Title of Invention	"A METHOD FOR THE MANUFACTURE OF A TRANSDERMAL DRUG"
Abstract	In a method of manufacturing such a system, an active substance is dissolved in a ratio less than saturation level in a solvent which is also a skin penetrating enhancer. The system (4) is coated as a layer onto a siliconized release paper (2) and laminated onto a backing strip.

Full Text

Title A method for the Manufacture of a Transdermal Drug. DESCRIPTION Technical Filed The invention relates to a method for the manufacture of a transdermal drug delivery system, that is a system for the administration of medicine through the skin of a patient and into the systemic circulation system. In this way, the medicine avoids passing through the gastro-intestinal tract and liver. Thus metabolism is to some extent avoided, and a smaller dose can be used. Background Art GB 2249956 contains a useful summary of the state of the art, and discloses such systems containing super-saturated solutions of an active ingredient within an adhesive layer by use of a carefully selected mixture of solvents. EP-A-276561 discloses a method for the manufacture of a transdermal drug delivery system in which the active ingredient, piroxicam, is mixed with an alkaline agent, the mixture obtained after the alkaline agent has been added is further dissolved and dispersed in a solubilizing agent such as crotamiton, and then the mixture is blended into an aqueous adhesive base to form a homogeneous pharmaceutical composition for use in tape form. The only example given using crotamiton as the solubilizing agent has a weight ratio of piroxicam to crotamiton of 1:2, which is well in excess of saturation concentration. The mixture is blended into an aqueous adhesive base from which a transdermal tape is formed by coating the mixture onto a peel-off liner and drying. WO-A-92/10231 discloses the use of sub-saturated solutions of the active ingredient, but only when the drug is hydrophobic. No skin penetration enhancer is contemplated. THE INVENTION The invention provides a method for the manufacture of a transdermal drug delivery system, which comprises the successive steps of: (a) dissolving a pharmaceutically active substance such as herein defined in a solvent such as herein defined which is one or more of the skin penetration enhancers crotamiton and diethyltoluamide (DEET), and optinally one or more other skin penetration enhancers, to form a solutin of active substance in the skin penetration enhancer(s) at a concentration less than saturation; (b) mixture the resulting solution which an adhesive such as herein defined in the form of a solution or an aqueous dispersion; (c) forming the mixture obtained in (b) into a coating on a release liner or backing sheet; and (d) drying the coating at a temperature less than the boiling point of the skin penetration enhancer or enhancers used as solvent in the dissolution step (a) to yield a transdermal drug delivery system for the administration of the pharmaceutically active substance through the skin of a patent and into the patient's systemic circulatiory system. The invention provides for effective transdermal delivery of any number of pharmaceutically active substances at less than the saturation concentrations. The invention selects, as a solvent to create the original solution of the pharmaceutically active substance, a solvent that is both a good solvent for the drug and a good skin penetration enhancer, and thus the creation of the initial solution of the active substance is made easier because the use of a separate aqueous or organic solvent is unnecessary. Because of the skin penetration enhancement properties of the solvent, good transdermal transport properties can be achieved even at sub saturated drug concentrations. Indeed the transdermal drug transport characteristics from sub saturated solutions have been found to be even better than those at saturated solutions have been found to be even better than those at saturated solutions have been found to be even better than those at saturated or supersaturated concentrations, which is the reverse of contrary to what is known in the art, as exemplified by Pick's Law. Investigations by the inventors found that two skin penetration enhancers in particular showed sufficiently high dissolution properties for a range of