Polymeric Diffusion Matrix Containing Clonidine

The present invention relates to a polymeric diffusion matrix containing clonidine. More particularly, the invention relates to a polymeric diffusion matrix containing clonidine characterized by a sustained release of clonidine.

A self-supporting polymeric diffusion matrix is provided for the sustained release of clonidine in order to transdermally deliver said clonidine to a patient and provide said patient with an antihypertensive effect, said matrix comprising from about 2 to about 60% by weight of a polar plasticizer; from about 6 to about 20% by weight polyvinylalcohol; from about 2 to about 10% by weight polyvinylpyrrolidone; and a pharmaceutically effective amount of clonidine to provide a sustained release of said clonidine over a prolonged period.

In one embodiment the polar plasticizer is glycerol present in an amount of from about 2 to about 60% by weight. In another embodiment the polar plasticizer is polyethylene glycol present in an amount of from about 2 to about 15% by weight. A still further embodiment contemplates a mixture of glycerol and polyethylene glycol wherein the latter is present in an amount by weight of from about 1 to about 5 parts per weight glycerol.

The self-supporting polymeric diffusion matrix generally contains a mixture of polyvinylalcohol and polyvinylpyrrolidone, although it will be understood that other polymeric mixtures may be used provided they yield the desired sustained release effect. For example, both the polyvinylalcohol and the polyvinylpyroolidone may be completely replaced with from about 1 to about 9% agar or agarose, and preferably from about 1.5 to 3% agar or agarose, 2% or agarose being particularly preferred.

As the polyvinylalcohol used in the present invention there is generally contemplated one having a molecular weight from about 50,000 to about 150,000, and more preferably about 100,000 to about 150,000, 115,000 having been used in related systems of the present inventors with success. The polyvinylalcohol should be hydrolyzed, generally at least to the extent of 90%, with a preferred embodiment being at least 95% hydrolyzed. Polyvinylpyrrolidone should have a molecular weight of from about 15,000 to about 85,000, and more preferably from about 20,000 to about 60,000. Polyvinylpyrrolidone with a molecular weight of 400,000 is a particularly preferred embodiment.

The amount by weight of the ingredients other than the polar plasticizer generally should be in the following ranges: polyvinylalcohol is generally present in an amount of from about 6 to about 20% by weight, with 10% being a preferred embodiment polyvinylpyrrolidone is present generally in an amount of from about 2 to about 10% by weight.

The amount of the clonidine to be delivered per day is generally about 0.2 to about 0.6 mg, preferably about 0.4 mg, which is generally lower than the oral dosage. To assure that the desired quantity of clonidine is delivered, an excess of the drug should be incorporated in the matrix.

The water-soluble polymer can be replaced with (in addition to agar) gum arabic, gum tragacanth, polyacrylic acid, polymethacrylic acid, polyvinyloxazolidone, polyvinylmorpholinone, and polyvinylpiperidone.

Polyalkylene glycols such as polyethylene glycol and polypropylene glycol may replace all or part of the glycerol.

It is possible to replace the polyvinylalcohol with polymers of hydroxyethylacrylate, polymers of hydroxyethylmethacrylate, polymers of hydroxypropylacrylate, and polymers of hydroxypropylmethacrylate.

It will be appreciated that clonidine may be added to the above mixture not only in the form of the pure chemical compound, but also in admixture withh other drugs that may be transdermally applied or with other ingredients which are not incompatible with the desired objective of transdermally administering the drug to a patient. Thus, simple pharmacologically acceptable derivatives of the drugs such as ethers, esters, amides, acetals, salts, and the like may be used. With some drugs such derivatives may actually be preferred.

In forming the matrix, excess water is not required. In accordance with a preferred aspect of the present invention, about 2% by weight clonidine is included in the diffusion matrix. The resultant homogeneous mixture is poured into forms preferably made of glass or stainless steel, these forms or templates producing a diffusion matrix having a thickness of about 1 to about 3 mm in accordance with a preferred aspect of the present invention. This diffusion matrix is either cast or cut into pieces of the desired size.

The following methods may be used for preparing the diffusion matrix of the present invention.

In a first method, the matrix is formed at atmospheric pressure. Water and glycerol are first mixed together.

