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SEMI-SOLID DOSAGE FORMS, PHARMACEUTICAL White Petrolatum, USP INSERTS AND TRANSDERMAL SYSTEMS Is a purified mixture of semisolid hydrocarbons from Are applied to the skin or inserted into body orifices in liquid, petroleum that...

SEMI-SOLID DOSAGE FORMS, PHARMACEUTICAL White Petrolatum, USP INSERTS AND TRANSDERMAL SYSTEMS Is a purified mixture of semisolid hydrocarbons from Are applied to the skin or inserted into body orifices in liquid, petroleum that has been wholly or nearby semi-solid or solid forms. decolorized. It is used for the same purpose as OINTMENTS petrolatum, but because of its lighter color, it is Definition considered more aesthetically pleasing by some Are semi-solid preparations intended for external pharmacists and patients. applications to the skin or mucous membranes, It is also known as White Petroleum Jelly usually but not always, they contain medicinal Ingredients: Yellow wax, Petrolatum agents. White Ointment, USP Are easily spread, their plastic viscosity may be This ointment differs from yellow ointment by controlled by modification of the limitation. substitution of white wax (bleached and purified Also known as Salve or Chrisma yellow wax) and white petrolatum in the formula. Uses Emollients ABSORPTION BASES - which makes the skin more pliable Absorption bases are of two types: Protective barriers Those that permit the incorporation of aqueous - which prevents harmful substances from solutions resulting in the formation of water-in-oil coming in contact with the skin (w/o) emulsions (Hydrophilic petrolatum). Vehicles Those that are water-in-oil (w/o) emulsions - in which to incorporate medication. (Emulsion bases) that permit the incorporation of Classification additional quantities of aqueous solutions (Lanolin). Based on Composition These bases may be used as emollients, although Oleaginous bases they do not provide the degree of occlusion Absorption bases afforded by the oleaginous base, and are not easily Water-removable bases removed from the skin with water washing, because Water-soluble bases the external phase of the emulsion is oleaginous. Based on Penetration These bases are useful as pharmaceutical adjuncts Epidermic ointments to incorporate small volumes of aqueous solutions Endodermic ointments into hydrocarbon bases. This is accomplished by Diadermic ointments incorporating the aqueous solution into the absorption base and then incorporating this mixture BASED ON COMPOSITION into the hydrocarbon base. OLEAGINOUS BASES Are anhydrous Also termed as Hydrocarbon bases. Insoluble in water On the application to the skin, they have an Not washable in water emollient effect, protect against the escape of However, it can absorb water. moisture, effective as occlusive dressings, can Permit the inclusion of water-soluble medicaments remain on the skin for long periods without drying through prior solution and uptake of the solution as out, and because of their immiscibility with water, the internal phase. and are difficult to wash off. Hydrophilic Petrolatum, USP Water and aqueous preparations may be A white petrolatum combined with 8% white wax, 3% incorporated, but only in small amounts with some stearyl alcohol, and 3% cholesterol which are added difficulty. to a water-in-oil emulsifier. When powders substances are to be incorporated Ingredients: into the hydrocarbon bases, liquid petrolatum Cholesterol Stearyl alcohol (mineral oil) may be used as the levigating agent. White wax White Petrolatum Petrolatum, USP Prepared form: Is a purified mixture of semisolid hydrocarbons Aquaphor obtained from petroleum. It is an unctuous mass, - which employs wool alcohol to render white varying in color from yellowish to light amber. petrolatum emulsifiable and is superior in It is also known as Yellow Petrolatum and its ability to absorb water. Petroleum Jelly. Polysorb A good base for oil-soluble ingredients. - which uses Sobitan Sesquioleate and Arlacel Forms an occlusive film on the skin. A as emulsifiers (Kessolin) and appears to Absorbs less than 5% water under normal conditions. be superior to the USP base. Does not become rancid Wax may be incorporated to stiffen the base. Lanolin, USP (Anhydrous Lanolin/Wool Fat) WATER-SOLUBLE BASES Is obtained from the wool of sheep, is a purified wax They do not contain oleaginous components. They like substance that has been cleaned, deodorized, are completely water washable and often referred to and decolorized. as greaseless. Because they soften greatly with the It contains not more than 0.25% water. Additional addition of water, large amounts of aqueous water may be incorporated into lanolin by mixing. solutions are not effectively incorporated into these Contains a high percentage of alcohol, esters and bases. alcohol containing fatty acids. They are mostly used for incorporation of solid Absorbs twice its weight in water and melts between substances. 