Pharmacologic principles behind eye drop dosing: From pharmacokinetics to clinical practice

Topical ocular therapy plays a crucial role in managing infectious and inflammatory diseases of the anterior segment. Its therapeutic efficacy depends not only on the intrinsic potency of the drug, but also on the appropriateness of the dosing regimen in relation to ocular pharmacokinetics and pharmacodynamics principles. Because less than 5% of an instilled dose reaches the intraocular tissues, achieving therapeutic efficacy requires tailoring dosing schedules to tear dynamics, barrier permeability, and formulation characteristics. Despite its central relevance to clinical outcomes, the application of pharmacokinectics/pharmacodynamics (PK/PD) principles to topical ocular therapy remains under-recognized and often inconsistently applied in routine practice. In this light, this review integrates experimental and clinical evidence on how pharmacologic principles guide the dosing of anti-microbial and anti-inflammatory agents. Among antibiotics, aminoglycosides benefit from high early peaks (peak concentratio/minimum inhibitory concentration [MIC]-driven), fluoroquinolones from sustained exposure (area under the curve/MIC-driven), and β-lactams from continuous time above MIC (T > MIC). These PK/PD parameters must also take into account the pathogen's susceptibility in addition to the intrinsic bacteriostatic or bactericidal activity of the drug. Similarly, corticosteroid and immunomodulator regimens require controlled loading and tapering to balance efficacy and safety, particularly in graft care and ocular surface disease. Advances in preservative-free systems, nanocarriers, and stimuli-responsive formulations promise greater precision, lower toxicity, and improved adherence. Integrating PK/PD-guided strategies into daily practice offers a rational framework for optimizing topical ocular pharmacotherapy across drug classes.