Transdermal Drug Delivery Systems

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candidates for diffusion through the stratum corneum, epidermis, and dermis: aqueous and lipid soluble substances

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Pharmaceutical Dosage Chapter 11: Transdermal Drug Delivery Systems Topical Dermatological Products y

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Drugs delivered into the skin for treatment of dermal disorders For local effects Skin as the target organ

Factors

Affecting Percutaneous Absorption

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Transdermal Products y

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Drugs delivered through the skin (percutaneous absorption) to the general circulation For systemic effects Skin: not the target organ

Transdermal Drug Delivery System (TDDS) y

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the passage of therapeutic quantities of drug substances through the skin and into the general circulation for their systemic effects Transderm scop  First transdermal (Ciba, now Novartis) approved  by the FDA in 1979  Prevents motion sickness, nausea, and vomiting resulting from the use of certain anesthetics

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Facilitate

Evidences of Percutaneous Drug Absorption y

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Evidences of percutaneous drug absorption  Measurable blood levels of the drug  Detectable excretion of the drug and/or its metabolites in the urine  Clinical response of the patient to the therapy Blood concentration needed to achieve (with TDDS) therapeutic efficacy determined by:  Comparative Comparative analysis of the patient¶s response to the drug blood levels Ideal for the drug  To migrate through the skin: blood supply without build up in the dermal layers

Cadaver Skin Permeation Testing y

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Skin is composed of:  Stratum corneum (the outer layer)  Living epidermis  Dermis: provide the skin barrier (blockade) layers to penetration by external agents Stratum corneum (keratinized tissue: major rate limiting  barrier of of TDDS) TDDS)  Behaves as a semipermeable artificial membrane drug molecules penetrate by passive diffusion

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Physical y

determine the feasibility of a compound to be incorporated into a TDDS

Chemical skin permeation enhancer: increases skin  permeability  permeability by damaging or altering the physiochemical physiochemical nature of the stratum corneum to reduce its diffusion substance Among the alterations of the stratum corneum are:  Increased hydration of the stratum corneum  Change in the structure of lipids and lipoproteins in the intercellular channels through solvent action or denaturation or both Some drugs inherent capacity to permeate the skin without chemical enhancer. Chemical permeation enhancer: render impenetrable substance useful in TDDS More than 275 chemical compounds have cited as skin  penetration  penetration enhancers enhancers that include: acetone, azone, dimethyl acetamide, dimethly formamide, dimethyl sulfoxide, ethanol, oleic acid, PEG, P G, and sodium lauryl sulfate Methods

to Enhance TDDS

Iontophoresis



Drug Penetration in the Barrier  y

Helps

Chemical Enhancers

Stratum Corneum y

Physical and chemical properties of drugs including its molecular weight, solubility, partition coefficient, and dissociation constant, the nature of the carrier vehicle, and the conditioning of the skin Drug concentration Area of application: the larger, the more drug is absorbed Greater physiochemical attraction to the skin than to the vehicle Can permeate skin: with molecular weights ranging from 100 to 800 (ideal molecular weight for TDDS: 400 or less) and adequate lipid and aqueous solubility Hydration of the skin favors percutaneous absorption Site with a thin horny layer than with a thick one The longer the medicated application is permitted to remain in contact with the skin and the greater is the total drug absorption

Drug molecules through the stratum corneum: deeper  epidermal tissues: dermis: vascularized dermal layer,  Becomes available for absorption into the general circulation y

Delivery of charged chemical compounds across the skin membrane using an applied electrical field  Drugs examined: lidocaine, dexamethasone, amino acids, peptides, insulin, verapamil,  propanolol,  propanolol, Delivered by rapid injection because of   rapid metabolism and poor absorption in oral delivery and from TDDS (large molecular size, ionic character)  Enhance TDDS for peptide or protein administration Sonophoresis  Studied as a means to enhance TDDS 1

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Influence

integrity of stratum corneum and thus affect penetrability Agents examined: hydrocortisone, lidocaine, and salicylic acid in such formulations as gels, creams and lotions

Different Purposes for  In-Vivo Skin Penetration Studies To verify and quantify: Cutaneous bioavailability of a topically applied  drug  Systemic bioavailability of a transdermal drug To establish bioequivalence of different topical formulations of the same drug substance To determine the incidence and degree of systemic toxicological risk following topical application of a specific drug or drug product To relate resultant blood levels of drug in human to systemic therapeutic effects

