THEROTICAL ASPECTS OF TRASDERMAL DRUG DELIVERY SYSTEM

Introduction:- Introduce to overcome the difficulties of drug delivery through oral route. Patients often forget to take their medicine, and even the most faithfully compliant get tired of swallowing pills, especially if they must take several each day. By passing the gastrointestinal (GI) tract would cause the GI irritation that frequently occurs and avoid partial first-pass inactivation by the liver. The transdermal therapeutic systems (TTS) are more convenient to use than that of the other formulations.

Currently Available TDDS:- Scopolamine (hyoscine) for motion sickness. Clonidine and nitroglycerin for cardiovascular disease. Fentanyl for chronic pain. Nicotine to aid smoking cessation. Transdermal glyceryl trinitrate for acute stroke therapy. Sufentanil patch for chronic cancer pain.

Advantages Of Transdermal Drug Delivery System:- Easy elimination of drug delivery during toxicity. Avoidance of first pass metabolism of drugs. Self administration is possible. Topical patches are a painless. Topical patches have fewer side effects than oral medications or supplements.

Disadvantages of TDDS:- The possibility of local irritation may develop at the site of application.

Generations of TDDS introduced by Prausnitz:- 1st generation: TDDS include traditional patches such a clonidine or estrogen. 2nd generation: TDDS include patches plus some type of enhancers to improve drug delivery. 3rd generation: TDDS use novel technologies to increase the scope of molecules that can be delivered through the skin.

Anatomy of Skin:- Epidermis:- Epidermis is outer most layer of skin. It can be sub-divided into five layers. Dermis:- 3-5 mm thick layer. It provides nutrient and O2 to skin. Hypodermis:- Hypodermis fat tissue supports the dermis and epidermis. Fig1:- Structure of Skin

Fig2:- various layer of epidermis Fig3:- A multilayer skin model showing sequence of transdermal permeation

Pathways Of Drug Absorption Through The Skin:- Transfollicular route Transcellular route Intercellular route Fig4:- Skin showing route of absorption

1. Transfollicular route: Shortest pathway It provides large area for difussion of drug Eg. Sodium Fluorescein 2. Transcellular route: Drug passes from corneocytes of stratum cornea. This route suitable for hydrophilic drug. 3. Intercellular route: Drug passes the alternating lipid and aqueous domain by portitionating into lipid bilayer diffuse into inner side Suitable for uncharged lipophilic drug

PERMEATION ENHANCERS:- A) Chemical Approach: Solvents Terpenes, terpenoids and essential oils Fatty acids and esters Surfactants Prodrug approach B) Physical Approach: Abrasion Electroporation Iontophoresis Laser Radiation C) Particulate system: Liposome

Techniques for TDDS:- A) Structure-based enhancement techniques Transdermal Patches Metered-Dose Transdermal Spray (MDTS) B) Electrically-based enhancement techniques physical approaches of permeation enhancers C) Velocity -based enhancement techniques Powderject Device

Types of Transdermal Patch:- a) Single Layer in Adhesive b) Multi-Layer in Adhesive

f) Micro reservoir system c) Vapour Patch d) Reservoir system e) Matrix system i) Drug in adhesive system ii) Matrix-dispersion system f) Micro reservoir system Fig7:-Vapour Patch

Transdermal Drug:- Approval year Drug Indication Product Name Marketing Company 1979 Scopolamine Motion Sickness Transderm-Scop Novarties Consumer Health (Parsippany, NJ) 1984 Clonidine Hypertension Catapres-TTS Boehringer Ingelheim (Rigefield, CT) 1990 Fentanyl Chronic pain Duragesic Janssen pharmaceutica (Titusvilla, NJ) 1991 Nicotine Smoking cessation Nicoderm, Habitrol, ProStep GlaxoSmithKine (Philadelphia, PA)

Preparation Of TDDS:- Preparation of TDDS by using proliposomes Free film method Mercury substrate method “IPM membranes” method “EVAC membranes” method Aluminium backed adhesive film method

Evaluation of Transdermal Patches:- Thickness Percentage Moisture content Percentage of moisture uptake Flatness Drug content analysis Skin irritation study Quick stick (peel-tack) test Stability studies In Vitro skin permeation study In vivo Studies

Conclusion:- Transdermal drug delivery is hardly an old technology, and the technology no longer is just adhesive patches. Advances in drug delivery systems have increasingly brought about rate controlled delivery with fewer side effects as well as increased efficacy and constant drug delivery. Now a day’s Transdermal drug delivery systems are used for hormonal drugs and insulin.

REFERENCES:- Aulton M.E, Pharmaceutics, the Science of Dosage Form Design, 2nd Edition, Elsvier Publisher, 2002, 499-533. Babiuk S, Baca-estrada M, Babiuk LA, Ewen C, Foldvari M. J Control Rel 2000; 66: 199-214. Dipen Patel, Sunita A. Chaudhary, Bhavesh Parmar, Nikunj Bhura, ”Transdermal Drug Delivery System: A Review” Arihant School of Pharmacy and Bio-Research Institute, Gandhinagar, Gujrat, India. Mezei M, Gulasekharam V. Life Sci 1980; 26: 1473-7. Nat Biotechnol,2006 Nov; 26(11): 1261-1268.

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