hydrophilic and hydrophobic drugs to be used as the solvent to created the original solution of the active substance. These sol vent/enhancers are crotamiton and diethyltoluamide (DEET). The process steps of the invention are as set out in claim 1. By using the active substance in, a ration less than saturation level, there is a reduced risk of crystallisation, a stable system can be manufactured, and a constant rate of delivery to the patient can be obtained. It is surprising that certain solvents act both as a skin penetration enhancer and as a solvent for the active substance. Such solvents/enhancers are crotamiton, diethyltoluamide (DEET) and mixtures thereof. The ratio of crotamiton to DEET in such a solvent mixture may be from 5:95 to 95.5% by weight of the total solvent/enhancer content depending on the delivery rate and extent of the delivery required for the active substance. By choosing a solvent/enhancer of sol vent/enhancers having a boiling point higher than any drying temperature applied to the system, and controlling the drying temperature, the solvent(s) do not evaporate, the solution of the active substance never becomes, and a high proportion of active substance remains in the system. The active substance/solvent(s) solution cab be maintained at 20°-30° for over one month. The pharmaceutically active substance may be: a-Adrenergic agonists such as Adrafinil, Adrenolone, Amidephrine, Aproclonidine, Clonidine, Ephedrine, Naphasoline and Tramazoline; ß-Adrenergic agonists such as Albuterol, Clenbuterol, Clorprenaline, Methoxyphenamine and Terbuterol; α-Adrenergic blockers such as Amosulalol, Dapiprasol, Ergoloid Mesylates, Prazosin, Terazosin, Yohimbine; ß-Adrenergic blockers such as Acebutolol, Alprenolol, Atenolol, Pindolol, Propanolol and Timolol; Anabolics such Androstenediol, Ethylstrenol, Methoandriol, Nandrolone, Oxzymesterone, Quinbolone and Stenbolone; Analgesic (narcotic) such as Alfentanil, Benzylmorphine, Buprenorphine, Codeine, Codeine Phosphate, Dihydrocodeine, Dihydromorphine, Fentanyl, Methadone Hydrochloride, Morphine, Morphine Derivatives, Narceine, Opium, Oxycodone, Oxymorphone, Phenazocine and Sufentanil; Analgesics (non-narcotic) such as Acetaminophen, Acetanilide, Acetylsalicylic Acid, Carbamazepine, Diflunisal, Indomethacin, Ketoprofen, Naproxen, Phenacetin, Salicylamide and Tramadol; Androgens such as Mesterolone, 17-Methylestosterone, Testosterone and Testosterone Propionate; Anaesthetics such as Amylocaine Hydrochloride, Bupivacaine, Lidocaine, Midazolam, Procaine, Tetracaine Hydrochloride, Thiopental Sodium and Zolarnine; Anti-acne drugs such as Algestone Acetophenide, Benzoyl Peroxide, Cyproterone, Resorcinal, Retinoic Acid and Tetroquinolone; Anti-amebic such as Chloroquine, Chlortetracyline, Dehydroeametine, Emetine, Teclogan, Thiocarbamizine, and Tinidazole; Antianginals such as Alprenolol, Amlodipin Diltiazem, Felodipine, Isosorbide Dinitrate, Nicardipine, Nifedipine, Nitroglycerin, Oxpernolol, Pindolol, Timoloil, Verapami; Antibacterial drugs such as Gentamicin, Kanamycin, Neomycin, Chloramphenicol, Chloramphenicol Pantothenate, Clindamycin, Lincomycin, Clarithromycin, Erthromycin and Cycloserine; Anti-estrogens such as Delmadinone Acetate, Tamoxifen and Toremifene; Antifungal drugs such as Clotrimazole, Econazole, Ketoconazole, Miconazole and Potassium Iodide; Antihistamines such as Chlorpheniramine, Dimethindene, Pheniramine, Triprolidine and Phenothiazine; Antihypertensive drugs such as Captoprill, Enalapril, Clonidine and Minoxidil; Anti-inflammatory drugs such as Mefenamic Acid, Flubiprofen, Ibuprofen, Indomethacin, Ketoprofen, Aspirin, Mesalamine, Olsalasine, Piroxicam and Tenoxicam; Anti-parkinsonian drugs such as Amantadine, Levodopa, Pergolide and Pridinol; Antipyretics such as Camphor, Menthol, Phenol, Polidocanol, Spirit of Camphor and Trimeprazine; Anti-seborrheic drugs such as Pyrithione, Resorcinol, Selenium Sulphides and Tioxolone; Antiseptics such as Chlorhexidine, Bismuth Iodide Oxide, Povidone Iodine, Triclosan, Triclosane Potassium, Carvacrol, p-Cresol, Chloroxine, Halquinol, Boric Acid, a-Terpineol and Chlorthexidine; Anti-ulcerative drugs such as Cimetidine, Enprostil, Omeprasol, Ranitidine and Trimoprostil; Anxiolytic drugs such as Buspirone, Bromazepam, Diazepam, Loxapine, and Meprobamate; Chlorinergic