Drugs for Glaucoma Flashcards
(49 cards)
What does the iris circular muscle do in the eye? What activates it?
- Constricts pupil to cause miosis
- Effect is due to activation of M3 receptors –> GPCR coupled to Gq
What does the iris radial muscle do in the eye? What activates it?
- Dilates pupil to cause mydriasis
- Effect is due to activation of alpha1 adrenergic receptors –> GPCR coupled to Gq
What does the ciliary muscle do in the eye?
- Causes accommodation of the eye to near vision
- Opens up trabecular meshwork, improves outflow of aqueous humor into the canal of Shlemm, decreasing intraocular pressure
What makes the ciliary muscle work?
- M3 receptors
What does the ciliary epithelium do in the eye?
- Produces (secretes) aqueous humor
What allows the ciliary epithelium to make aqueous humor?
- Beta adrenergic receptor activation increases humor production
- Alpha2 adrenergic activation decreases humor production
What is a part of the regulation of intraocular pressure?
- Production of aqueous humor
- Outflow of aqueous humor
What plays a role in the production of aqueous humor?
- Sympathetic nervous system –> Beta and alpha2 receptor activation
- Carbonic anhydrase
How does carbonic anhydrase help with the production of aqueous humor?
- Functions to transports sodium and bicarbonate ions from the ciliary body to the aqueous humor
- Increase in osmotic pressure of the aqueous humor enhances transport of water to the humor to increase its volume
What plays a role in the outflow of aqueous humor?
- Muscarinic receptors
- Prostaglandin F2alpha improves uveoscleral or unconventional outflow
- Sympathetic nervous system –> contraction of iris radial muscle or relaxation of ciliary muscle
What are the types of primary glaucoma?
- Open angle glaucoma
- Closed angle glaucoma
What is open angle glaucoma?
- Chronic progressive disease with no apparent mechanical blockage for the humor outflow
What is closed angle glaucoma?
- Acute intermittent partial or complete blockage of the outflow, may have to be treated as an emergency to avoid vision loss
What could be some causes of secondary glaucoma?
- Secondary to other diseases
- Trauma
- Surgery
- Drug-induced
What drug classes help reduce aqueous humor production?
- Beta blockers
- Alpha2 adrenergic agonists
- Carbonic anhydrase inhibitors –> both topical and systemic
What drug classes help increase aqueous humor outflow?
- Prostaglandin analogs
- Alpha2 adrenergic agonists
- Direct cholinergic agonists
- Inhibitors of cholinesterase (indirect acting cholinergic agonists)
What is the MOA of beta blocker in glaucoma?
- Reducing the production of aqueous humor by the ciliary body via blocking beta receptors
Why is use of beta blockers common in glaucoma?
- Convenience of dosing
- Relative lack of local adverse effects?
What beta blocker is favored? Why?
- Timolol
- Lacks local anesthetic effects (propranolol and some others possess local anesthetic activity)
- Available as generic
- Full antagonist
What are some systemic adverse effects of beta blockers?
- Negative inotropic effect and bradycardia
- Bronchospasm
- Hyperlipidemia
- Exacerbation of hypoglycemia
- May interact with CCBs causing an increased risk of cardiac depression and heart block
What patients should use of beta blockers be cautioned?
- Patients with bradycardia, AV block, or heart failure
- Those with diabetes or receiving oral beta blocking therapy
What are some local adverse effects of beta blockers?
- Ocular irritation
- Dry eyes
What are some alpha2 agonists used in glaucoma?
- Brimonidine
- Apraclonidine
What is the MOA of alpha2 agonists in glaucoma?
- Decrease rate of the aqueous humor production
- Increase uveoscleral outflow by relaxing ciliary muscle
