Therapeutic drug delivery systems. Transdermal drug delivery systems (TDDS) - advantages, recent achievements and current status of the Bulgarian and global market

Abstract

Therapeutic systems (TS) are contemporary drug delivery forms, designed to improve the therapeutic potential of drugs through maintenance of therapeutic drug levels for extended period of time. TS provide controlled or sustained drug release, intended to reach the systemic circulation or remain and act locally on the site of application. Transdermal Drug Delivery Systems (TDDS) are pharmaceutical preparations to be applied to the intact skin for systemic absorption and occupy more than 30% of the global market share of TS. TDDS ensure a constant plasma concentration of the active ingredients in the therapeutic window from 24 hours to 7 days by non-invasive and easy administration. Important advantages of TDDS include avoidance of first-pass metabolism and gastro-intestinal adverse effects, improved drug stability and etc. First generation TDDS (Transderm-Scop, Transderm-Nitro, Estraderm, Nicoderm and etc.) accomplish remarkable success and benefits in the treatment of motion sickness, angina pectoris, quit smoking and contraceptive therapy. The constantly growing scientific interest and adjustment of well-known physical and chemical methods (as iontophoresis, sonophoresis, microneedles and etc.) to TDDS as additional force to enhance drug permeation through stratum corneum, leads to next TDDS generations by overstepping beyond the preferable TDDS stereotype of the small, less than 300 Da, molecule with balanced lipophilicity. The number of the TDDS on the market increases every year, as the highest progress is observed in the field of Central Nervous System’s diseases - dementia, depression, Parkinson, migraine. The market share of TDDS on the glob-al pharmaceutical market reaches up to 12% and is estimated to be approximately 31.5 billion, while their role and disposal on the Bulgarian market is still limited.