AYURVEDIC REVELATION IN TRANSDERMAL DELIVERY OF DRUGS SINCE 2000 BC

THE TRANS DERMAL ACTION OF AYURVEDIC OILS

Transdermal delivery is the movement of compounds(drugs) across the skin into the systemic circulation. Epidermis is the outer epithelial portion of the skin. The outer most layer of epidermis called stratum corneum poses the major resistance to transdermal transport. Blood & lymphatic vessels, nerve endings, hair follicles and sebaceous glands are embedded within the dermis.Regardless of skin dosage forms eg., creams,gels,ointments,suspensions,emulsions & patches, drug molecules that are in contact with the skin may penetrate the skin through three possible ways. One is through the appendageal shunt route, which includes the sweat ducts, hair follicles and sebaceous glands. Since these occupy only 0.1% of surface area of the skin, drug penetration through this mode is difficult.The intracellular and transcellualr mode of transport are the other two routes which pave way for majority of drugs to be absorbed through the skin. The main barrier for the drugs to pass through the skin is via the “stratum corneum”, which is the outermost layer of epidermis(the outer layer of skin). The corneocytes formed by keratin pigments and lipids form the” brick and mortar” structure of the sratum corneum. The corneocytes are hydrophilic while the lipids are hydrophibic, this dual nature enables the transmission of water and fats through diffusion and tortuos transport respectively.

The methods of enhancing bio availability of transdermal drug application in Ayurveda is done by increased temperature that induces sudation, hydration through enhanced sweating and by massage for effecting a manual type of iontophoresis. Even the external use of oils increases body temperature which in turn favours production of sweat by sweat glands. Though this is not excreted at the moment because of partial closure of sweat pores by the film of fat, subsequent application of heat releases the barricade of fat to effect full oleation used in conjuction with sudation in Ayurveda, it provides both hydration and temperature increase.Thus Ayurveda has its own concept of a rich tradition of transdermal therapeutical system, it is convinient, effective, eliminates variables that influence gut absorption, it enters the systemic circulation directly, it provides a controlled constant drug administration, displaying a single pharmacological effect, it is patient friendly as it eliminates the effect of taste or gastric irritation. Little wonder that when the world is still in its experimental stages by introducing topically acting counter irritants, NSAIDS, steroids, & transdermal clinical patches of oestradiol, clonidine, nitroglycerine, testosterone etc, Ayurveda has addressed transdermal use of medicenes in versatile conditions from neurological affections to rheumatological conditions and also for skin ailments in various modes and methods around 2500 years ago, oleation done externally through skin is only one example.