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In-Vivo

Skin Penetration Studies

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Materials y

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Most

relevant studies performed in humans and animal models (predictors of human response) Used In-Vitro Skin Penetration Studies Skin penetration may be tested in vitro using:  Various skin tissues (human or animal) in a diffusion cell  Using human skin: limited because of difficulties of procurement, storage, expense, and variation in permeation  Animal skin: shown to be effective like shed snakeskin (Elaphe obsolete, black rat snake) which is nonliving, pure stratum corneum, hairless and similar to human skin but slightly less permeable Living Skin Equivalent ( LSE) Test Skin (Organogenesis Inc.)  Product developed as an alternative for dermal absorption studies  An organotypic culture of human dermal fibroblasts in a collagen-containing matrix and stratified epidermis composed of human epidermal keratinocytes

The Transderm-Nitro System Comprises of  Four Layers y

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Diffusion Systems and Principle Utilized y

Diffusion cell systems  Employed in vitro to quantify the release rates of  drugs from topical preparations  Skin membranes or synthetic membranes employed as barriers to the flow of drug and vehicle to stimulate the biologic system

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Monolithic

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system Incorporate a drug matrix layer between backing and frontal layers Drug matrix layer  Composed of polymeric material (drug  is dispersed)  Controls the rate at which the drug is released for percutaneous absorption

A tan-colored backing layer (aluminized plastic) that is impermeable to nitroglycerin A drug reservoir or matrix system containing nitroglycerin adsorbed on lactose, colloidal silicon dioxide, and silicon medical fluid An ethylene-vinyl acetate copolymer membrane that is  permeable to nitroglycerin A layer of hypoallergenic silicon adhesive: a protective  peel strip that is removed from the adhesive surface prior to use

Different Layers of the Transdermal Drug Delivery System

Two Categories of the TDDS y

2 types either with or without an excess of drug with regard to its equilibrium solubility and steady: state concentration gradient at the stratum corneum  As the concentration of the drug in the device diminishes below the skin¶s saturation limit  Transport of drug from device to skin declines  Most TDDs designed to contain an excess of  drug  Drug-releasing capacity beyond the time frame recommended for  replacement Membrane-controlled transdermal system  Designed to contain drug reservoir or pouch (in liquid or in gel form, a rate controlling membrane)  Backing, adhesive, and protecting layers  Examples of this technology: TransdermNitro (Novartis) and Transderm-Scop (Novartis)  Advantage over monolithic systems: release rate of drug remains constant when the drug solution in the reservoir remains saturated  Prepared by preconstruction of the delivery unit filling the drug reservoir: sealing or lamination  Continuous process  Serves as a rate-controlling mechanism or factor:  Drug delivery device If the drug is delivered to the o stratum corneum at a rate less than the absorption capacity  Skin If the drug is delivered to the o skin area to

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Occlusive or blockade backing membrane  Protects the system from environmental entry and from loss of drug from the system or moisture from skin Drug reservoir or matrix system Stores and releases the drug at the skin site  R elease liner   R emoved before application and enables drug release Adhesive layer   Maintains contact with the skin after application

Backing Layer  y

Must

be occlusive 2

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Adhesive Layer  y

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To retain the skin moisture and hydrate the site of  application for increase drug penetration Used as backing liners  Transparent or pigmented films of propylene,  polyethylene, and polyofelin

Must

be pressure sensitive Adheres to the skin with minimal pressure and remains in place for intended period of wear  Should be non-irritating, permit unimpeded drug flux to the skin, compatible with all other systems, allow easy peel-off  after use Commonly used as adhesive: polybutyl acrylate

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Different Design Objectives of TDDS y

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Deliver the drug to the skin for percutaneous absorption at therapeutic levels at an optimal rate Contain medicinal agents having necessary  physiochemical characteristics to release from the system, and partition to the stratum corneum Occlude the skin to ensure one way flux of drug into the stratum corneum Have a therapeutic advantage over other dosage forms and drug delivery systems  No irritation or sensitize the skin Adhere well to the patient¶s skin and have size, appearance, and site placement that encourage acceptance

Advantages of TDDS y

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Avoid:  Gastrointestinal absorption difficulties  First-pass effect  Inconvenience of parenteral therapy Substitute for oral administration of medication Provide extended:  Therapy with a single application  Activity of drugs having a short half- life through the reservoir of drug in the therapeutic delivery system and its controlled release Drug therapy may be terminated rapidly by removal of the application from the surface of the skin Identified easily and rapidly in emergencies

