Drug – bio-affecting and body treating compositions – Solid synthetic organic polymer as designated organic active... – Polymer from ethylenic monomers only
Patent
1985-05-14
1987-02-10
Robinson, Douglas W.
Drug, bio-affecting and body treating compositions
Solid synthetic organic polymer as designated organic active...
Polymer from ethylenic monomers only
424128, 514635, 514840, A61K 3155, A61K 3174, A61K 3342
Patent
active
046422340
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the disinfection of contact lenses and has particular, but not exclusive, application to the disinfection of hydrophilic soft contact lenses. It provides aqueous disinfecting solutions, compositions for making said solutions, and methods of disinfecting hydrophilic soft contact lenses.
Contact lenses are thin convex lenses placed directly on the eye surface to correct sight defects. There are two general categories of contact lenses, namely hard lenses and soft lenses. Hard lenses are made of glass or, more usually, hard plastics, especially cross-linked polymethylmethacrylate. Soft lenses may be made of hydrophobic plastics, especially cross-linked dimethyl polysiloxane, but usually are made of hydrophilic plastics, especially polyhydroxyethyl methacrylate cross-linked with hydroxyethyl dimethacrylate.
The disinfection of hydrophilic soft lenses using chemical agents presents a particular problem in that the lenses can absorb chemical agents from disinfecting solutions in which they are soaked. The most commonly used disinfecting solutions for soft contact lenses are aqueous solutions containing a chlorhexidine salt and it is well established that a sufficiently high concentration of chlorhexidine salt can build up in the lens to cause irritation and, sometimes, damage to the eye of the lens wearer. Accordingly, the concentration of chlorhexidine salt in the disinfecting solution should be maintained at a sufficiently low, but effective, level (below about 0.005% by weight, calculated as chlorhexidine digluconate) to reduce the risk of eye irritation. It has recently been proposed in UK Patent Specification No. 2090013A that eye irritancy resultant from chlorhexidine salt disinfection can be obviated by the use of a substantially isotonic aqueous solution containing 0.0012 to 0.003% of a chlorhexidine salt if the ionic species of the tonicity adjusting agent produces a tonicity equivalent to not more than a 0.3% solution of sodium chloride.
Prior art aqueous disinfecting solutions for hydrophilic soft lenses are made up with de-ionized, or otherwise specially purified, water thereby avoiding problems arising from hard water and chlorination if tap water was to be used. The calcium and magnesium salts in hard water would cause opaque deposits to build up on the lens. Further, chlorine would be absorbed and concentrated in the lens in the same manner as chlorhexidine salt discussed above. Whilst there have been theoretical proposals to provide chlorhexidine salt-containing tablets for dissolution to form the aqueous disinfecting solutions, to the best of our knowledge and belief, chlorhexidine salt-containing solutions have always been supplied to the user ready made up.
The term "tap water" is used herein to mean water which has not been de-ionized or specially purified but is sufficiently uncontaminated by impurities to be of a potable standard. Typically such water is supplied as drinking water from treatment plants through mains to a tap or faucet. However, the term is not restricted to water supplied from a tap or faucet and includes water of equivalent quality from other sources.
It is an object of the present invention to provide an aqueous disinfecting solution for hydrophilic contact lenses made up with tap water, which solution does not cause opaque deposits on the lens and is non-irritant to the eye of the wearer. It is another object to provide a tablet, or other solid formulation, of a composition which can be dissolved in tap water to provide such a disinfecting solution.
According to a first aspect of the present invention, there is provided a non-eye-irritant disinfecting solution for hydrophilic soft contact lenses, said solution being obtained by the addition to tap water (as hereinbefore defined) of:
an ophthalmically acceptable chlorhexidine salt;
a sequestering agent for calcium and magnesium cations; and
a dechlorinating agent.
According to a second aspect of the present invention, there is provided a composition for addition to tap water (as hereinbefo
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"Kinetics of a Transient Iodine Disinfecting System", by M. F. Turner et al., British Pharmaceutical Conference, Sheffield 1977, p. 65P, Sep. 12-14.
"Kinetics of a Transient Iodine Disinfecting System for Hydrophilic Contact Lenses", J. K. Andrews et al., Journal of Pharmacy and Pharmacology, British Pharmaceutical Conference 1977, p. 56P, 1977, Sep. 12-16.
Davies David J. G.
Meakin Brian J.
Rees John E.
Robinson Douglas W.
University of Bath
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