“First, the necessity to use oils or oil based carriers may lend the preparations an unpleasant taste or otherwise reduce palatability, in particular for the purposes of long-term therapy. These effects can be masked by presentation in gelatine capsule form. However, in order to maintain the cyclosporin in solution, the ethanol content has to be kept high. Evaporation of the ethanol, e.g. from capsules or from other forms, e.g. when opened, results in the development of a cyclosporin precipitate. Where such compositions are presented in e.g. soft gelatine encapsulated form, this particular difficulty necessitates packaging of the encapsulated product in an air-tight compartment, for example an air-tight blister or aluminium-foil blister-package. This in turn renders the product both bulky and more expensive to produce. The storage characteristics of formulations as aforesaid are far from ideal.” 12. Thus the first problem with existing formulations that is identified is the problem caused by the presence of alcohol in the formulation. The second is variation between groups of patients and, even for a single patient, of bioavailability of the active ingredient: “Bioavailability levels achieved using existing oral cyclosporin dosage systems are also low and exhibit wide variation between individuals, individual patient types and even for single individuals at different times during the course of therapy. Thus reports in the literature indicate that currently available therapy employing the commercially available Ciclosporin drink solution provides an average absolute bioavailability of ca. 30% only, with marked variation between individual groups, e.g. between liver (relatively low bioavailability) and bone-marrow (relatively high bioavailability) transplant recipients. Reported variation in bioavailability between subjects has varied from anything between one or a few percent for some patients to as much as 90% or more for others. And as already noted, marked change in bioavailability for individuals with time is frequently observed.” 13. On page 7 of the specification, the proposals already made to meet these problems are discussed, and it is observed that the overriding difficulty is the consequence of the inherent insolubility of the cyclosporins in aqueous media. The specification refers to the additional need for a topical delivery system for the drug, and sets out its solution to the problem at the foot of page 7: “By the present invention there are provided novel cyclosporin galenic formulations in the form of a micro-emulsion pre-concentrate and/or based on the use of particular solvent media as hereinafter defined, which meet or substantially reduce difficulties in cyclosporin, e.g. Ciclosplorin, therapy hitherto encountered in the art. In particular it has been found that the compositions of the invention permit the preparation of solid, semi-solid and liquid compositions containing a cyclosporin in sufficiently high concentration to permit, e.g. convenient oral administration, while at the same time achieving improved efficacy, e.g. in terms of bioavailability characteristics.” 14. It is said (foot of page 8) that the invention of the patent in suit enables the preparation of compositions which are non-alkanol based, for example, free or substantially free of ethanol. The first aspect of the invention is stated on page 9: “In a first aspect, the present invention specifically provides pharmaceutical compositions comprising a cyclosporin as active ingredient, which compositions are in the form of an “oil-in-water microemulsion pre-concentrate”.” 15. The key concept is thus a mixture (pre-concentrate) which will form a microemulsion when added to an aqueous medium. The passage which follows, which defines the term “oil-in-water microemulsion pre-concentrate”, is of particular importance: “By the term “oil-in-water microemulsion pre-concentrate” as used herein is meant a system capable on contacting with, e.g. addition to, water of providing an oil-in-water microemulsion. The term microemulsion as used herein is used in its conventionally accepted sense as a non-opaque or substantially non-opaque colloidal dispersion comprising water and organic components including hydrophobic (lipophilic) organic components. Microemulsions are identifiable as possessing one or more of the following characteristics. They are formed spontaneously or substantially spontaneously when their components are brought into contact, that is without substantial energy supply, e.g. in the absence of heating or the use of high shear equipment or other substantial agitation. They exhibit thermodynamic stability. They are monophasic. They are substantially non-opaque, i.e. are transparent or opalescent when viewed by optical microscopic means. In their undisturbed state they are optically isotropic, though an anisotropic structure may be observable using e.g. x-ray technique. Microemulsions comprise a dispersed or particulate (droplet) phase, the particles of which are of a size less than 2,000 A, hence their optical transparency. The particles of a microemulsion may be spherical, though other structures are feasible, e.g. liquid crystals with lamellar, hexagonal or isotropic symmetries. Generally, microemulsions comprise droplets or particles having a maximum dimension (e.g. diameter) of less than 1,500 A, e.g. typically from 100 to 1,000 A. [For further discussion of the characteristics of microemulsions see, e.g. Rosof . . . ; Friberg . . . ; and Müller . . . . ] From the foregoing it will be understood that the “oil-in-water microemulsion pre-concentrates” of the invention are galenic systems comprising a cyclosporin as active ingredient capable of forming an oil-in-water microemulsion, spontaneously or substantially spontaneously on contact with water alone.”
‘1. A pharmaceutical composition comprising a cyclosporin as active ingredient, 1) a hydrophilic phase, 2) a lipophilic phase, and 3) a surfactant, which composition is an “oil-in-water microemulsion pre-concentrate.”’ 17. A very substantial amount of text follows. Its function is mainly to give examples of suitable materials, but there is also explanatory material dispersed throughout.
"Microemulsions obtained on contacting the 'microemulsion pre-concentrate' compositions of the invention with water or other aqueous medium exhibit thermodynamic stability, that is they will remain stable at ambient temperatures, e.g. without clouding or regular emulsion size droplet formation or precipitation, over prolonged periods of time."
‘Q…If it was written like that and you had something with particles less than 2000 angstrom and particles more than 2000 angstroms, whether you would call the resultant product a microemulsion or not? A. I think there is probably a misunderstanding here. I would call a microemulsion coexisting with something else anyway. I would never call it, if it had two populations, a microemulsion per se. That would just be totally wrong. I would say that the particles that are microemulsion particles and particles that are something else. Does that answer your question? Q. It is the answer you have given to my question. Let me add one further rider to that description. Assume that it is said that the particles are of a size less than 2000 angstroms hence their optical transparency. You have added into it optical transparency. Would you then be prepared to call a mixture of 2000 angstrom and smaller particles and 2000 angstrom larger particles a microemulsion or not? A. Absolutely not. I would not call it a microemulsion. I thought a microemulsion was something else so the same thing still stands. If I could prove that there are particles of less than 2000 angstroms that are thermodynamically stable, isotropic, have the correct components making them a form of microemulsion droplets. Q. Would you call the system a microemulsion? A. No, I have just said that it would be whatever it was. For example, a suspoemulsion. You get suspensions and emulsions. You could have suspomicroemulsions. It is appropriate for whatever components are in there.’