Formulation and Availability of Timolol in Certain Ocular Drug Delivery Systems

Abstract

Traditionally, topical drug delivery is preferred in the eye to avoid under and over medication and undesired side effects of systemic administration. Nevertheless, conventional eye drops deliver drugs in a pulsatile fashion that is called "pulse entry effect". Additionally, ophthalmic solutions and suspensions are compromised in their effectiveness by several limitations such as, the poor corneal penetration due to the hydrophobic nature of the upper epithelial layers of the cornea, rapid nasolacrimal drainage, nonproductive absorption through the conjunctiva, and complex tear fluid dynamics. To achieve effective ophthalmic therapy, an adequate amount of the active ingredient must be delivered and maintained at its site of action within the eye. Therefore, here arises the value of formulating controlled drug delivery systems to the eye. Nanoparticles as drug carriers have attracted more and more interest in the last decade. The major goal in employing nanoparticles was the controlled and sustained• release of the pharmacologically active agent to the specific site of action are the therapeutically optimal rate and dose regimen and therefore provide increased drug efficacy, reduced toxicity and prolonged therapeutic activity. Studies that have investigated the potential of nanoparticles for ocular drug delivery have shown several promising results compared to conventional ocular dosage forms. Glaucoma is one of the most serious ocular diseases; it is frequently asymptomatic at the time of diagnosis, but it can result in progressive visual field loss and eventual blindness. Timolol maleate, a non- selective beta- adrenergic blocking agent, represents one of the most significant advances in the topical treatment of glaucoma. Timolol maleate administered directly to the eye as ophthalmic drops appears to be rapidly absorbed, producing a decrease in the intra-ocular pressure through the reduction of the aqueous humour formation rate.