Block 5 Flashcards
(121 cards)
What are the systemic effects of topically administered beta blockers?
May cause decrease in HR
Brochospasm
CNS depression
*risky for asthma, lung disease, or vessel spasm patients
Typically used for open-angle glaucoma (non selective b/c you want to block beta 2)
What are the systemic effects of topically administered Muscarinic blockers?
May cause increased HR
Dry mouth
Hallucinations
(The sympathetics)
Typically used for cycloplegia (ex. Atropine)
What are the systemic effects of topically administered alpha 2 agonists?
Fatigue, lethargy (low sympathetics)
Typically used for open angle glaucoma (ex. Methyldopa)
What is the pH of tears?
7.4 (same as blood)
What is the volume of the tear layer?
8-10 uL
What is the total volume that can be held for a brief time in the eye if the eyelids are not squeezed after dosing?
30 uL
What is the lowest volume of drug delivered by an eye drop?
25 uL
What is the normal tear flow rate and what happens to it with age?
Normal rate is 0.5-2.2 uL/min
It decreases with age
What does the flow rate have to do with dry eye?
Those whose flow rate is at the lower limit
A typical drop of medication is not diluted as much in a dry eye patient thus resulting in greater drug absorption
What 2 things influence drug absorption by the anterior segment of the eye?
Tear flow rate
Tear volume
Where is the major site of absorption for topically administered drugs?
Cornea
Where is the storage location (depot) for lipophilic drugs?
Corneal epithelium
Where is the storage location (depot) for hydrophilic drugs?
Corneal stroma
What is an example of a prodrug that is popular for glaucoma?
Latanoprost
It’s a PGF2 alpha agonist
When activated to latanprost acid, it concentrates in the aqueous humor and increases fluid drainage to lower IOP
In the eye it lasts 24 hours, systemically it only lasts 17 minutes
What is an example (drug) of an active metabolite? (The parent drug is active and that drug forms an active metabolite)
Loteprednol (parent drug is prednisolone)
Rapidly inactivated in the eye thus having fewer side effects than parent drug (less likely to increase IOP)
**this is the case where a shorter acting drug is more beneficial
What structures remove many drugs and metabolites from the vitreous humor and retina?
Retinal blood vessels
Which structures remove drugs from the iris and ciliary body?
Uveal blood vessels
What are ways to reduce systemic toxicity for topically administered drugs?
Store meds away from kids
Wipe excess solution or ointment from the lids and lashes
Use the lowest concentration and minimal dosage frequency
Consider the potential adverse effects of a drug compared to its benefit
Recognize adverse drug reactions
Drugs get into systemic circulation via the conj capillaries, nasal mucosa from lacrimal system, or after swallowing
What are the purpose of preservatives in ocular formulations?
Preservatives kill bacteria and fungi that may contaminate drug bottles, however they are harsh chemicals that can harm the cornea and conj epithelial cells
Chronic exposure can lead to dry eye due to poor production of tear film
Most commonly used in ophthalmic solutions is a detergent BAK - causes serious and irreversible side effects in the eye
2nd gen less toxic preservatives being used are oxidizing preservatives
Recently, ionic buffered preservatives are inactivated by the eye and thought to be least toxic
What is the purpose of vehicles in ocular formulations?
It is an agent other than the active drug that is added to the formulation to provide proper tonicity, buffering, and viscosity to complement the drug action
High molecular weight polymers increase viscosity and delay washout from the tear film which increases drug bioavailability
Polyionic molecules (oil based ointments) provide longer retention of drugs at the corneal surface
What are the various options for topical drug administration?
Solutions and suspensions (eye drops) Sprays Ointments Lid scrubs Gels
Which option of topical application tends to last the longest?
Ointments - it acts as a reservoir to enhance drug contact time
What are lid scrubs used for?
Blepharitis
What are the steps for instilling topical solutions or suspensions?
Tilt head back
Gently grasp lower lid and pull away from eye
Place dropper over eye by looking at it
Look up, apply drop
Look down for a few seconds after applying drop
Release lid
Gently close eyes for 2-3 minutes