36°C and 42°C. Polyethylene Glycol (PEG) Ointment, NF Modified Lanolin, USP Is a polymer of ethylene oxide and water Is a lanolin processed to reduce the content of free represented by the formula H(OCH2CH2)nOH, in lanolin alcohols and any detergent and pesticide which n represents the average number of residue. oxyethylene groups. The numeric designations associated with PEGs refers to the average WATER-REMOVABLE BASES molecular weight of the polymer. Are oil-in-water emulsions commonly called PEG having a molecular weight below 600 are clear, Creams. Because the external phase of the emulsion colorless liquids; those with molecular weight above is aqueous, they are easily washed from the skin 1,000 are wax like materials; and those with and are often called water-washable bases. molecular weight in between are semisolids. The They may be diluted with water or aqueous greater the molecular weight, the greater the solutions. They can absorb serous discharges. viscosity of PEGs ranging from average molecular Hydrophilic Ointment, USP weight of 200 to 8,000, An oil-in-water emulsion employing Sodium Lauryl Ingredients: Sulfate as an emulsifying agent. It absorbs about PEG 3350, PEG 400 30% - 50% W/W without losing consistency, and Consist of a blend of water-soluble polymeric glycol readily miscible with water and thus can be removed that forms a semi-solid base capable of solubilizing from the skin easily. water-soluble drugs and some water-insoluble Ingredients: drugs. Compatible with a wide range of drugs. White petrolatum sodium lauryl sulfate Contains 40% PEG 4000 and 60% PEG 400. Only a propylene glycol stearyl alcohol small amount of liquid (less than 5%) can be purified water methylparaben incorporated without loss of viscosity, and this can propylparaben be made stiffer by increasing the amount of PEG Cold Cream 4000 to 60%. A water-in-oil emulsion prepared by melting white Propylene Glycol and Propylene Glycol-Ethanol wax and spermaceti, expressed almond oil together, Form a clear gel when mixed with 2% hydroxypropyl adding hot aqueous solution of sodium borate, stir cellulose. until cool This has become popular as dermatologic vehicles. Mineral oil may be used to make a more stable cold cream. BASED ON PENETRATION Almond oil may be used to make a better emollient Epidermic Ointments base. Demonstrate no or at the most very slight Vanishing Cream penetration. An oil-in-water emulsion which contains large Petrolatum, Waxes, and their combinations percentage of water as well as humectants Endodermic Ointments (Glycerin, Propylene glycol) - which retards surface Possess some powers of penetration into the deeper evaporation of the product. layers of the skin. The most common cream available in the market Vegetable oils, Lard, Wool fat, Lanolin, and/or its due to large amount of water contained and an acid combinations (Stearic acid). An excess of stearic acid in the Diadermic Ointments formula helps to form a thin film when the water Which penetrates the skin thus offering a better evaporates. opportunity for absorption of the medicaments. Other Water-Removable Bases Dermovan - a hypoallergenic greaseless emulsion base. Unibase - a non-greasy emulsion base that absorbs about 30% of its weight in water and has a pH close to the skin.  METHODS OF PREPARATION Ointments are prepared by two general methods by Incorporation and Fusion depending primarily on the nature of the ingredients. Insoluble substances should be first reduced to the finest possible form and levigated before incorporation, by levigating with a small amount of a compatible levigating agent or by the base itself. INCORPORATION The substances are incorporated into the ointment by levigation. Mortar and Pestle Large amount or quantities of liquid are to be incorporated into a base. Ointment Slab Ground-glass plate and two 5-6 inches full blade hard steel spatulas. Hard rubber or Tested plastic spatulas. Ointment Mill Is an electronic