best NLC formulations possessed a 2 times higher AUC compared to Andriol Testocaps®. Highest bioavailability was obtained with 200 nm NLC. Nature of the lipid for the particle matrix and the drug loading (15 %, 30 %) affected distinctly the shape of the serum profile (cmax, tmax, prolongation of serum levels). Modification of these parameters should allow controlled adjustment of the serum profile to therapeutic needs. Due to the reduced volume of the nanocarriers, application of a single dose in one unit is possible.