The subcutaneous injection of insulin for the treatment of diabetes mellitus can lead to patient non-compliance, discomfort, pain and local infection is a chronic metabolic health disease affecting the homeostasis of blood sugar levels in human beings. Oral route of drug delivery system has been the most widely accepted means of drug administration other than invasive drug delivery systems. For the development of an oral insulin delivery system, we have to focus on overcoming the various gastro-intestinal barriers for insulin uptake from the gastrointestinal tract. To overcome these barriers various types of formulations such as insulin conjugates, micro/nanoparticles, liposomes, hydrogel, capsule, and tablets are designed to deliver insulin orally. Various potential ways to administer insulin orally has been explored over years but a fluctuating level of insulin release have been recorded. A number of advancement has taken place in the recent years for understanding the needs of improved oral delivery systems of insulin. This review article concentrates on the challenges for oral drug delivery of insulin as well as various carriers used for the oral drug delivery of insulin and also provides the relevant information about the clinical tested formulations of oral insulin and its patents.

Apium graveolens (Hindi name: Celery) belongs to family Apiaceae of order Apiale and is a biennial plant. It is about 25-250 cm in height and found in western Uttar Pradesh, northwestern Haryana, Punjab, Himalayas and in some parts of Europe. Fourocoumarin, coumarin and phenols are main categories of phytoconstituents present in it. Celerin, bergaten, aiumoside, aimuetin, aigravin, osthenol, seselin are the main active phytoconstituents of active constituents. Different parts of the plant have various medicinal applications such as antibacterial activity, cardiovascular activity, antidiabetic activity, anti-depressant activity, hypolipidemic effect, effect on kidney, effects on male hormones, spermatogenesis and cytoprotective activity etc. The present review aims at the exploration of pharmacognostical, phytochemical and pharmacological studies of celery. Finally, the review concludes that this would be significantly and scientifically useful for both professional of academia and pharmaceutical industry those are doing research on this plant.

Due to ease of administration, versatility, painless and paramount patient compliance oral administration is considered as most satisfactory route for the administration of drug. For drug absorption in oral cavity, sublingual area is most permeable to drugs. The sublingual route bypasses the hepatic first-pass metabolism, which assist greater bioavailability with better patient compliance. Sublingual route is the most suitable now a days because people need effective relief within a short period. These tablets have the advantage of rapid disintegration and dissolution in saliva. For the instant drug delivery to paediatric and geriatric patients fast disintegrating sublingual tablets have shown significant improvements for specific patient group. This review enlightens the mechanism of sublingual absorption, physicochemical properties of a few sublingually administered drugs, factors affecting sublingual absorption, advantages, and evaluation parameters.