Disadvantages of TDDS y

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Only relatively potent drugs are suitable candidates for  transdermal delivery Some patients develop contact dermatitis at the site of  application

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Include:

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Transdermal Scopolamine (transderm scop system)  Patch is worn (at least 4 hours before the antinausea effect is required) in a hairless area behind the ear   Prevents motion sickness, nausea and vomiting resulting from the use of certain anesthetics and analgesics used in surgery Transdermal Nitroglycerin  For prophylactic treatment of angina

taken sublingually: relatively low dose, short plasma half-life, high peak plasma levels, and inherent side effects Examples: Deponit (Schawarz), Minitram (3M  Pharmaceuticals), Nitro-Dur (Key), and Transderm-Nitro (Novartis) Transdermal Clonidine (Catapres TTS)  First trandermal system for hypertension Transdermal Nicotine (Nicotrol)  As adjunct in smoking cessation programs  Effective aid in quitting smoking  Provides sustain blood levels of nicotine replacement therapy Transdermal Estradiol  Treatment of moderate to severe vasomotor  symptoms associated with menopause, female hypogonadism, female castration, primary ovarian failure, and atrophic conditions caused by deficient endogenous estrogen production (atrophic vaginitis and kraurosis vulvae)  Examples: Vivelle (Novartis) Transdermal Testosterone  For optimal absorption, applied to clean, dry scrotal skin that has been dry-shaved  Placed on the scrotum (stretching the scrotal skin with one hand and pressing the adhesive side of  the TDDS against the skin with the other hand, holding it in place for about 10 seconds) Androderm TDDS: applied nightly to a clean, dry  unbraded area of the skin of the back, abdomen, upper arms, or thighs

Other Transdermal Therapeutic Systems

Examples of Transdermal Drug Delivery Systems y

When

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Diltiazem, isosorbide dinitrade, propranolol, nifedipine, mepindolol, and verapamil, cardiovascular  agents Levonorgestrel with estradiol for hormonal contraception Physostigmine and xanomeline for Alzheimer¶s disease therapy  Naltrexone and methadone for substance addiction Buspirone for anxiety Bupropion for smoking cessation Papaverine for male impotence

Clinical Considerations in the Use of TDDSs Percutaneous absorption varies with the site of application Applied to clean, dry skin: relatively free of hair and not oily, irritated, inflamed, broken, or callused Use of skin lotion: avoided at the application site: affect skin hydration and can alter the partition coefficient  between the drug and the skin Should not be physically altered by cutting since it destroys the integrity of the system Should be removed from its protective package or backing Placed at a site not subjected to being rubbed off by clothing or movement Worn for full period stated in the products instructions The patient or caregiver should clean the hands thoroughly  before and after applying TDDS. In case of sensitivity or intolerance, the patient should seek  revaluation TDDS should be folded in half: cannot be reused 3

Crystal

R eservoir

Technology

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in smaller patches with a more controlled and sustained drug release

R esulted

Drug R eservoir-in-Adhesive

Single Layer Drug-in-Adhesive

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y y y

Backing

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Fentanyl

 Nicotine

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Drug-in-Adhesive

Backing

Drug Membrane Adhesive Liner 

Drug Matrix-in-Adhesive

Backing

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Drug-in-adhesive Membrane

Therapeutic Agent Clonidine

Estradiol

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Drug-in-adhesive Liner 

Multilayer y

Drug-in-adhesive Liner 

y y

TDDS

Backing

Adhesive Drug liner 

Design and Content

Comments

layer patch: (a) Backing of pigment polyester film (b) R eservoir of clonidine, mineral oil,  polyisobutylene, colloidal silicone dioxide (c) Microporous polypropylene membrane controlling rate of delivery (d) Adhesive formulation of agents Four layer patch: (a) Transparent polyester film (b) R eservoir of estradiol, alcohol gelled with hydroxypropyl cellulose, (c) Ethylene vinyl acetate copolymer  membrane (d) Adhesive formulation of light mineral oil,  polyisobutylene

Transdermal therapeutic system to deliver  therapeutic dose of antihypertensive drug at constant rate for 7 days. TDDS generally applied to hairless or shave are of upper arm or torso

Vivelle (Novartis)

Three-layer patch: (a) Translucent ethylene vinyl alcohol copolymer film (b) Estradiol in matrix of medical adhesive of   poly isobutylene, ethylene vinyl acetate copolymer  (c) Polyester release liner, removed prior to application

Use and application similar to Estraderm TDDS

Climara (Berlex )

