A Comprehensive Review: Transdermal Drug Delivery System: A Tool For Novel Drug Delivery System

In the recent decade, skin delivery (topical and transdermal) has gained an unprecedented popularity, especially due to increased incidences of chronic skin diseases, demand for targeted and patient compliant delivery and interest in life cycle management strategies among pharmaceutical companies. Transdermal drug delivery system was presented to overcome the difficulties of drug delivery especially oral route. Transdermal drug delivery refers to a means of delivering drugs through the surface of the skin for local or systemic treatment. The drug functions after absorption through the skin into the systemic circulation via capillary action at a certain rate. Transdermal patches are now widely used as cosmetic, topical and transdermal delivery systems. These patches represent a key outcome from the growth in skin science, technology and   expertise developed through trial and error, clinical observation and evidence-based studies that date back to the first existing human records. A transdermal patch is a medicated adhesive patch that is placed on the skin to deliver a specific dose of medication through skin and into the bloodstream. An advantage of a transdermal drug delivery route over other types of delivery system such as oral, topical, intravenous (i.v.), intramuscular (i.m.), etc. is that the patch provides a controlled release of the medication into the patient, usually through either a porous membrane covering a reservoir of medication or through body heat melting thin layers of medication embedded in the adhesive. The main disadvantage to transdermal delivery systems stems from the fact that the skin composition offers very effective barrier that allow only small molecule based drugs to penetrate the skin and pass through the barrier. Sildenafil citrate (SLD) is a selective cyclic guanosine monophosphate-specific phosphodiesterase type 5 inhibitor used for the oral treatment of erectile dysfunction and more recently, it has been used for the treatment of pulmonary arterial hypertension and the enhancement of uteroplacental perfusion in case of fetal growth retardation. The challenges facing the oral administration of the drug include poor bioavailability and short duration of action that requires frequent administration. The main objective of transdermal drug delivery system is to deliver drugs into systemic circulation through skin at predetermined rate with minimal inter and intrapatient variations.
Keyword: Skin delivery, Transdermal drug delivery, Oral rout, Sildenafil citrate, Pulmonary arterial hypertension