OPTH Lec07 and 08 Flashcards
(110 cards)
Bioavailability
% of unchanged drug that is absorbed in the circulation; want to increase bioavailability of eye drops
Surfactants
increase solubility of hydrophilic drugs; Improves penetration through the cornea Benzalkonium Chloride = MC Emulsifies cell walls – improves penetration, but can cause ocular surface damage
How can we improve bioavailability
Osmotics – adjust tonicity of drops to prevent reflex tearing Non-ionized forms of drugs = lipid soluble, thus better penetration
How are eye drop measurements expressed
Parts per 100 1% = 1 gram per 100 cc How many mg of atropine in 5cc of a 1% solution? (1 gram/100 cc ) * 5 cc = .05 grams = 50 mg
Administration of Eye Drops
Drugs to Nasolacrimal duct to Mucosa No first pass effect through GI tract and liver
Anesthetic Eye Drops do what?
Prevents generation and conduction of nerve impulse Anesthesia impedes sodium access to the axon by blocking transmembrane sodium channels
Name the Anesthetic Eye Drops:
tetracycline, proparacaine
What does tetracaine do?
Onset: 15-20 seconds Duration: 15 – 20 minutes Corneal Toxicity, Never prescribe for home use
What does proparacrine do?
Better tolerated than tetacaine Onset: 12.9 seconds Duration: 20 minutes Allergic Dermatitis
What kind of neurons are there in the symp nervous system?
1st order - from in hypothalamus, descend to IML horn of lower cervical and upper thoracic spinal cord 2nd order - Pass through sympathetic chain and synapse in superior cervical ganglion 3rd order - Travel to the eye with branches of carotid artery to innervate smooth muscles and glands
What kind of receptors are there in the symp nervous system and where are they?
Alpha 1 – most vascular smooth muscle, pupillary dilator, heart Alpha 2 - adrenergic and cholinergic nerve terminals Beta 1 – heart, fat cells Beta 2 – respiratory and vascular smooth muscle, skeletal muscle
Name the alpha drugs that act on autonomics:
norepinephrine, epinephrine
Naem the beta drugs that act on autonomics:
epinephrine, isoproterenol
What are alpha blocking drugs?
thymoxamine
Which drugs do you use for Galucoma?
Beta blocking – timolol, betaxolol, levobunalol, etc. Alpha agonist – clonidine, apraclonidine, brimonidine
What does Epinephrine do?
Increases trabecular outflow; Small increase in aqueous production; Vasoconstriction; Mydriasis; Mostly alpha, slight beta effect
Describe Epinephrine Toxicity:
o Nervousness, anxiety, tachycardia, headache o May exacerbate CAD, HTN, Thyrotoxicosis o Corneal pigmentation, madarosis, turns contact lenses black o Rebound Hyperemia o Conjunctival Pigment Deposits
What does Phenylephrine do?
Direct acting, alpha agonist; Alpha-1 selective, little effect on Beta; Used for mydriasis; Onset 15-60 mins, duration 3.7 hours; No effect on ciliary muscle
What is the toxicity of phenylephedrine?
Acute Hypertension Seen with 10% solution Never use 10% in infants Hypersensitivity in patients with diabetic neuropathy Pulmonary Edema, arrhythmia
What does clonidine do?
– Central acting, even topically – Alpha 2, some alpha 1 agonist – Decreases aqueous production by vasoconstricting the ciliary body – Little effect on pupil. Accommodation, or vision – Multiple cardiovascular effects
What is apraclonidine?
– Alpha agonist, mostly alpha 2 – Lowers IOP by suppressing aqueous production – Vasoconstriction of the ciliary body may also play a role – Does not cross blood brain barrier in adults – Can cause somnolence in children – No effect on BP, almost no cardiac effects
What are the side effects of apraclonidine?
Transient dry nose, mouth (30-40%) Eye lid retraction Mydriasis Conjunctival blanching Do not use in kids!
What is brimonidine and what is it used for?
– Alpha agonist, primarily alpha-2 – Decreases aqueous production – Increases uveoscleral outflow – Less allergy than apraclonidine – No heart rate/BP effects – Can cause sedation by stimulating central alpha-2 receptors
What are the side effects of Brimonidine?
10-30% dry mouth, burning, fatigue, redness Visual Disturbance Contraindicated in young children due to somnolence