The pharmaceutical form known as “soft gelatin capsule” (SEC capsules) is used to administer, mainly orally, non-crystalline and poorly water-soluble active ingredients. For example preparations of progesterone and vitamin complexes are present on the market in the form of soft gelatin capsules.
Soft gelatin capsules are composed of a shell containing plasticized gelatin which encloses a filling material, normally composed of a liquid or semi-liquid lipophilic active ingredient, of a solution of a lipophilic active ingredient or of a pasty product and having characteristics that will not dissolve the shell.
However, these formulations have the drawback of often having reduced efficacy due to poor bioavailability of the active ingredients contained therein.
Cyclodextrins are cyclic sugars which have the particularity of complexing lipophilic molecules, considerably increasing their water solubility. It is known that progesterone and some vitamins form water-soluble complexes with cyclodextrins, that have thus greater bioavailability compared to the corresponding non complexed compounds.
Nonetheless, these complexes cannot be used in the formulation of soft gelatin capsules, since in this case the solution to be encapsulated would have characteristics that cause solubilization of the gelatin of the shell of the capsules thus rendering the formation, or the stability, of the capsule unachievable.
From WO 99/33924 there are known gelatin compositions derived from non-bovine or non-pig, preferably fish origin. To improve the workability, in particular the flowing properties, of the aforementioned “alternative” gelatins, to be employed in the pharmaceutical, veterinary, food or cosmetics field, the incorporation of a setting system comprising hydrocolloids and optionally cations and/or sequestering agents in amounts of less than 5%, preferably 0.01 to 3% is described. Among the sequestering agents employable in the alternative gelatins, also beta-cyclodextrin is mentioned as possible constituent of the setting system.
Japanese Patent No. 62-249935 published in 1987 reports of gelatin substrates containing 10-2% of cyclodextrin, preferably beta-cyclodextrin, displaying improved shelf-life properties, as far as conservation of the so-modified gelatin's disintegration properties is concerned. The preparations employed for the confirmatory tests reported in this publication, do not comprise, however, the inclusion of active principles.
Therefore, the problem remains of developing formulations of soft gelatin capsules which allow the bioavailability of the drugs contained therein to be increased.