Administration of drugs to eye
* Indicates drug not licensed for this use in this speces.
- Both local and systemic routes are available. Local routes include topical, subconjunctival and intravitreal.
- Choice of route of administration depends on location of disease (eg eyelids, ocular surface, anterior segment, posterior segment), pharmacology of drug (eg ability to penetrate cornea and blood-ocular barriers), potential for systemic side effects and availability of drug preparations.
- Subconjunctival administration is reserved when topical application is not possible or the disease is not responding to topical therapy. Following topical anesthetic the drug is injected under bulbar conjunctiva.
- Intravitreal injections are rarely performed.
- Systemic therapy is needed to reach therapeutic drug levels in the eyelids and posterior segment.
Topical drug preparations
- Drop and ointment forms exist and should be applied directly to the surface of the eye, eg lower conjunctival sac or cornea.
- Drops easier to apply but have decreased ocular surface contact times necessitating more frequent application.
- Ointments have prolonged corneal contact time, require less frequent application, have lubricating properties but can cause blurring of vision.
- Corneal penetration and intraocular delivery of topical drugs is variable. To penetrate the corneal epithelium and stroma the drug should have both lipophilic and hydrophilic properties.
- Most topical drug formulations contain preservatives such as benzalkonium chloride
. These can be irritating and epitheliotoxic. - If more than one drug preparation is to be applied, separate administration by >5 min.
- Topically applied drugs can have systemic effects, eg atropine, phenylephrine and corticosteroids.
Sources
Publications
Refereed papers
- Recent references from PubMed .
Other sources of information
- Ramsey I (2008) BSAVA Small Animal Formulary. 6th edn. British Small Animal Veterinary Association . ISBN 978 1 905319 11 4.
- British National Formulary (2008) 55th edn. BMJ Group and RPS Publishing.
- Petersen-Jones S & Crispin S (2002) BSAVA Manual of Small Animal Ophthalmology . 2nd edn. British Small Animal Veterinary Association. ISBN 0 905214 54 4