agents such as Bethanechol Chloride, Physostigmine and Pyridostigmine Bromide; Depigmentors such as Hydroquinine, Hydroquinone and Monobenzone; Estuogens such as Benzestrol, Dienestrol, Diethylstilbestrol, Dimestrol, Methestrol, Conjugated estrogenic Hormones, Equilenin, Equilin, Estradiol, EstradiolBenzoate, Estradiol 17ß-Cypionate, Estriol, Estrone, Ethinyl Estradiol, Mestranol, Moxestrol, Quinestradiol and Quinestrol; Gonadotropic hormones such as LH and PMSG; Nootropic agents such as Aceglutamide, Antiracetam, Piracetam, Pyritinol and Tacfine. Progestogens such as Allylestrenl, Anagestone, Chlormadinone Acetate, Delmadinone Acetate, Demegestone, Desogestrel, Dimethisterone, Dydogesterone, Ethisterone, Ethynodiol, Flurogestone Acetate Gestodene, Gestodene Caprolate, Haloprogesterone, 17-Hydroxy-16-methylene-progesterone, 17-α-Hydroxyprogesterone, 17-α-Hydroxygesterone Caprolate, Lynestrenol, Medrogestone, Medroxyprogesterone Megestrol Acetate, Melengestrol, Norethisterone, Norethisterone Acetate, Noretynodrel, Norgesterone, Norgestimate, Norgestrel, Norgestrienone, Norvinistyerone, Pentagestrone, Progesterone, Promegestrone, Quingestrone and Trengestone; Respiratory stimulants such as Almitrine, Doxapram, Lobeline, Sodium Succinate and Tacrine; Vitamins, vitamin sources and vitamin extracts such as Vitamins A, B, C, D, E and K and derivatives thereof, Calciferols, Glycyrrhiza and Mecobalamin; or Vulnerary agents such as Acetylcysteine, Allantoin, Asiaticoside, Cadexomer Iodine, Chi tin, Dextranomer and Oxaceprol. The solvent/enhancer is Crotamition, Diethyltoluamide (DEET), or a mixture thereof. If desired the solution obtained in step (a) can also incorporate at least one of: Transcutol (Diethylene 'glycol monoethyl ether), Labrafil M1944CS (unsaturated polyglycolysed glycerides), Labrasol (Glyceryl and polyethylene glycol esters), Tea-tree oil (Oil of Melaleuca), Propylene Glycol, MP DIOL (2-Methyl-l,3-Propanediol) and Polyethylene Glycol. It Will be appreciated that the amount of active substance to be incorporated in the delivery system is dependent or governed by the drug composition and/or concentration, the desired therapeutic effect for a patient, and the period for which the delivery system is to provide a therapeutic drug level. Preferably, the active substance is present in an, amount from 0.1% to 50% by weight of the coating material (i.e. an aqueous emulsion or adhesive solution). More preferably, 0.3% to 30% by weight of the coating material. The active substance is generally incorporated in the solvent/enhancer at room temperature (25°C or Below) and in a ratio less than 90% of saturation level to prevent crystal formation during storage. Dissolution may be aided by sonication or warming. The resulting solution can be added slowly to the adhesive which may be in the form of an aqueous dispersion or solution, and mixed. The adhesive can be an acrylate, silicone or polyisobutylene. An adhesive thickener may be added to the mixture at about a 50% solution/water mix to produce a thicker spreading solution for reverse roll coating or knife over roll coating. The resulting delivery system may then be coated onto a release liner, which may be a siliconised polyester such as type FL 2000 (commercially available), or paper, which naturally is impermeable to the active substance. The system can then be dried by circulating hot air, and laminated onto a backing sheet, which may be a 3M Health Care Type 1220, the backing sheet naturally being impermeable to the active substance. The layer may be coated to a wet-coat thickness of from 20 to 500 µ. Alternatively, the delivery system mixture may be spread or coated onto the backing sheet, and then laminated to the release liner. The hot air circulation may be effected at gradually increased temperatures from 50°Ctol40°C. In accordance with the present it relates to a method for the manufacture of a transdermal drug, which comprises the successive steps of: (a) dissolving a pharmaceutically active substance selected from the groups of ct- Adrenergic agonists, ß-Adrenergic agonists, α-Adrenergic Mockers, ß- Adrenergic blockers, Anabolics, Analgesic (narcotic), Analgesics (non- narcotic), Androgens, Anaesthetics, Anti-acne, Anti-amebic, Antianginals, Respiratory stimulants, Vitamins, Vitamin sources and