Increasing the Bioavailability of Eye Drops

Promising formulations M1, M2, M3 and M4 were evaluated for pH, drug content, in vitro gelling, in vitro drug release, in vivo drug release, viscosity and stability. The drug contents were 82.5%, 86.7%, 85.3% and 90.8%, respectively, and for formulations M1, M2, M3, and M4 320 cP, 405 cP, 440 cP, And a viscosity of 500 cP was observed. The cumulative release rates are 37.9%, 47.7%, 48.2% and 49.7%. The formulation developed was therapeutically effective, stable, irritating, and lasting 12 hours.

One of the first improvements to conventional form ophthalmic drugs is the introduction of polymers into the formulation which results in longer contact times between the active ingredient and the corneal surface and thereby increases its bioavailability . The following possibilities for modifying the bioavailability of the ophthalmic form of the active ingredient include introducing an excipient into the formulation which enhances penetration of the drug into the eye. These excipients include chelating agents, surfactants and cyclodextrins that form inclusion complexes with the active ingredient. This increases the solubility, permeability and bioavailability of poorly soluble drugs

Cyclodextrin is a cyclic oligosaccharide capable of forming inclusion complexes with the active ingredient and thereby increasing the solubility of the hydrophobic compound in water without changing their molecular structure. As carriers, they can hold the hydrophobic drug in solution and transport them to the surface of the biofilm. In the case of eye drops, the optimal bioavailability of the active ingredient is obtained in water droplets containing the appropriate concentration of cyclodextrin (<15%). The cyclodextrin which is most commonly used in developmental forms applied to the eyeball is 2-hydroxypropyl-cyclodextrin, which has no stimulatory effect. Eye drops containing drug inclusions, ie dexamethasone or pilocarpine and 2-hydroxypropyl-cyclodextrin, are well tolerated and ensure improved bioavailability compared to conventional ones.

Eye drops can be obtained in the form of an aqueous solution and one or more oily solutions, emulsions or suspensions of one or more active ingredients which may contain preservatives when stored in a multipurpose package. These forms are sterile and isotonic. The optimum pH of the eye drop is equal to the pH of the tear fluid of about 7.4. In determining whether to buffer the drug in this form, the stability of the active ingredient and the tolerance of the tissue to the formulation should be considered. If the pH exceeds the acceptable range of 4 to 8 by the eye, the patient may feel uncomfortable, there may be irritation, and the bioavailability of the drug may be reduced due to the increase in tears.