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tdds

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A Seminar on TRANSDERAL DRUG DELEVERY SYSTEM by Mr.Sudhakar A. Bhondve M. Pharm. Part I ( Sem -II) Mr. K.K.Mali ASST. PROFESSOR YSPM’s Yashoda Technical Campus,faculty of pharmacy Satara Under Guidance of

CONTENT:

CONTENT INTRODUCTION ADVANTAGES DISADVANTAGES ANATOMY OF SKIN DRUG PENETRATION PATHWAY MECHANISM OF DRUG PERMEATION FACTOR AFFECTING TRANSDERMAL PERMEABILITY

INTRODUCTION:

INTRODUCTION Definition “It is a self contained descrete dosage form which when applied to the intact skin delivers the drug through the skin at a controlled rate to the systemic circulation”

ADVANTAGES:

ADVANTAGES Reduce the first pass metabolism Self medication is possible Reduce the dose frequency Reversibility of drug delivery Better patient compliance Reduce the side effects Noninvasive method (no needle or injection)

DISADVANTAGES:

DISADVANTAGES Poor diffusion of large molecules Skin irritation Limited dose is required Can not deliver ionic drugs Can not achieve high conc. i n blood Not suitable for irritating drugs Can not deliver drug in pulsatile manner

ANATOMY OF SKIN:

ANATOMY OF SKIN Microscopically Skin is a multy layered organ composed of 3 layers Epidermis Dermis Subcutaneous fatty tissue

ANATOMY OF SKIN:

ANATOMY OF SKIN

ANATOMY OF SKIN:

ANATOMY OF SKIN Epidermis - It is the outermost layer of skin - It is composed of stratified epithelium cells - It composed of 2 layers i . Stratum corneum ii. Stratum germinativum

ANATOMY OF SKIN:

ANATOMY OF SKIN i . Stratum corneum It is the outermost layer of epidermis It consist of flattened, dehydrated, keratinised cells. ii. Stratum germinativum It is regenerative layer of epidermis It contains basal cells these multiply and undergo slow upword migration

ANATOMY OF SKIN:

ANATOMY OF SKIN This process of regeneration of the stratum corneum is made up of 3 layers of stratum germinativum stratum spinosm (Prickly layer) stratum granulosm (Granular layer) stratum lucidum (Clear or basal layer )

ANATOMY OF SKIN:

ANATOMY OF SKIN

ANATOMY OF SKIN:

ANATOMY OF SKIN TISSUE WATER CONTENT FUNCTION Stratum corneum 20 % To maintain flexibility & softness. Stratum Germinativum 70% Regenerates new Stratum corneum.

ANATOMY OF SKIN:

ANATOMY OF SKIN 2. Dermis It is the gel like structure It is composed of network of collagen and elastic fibers and it contains blood vessels, lymphatic and nerve ending They support to the epidermis

ANATOMY OF SKIN:

ANATOMY OF SKIN 3 . Subcutaneous fatty tissue -It contain fatty tissues

Drug penetration pathway:

Drug penetration pathway Passive diffusion of drug through skin Through the stratum corneum Transfolicular Through the sweat gland

Mechanism of drug permeation:

Mechanism of drug permeation Within stratum corneum molecule may penetrate either transcellularly or intercellularly .

Mechanism of drug permeation:

Mechanism of drug permeation Process of Transdermal permeation

Mechanism of drug permeation:

Mechanism of drug permeation Sorption of a parenteral molecule on to the surface layers of stratum corneum Diffusion through it & viable epidermis & finally at the papillary layers of dermis The molecule is taken up into the microcirculation for subsequent systemic distribution The viable tissue layers & the capillaries are relatively permeable & the peripheral circulation is sufficiently rapid so that for the great majority of penetrant, diffusion through the stratum corneum is often the rate limiting step It consist of series of steps in squence …

Mechanism of drug permeation:

Mechanism of drug permeation

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FACTORS AFFECTING TRANSDERMAL PERMEABILITY 1. Physico chemical properties of parent molecule a)Solubility and partition co- efficient b)pH condition c) Penetrant concentration 2 . Physico chemical properties of drug delivery system a) Release characteristic b) Composition of drug delivery system c) Permeation enhancer used

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3. Physiological and pathological condition of skin a)Lipid film b)Skin hydration c)Skin temperature d)Effect of vehicle e)Pathological injury to skin 4. Biological factors a)Skin age b)Thickness of S. Corneum c)Skin condition FACTORS AFFECTING TRANSDERMAL PERMEABILITY

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1. Physico chemical properties of parent molecule a) Solubility and partition co- efficient : Solubility of a drug influences its ability to penetrate the skin. Drug solubility determines concentration presented to absorption site which will effect rate and extent of absorption. Skin permeation can be enhanced by increasing lipophilic character of drug, so that drug penetrates through STC but not through epidermis due to decreased water solubility. Drug which is lipid & water soluble is favored. FACTORS AFFECTING TRANSDERMAL PERMEABILITY