Vitamin extracts Vulnerary agents" antibaceterial drug, anti-estrogens, Anti-fungal, antihistamines, antihypertensive drugs, anti-inflammatory drugs, anti- parkinsonian drugs, antipyretics, anti-seborrheic drugs, antiseptics, anti- ulcerative drugs, anxiolytic drugs, chlorinergic agents, depigmentors, estrogens, gonadotropic hormones, nootropic agents and progesterogens in a solvent such as herein defined which is one'or more of the skin penetration enhancers crotamiton and diethyltoluamide (DEET) to form a solution of active substance in the skin penetration enhancer(s) at a concentration less than saturation; (b) mixing the resulting solution with an adhesive such as herein defined in the form of a solution or an aqueous dispersion; (c) forming the mixture obtained in [b] into a coating on a release liner or backing sheet; and (d) drying the coating at a temperature less than the boiling point of the skin penetration enhancer or enhancers used as solvent in the dissolution step [a] to yield a transdermal drug delivery system for the administration of the pharmaceutically active substance through the skin of a patient and into the patient's systemic circulatory system. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING Fig. 1 is section through an adhesive tape for application to the skin of a patient comprising a drug delivery system according to the invention. A delivery system comprising an active substance, adhesive and solvent/skin penetration enhancer 4 is coated as a layer onto a siliconized release paper 2 and laminated onto a backing strip 6. The following Examples of ingredients in parts by weight may be used in the production of delivery systems as described above: (Table Removed) Manufacturing Method (illustrative) A) Delivery system using adhesive - aqueous emulsion The active substance is dissolved in the solvent by means of heating and mixing over a 45°-55°C water bath with agitation. When the solution is optically clear, it is checked microscopically for absence of crystals. The adhesive is weighed into a separated mixing vessel, diluted with water if necessary over a period not exceeding 30 mins to achieve the requisite viscosity. The active substance/solvent solution is gradually added to the adhesive solution with mixing. The pH is adjusted to 6.5-7.5 and a thickener is added (if appropriate) to obtain a suitable viscosity (eg 900-100 cps) for the selected coating process such as reverse roll coating or knife over roll coating. The resultant aqueous emulsion is coated onto a release liner (typical coating thickness 20-500 µ), and dried by passing in sequence through ovens at 50-140°C. the product is then laminated onto a backing sheet. B) Delivery system using an adhesive solution The active substance is dissolved in a solvent by means of heating and mixing as described above. The adhesive is weighed in a separate vessel and the active substance/solvent solution is gradually added to the solution of adhesive with mixing. The resultant adhesive solution is coated onto a release liner, dried by passing in sequence through ovens at 50-140°C. The product is then laminated onto a backing sheet. In-vitro drug delivery through the skin In-vitro skin permeation experiments with human skin have been on systems made from the above ingredients carried out using Franz-type diffusion cells, and the studies were carried out on a Hanson Microette system. Dermatomed human skin sections were mounted onto the Franz cells and transdermal drug delivery systems mounted on tape backings (105cm2) were placed on the stratum corneal surface of the skin. Each Franz cell contained 7ml of ethanol phosphate buffered saline as the receptor medium, maintained at 32°C. At predetermined time intervals 0.7ml of the receptor solution was sampled and an equal amount replaced. The samples were analysed by High pressure Liquid Chromatography. The skin mass transport of Estradiol and Norethisterone Acetate has been found to be enhanced by the solvent / skin penetration enhancer DEET and / or Crdtamiton in a concentration below saturation. Further, the active substance flux profile follows the solvent flux profile, the latter showing high skin penetration flux during the first 20 hours of application. Indications The main indications are in both peri-menopausal and menopausal