Polymeric Ophthalmic Drug Delivery Systems: Preparation and Evaluation of Pilocarpine-Containing Inserts

Abstract

Ophthalmic drugs are traditionally administered as solutions (collyria) or as anhydrous (petrolatum) ointments. However, it is well known that solutions do not result in administration of a precise and consistent dosage, since the induced lacrimation and reflex blinking that follow instillation quickly remove the drug from the precorneal area. Furthermore, eyedrop instillation typically results in a pulse entry mechanism, with undesirable transient peaks of drug concentration in the aqueous humour, and periods of nonmedication in the time intervals between pulses. Ointments, on the other hand, are somewhat better retained, but induce discomfort and blurred vision. Moreover, on account of their greasy nature they do not release effectively all types of drugs, and show poor patient compliance. These factors have stimulated the search for more sophisticated ophthalmic dosage forms, capable of delivering a precise drug dosage, and of maintaining an optimal concentration in the precorneal area for an extended period of time, thus rendering unnecessary a frequent administration of eyedrops.