mortar and pestle or a device called Unguator. This device can be controlled manually or via computer software. Is convenient and ideal for making ointments in lots of 5 lbs. or more. Ointment Parchment Pad It is best not to allow too long in contact of the ointment with the parchment, as it may soften and tear. Organic Solvents: Ether, Chloroform, Alcohol – should not be used for dissolving the drug because the drug may crystallize as the solvent evaporates. FUSION All or some of the components of an ointment are combined by being melted together and cooled with constant stirring until congealed. Components not melted are added to the congealing mixture as it is being cooled and stirred. Naturally, heat-labile substances and any volatile components are added last, when the temperature of the mixture is low enough not to cause decomposition or volatilization of the components. PACKAGING, STORAGE, AND LABELING Ointments and other semisolid preparations are packaged either in large-mouthed ointment jars or metal or plastics tubes. Semisolid preparations must be stored in well-closed containers to protect against contamination and in a cool place to protect against product separation in heat. When required, light sensitive preparations are packaged in opaque or light-resistant containers. In addition to the usual labeling requirements for pharmaceutical products, the USP directs the labeling for certain ointments and creams including proper storage conditions, dosing and administration.  CREAMS GELS Definition Definition Are semi-solid preparations containing one or more Also known as Jellies. medicinal agents dissolved or dispersed in either an Are semi-solid systems consisting of dispersions of oil-in-water emulsion or in another type of small or large molecules in an aqueous liquid vehicle water-washable base. rendered jelly-like by the addition of a gelling Patients and physicians prefer creams to ointments agents. because they are easier to spread and remove than Are semi-solid that can have properties ranging many ointments. from soft and weak to hard and tough. The so-called Vanishing Creams are oil-in-water Are defined as a substantially dilute cross-linked emulsions containing large percentage of water and system, which exhibits no flow when in the stearic acid or other oleaginous components. After steady-state. application of the cream, the water evaporates, Has been defined phenomenologically as a soft, leaving behind a thin residue film of stearic acid or solid or solid-like material consisting of two or more other oleaginous component. components, one of which is a liquid, present in substantial quantity. Preparation Creams may be formulated from a variety of oils Gelling Agents both mineral and vegetable, and from fatty alcohols, Macromolecules: Carbomer 935 fatty acids, and fatty esters. Cellulose derivatives: The solid excipients are melted at the time of Carboxymethylcellulose or preparation. Hydroxypropylmethylcellulose Emulsifying agents includes nonionic surfactants, Natural gums: Tragacanth detergents, and soaps. Soaps are usually formed Other Agents from a fatty acids in the oil phase hydrolyzed by a Drug substance base dissolved in the aqueous phase in situ during Water the preparation of creams. Co-solvents: Alcohol and/or propylene glycol Antimicrobial preservatives: Composition Methylparaben, propylparaben, or Four (4) main ingredients of cold cream: Chlorhexidine gluconate Water Stabilizers: Edetate disodium Oil Emulsifier Preparation Thickening agent Gels formed with large organic molecules may be formed by dispersing the molecule in the continuous Application and Use phase (by heating starch), by cross-linking the Primary application in topical skin products and in dispersed molecules by changing the pH (as for products used on mucous. membranes, such as carbomers), or by reducing the continuous phase (as rectally and vaginally. for jellies formed with sucrose) The provision of a barrier to protect the skin Care should be taken to ensure uniformity of the To aid in the retention of moisture. APIs by dispersing them by vigorous mixing or As emollient. milling or by shaking if the is less viscous. As vehicle for drug substance such as local anesthetics, anti-inflammatories, hormones, Application antibiotics, antifungals or counter-irritants. Topically applied onto the skin, eyes, nasally, vaginally and rectally. Administered by the topical oromucosal routes. Antibiotic- containing gels can be administered by teat infusion in veterinary medicine to treat mastitis. Packaging and Storage Should be stored in tight containers to prevent water loss. Avoid freezing.  