Page 107 - Pharmaceutics IV (02-06-01305)

Ophthalmic DD: routes & pharmacokinetics

Fate of topically delivered drugs

Noncorneal, nonproductive absorption and precorneal drainage
• Nonproductive routes lead to the removal of drug from the precorneal

area and do not result in direct ocular uptake
• These noncorneal pathways include:
➢ Conjunctival uptake: via conjunctival blood vessels into the

systemic circulation (systemic toxicity!)
➢ Nasolacrimal drainage: drug clearance from the eye, limiting drug

ocular contact and ocular absorption.

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Ophthalmic DD: routes & pharmacokinetics

Fate of topically delivered drugs

Noncorneal, nonproductive absorption and precorneal drainage
• A number of factors can influence nasolacrimal drainage

• Low instilled volume (concentration!)
Drop volume • Five-minute spacing between drops

• Non-irritant: as close as possible to natural tear
Formulation fluid (pH, osmolarity, …)
composition • Doesn’t adversely interact with tear fluid

components

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Salma E. EL-Habashy 104