Drugs in the eye

Question 1

What is the mechanism of action of tropicamide?

Answer 1

mAchR Antagonist, blocking the actions of the parasympathetic nervous system. Therefore, this paralyses the pupillary constrictor response and the ciliary muscles which usual contract in response to bright light

Question 2

What is the mechanism of action of cocaine?

Answer 2

acts a local anaesthetic and mimics the actions of the sympathetic NS causing vasodilation, peripheral vasoconstriction (white sclera) and loss of the corneal reflex

Question 3

What is the MOA of tetracaine?

Answer 3

Acts as a local anaesthetic, blocking Na+ channels and causing a loss in the corneal reflex

Question 4

What is the MOA of pilocarpine?

Answer 4

mAchR agonist, exciting the PNS causing pupillary constriction and vasodilation of the blood vessels - causes blood shot eyes (Acts on BV’s causing them to release NO and dilate BV’s). It also pulls open the canal of Schlemm leading to a reduction in the intraocular pressure

Question 5

What is the MOA of phenylephrine?

Answer 5

causes vasodilation and peripheral vasoconstriction - alpha adrenoreceptor agonist - activates the sympathetic nervous system