MISCELLANEOUS SEMI-SOLID DOSAGE FORM PLASTERS PREPARATIONS Are solid or semi-solid adhesives masses spread upon a backing material or paper, fabric, moleskin PASTES or plastic. The adhesive material used is a rubber Are semi-solid preparations intended for application base or a synthetic resin. to the skin. Adhesive tape used to be official under the title They are generally contain a large proportion of Adhesive Plaster, the use of this material being well solid material (such as 25%) than ointments and known. therefore are stiffer. When prepared with an oleaginous base they are Application and Use greasy than their counterpart ointments due to the Applied to the skin to provide prolonged contact at reduced amount of the base. the site. Medicated plasters provide effects at the site of Preparation application. They may be cut to size to conform to Are prepared in the same manner as ointments, by the surface to be covered. direct mixing or the use of heat to soften the base Unmedicated plasters provide protection or prior to incorporating the solids, which have been mechanical support at the site of application. comminuted and sieved. However, when levigating agent is to be used to Product render the powdered component smooth, a portion Salicylic Acid Plaster - use on the toes for the of the base is often used rather than a liquid, which removal of corns with keratolytic action of Salicylic would soften the paste. acid (10- 40% concentration) Because of the stiffness, it remain in place after application and are effectively employed serous Glycerogelatin secretions. Because their stiffness and Are plastic masses containing: impenetrability, pastes are not suited for application ○ Gelatin (15%) to hairy parts of the body. ○ Glycerin (40%) When prepared with an oleaginous base they are ○ Water (35%) greasy than their counterpart ointments due to the ○ and an added medicinal substance (10%) as reduced amount of the base. Zinc Oxide. Application Preparation Applied on the skin, but not suited for hairy parts of Softening the gelatin in water for about 10 minutes. the body – due to its stiffness and impenetrability. Heat on a steam bath until the gelatin is dissolved. Add the medicinal substance mixed with glycerin. Product Allow the mixture to cool with stirring until Zinc Oxide Paste - is prepared by mixing 25% each congealed. of zinc oxide and starch with white petrolatum. Application Applied to the skin for longer residence. They are melted before application, cooled to slightly above body temperature, and applied to the affected area with a fine brush. Following application, the glycerogelatin hardens, is usually covered with a bandage and is allowed to remain in place for a period of weeks. Product Zinc Gelatin Use in the treatment of varicose ulcers. It was also known as “Zinc Gelatin boot” due to its ability to form a pressure bandage. Packaging of Semi-Solid Topical dermatologic products - packaged in either jars, tubes, or syringes. Ophthalmic, nasal, vaginal and rectal solid products - tubes or syringes  SUPPOSITORIES Types Rectal Definition Are inserted into the rectum with the fingers. Are solid dosage forms in which one or more active Are cylindrical and have one or both ends tapered. pharmaceutical ingredients (APIs) are dispersed in Some are shaped like a bullet, a torpedo, or the little a suitable base molded or otherwise formed into a finger. suitable shape for insertion into the rectum to ○ Length: Usually about 32 mm (1 1⁄2 inches) provide local or systemic effect. ○ Weight: Adult: 2 grams - when made of Are solid dosage forms intended for insertion into cocoa butter (pencil-like shape) body orifices where they melt, soften, or dissolve ○ Infants: 1 gram and exert localized or systemic effects. Vaginal Derived from the Latin word supponere which Also called Pessary or Pessaries means “to place under”, as from sub (under) and Are usually globular, oviform, or cone- shaped ponere (to place). ○ Weight: about 5 grams - when made cocoa butter base Uses Weights may vary depending on Used rectally, vaginally, and occasionally urethrally. the base use and the individual manufacturer’s product Local action: Urethral Once inserted, the base melts, softens or dissolves, Also called Bougies