Oc Pharm 1 (Ocular Anesthetics)

What is algesia defined as?

ability to sense pain

What is esthesia defined as?

ability to perceive sensation

What is kinesia defined as?

movement

How do ocular anesthetics work?

produces reversible block to peripheral nerve impulses

What are diagnostic indication for the use of topical anesthetics?

applanation tonometry, gonioscopy, force duction testing, scleral depression

What are procedure indication for the use of topical anesthetics?

FB removal, corneal debridement, corneal refractive surgery, cataract surgery, incision/curettage, eyelid biopsy, eyelid surgery

What physiochemical properties of anesthetics allow the drug to penetrate into the desired location?

Amphiphilic property

Where are esters metabolized by?

plasma cholinesterase

Where are amides metabolized?

the liver

Why do esters have a shorter duration of action?

they undergo local metabolism

What are common ester ocular anesthetics?

tetracaine, benoxinate, proparacaine

What are common amide ocular anesthetics?

lidocaine

Which class of ocular anesthetics have a higher likelihood of allergy in patients?

Esters because they degrade into PABA (para-amino benzoic acid)

Is there cross-reactivity between amide and ester derivatives?

No

What is the mechanism of action of anesthetics?

Na+ channel blocker

What is the onset of anesthetics in mucosal tissue?

rapid

What can prolong the duration of a local anesthetic?

pairing it with epinephrine

How does epinephrine aid in prolonging the duration of action?

prevents metabolism/breakdown of the drug

What are disadvantages of the use of topical anesthesia?

does not provide complete nerve block

What are advantages of the use of topical anesthesia?

less complications overall, immediate recovery, rapid onset, decreased blink reflexes

What pregnancy category are topical anesthetics?

C

What is the most common preservative in topical anesthetics?

BAK (benzalkonium chloride)

Which topical anesthetic is used for cataract surgery?

1% Tetracaine HCl solution

Which topical anesthetics are used for corneal procedures, tonometry and gonioscopy?

0.5% Tetracaine HCl solution and 0.5% Proparacaine HCl solution

Which topical anesthetics are used for applanation tonometry?

0.5% Proparacaine HCl with 0.25% NaFl and 0.4% Benoxinate HCl with 0.25% NaFl

Which topical anesthetic is a good option for tonometry on contact lens wearers?

0.35% Disodium Fluorexon/0.4% Benoxinate HCl solution

Which characteristic of 0.35% Disodium Fluorexon/0.4% Benoxinate HCl solution makes it a good option for contact lens wearers since it does not absorb into hydrogel soft contact lenses?

fluorexon has a high molecular weight

What is the only amide topical anesthetic available?

0.35% Lidocaine HCl solution

What is an ADR associated with the overuse of topical anesthetics?

desquamation of corneal epithelial cells, induces dry eye signs

What is the limit drop number of tetracaine to prevent ocular toxicity?

7

What is the limit drop number of proparacaine to prevent ocular toxicity?

14

What allergic reaction is associated with topical anesthetic use?

Blepharoconjunctivitis

What are advantages of local anesthesia?

easily administered, reliable, safe

What are disadvantages of local anesthesia?

may require high volumes of anesthetic, distorts anatomy, systemic effects

What can be added to an anesthetic to prolong anesthetic action and promote hemostasis?

Epinephrine

In which co-morbid conditions is epinephrine contraindicated?

Angle closure glaucoma, brain injury, coronary insufficiency, peripheral vascular disease, labor and delivery

What are contraindications of epinephrine?

contaminated wounds, pts taking MAO inhibitors, peripheral vascular disease

In which co-morbid conditions should epinephrine be used with caution?

Stable diabetes, HTN, ateriosclerosis, thyrotoxicosis, heart block, cerebrovascular disease

What can the use of lidocaine cause?

vasodilation

Which injectable anesthetic is best to use in a contaminated wound, vascular disease, and if cerebrovascular or cardiovascular risk is present?

Lidocaine

Which injectable anesthetic is useful to use in highly vascular areas like the eyelids?

Lidocaine + Phenylephrine