M. Tech. Pharmaceutical Sciences / Following the discovery of an active pharmaceutical ingredient, attempts were made to improve its delivery to the site of action and thereby its effectiveness. Insulin and other therapeutic proteins are administered almost exclusively parenterally because of their poor absorption after oral administration, but this route is associated with disadvantages including pain, discomfort and lipohypertrophy at the site of injection. A suitable absorption enhancer which could effectively improve the absorption of poorly absorbable drugs from the gastrointestinal tract would contribute to the development of an effective oral drug delivery system for these drugs. One such attempt was the formulation of the active ingredient into an appropriate dosage form for a specific route of administration to improve other properties such as manufacturability, stability and bioavailability. Formulation studies led to the development of substances called excipients, which were incorporated into dosage forms, in addition to the active pharmaceutical ingredient, to improve the properties of the final product. Aloe vera gel previously showed the ability to increase the bioavailability of vitamins and to enhance the in vitro transport of a macromolecular drug across intestinal epithelial cell monolayers. However, the effect of leaf materials from aloes, indigenous to South Africa, on drug transport across intestinal epithelia has not previously been investigated. The aim of this study is to evaluate the in vitro drug transport enhancement potential of the gel and whole leaf extract of Aloe ferox, Aloe marlothii, Aloe speciosa and compare them with that of Aloe vera across Caco-2 cell monolayers, as well as across excised rat intestinal tissues.