Compositions, Formulation, Pharmacology, Pharmacokinetics, and Toxicity of Topical, Periocular, and Intravitreal Ophthalmic Drugs

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The unique anatomy and physiology of the eye make it a highly protected organ. Drug delivery to the eye has become a major challenge to ocular pharmacologists and drug delivery scientists. Designing an effective therapy for ophthalmic disorders, especially for the chronic posterior segment diseases, has been considered a formidable task. Ocular static, dynamic, and precorneal barriers prevent administered drug from reaching the target site at therapeutic concentrations. Topical drops occupy a majority of the marketed ophthalmic products because of easy self-administration, cost-effectiveness, and most importantly patient compliance, whereas other routes of drug administration such as periocular and intravitreal routes require attention of a medical specialist to administer the dose. Drug delivery via periocular and intravitreal routes demonstrated better therapeutic outcomes in front and back of the eye diseases. Though intravitreal route appears to be promising to attain high drug concentrations in back of the eye tissues, however, this route is often limited by postdosing adverse effects such as retinal detachment and endophthalmitis. Periocular injections are associated with fairly high patient compliance relative to intravitreal injections. This chapter provides an overview of various routes of drug administration to anterior and posterior ocular tissues such as topical, periocular (subconjunctival, subtenon, peribulbar, retrobulbar, and juxtascleral), and intravitreal injections. These routes are currently widely recommended in clinics as effective treatment modalities for ocular pathologies. Further this chapter emphasizes drug product composition, dosage regimen, pharmacodynamic and pharmacokinetic profiles, and adverse effects associated with the use of selected drug products administered by these routes.