women for the control in the former of the symptoms of the menopause such as hot flushes, sweating and the other symptoms of the peri-menopause, and in the case of the menopause the prevention of osteoporosis and cardiac events such as coronary thrombosis. WE JCLAIM: 1. A method for the manufacture of a transdermal drug, which comprises the successive steps of: (a) dissolving a pharmaceutically active substance selected from the groups of a- Adrenergic agonists, ß-Adrenergic agonists, α-Adrenergic blockers, ß- Adrenergic blockers, Anabolics, Analgesic (narcotic), Analgesics (non- narcotic), Androgens, Anaesthetics, Anti-acne, Anti-amebic, Antianginals, Respiratory stimulants, Vitamins, Vitamin sources and Vitamin extracts Vulnerary agents" antibaceterial drug, anti-estrogens, Anti-fungal, antihistamines, antihypertensive drugs, anti-inflammatory drugs, anti- parkinsonian drugs, antipyretics, anti-seborrheic drugs, antiseptics, anti- ulcerative drugs, anxiolytic drugs, chlorinergic agents, depigmentors, estrogens, gonadotropic hormones, nootropic agents and progesterogens in a solvent such as herein defined which is one or more of the skin penetration enhancers crotamiton and diethyltoluamide (DEBT) to form a solution of active substance in the skin penetration enhancer(s) at a concentration less than saturation; (b) mixing the resulting solution with an adhesive such as herein defined in the form of a solution or an aqueous dispersion; (c) forming the mixture obtained in [b] into a coating on a release liner or backing sheet; and (d) drying the coating at a temperature less than the boiling point of the skin penetration enhancer or enhancers used as solvent in the dissolution step [a] to yield a transdermal drug delivery system for the administration of the pharmaceutically active substance through the skin of a patient and into the patient's systemic circulatory system. 2. A method as claimed in claim 1, wherein the solvent used in step [a] comprises the skin penetration enhancers crotamiton and DEBT in a ratio of from 5:95% to 95:5% by weight. . A method as claimed in claim 1 or claim 2, wherein the solution obtained in step [a] additionally incorporates at least one of: transcutol (diethylene glycol monoethyl ether), Labrafil (unsaturated polyglycolysed glycerides), Labrasol (glyceryl and polyethylene glycol esters), lauroglycol (propylene glycol laurate), tee tree oil (oil of melaleuca), propylene glycol, 2-methyl-l, 3-propanediol and polyethylene glycol. 4. A method as claimed in any one of claims 1 to 3, wherein the active substance is dissolved in step [a] in the skin penetration enhancer(s) to form a solution at a concentration of less than 90% of saturation. 5. A method as claimed in any one of claims 1 to 4, wherein the active substance is estradiol or a mixture of estradiol and norethisterone acetate. 6. A method as claimed in any one of claims 1 to 5, wherein the adhesive is a solution or aqueous dispersion of an aery late or polyisobutylene or silicone adhesive. 7. A method as claimed in any one of claims 1 to 6, wherein the coating is formed in step [c] on a release liner and the coating, after drying in step [d], is laminated on to a backing sheet. 8. A method as claimed in any of claims 1 to 6, wherein the coating is formed in step [c] on a backing sheet and the coating, after drying in step [d] is laminated on to a release liner. 9. A method as claimed in any one of claims 1 to 8, wherein the drying temperature of step [d] is increased gradually from 50° C to 140°C. 10. A method for the manufacture of a transdermal drug substantially as herein described with reference to forgoing description and accompanying drawings.

Documents:

in-pct-2001-00649-del-abstract.pdf

in-pct-2001-00649-del-assignment.pdf

in-pct-2001-00649-del-claims.pdf

in-pct-2001-00649-del-correspondence-others.pdf

in-pct-2001-00649-del-correspondence-po.pdf

in-pct-2001-00649-del-description (complete).pdf

in-pct-2001-00649-del-drawings.pdf

in-pct-2001-00649-del-form-1.pdf

in-pct-2001-00649-del-form-19.pdf

in-pct-2001-00649-del-form-2.pdf

in-pct-2001-00649-del-form-3.pdf

in-pct-2001-00649-del-form-5.pdf

in-pct-2001-00649-del-gpa.pdf

in-pct-2001-00649-del-pct-210.pdf

in-pct-2001-00649-del-pct-304.pdf

in-pct-2001-00649-del-pct-409.pdf

in-pct-2001-00649-del-pct-416.pdf