distributing the medicaments it carries to the tissue Are slender, pencil-shaped intended for insertion of the region. into the male or female urethra. ○ Rectal Male: - pain, constipation, irritation, Diameter - 3-6 mm itching, and inflammation Length: 140 mm (14 cm) associated with hemorrhoids or Weight: about 4 grams - when made of cocoa butter other anorectal disorders. Female: ○ Vaginal Length: 70 mm (7 cm) - contraceptives, antiseptics in Weight: about 2 grams - when made of cocoa butter feminine hygiene, antibacterial Systemic action: Burginarium The mucous membranes of the membranes of the same as urethral suppositories but shorter and rectum and vagina permit the absorption of many thinner. soluble drugs. ○ Rectal - is frequently as the site for the BASES systemic absorption ○ Vaginal FATTY or OLEAGINOUS BASES - is not as frequently used for this Cocoa Butter (Theobroma Oil) purpose. The most widely used suppository base. Good base for rectal suppositories, but it is Application less ideal for vaginal and urethral Suppositories come in various shapes and weights. suppositories. The shape and size must be such that it can be White wax can replace part of it to obtain a easily inserted into the intended orifice without proper melting point. causing undue distension, and once inserted, it must be retained for the appropriate period. Hydrogenated Fatty Acids of Vegetable Oils Are intended for insertion into body orifices where Kernel oil and Cottonseed oil they melt, soften, or dissolve and exert localized or systemic effects. Glycerin with Higher Molecular Weight Fatty Acids These are fat-based compounds containing compounds of Glycerin with the higher molecular weight fatty acids such as Palmitic acid and Stearic acids. Glyceryl Monostearate and Glyceryl Monopalmitate  TYPES with respect to the VEHICLE or BASES used WATER-SOLUBLE and WATER-MISCIBLE BASES First Type Polyethylene Glycols (PEG) Are those prepared with Cocoa/Cacao Are polymers of ethylene oxide and water, Butter or Theobroma Oil prepared to various chains lengths, ○ Cacao Butter molecular weight, and physical states. - will soften when used with: They are available in a number of molecular Phenol, Camphor, Chloral weights ranges, the more commonly used hydrate, and other volatile being polyethylene glycol 300, 400, 600, oils. 1000, 1500, 1540, 3350, 4000, 6000, 8000. - However this can be These bases are water soluble; however, the remedied by the addition dissolution process is very slow. of: These do not melt at body temperature but Wax or Spermaceti to raise rather dissolve slowly in the body’s fluids. the melting point in the Therefore, the base needs not to be warmest weather. formulated to melt at body temperature. ○ Theobroma Oil In rectum and vagina, where the amount of - Acts by melting at body fluid is very small, they dissolve very slow, temperature. but they soften and spread. Second Type At room temperature: Are those prepared with Glycerin and Gelatin PEG 300, 400, 600 ○ Are water-soluble or water miscible - clear, colorless liquid ○ Are employed to provide a continuous PEG 1000 medicating or germicidal action - white semi-solid ○ By mixing the aqueous solution of PEG 1500, 1540 suspension of the medicament with glycerin - fairly firm semi-solid and gelatin. PEG 3350, 4000, 6000 - firm, wax-like solids Third Type Are the Glycerin or Soap suppositories shaped from Glycerinated Gelatin Castille soap May be prepared by dissolving granular gelatin ○ This performs their function in part (20%) in glycerin (70%) and adding a solution or mechanically and in part by dissolving and suspension of the medication (10%). producing some irritation. May have a tendency to absorb moisture due to the ○ Their chief value is as stimulation to hygroscopic nature of glycerin, they must be peristalsis, through their presence in the protected from atmospheric moisture for them to rectum. maintain their consistency. ○ They are mostly for small children to avoid Is most frequently used in the preparation of the use of laxatives vaginal suppositories, where the prolonged localized action of the medicinal agent is usually desired. METHODS OF PREPARATION Is slower to soften and mix the physiologic fluids 1. Molding (Fusion) than in cocoa butter and therefore provides a more Suppository Molds: prolonged release. Is the principal way of making suppositories May be formulated also into urethral suppositories commercially. prepared by