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b) pH & penetration concentration: Moderate pH is favorable because if solutions with high or low pH will result in destruction to the skin. e.g. In case of ephedrine and scopolamine, the transdermal flux of the drug increases with increasing pH up to approximately 1.2 higher than their Higher the concentration of the drug in vehicle faster the absorption. FACTORS AFFECTING TRANSDERMAL PERMEABILITY

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2. Physico -chemical properties of drug delivery system a) Release characteristic Solubility of drug in vehicle affect on the release rate. b) Composition of drug delivery system It not only effects the rate of drug release but also the permeability through STC. -Example :- methyl salicylate is more lipophilic than its parent acid (Salicylic acid). When applied to skin from fatty vehicle methylsalicylate yielded higher absorption . c) Permeation enhancer used FACTORS AFFECTING TRANSDERMAL PERMEABILITY

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3) Physiological and pathological condition of skin a) Lipid film: It acts as protective layer to prevent removal of moisture from skin. Deffating of this film will decrease TD absorption. b) Skin hydration: It can be achieved by covering skin with plastic sheeting, which leads to accumulation of sweat, condensed water vapors, increase hydration and increase porosity. FACTORS AFFECTING TRANSDERMAL PERMEABILITY

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c)Skin temperature: Skin temp. increases absorption of drugs also increase. e.g. aspirin- 51°C d) Effect of vehicle: . A vehicle can influence absorption by its effect on physical state of drug and skin. Example greases, paraffin bases are more occlusive while water in oil bases are less. e)Pathological injury to skin Cut inflammation, rashes, mild burn where promote the absorption.51 FACTORS AFFECTING TRANSDERMAL PERMEABILITY

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4) Biological factors: a) Skin age: Skin of foetus ,young ones and elders is more permeable than adult tissue . c)Thickness of stratum corneum : e.g. Absorption is low from region as foot and palm b) Skin metabolism: Viable epidermis is metabolically active than dermis. If topically applied drug is subjected to biotransformation during permeation local and systemic bioavailability is affected. FACTORS AFFECTING TRANSDERMAL PERMEABILITY

FORMULATION ASPECTS:

FORMULATION ASPECTS Basic Components Of TDDS: Polymer matrix / Drug reservoir Drug Permeation enhancers Pressure sensitive adhesive (PSA) Backing laminates Release liner Other excipients like plasticizers and solvents

PowerPoint Presentation:

1. Polymer matrix / Drug reservoir Polymers are the backbone of TDDS, which control the release of the drug from the device. Polymers used in TDDS should have biocompatibility and chemical compatibility with the drug and other components of the system such as penetration enhancers and PSAs. FORMULATION ASPECTS

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A)Natural Polymers: e.g. cellulose derivatives, zein , gelatin, shellac,gums , B)Synthetic Elastomers : e.g. rubber, nitrile , butylrubber . C)Synthetic Polymers: e.g.polyvinylalcohol,polyvinylchloride , polyethylene. FORMULATION ASPECTS

FORMULATION ASPECTS:

FORMULATION ASPECTS 2.drugs It is generally accepted that the best drug candidates for passive adhesive transdermal patches must be; non ionic, low molecular weight (less than 500 Daltons), have adequate solubility in oil and water (log P in the range of 1-3), a low melting point (less than 200°C) potent (dose in mg per day).

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3.Permeation enhancers These are the chemical compounds that increase permeability of stratum corneum so as to attain higher therapeutic levels of the drug candidate. Penetration enhancers interact with structural components of stratum corneum i.e., proteins or lipids. They alter the protein and lipid packaging of stratum corneum , thus chemically modifying the barrier functions leading to increased permeability. FORMULATION ASPECTS

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4.Pressure sensitive adhesive (PSA) A PSA is a material that helps in maintaining an intimate contact between transdermal system and the skin surface. It should adhere with not more than applied finger pressure, be aggressively and permanently tachy , exert a strong holding force. Ideally, PSA should be physicochemically and biologically compatible and should not alter drug release. e.g. Polyacrylates, polyisobutylene and silicon based adhesives are widely used in TDDSs. FORMULATION ASPECTS

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5. Backing laminates While designing a backing layer, the consideration of chemical resistance of the material is most important. Examples : polyethylene polyester films. FORMULATION ASPECTS

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6. Release liner During storage the patch is covered by a protective liner that is removed and discharged immediately before the application of the patch to skin. e. g. polyester foil and metallized laminates. FORMULATION ASPECTS

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7.Other excipients like plasticizers and solvents Various solvents such as chloroform, methanol, acetone, isopropanol and dichloromethane are used to prepare drug reservoir . In addition plasticizers e.g.polyethylene glycol and propylene glycol are added to provide plasticity to the transdermal patch. FORMULATION ASPECTS

Marketed formulation:

Marketed formulation Motion sickness (scopolamine) Depression ( selegiline )

References -:

References - Controlled Drug Delivery : Concepts and Advances : S.P.Vyas & Roop K Khar : Chapter 10 : “ Transdermal Drug Delivery” : Pg No. 411 – 476

THANK YOU:

THANK YOU

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