Cyclodextrins are used to make pharmaceutical solutions by capturing hydrophobic molecules as guest hosts. Because inclusion compounds of cyclodextrins with hydrophobic molecules are able to penetrate body tissues, these can be used to release biologically active compounds under specific conditions. For example, testosterone is complexed with hydroxy-propyl-beta-cyclodextrin (HPBCD), 95% absorption of testosterone was achieved in 20 minutes via the sublingual route but HPBCD was not absorbed, whereas hydrophobic testosterone is usually absorbed less than 40% via the sublingual route.