Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Liposomes
Patent
1997-11-12
1999-12-21
Page, Thurman K.
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Liposomes
424455, 424456, 424460, 424461, 514937, 514938, 514944, A61K 966, A61K 9127, A61K 964
Patent
active
060045809
DESCRIPTION:
BRIEF SUMMARY
This application is a continuation of a 371 of PCT/FI95/00234, filed Apr. 28,1995.
The invention relates to pharmaceutical compositions derived from microemulsion-based gels and method for their preparation. The invention further relates to gels as such based on o/w type microemulsions or microemulsions of bicontinuous structure.
Since the year 1990 water soluble enzymes have been immobilized in microemulsion-based gels (G D Rees, Thesis, University of East Anglia, (1990); G D Rees et al., Biochim Biophys Acta, 1073, (1991), 493; G D Rees & B H Robinson, Advanced Materials 5, (1993), 608; G D Rees et al., Indian J Chem, 32B, (1993), 30). The microemulsions used are of a water-in-oil type (w/o or "water in oil") in which the enzyme is dissolved in'water droplets surrounded by oil. For the stabilization of these microemulsions only surfactant AOT, which will be presented in greater detail later, has been used. Due to addition of gelatine and water the microemulsion is brought into a suitable form which can be added into the reaction vessel and, after the reaction has finished, removed therefrom. Hence the enzymes in a microemulsion-based gels are again available for use in the next reaction. However, these gels can be used only in organic solvents.
This invention relates to employment of said microemulsion gel technique as dosage forms of drugs, in particular systemic, like oral dosage forms. Depending on whether the drug is lipo-soluble or water soluble, a microemulsion which is of an oil-in-water type (o/w, "oil in water") or a water-in-oil-type (w/o, "water in oil") or a microemulsion with a so-called bicontinuous structure is used. The concept bicontinuous structure will be considered in greater detail later.
So far no workable pharmaceutical preparation has been presented in which the drug is immobilized in a microemulsion-based gel.
BACKGROUND
MICROEMULSIONS
Due to their excellent dissolution properties microemulsions have been increasingly used in various technological fields. They are used, for instance as detergents, in oil recovery and as the reaction environment of enzyme catalysts.
Microemulsions are also used as dosage forms of drugs. The British patent publications GB 2222770, 2228198 and 2257395 describe microemulsion concentrates containing cyclosporin which form o/w type microemulsions after addition of water.
Microemulsion denotes a thermodynamically stable and optically isotropic solution which consists of water (or more generally hydrophilic component), oil (or more generally lipophilic component) and surfactant which denotes a surface active substance with an amphilic character. Microemulsions are macroscopically, e.g. when observed visually, homogeneous one-phase solutions. However, if observed on microscopic level, it is noted that they are most heterogeneous. Microemulsions are composed of microscopic continuous domains of water or oil which are separated from one another by a monomolecular layer of the surfactant. The role of surfactant is stabilization of the microemulsion, for instance through decreasing interfacial tension. The microemulsion is of an oil-in-water type (o/w, "oil in water"); a water-in-oil type (w/o, "water in oil") or has a bicontinuous structure (will be explained in more detail later).
The monomeric solubility of the surfactant both in water (hydrophilic component) and in oil (lipophilic component) must be low so that the surfactant could form a microemulsion with the highest possible stability.
The surfactant may be ionic or non-ionic. If the surfactant is ionic, it must have two hydrocarbon chains to form a microemulsion. If the ionic surfactant does not have two hydrocarbon chains, a neutral inorganic salt and a co-surfactant must be added. A short-chain alcohol is often used as the co-surfactant. When a two-chained ionic or a non-ionic surfactant is used, the microemulsion may be formed without any additives. In case the surfactant is too lipophilic to form spontaneously microemulsions in water, a component like ethanol may be added which reduces hydro
REFERENCES:
patent: 4619926 (1986-10-01), Eckert
patent: 5206219 (1993-04-01), Desai
patent: 5294249 (1994-03-01), Luisi
patent: 5342625 (1994-08-01), Hauer et al.
P. L. Luisi et al. "Organogels from water-in-oil microemulsions", Colloid and Polymer Science. 268: 356-374, 1990.
P.L. Luisi et al., "Organogels From Water-in-oil Microemulsions", 268 Colloid & Polymer Science 356-374 (1990).
Backlund Sune
Eriksson Folke
Rantala Maria
Rantala Pertti
Varho Kari
Channavajjala Lakshmi
Leiras Oy
Page Thurman K.
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