Controlled release composition

Abstract

A composition for controlled delivery of at least one active substance into an aqueous medium by erosion at a preprogrammed rate of at least one surface of the composition, comprising a matrix comprising the active substance, the matrix being erodible in the aqueous medium in which the composition is to be used, and a coating having at least one opening exposing at least one surface of said matrix, the coating comprising a first cellulose derivative which has thermoplastic properties and which is substantially insoluble in the aqueous medium in which the composition is to be used, and at least one of a second cellulose derivative which is soluble or dispersible in water, a plasticizer, and a filler. The coating is a coating which crumbles and / or erodes upon exposure to the aqueous medium such as a body fluid. The first cellulose derivative may be, e.g., ethylcellulose, cellulose acetate, cellulose propionate or cellulose nitrate, and the second cellulose derivative may be, e.g., methylcellulose, carboxymethylcellulose or salts thereof, cellulose acetate phthalate, microcrystalline cellulose, ethylhydroxyethylcellulose, ethylmethylcellulose, hydroxyethylcellulose, hydroxyethylmethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, hydroxymethylcellulose or hydroxymethylpropylcellulose.

Description

FIELD OF THE INVENTION The present invention relates to a composition for controlled delivery of an active substance into an aqueous medium. BACKGROUND OF THE INVENTION It is known to obtain sustained release of an active substance, e.g. a pharmaceutically active powder, by embedding it in a matrix of an insoluble substance from which the active substance will gradually diffuse. Sustained release of an active substance contained in a tablet core may also be achieved by applying to the core a semi-permeable coating through which water and dissolved active substance may diffuse or an insoluble coating provided with a hole through which the active substance is released. Gradual release of an active substance may furthermore be obtained by microencapsulating particles of an active substance in one or more layers of film which may be of different types, e.g. of a type which mediates diffusion of the active substance or release thereof in the intestines. These conventional ways of prov...

AI Technical Summary

Benefits of technology

Due to the controlled release of the active substance from the composition of the invention, it is possible to obtain a substantially constant rate of release or a controlled pulsatile release of the active substance over a specific period of time. Adherence to a strict dosage regimen, e.g. requiring administration of a drug at set intervals up to several times a day, may therefore be dispensed with. Furthermore, it is possible to include two or more different active substances in the composition of the invention, adapted to be released at different concentrations and / or intervals, thus making it easier for patients to follow a prescribed regimen.

An additional advantage of the composition of the invention is that it may be produced by relatively simple and inexpensive methods, e.g. by extrusion, as will be explained in more detail below. Furthermore, the composition allows for the incorporation of high concentrations of the active substance relative to the composition's size. This is obviously a great advantage, notably when the composition is to be used for the delivery of a pharmaceutically active substance, since it allows for the delivery of the required amount of the active substance without the composition being unnecessarily large. Compositions of the invention in which the matrix contains a surface active agent may furthermore be used for the delivery of sparingly soluble or non-soluble pharmaceutical powders which can otherwise be difficult to administer, since such substances are compatible with the lipophilic domains of the surface active agent.

Problems solved by technology

These conventional ways of providing sustained release of an active substance have certain drawbacks, in that it is difficult to maintain a constant concentration of the active substance, for example a constant concentration of a pharmaceutically active substance in plasma for the entire period when the dosage form is present in the body.

In particular, this may be the problem with drugs which have a brief half-life in the body.

Furthermore, the penetration of water through diffusion coatings may cause hydrolysis of active substances which are unstable in an aqueous environment.