Adrenergic Drugs Flashcards
Where are alpha 1 recetpros found? Action?
Postjunctional
Found on dilator muscle, ciliary muscle, sphincter muscle
Inhibitory action
What beta recetptors are found in the eye and where?
Beta 2 in ciliary processes and trabecular meshawork
What are mechanisms of action of catecholamines on IOP?
Decrease aqueous production through effect on non-pigmented ciliary epithelium or decreasing ciliary blood flow
Increase in outflow facility of aqueous
Uveoscleral flow increased indirectly by decrease in episcleral resistance
How does mydriasis occur with catecholamines?
Active stimulation of dilator muscle and active inhibition of sphincter muscle via alpha receptors
What effect do catecholemines have on eye vasculature?
Stimulation of alpha receptors will cause vasoconstriction
How does timolol act?
Relatively selective beta 1 agonist
Acts on beta 2 receptors in eye by aqueous conc of timolol - high enough to simulate beta 2
What is the duration of action o?f timolol?
12-24 hours
Twice daily administration
What effect does timolol have on pupil
None
No effect on pupillary or ciliary muscles
What are side effects of ocular beta blockers?
Bradyarrhythmia
Negative inotropy
Bronchospasm in asthmatics or COPD
Decreases HDL cholesterol by 8% - increase risk of MI
Impotence
Depression
What is beta 1 selective beta blocker? Where does this act?
Betaxolol
Cardioselective
Least effective in lowering IOP
What is tachyphylaxis?
Down regulation of receptors results in loss of response to agonist action
What can prolonged beta blocker use result in ?
Upregulation of beta 2 adrenergic receptors in the iris and ciliary body resulting in reduced ocular hypotensive efficacy of topical beta blockers
What is iopidine?
Apraclonidine hydrochloride
Selective alpha2 agonist
