Ocular absorption pharmacokinetics

For all routes of administration, the absorption, distribution, and elimination kinetics are important for obtaining the desired therapeutic effect. For drugs expected to act in the eye after ocular absorption, pharmacokinetic parameters are difficult to obtain in both animals and humans. Accordingly, it has been proposed to rely essentially on pharmacodynamic measurements by use of a specific biological response after topical administration (258,259). For example, the apparent absorp-... 

Fig. 9 Pharmacokinetic scheme for ocular absorption, distribution, and elimination.

Dey, S., Gunda, S., Mitra, A. K. Pharmacokinetics of Erythromycin in Rabbit Corneas after Single-Dose Infusion Role of P-Glycoprotein as a Barrier to in Vivo Ocular Drug Absorption. J. Pharmacol. Exptl. Then 2004, 311, 246-256. 

The inherent pharmacologic properties of a drug determine its pharmacodynamic effects, and drug absorption, distribution, metabolism, and excretion are determined by the pharmacokinetic effects. The ease with which a drug passes into the systemic circulation and its ability to penetrate the blood-brain, blood-aqueous, or blood-retinal barriers determines the propensity to affect ocular tissues and functions. 

Example Pilocarpine (Isopto Carpine, Pilopine HS. Ocusert Pilo-20 and -40) Route Ophthalmic Pregnancy category C Pharmacokinetic Some systemic absorption binds to ocular tissue excretion UK PB UK ... 

Dey S, Gunda S, Mitra AK. Pharmacokinetics of erythromycin in rabbit corneas after singledose infusion role of P-glycoprotein as a barrier to in vivo ocular drug absorption. J Pharmacol Exp Ther 2004 311(l) 246-255. Epub June 2, 2004. Erratum in J Pharmacol... 

The pharmacokinetics and constraints of ocular drug absorption have been thoroughly reviewed in a number of excellent papers They will be briefly discussed in the... 

The time pattern of drug absorption and disposition in the eye following topical administration is a complex phenomenon, influenced by the drug, the vehicle, and by anatomical/physiological factors. In order to understand the pharmacokinetics of ocular drugs it is necessaiy to consider the absorption, distribution and disposition of drugs in three areas of the eye (a) the preocular (precorneal) area, (b) the cornea, and (c) the interior of the eye. A picture of the pathways for absorption, and of their complex interrelations is given in Fig. 2. 

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