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Ocular Pharmacology > Topical Ocular Anesthetics > Flashcards

Topical Ocular Anesthetics Flashcards

1
Q

Name the four major molecular components of any topical ocular anesthetic

A

Hydrophobic Aromatic Ring
Linkage Site (Amide or Ester)
Intermediate Chain
Hydrphilic Ionizable Amide

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2
Q

With the aromatic ring on a topical anesthetic, what effect could it have on the drug?

A

Para or Meta arrangement of molecules along the ring seems to effect cross drug allergic sensitivity

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3
Q

About what is the ideal intermediate chain length for ocular anesthetics?

A

2 carbons

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4
Q

Describe characteristics of ester linkages

A

Relatively easy to metabolize by pseudocholinesterase which is found all over the body
More likely to cause an allergic reaction than an amide bond

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5
Q

Give some example chemicals that use ester linkages

A

Benoxinate and Tetracaine - esters of para-amino benzoic acid (PABA)
Proparacaine - Ester of meta-amino benzoic acid

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6
Q

Describe characteristics of amide linkages

A

Must be metabolized in the liver and tend to have a longer duration of action

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7
Q

Give an example of a chemical using an amide linakge

A

Lidocaine (Xylocaine); used as an anti-arrhythmic

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8
Q

If one is allergic to a drug that uses an ester linkage, would they experience cross sensitivity to a drug using an amide linkage?

A

No additional allergic risk

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9
Q

In terms of pH and acid/base chemistry, what characteristics make for the best topical ocular anesthetics?

A

Weak bases that ionize at body pH

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10
Q

Describe the four principles behind a topical ocular anesthetic’s MOA

A

Reversible block of nerve conduction
Increasing excitation threshold
Increasing refractory period
Decreasing velocity of the nerve impulse

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11
Q

An effective topical ocular anesthetic blocks what?

A

Sodium influx into cell

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12
Q

Does a topical ocular anesthetic bind the sodium channel inside or outside of the cell?

A

Inside

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13
Q

Describe how a local anesthetic must get to and bind a sodium channel

A

1) Must be in non-ionized state to travel through lipid membrane of the cell
2) Within the cell must reconvert from non-ionized to ionized state
3) In the ionized state, LA must bind and block sodium channel

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14
Q

Describe Tetrodotoxin and how it interacts with the sodium channel

A

Binds to a sodium channel from outside of the cell and irreversible, will kill you

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15
Q

Describe the neuron characteristics that make it easier to anesthetize that neuron

A

Smaller and unmyelinated neurons are easiest to anesthetize. If myelinated then size also contributes to sensitivity

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16
Q

Name the sensations in most sensitive to least sensitive to anesthetizing

A 
Pain
Temperature
Touch, vibration
Pressure
Motor
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17
Q

Name the sensations in fastest to slowest recovering from anesthetizing

A 
Motor
Pressure
Touch, vibration
Temperature
Pain
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18
Q

If a neuron recovers from anesthetizing very fast, what qualities could you attribute to that neuron?

A

Probably a large and myelinated neuron

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19
Q

Describe the indication for the use of topical anesthetics and give examples of such times an optometrist would want to use one

A

Indicated for increasing patient comfort by decreasing pain and irritation
Tonometry
Anterior segment exam
Fundus CL exam
Forced duction testing
FB removal
Corneal epithelium debridement
Increase effectiveness of drugs (though not done just for this purpose, rather a benefit of how the exam is set up)
Electroretinography
Lacrimal drainage procedures
To decrease discomfort caused by other ocular agents like cyclopentate or possibly tropicamide

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20
Q

What effect could inflammation have on the efficacy of a topical anesthetic?

A

As most LA’s we use are weak bases they become ionized in the acidic environment during inflammation. This combined with the increased bloodflow due to inflammation causes worse drug absorption ad more of the drug to be removed from the eye before it absorbs

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21
Q

What effect does epinephrine have on anesthetics; how about topical anesthetics?

A

Epinephrine causing vessel constriction to reduce bloodflow in and out of the area to try and keep as much of the anesthetic at the local area.
This effect doesn’t work with topical ocular anesthetics

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22
Q

What happens when a topical ocular anesthetic gets old?

A

Gets discolored and can cause more irritation

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23
Q

What is maximum effective concentration and what is that concentration in some of the drugs?

A

Increasing the concentration beyond this level will not cause a better clinical effect, just toxicities
 Proparacaine 0.5%
 Benoxinate 0.5%
 Tetracaine 1.0%
 Cocaine 20.0%
Keeping in mind that in practice this dose may be less (1% tetracaine hurts like hell)

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24
Q

What are some ocular toxicities of the local anesthetics?