Three-layer patch: Use and application similar to Estraderm (a) Translucent polyethylene film TDDS and system may be applied weekly (b) Acrylate adhesive matrix containing estradiol (c) Protective liner of siliconized or  fluoropolymer-coated polyester film, removed prior to use Four layer patch: Transdermal therapeutic system providing (a) Backing layer of polyester film continuous 72 hour systemic delivery of  (b) R eservoir of fentanyl, alcohol gelled with  potent opioid analgesic and indicated in hydroxyethyl cellulose  patients with chronic pain requiring opioid (c) R ate controlling ethylene-vinyl acetate analgesia copolymer membrane (d) Fentanyl containing silicone adhesive Multilayer round patch: Transdermal therapeutic system providing (a) Aluminized backing film continuous release systemic delivery of  (b) Pressure sensitive acrylate adhesive nicotine to aid smoking cessation. Patched (c) Methacrylic acid copolymer solution of  somewhat vary in nicotine content and nicotine dispersed in pad of nonwoven dosing schedules. viscose, cotton (d) Acrylate adhesive layer  (e) Protective aluminized release liner that

Catapres-TTS (Boehringer  Ingelheim)

Estraderm (Novartis)

Duragesic (Janssen)

Habitrol

(Nivartis Consumer)

Four

Transdermal system to release 12b-estradiol continuously. Patch is generally applied to trunk, including abdomen and buttocks, alternating sites twice a weekly over 3-week  cycle with dosage frequency adjusted as required

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overlies adhesive layer, removed prior to use  Nicoderm CQ (SmithKline Beecham Consumer)

 Nicotrol (McNeil Consumer)

Prostep (Lederie)

 Nitroglycerin

Deponit (Schwarz Pharma)

 Nitroglycerin

Nitro- Dur  (Key)

 Nitroglycerin

Transderm Nitro (Novartis)

Scopolamine

Transderm Scop (Novartis Consumer)

Testosterone

Testoderm (Alza)

Adroderm (SmithKline Beecham)

Multilayer

rectangular patch: (a) Occlusive backing of aluminum,  polyester, ethylene-vinyl acetate copolymer  (b) R eservoir of nicotine in ethylene-vinyl acetate copolymer matrix (c) R ate-controlling polyethylene membrane (d) Polyisobutylene liner, removed prior to application Multilayer

rectangular patch: (a) Outer backing of laminated polyester film (b) R ate-controlling adhesive nonwoven material, nicotine (c) Disposable liner, removed prior to use Multilayer

round patch: (a) Beige foam tape acrylate adhesive (b) Backing foil gelatin low density  polyethylene coating (c) Nicotine gel matrix (d) Protective foil with well (e) R elease liner removed prior to use Three-layer system: (a) Covering foil (b) Nitroglycerin matrix with polyisobutylene adhesive, plasticizer, release membrane (c) Protective foil, removed prior to use  Nitroglycerin in gel like matrix of glycerin water , lactose polyvinyl alcohol, povidone, sodium citrate sealed in polyester, foil,  polyethylene laminate Four-layer patch: (a) Backing layer of aluminized plastic (b) R eservoir of nitroglycerin absorbed on lactose, colloidal silicone dioxide, ilicone medical fluid (c) Ethylene-vinyl acetate copolymer  membrane (d) Silicone adhesive Four Layer patch: Continuous release of drugs over 3 days to (a) Backing layer of aluminized polyester   prevent nausea, vomiting of motion sickness. film Patch is placed behind ear. For repeated (b) R eservoir of scopolamine, mineral oil, administration, first patch is removed and  polyisobutylene second placed behind other ear. Also (c) Microporous polypropylene membrane approved to prevent nausea of certain for rate delivery of scopolamine anesthetics and analgesics during surgery. (d) Adhesive of polyisobutylene, mineral oil, scopolamine Three-layer patch: Patch is placed on scrotum in treatment of  (a) layer of polyethylene testosterone deficiency Backing terephthalate (b) Matrix film layer of testosterone, ethylene-vinyl actetate copolymer  (c) Adhesive strips of polyisobulylene, colloidal silicone dioxide Five-layer

patch: (a) Backing film of ethylene-vinyl acetate copolymer, polyester laminate (b) R eservoir of testosterone, ,alcohol, glycerin, glyceryl monoleate, methyl laureate gelled with acrylic acid copolymer  (c) Microporous polyethylene membrane (d) Acrylic adhesive

Patch is placed on back, abdomen, upper  arms, or thighs for treatment of testosterone deficiency

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(e) Adhesive polyester laminate

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