transdermal drug delivery systems

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Transdermal Drug Delivery System (TDDS) PRESENTED BY: RAVI MOTKA M.PHARM SEM II PHARMACEUTICS 1 C. U. SHAH COLLEGE OF PHARMACY AND RESEARCH WADHWANCITY

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Introduction Advantages Disadvantages Ideal Characteristics of drug candidate for TDD Factor affecting the Transdermal route Structure of skin Routes for drug penetration through skin Different Types of Transdermal Patches Main Components of Transdermal Patch References. Contents: 2

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Introduction Most common form of delivery of drugs “oral route” Advantages Drawbacks How to overcome these difficulties……???? 3

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“Transport of therapeutic substances through the skin for systemic effect.” Various drug delivery systems……. Transdermal drug delivery system (TDDS) 4

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Longer duration of action resulting in a reduction in dosing frequency. Increased convenience to administer drugs. Reduced side effects and improved therapy due to maintenance of plasma levels up to the dosing interval. More uniform plasma level, improved bioavavailablity. Flexibility of terminating the drug administration by simply removing the patch from the skin. Advantages: Cont…. 5

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Avoidance of the 'first pass effect’ Ability to modify the properties of the biological barrier to absorption ( Penetration Enhancement). Avoids problems associated with gastrointestinal absorption due to pH, enzymatic activity, drug-food interactions etc. Substitutes oral administration when the route is unsuitable as in case of vomiting, diarrhea. Advantages: 6

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Limited skin permeability. Possibility that a local irritation at the site of application. The skin changes from one site to another on the same person, from person to person and with age. Cannot use for large molecule. Erythema, itching, and local edema can caused by the drug, the adhesive, or other excipients in the patch formation. Skin irritation and allergic response. The drug must have some desirable physicochemical properties for penetration through stratum corneum. Disadvantages: 7

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Must be non-ionic. Low molecular weight. Have adequate solubility in oil and water. Dose is less than 50 mg per day, and ideally less than 10 mg per day. Ideal Characteristics of drug candidate for TDD: 9

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Physicochemical properties of drug pKa molecular size stability binding affinity solubility partition coefficient Integrity and thickness of stratum corneum Density of sweat glands and folicles Skin hydration Metabolism Vehicle effects Factor affecting the Transdermal route: 10

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Structure of skin: 11

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Epidermis: four sub-layers: Stratum corneum Stratum granulosum Stratum spinosum Stratum basale Major barrier to molecular transport is provided by Stratum corneum (SC). It is highly hydrophobic and contains 10 – 15 layers of interdigitated corneocytes, which are constantly shed and renewed. 12

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Dermis: Acellular, Rich in blood vessels, lymphatic vessels and nerve endings. An extensive network of dermal capillaries connects to the systemic circulation. Subcutaneous Tissue: The subcutaneous fat (subcutis, hypoderm) provides a mechanical cushion and a thermal barrier; it synthesizes and stores readily available high-energy chemicals. 13

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ROUTES FOR DRUG PENETRATION THROUGH SKIN: (A) Macro-route: across the intact horny layer, through the hair follicles with the associated sebaceous glands, or via the sweat glands 14

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(B) Micro-route: 15

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Different Types of Transdermal Patches: Drug in adhesive system Drug in matrix dispersion system Reservoir system Microreservoir system 16

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MATRIX SYSTEM Drug in adhesive system 17 adhesive diffusion controlled TDDS

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2) MATRIX SYSTEM matrix dispersion system (matrix diffusion controlled system) 18

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3) Reservoir system (membrane moderated tdds) Film Backing Drug Layer Protective Peel Strip (removed prior to use) Rate-controlling Membrane Contact Adhesive 19

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4) Microreservoir system 20

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21 Main components of a Transdermal Patch: Backing films Release liners Pressure-sensitive adhesives Active ingredients Permeation enhancers Microporous or semi-permeable membranes Pouching materials

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22 The role and characteristics of film is: To protect the active layer and safeguard the stability of the system, and To affect skin permeation and tolerance, depending on occlusion or breathability. It must also be flexible, comfortable and must present good affinity with the adhesive, as well as excellent printability.   The most common materials used polypropylene, polyethylene (both high and low density), polyesters, PVC Nylon, etc. Backing Films

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23 Release liners A release liner is a film covered with an anti-adherent coating. The role of the release liner is: To protect the system as long as it is in the package, and it is removed just before the adhesion of the TDDS to the skin. Release liners play a crucial role in the stability of the product and in its safe and functional use. An incorrect release liner does not permit the easy release of the patch, and can interfere with the active or other components, thereby reducing its shelf life.

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24 There are several combinations of film and anti-adherent coating that are suitable, and the choice made depends on the ingredients of the system. The most common films used as release liners are paper-based, plastic film-based and composite films. The two major classes of coating are silicones and fluoro-polymers.

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25 Pressure-Sensitive Adhesives (PSA) The PSA must stick to the skin immediately and stay there for as long as it is needed. The correct choice of PSA has a critical effect on the stability of the system, the release of the active drug, the dermatotoxicity potential, and the accurate administration of the drug. There are three major families of PSAs: Rubber-based PSAs, Acrylic PSAs in the form of acrylic solutions, Emulsion polymers or hot melts, and silicon PSAs.

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26 Chemical Enhancers / Accelerants / Absorption Promoters Lipid Action Protein Modification Partitioning Promotion three possible mechanism for enhancing the permeation of drug through skin. Cont…..

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27 Chemical classes of penetration enhancers

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28 Microporous or Semi-Permeable Membranes There are two types of porous membranes. I Ethylene Vinyl Acetate Membranes (EVA)   II Microporous Polyethylene Membranes

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29 Pouching Materials: There are three main layers in the composite materials used for pouches: the internal plastic heat sealable layer, the aluminium foil layer and the external printable layer. Most patches for use in a TDDS are packaged as unit doses in sealed pouches. The pouching material is therefore critical to the stability and integrity of the product. This packaging component compensates for the stability or the instability of the system.

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30 References… Controlled Drug Delivery : Concepts and Advances : S.P.Vyas & Roop K Khar : Chapter 10 : “Transdermal Drug Delivery” : Pg No. 411 – 476 Encyclopedia of Pharmaceutical Technology : James Swarbrick and James Boylan : Volume 18 : “Transdermal Drug Delivery Devices : System Design and Composition” : Pg No. 309 – 337 M.E.Aulton, Pharmaceutics : The Science of Dosage Form Design, Second Edition, Part Four, Dosage Form Design and Manufacture, Chapter 33, “Transdermal Drug Delivery”, Pg No. 499 - 533

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Thank You…!.! 31