A

Toxicities due to decreasing nerve conduction, topical anesthetics not as likely as systemic.
Mild epithelial staining, edema with cytotoxic LA and/or preservatives
Conjunctival hyperemia for a few minutes
Decreased TBUT
Decreased blink reflex, can lead to driness
Burning and stinging
Decreased tear secretion

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25
Q

Describe the epithelial toxicities with LA’s

A

Can be serious enough for medical treatment and some people can have an exaggerated (damage in minutes)
Cause epithelial erosion and inhibits regeneration
Possible rapid blurring VA from diffuse desquamation, edema and photophobia and pain

Treatment: Epithelium can heal spontaneously, more severe cases involve systemic analgesics, artificial tears and cold compresses

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26
Q

Describe the allergic response that can be seen with LA’s

A

Type IV delayed hypersensitivity that tends to be a dermatologic response
Swollen injected conjunctiva, burning and itching
With OD’s it may manifest as peeling and cracking skin on fingertips

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27
Q

Describe the systemic toxicities seen with topical LA’s

A

None with PROPER use of LA’s
However, toxicities are based on central depressants
Early - Anxiety, nervousness, tremors and convulsions
Later - CNS depression, depressed respiration, unconsciousness
Syncope - more of an emotional response
Possibly death

28
Q

How can one prevent the systemic toxicities with ocular LA’s?

A

Proper dosages! (No more than 5mg tetracaine, or 10 mg of proparacaine)
Be sure the patient is reclined incase of fainting
Be conservative in myasthensia gravis patients and patients using AchE inhibitors
Caution in:
Patients with known hypersensitivity, patients who have decreased liver function, patients with hyperemic conjunctivitis due to increasing systemic drug absorption

29
Q

What are the contraindications for the ocular LA’s?

A

Allergic hypersensitivity
If the patient needs to have a culture taken after the LA (do it before)
NEVER allow the patient to self-administer, will cause severe corneal damage

30
Q

Describe Tetracaine 0.5% characteristics

A

Prototypical ocular LA though not used often
Causes the most stinging
Para-amino benzoic acid derivative

31
Q

Describe Proparacaine (Ophthaine) (0.5%)

A

The current drug of choice for local ocular anesthetics
Causes the least stinging
Possible to develop an alelrgic hypersensitivity but takes months

32
Q

What can proparacaine be comboed with?

A

Fluroscein and preserved with thimerosal

33
Q

What is the long term effect on epithelial debridement after any LA is instilled in the eye?

A

Significantly higher epithelial debridement is seen after any LA is used on the eye for hours after the drop is used

34
Q

Describe the effect varying concentrations of LA’s would have on duration of action

A

Higher dose, longer it takes the drug to wear off

35
Q

What is the effect of age and LA concentration?

A

A lower concentration doesn’t work as well on younger age groups. Need a higher concentration to effect them.

36
Q

What is the trade name for Benoxinate?

A

Fluress

Available as a combination with flurosecein

37
Q

Benoxinate (Fluress) 0.4%

A

Combined with flurosecein; no documented cases of contamination so good at preventing it

38
Q

What is the trade name for Lidocaine?

A

Akten

39
Q

Lidocaine (Akten)

A

Anesthetic GEL that is an AMIDE derivative and not ester

40
Q

When would you want to use Lidocaine?

A

Patient is allergic to ester derivative LA’s

Need to perform a surgical procedure and want a longer lasting anesthetic

41
Q

Describe and detail the use of cocaine as a LA

A

Can be used as an LA, but causes significant toxicities, can debride the epithelium significantly
But can be used to confirm/disprove presence of Horner’s syndrome

42
Q

Describe the qualities of injected LA’s

A

Rate of absorption dependent on rate of circulation and surface area
Can combine with epinephrine to increase efficacy and decrease systemic toxicities by constricting vessels to reduce bloodflow

43
Q

What is the effect and use of Hyaluronidase?

A

Can be used with injected LA’s as an enzyme and increases drug’s access to intracellular side by breaking down extracellular matrix slightly.

Not too commonly used anymore

44
Q

Where would ester based LA’s be metabolized? (Give examples of drugs)

A

Metabolized via esterases throughout the entire body; tend to have a shorter duration of action than amide based

Tetracaine
Proparacaine
Benoxinate

45
Q

Where would amide based LA’s be metabolized (Give example of a drug)

A

Metabolized in the liver; tends to have a longer duration of action than ester based

Lidocaine

46
Q

What effect would liver dysfunction have on treating a patient with lidocaine?

A

Effect may last much longer than originally intended

47
Q

What would it indicate for patient selection if they stated they were being treated for myasthenia gravis or accommodative esotropia?

A

Myasthenia gravis - May be on AchE inhibitors, causing longer duration of action

Accomodative Esotropia - Treated with ecothiophate which is an AchE inhibitor

48
Q

What would one use to treat chronic ocular pain?

A

Systemic analgesics, DO NOT use topical anesthetics

49
Q

Explain prostaglandins and their role in pain

A

Prostaglandins released during pain response, mediate the response.

