Drug – bio-affecting and body treating compositions – Topical body preparation containing solid synthetic organic... – Ophthalmic preparation
Patent
1998-08-05
2000-05-02
Azpura, Carlos
Drug, bio-affecting and body treating compositions
Topical body preparation containing solid synthetic organic...
Ophthalmic preparation
A61K 3174
Patent
active
060569506
DESCRIPTION:
BRIEF SUMMARY
SPECIFICATION
The present invention concerns ophthalmic solutions viscosified with tamarind seed polysaccharide. More specifically, the invention relates to the use of a natural polysaccharide, which is contained in high amounts in the material of natural origin known as tamarind gum, as viscosity enhancer for preparations to be administered into the conjunctival sac. Said polysaccharide may be used for replacing and stabilising the natural tear fluid, or as a vehicle for ophthalmic medicaments, with the function of prolonging the residence time of said medicaments at the site of action, so as to enhance their activity.
BACKGROUND OF THE INVENTION
As it is known, ocular tear fluid is an organised liquid structure which coats the conjunctiva and the exposed surface of the eyeball. In normal conditions, the tear film appears to be a complex three-layered structure, comprising: (mucin) produced by specialised cells (i.e. the conjunctival goblet cells) which are present in the conjunctival epithelium--said layer is adsorbed on the cornea, thus forming a hydrophilic surface; consisting essentially of water, electrolytes, proteins, enzymes and mucin; water evaporation rate from the tear film.
The eyelids movement squeezes the mucus out of the conjunctival cells and introduces it into the fornices, and from there the mucus is uniformly distributed on the whole corneal surface by the blinking movements of the eyes.
The three-layers structure described above constitutes a complex physiological system, mainly directed to protect the eye surface, to maintain the hydration, the lubrication and the clearness of the corneal surface, and to cooperate in producing a correct vision. The perfect equilibrium and continuous renovation of said physiological system is a necessary condition for it to be able to carry out said functions. For the said equilibrium and renovation to be realised, a constant but not excessive water evaporation from the tear fluid must take place, so as to keep the osmolarity thereof to the physiological level of about 300 mOsm/l, and the tear film must be continuously redistributed on the corneal surface as a result of blinking.
The integrity of the internal mucin layer represents one of the essential elements of the maintenance of the tear film stability. This because mucin enhances the wettability of the corneal surface, allows the aqueous film to keep adhering to the exposed surface in a continuous and homogeneous way, thus safeguarding its stability, and increases the viscosity of the lacrimal fluid, preventing it from flowing away too rapidly from the conjunctival sac. When mucin is absent or insufficient the cornea becomes non-wettable and, as a consequence of the unbalance between electrolytes and glycoproteins present, the tear film becomes unstable and subject to breaking, with formation of dry areas.
Various diseases or abnormal conditions of the eye manifest themselves with discontinuities of the tear fluid, as a result, e.g., of an insufficient blink frequency, of the prolonged use of contact lenses, of the administration of some systemic drugs or, more frequently, of a senile hyposecretion. In this connection, the term "dry eye" syndrome is commonly used to refer to the ophthalmic condition resulting from the reduction or the instability of the tear film while, more properly, the typical alterations of the corneal surface occurring in this connection are referred to by the term "keratoconjunctivitis sicca".
In such situation a degeneration of the conjunctival cells occurs, resulting in increased desquamation, loss of the cell surface microfolds, breaking of the epithelial cells membrane and reduction of the number of mucin-producing goblet cells. This cellular degeneration, being responsible of the reduction of the density of goblet cells and of the lack of mucin, is held to be the origin of most clinical symptoms occurring in dry eye syndrome, such as dryness, irritation, photophobia and foreign body sensation.
Another phenomenon which is unanimously considered to be a sign of an irr
REFERENCES:
Database WPI, Week 9517, Derwent Publications Ltd., London, GB; AN 95-126104 XP002030113 & JP 07 048 278 A (Taiho Pharm Co., Ltd.), Feb. 12, 1995.
Bianchini Pietro
Boldrini Enrico
Burgalassi Susi
Giannaccini Boris
Luciani Giulio
Azpura Carlos
FARMIGEA S.p.A.
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