Common Drugs Use in Ophthalmology - Mahidol

[Pages:40]Common Drugs Use in Ophthalmology

Rungroj Lertvithayasakul, MD Varintorn Chuckpaiwong, MD

Department of Ophthalmology, Ramathibodi Hospital School of Medicine, Mahidol University

Route of Administration

Local

? Topical ? Intravitreous ? Subconjunctival ? Subtenon ? Retrobulbar ? Intracameral

Systemic

Blood aqueous barrier Blood retinal barrier

Eyedrops

50 ?l per drop

? Only 20 % of the administered drugs is retained ? One drop is enough.

Volume of fluid held by cul-de-sac 7 ? 10 ?l

Drug eliminating mechanisms

Lacrimal gland

Tear production: 1.2 ?l /min

Nasal cavity

Turn over rate 16 % per min Remaining 4 min : 50 %

10 min : 17 %

Surface area of 150 - 200 cm 2 ( 13 times of conjunctiva )

200 times of cornea

Drug eliminating mechanisms

If the drug is irritating to the eye

Dilution of drug Overflow drainage

Improve ocular and decrease systemic absorption

Digital pressure at medial canthal area

Keep eyes closed for 5 min after taking drops

Wait 10 minutes between drops Frequency ~ duration of action Order of using ~ pH

Drug Penetration

Precorneal area Cornea Anterior Segment Aqueous Humor

Drug Penetration

Factors that determine the amount of medication to penetrate the cornea

? Drug concentration ? Viscosity ? Lipid/water solubility ? pH ? Surfactants ? Reflex tearing ? Preservative

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