Prostaglandin inhibitors will prevent part of this response and

50
Q

Describe some ocular related uses for analgesics

A 
Acute pain relief
Foreign body removal
Corneal abrasion
Corneal trauma
Inflammation or trauma after surgery
51
Q

Name the Propionic Acid based systemic analgesics

A 
Ibuprofen (Advil, Motrin, Nuprin)
Naproxen (Naprosyn)
Naproxen sodium (Anaprox, Aleve)
Fenoprofen (Nalfon)
Ketoprofen (Orudis)
Ketoprofen (Daypro)
52
Q

Name the selective COX-2 inhibitor based systemic analgesic

A

Celecoxib (Celebrex)

53
Q

Between ketoprofen, ibuprofen and aspirin which tends to last longest and have the fastest onset?

A

Keptoprofen, Ibuprofen, aspirin

54
Q

Describe a good indication for the use of acetaminophen over another analgesic

A

No antiinflammatory action
Used if a patient can’t tolerate ASA or non-salicylate NSAIDs
Less risk of GI upset, bleeding and no concern about ASA sensitivity

55
Q

Describe some characteristics of the opiate alagesics

A

There is no ‘ceiling effect’, keep giving, keeps getting better
Addiction liability however (reduced in oral/analgesic use)
Severe pain is a good indicated use (blocks both pain and suffering)

56
Q

Describe and then compare Tramadol to Codeine

A

Tramadol; non-opiate analgesic but does act at mu pain receptors
Will also block reuptake of NE and 5-HT (caution in those using MAOIs as will over do it)

57
Q

Should a patient be taking a combination analgesic (Generally NSAID with opiate) what should you caution them?

A

Drug induced nausea, vomiting and/or constipation
Take drug with food to reduce GI upset
Avoid taking any CNS depressants
May experience breathing difficulties

58
Q

Name the most frequently prescribed Schedule II combination systemic analgesic

A

Percocet (APAP + Oxycodone)

Percodan (ASA + Oxycodone)

59
Q

Name the most frequently prescribed Schedule III combination systemic analgesics (less heavily controlled than Schedule II)

A

Vicoden (APAP + Hydrocodone) (number 1 prescribed in the US)
Vicoprofen (Ibuprofen + Hydrocodone)
Tylenol #3 (APAP + codeine)

60
Q

What are the contraindications for ASA/NSAID/APAP?

A

History of adult onset asthma
Nasal polyps, ASA sensitivity and the Aspirin Triad in general
Active upper GI disease
Bleeding disorders or going through anticoagulant therapy
Chronic liver/kidney disease
Near term pregnancy
Children with undiagnosed flu (Reye’s Syndrome)
Hypertension/congestive heart failure
History of heavy alcohol use
An invasive surgery in the near future or recently performed (affecting wound healing)

61
Q

What are the contraindications for opiate use?

A

Allergic sensitivity to opiates
Acute bronchial asthma/other COPD
Kidney/liver disease
(Do not use pentazocine if patient is on a chronic opiate agonist)
Patient is using other CNS depressants like alcohol or sleeping pills
Pregnancy or nursing

62
Q

Describe what would change if you use analgesics in the elderly

A

More likely to have GI upset, so take with food
Kidney/liver function decreases
Use Sulindac or Ibuprofen as these are pretty safe
Use an APAP in a patient with a bleeding problem (Acetaminophen)

63
Q

For an elderly patient with GI upset with their current analgesic, what alternative could you offer?

A

Misoprostol (Cytotec) as it is a prostaglandin analog to replace the missing prostaglandins
Can use Celexcib (Celebrex) as well due to the more selective COX-2 inhibition

64
Q

Name the topical ocular NSAIDs we use

A 
o	Flurbiprofen (Ocufen) 0.03%
o	Ketorolac (Acuvail) 0.45% non preserved
o	Ketorolac (Acular LS) 0.4% 
o	Diclofenac (Voltaren) 0.1% Though this happens with the other compounds, this has the most history of ‘corneal melting’ along with ketorolac
o	Bromfenac (Bromday) 0.09% claims much lower irritation scores versus ketorolac
o	Nepafenac (Nevanac) 0.1% (Prodrug for amfenac; must be converted going through the cornea) – improved ocular penetration, new formulation 0.3%
65
Q

What toxicities can be seen with topical ocular NSAIDs?

A

Transient burning and stinging to the conjunctiva
Less frequent: allergic reactions, punctate keratitis, decreased wound healing, ocular bleeding
Rarely see: epithelial breakdown, corneal thining/erosion, and/or ulcer into perforation

66
Q

What contraindications are there for topical ocular NSAIDs?

A 
Contact Lenses
ASA sensitivity
Pregnancy
Bleeding history
Corneal breaks/damage

Ocular Pharmacology (11 decks)

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