A polar plasticizer such a glycerol is a necessary component in the matrix. A matrix formed without a polar plasticizer is not flexible and has poor diffusional contact with the skin causing unreliable diffusion release.

The polyvinylalcohol and polyvinylpyroolidone are then added to the polar plasticizer-water mixture at room temperature, withh agitation. The mixture is heated to a temperature within the range of from about 90 to about 95.degree. C. at atmospheric pressure to extend the polymers. If desired, the mixture may be maintained at an elevated temperature of a period of time, based on polymer stability, prior to addition of the drug. Thus, the mixture is stable for a period of time and may be kept for such a period before being mixed with the drug to be delivered to the patient. Thereafter, the mixture is temperature-adjusted and the drug to be applied to the patient is then added to the mixture, with thorough agitation. Once a homogeneous mixture of the polymer solution and drug is obtained, the mixture is ready to be cast to form in a drug-containing diffusion matrix. After casting the mixture is cooled to a temperature such that gelation occurs. In a preferred embodiment, the drug may be dissolved by agitation in a suitable solvent such as glycerin and water. The thus-obtained solution can be maintaineed at room temperature for prolonged periods without deterioration.

It has been found that curing is facilitated by subjecting the matrix to a temperature down to about -20.degree. C. immediately after casting. The setting period is quickened considerably.

Sodium dodecyl sulfate or sorbitan (Tween-20) or other detergents may be added in an amount of 0.1 to 10% by weight, based on the matrix, as a dispersing agent, if desired.

An absorption facilitator to insure skin penetration such as dimethylsulfoxide, decylmethylsulfoxide, or other penetration enhancers may be added.

The present drug delivery device comprises the drug-containing diffusion matrix and means for fastening the matrix to the skin of a patient. Such means can take various forms, such as an occlusive backing layer forming a kind of "bandage" with the diffusion matrix being held against the skin of a patient being treated. A polyethylene or Mylar tape is contemplated as one form of occlusive layer in accordance with the present invention. It can also take the form of an elastic band, such aas a cloth band, a rubbery band or other material. Here, the diffusion matrix is placed directly on the skin and held in place by such elastic band which typically will be placed over the arm or wrist of the patient. An intermediate adhesive layer between the diffusion matrix and the skin capable of permitting the transdermal application of the drug can also be used.

The invention is illustrated by the following nonlimiting Examples:

Together there are mixed 30 gm glycerol and 45 ml water. This mixture is heated to 90.degree. C.; after reaching at least 70.degree. C. there are slowly added 15 gm polyvinylalcohol (PVA 100% hydrolyzed, molecular weight 115,000) and 8 gm polyvinylpyrrolidone (mw 40,000). The mixture is stirred at 90.degree. C. until solution is effected, which may take about 10 minutes; it will be appreciated that with larger quantities, a considerably longer period of time may be needed. 98 ml of this solution is then mixed with 2 gm clonidine, this mixture then being mechanically stirred until homogeneous. The homogeneous mixture is then poured into forms made of glass or stainless steel which serve as templates to produce a diffusion matrix having a thickness of about 2 to about 3 mm. This diffusion matrix is then cut into pieces with a total surface area suitable for the administration of a pharmaceutically effective amount of clonidine.

The diffusion matrix is applied to the skin of a patient in need of an antihypertensive effect, the clonidine being transdermally delivered to the skin of the patient. The diffusion matrix is ideally applied to the skin of the patient by means of a single-piece bandage having the diffusion matrix in the center under the occlusive layer, the bandage being provided to the patient with a peel-of cover much like a "band-aid".

In place of the glycerol of Example I, there is substituted 5 gm polyethylene glycol having a molecular weight of 1000 and 25 ml water. The resultant diffusion matrix is more rigid than that of Example I.

In place of the glycerol of Example I, there is substituted 5 gm polyethylene glycol (mw 1,000), 4 gm glycerol and 21 ml water. The resultant diffusion matrix shares the improved rigidity of the diffusion matrix of Example II, while providing contact with the skin characteristic of the glycerol in this type of diffusion matrix.

In place of the polyvinylalcohol and polyvinyl pyrrolidone of Example I, there is substituted 2% by weight agarose, yielding a diffusion matrix for the transdermal delivery of clonidine.