dissolving granular gelatin (60%) in Capable of producing 6-12 or more suppositories glycerin (20%) and medicated aqueous portion Molds are made of Stainless steel, Aluminum, Brass (20%). or Nickel-Copper alloys, or plastic. Are much more easily inserted than suppositories Primary bases used are: Cocoa butter, Polyethylene with a cocoa butter base, owing to the brittleness of glycol, Glycerinated gelatin cocoa butter and its rapid softening at body Mineral oil is used as lubrication. temperature. Preparation: Melting of the base Incorporation of any of the medicaments Pouring the melt into molds Allowing the melt to cool and congeal into suppositories Removing the formed suppositories from the mold.  STORAGE Lubrication of the Molds: Cocoa butter suppositories Cocoa butter or Polyethylene glycol - must be stored below 30°C and preferably - lubrication is seldom necessary as these in a refrigerator (2°C to 8°C) materials contact sufficiently on cooling to Glycerinated suppositories can be stored at separate from the inner surfaces and allow controlled room temperature (20°C to 25°C). easy removal. Suppositories made from a base of Polyethylene Glycerinated gelatin glycol may be stored at usual room temperature. - lubrication is usually necessary. A thin coating of mineral oil applied within the OFFICIAL BASES finger to the molding surfaces usually Cocoa Butter or Theobroma Oil suffices. High Molecular Weight Polyethylene Glycol (PEG) Should be used carefully with thermolabile drugs Glycerinated Gelatin and insoluble powders ○ Insoluble powders in the liquid may settle during pouring causing a non-uniform drug INSERTS distribution. Are solid dosage forms that are inserted into a naturally ○ Hard crystalline materials occurring (nonsurgical) body cavity other than the mouth or - can be incorporated by dissolving rectum, including the vagina and urethra. the crystals in a minimum volume of suitable solvent prior to VAGINAL INSERTS (TABLETS) incorporation into the base. Are usually ovoid in shape and are accompanied in Ex: Iodine, Merbromine their packaging with a plastic inserter, a device for ○ Vegetable extracts easy placement of the tablet within the vagina. - can be incorporated by moistening It contains the same types of anti-infective and with few drops of alcohol and hormonal substances as the vaginal suppositories. levigating with a small amount of Application melted cocoa butter. The tablets are intended to disintegrate within the vagina releasing their medication. 2. Compression Some are Capsules of Gelatin Is generally employed when cocoa butter is - containing medication to be release used as a base. intravaginally. Capable of producing a 2 g suppository. Preparation Preparation: Compression Uniform mixture of drug and base (hand- Filler: Lactose rolling method) Disintegrating Agent: Starch Mixture is placed into a chamber mold. Dispersing Agent: Polyvinylpyrrolidone Mold is then cooled. Lubricant: Magnesium Stearate 3. Hand Rolling and Shaping MEDICATION STICKS Involves molding the suppository with the Are a convenient form for administering topical fingers after the formation of plastic mass. medications. Their development is interesting because it involves the history of cosmetics, which parallels human PACKAGING history. Glycerin and Glycerinated gelatin suppositories are Are cylindrical in shape and generally range from packaged in tightly closed containers to prevent a 5-25 g. change in moisture content. Use Suppositories prepared from a Cocoa butter base Used for both cosmetics and medical purposes, are individually wrapped or otherwise separated in includes styptic pencils and lip balm sticks which compartment boxes to prevent contact and became available in the early 1940’s. adhesion. Today, medication sticks provide pharmacists, Suppositories containing light-sensitive drugs are patients and primary care providers with a unique, individually wrapped in an opaque material such as convenient, relatively stable, easy-to-prepare a metallic foil. dosage form for the topical delivery of drugs. Preparation Ease of rapid identification of the medication in Medication sticks are prepared similar to emergencies due to the physical presence, features suppositories except that the melt is poured into the and identifying-marks on the TDDS. administering device, or tube. Application Disadvantages They come in different sizes and shapes, are readily Only relative potent drugs are suitable