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22.1 COMMONLY USED EYE MEDICATIONS

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The following is a concise formulary of commonly used ophthalmic drugs. Product leaflets, package inserts, and standard pharmacology and toxicology texts should be consulted for more detailed information.

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TOPICAL ANESTHETICS

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Topical anesthetics are useful for diagnostic and therapeutic procedures, including tonometry, removal of foreign bodies or sutures, gonioscopy, corneal or conjunctival scraping, and minor surgical operations on the cornea and conjunctiva. Cataract (phacoemulsification) surgery is increasingly being carried out under topical anesthesia, supplemented if necessary by (intracameral) injection of local anesthetic into the anterior chamber (see later in the chapter) or oral or intravenous sedation. One or two instillations of topical anesthetic are usually sufficient, but the dosage may be repeated during the procedure.

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Proparacaine, tetracaine, and benoxinate are the most commonly used topical anesthetics. For practical purposes, they can be said to have equivalent anesthetic potency. Lidocaine 3.5% gel (Akten) and cocaine 1–4% solution are also used for topical anesthesia.

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Note: Topical anesthetics should never be prescribed for home use, since prolonged application may cause corneal complications and mask serious ocular disease.

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Benoxinate Hydrochloride
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  • Preparation: Solution, 0.4% combined with 0.25% fluorescein sodium (Flurate, Fluress).

  • Dosage: 1 drop and repeat as necessary.

  • Onset and duration of action: Anesthesia begins within 1 or 2 minutes and lasts for 10–15 minutes.

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Proparacaine Hydrochloride (Proxymetacaine)
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  • Preparations: Solution, 0.5% (Alcaine, Ophthaine, Ophthetic); 0.5% combined with 0.25% fluorescein (Fluoracaine).

  • Dosage: 1 drop and repeat as necessary.

  • Onset and duration of action: Anesthesia begins within 20 seconds and lasts 10–15 minutes.

  • Comment: Least irritating of the topical anesthetics and most suitable for corneal scraping for microbiological cultures.

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Tetracaine Hydrochloride (Pontocaine)
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  • Preparation: Solution, 0.5% (Altacaine, Opticaine).

  • Dosage: 1 drop and repeat as necessary.

  • Onset and duration of action: Anesthesia occurs within 1 minute and lasts for 15–20 minutes.

  • Comment: Stings considerably on instillation.

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LOCAL ANESTHETICS FOR INJECTION

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Lidocaine, mepivacaine, and ropivacaine are shorter-acting local anesthetics for eye surgery. Longer-acting agents are bupivacaine and levobupivacaine. A combination of drugs from the two groups may be used. Local anesthetics are extremely safe when used with discretion, but the physician must be aware of the potential systemic toxic action when rapid absorption occurs from the site of the injection, with excessive dosage, or following inadvertent intravascular injection. When combined with a local anesthetic to prolong the duration of effect, the concentration of epinephrine (adrenaline) should not exceed 1:200,000, particularly in older patients, due to the risk of cardiac arrhythmia. The addition of hyaluronidase encourages spread of local anesthetic and shortens the onset to as little as 1 minute. It is commonly used in peribulbar injections prior to intraocular surgery. For peribulbar and sub-Tenon’s injections, 5–10 mL of local anesthetic is usually sufficient, and 15 mL is the maximum volume.

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