candidates transportable, and can be applied directly to the for transdermal delivery due to the natural limits of affected site of the body. drug entry imposed by the skin’s impermeability. The stick is pushed up from the bottom or using a Some patients may develop contact dermatitis at screw-type device to raise the stick. the site of application due to one or more of the Package system components, necessitating discontinuation. They are generally packaged in an applicator tube for topical administration, and the applicator can be Examples adjusted to continually expose new, fresh stick from Transdermal Scopolamine inside the tube. Transdermal Nitroglycerin Transdermal Clonidine TRANSDERMAL DRUG DELIVERY SYSTEMS (TDDSs) Transdermal Nicotine Transdermal Estradiol It facilitates the passage of therapeutic quantities of drug Transdermal Testosterone substances through the skin and into the general circulation Transdermal Contraceptive System for their systemic effect. Transdermal Methylphenidate Percutaneous absorption” ○ The evidence of percutaneous drug absorption may be found through PATCHES measurable blood levels of the drug, Are designed to deliver a constant and controlled detectable excretion of the drug and/or its dosage over extended periods of time for systemic metabolites in the urine, and through the therapy. clinical response of the patient to the Due to the barrier properties of the skin, relatively administered drug therapy. few drug molecules have the appropriate The blood concentration needed to achieve physiochemical and therapeutic properties for therapeutic efficacy may be determine by sustained transdermal delivery. comparative analysis of patient response to drug However some successful products have reached blood levels. the market such as scopolamine, nicotine, estradiol, It is considered ideal if the drug penetrates through fentanyl, testosterone and glyceryl trinitrate the skin to the underlying blood supply without drug transdermal patches. build up in the dermal layers. The Lidoderm (Lidocaine; Endo) 5% patch consists of an adhesive material containing 5% lidocaine, Advantages which is applied to a nonwoven polyester felt They can avoid GI drug absorption difficulties backing and covered with a PET film release liner. caused by GI pH enzymatic activity and drug The release liner is removed just prior to application. interactions with food, drinks, or other orally The patch is 10 X 14 cm. Each patch contains 700 mg administered drugs. of lidocaine in an aqueous base They can substitute for oral administration of medication when that route is unsuitable, as in USE AND APPLICATION instances of vomiting and or diarrhea. To treat post herpetic neuralgia. They avoid the first-pass effect Applied to intact skin to cover the most painful area. The systems are noninvasive, avoiding the Depending upon the direction for use, the patient inconvenience of parenteral therapy. can apply up to three patches, only once for up to 12 They provide extended therapy with a single hours within a 24-hour period. application, thereby improving patient compliance over other dosage forms requiring more frequent dose administration. The activity of drugs having short half-lives is extended through the reservoir of drug present in the therapeutic delivery system and its controlled release characteristics. Drug therapy may be terminated rapidly by removal of the application from the surface of the skin.  TAPES Is a dosage form that is suitable for delivering drugs to the skin. It consists of a drug that is impregnated into a flexible, durable woven fabric or extruded synthetic material that is coated with an adhesive agent. Typically, the drug is present in the dry state. The adhesive layer is designed to retain the tape securely in place without the aid of additional bandaging. Are not designed to control the release rate of the drug-like transdermal patches. The active drug content is expressed as an amount per surface area with respect to the tape surface exposed to the skin. The use of an occlusive dressing over the tape enhances the rate and extent of delivery of the drug to deeper layers of the skin and may result in greater systemic absorption of the drug. Application A portion of the tape slightly larger than the area to be treated is cut and removed from the backing paper. It should be applied to folds in the skin but rather to a smooth skin surface. It should be applied to dry skin.