Wk 15 - Miotics

Question 1

Parasympathetic pathway

Answer 1

Remember that the ciliary muscle and iris sphincter muscle are controlled by parasympathetic fibers
Preganglionics begin at Edinger-Westphal nucleus in the brainstem, then synapse at ciliary ganglion.
o 3% of postganglionic fibers release Ach onto the iris sphincter muscle, causing pupil constriction
o 97% of postganglionic fibers release Ach onto the ciliary muscle, causing contraction and accommodation

Question 2

Cholinergic agonists

Answer 2

AKA Miotics AKA parasympathomimetics
• These drugs mimic the parasympathetic effects of acetylcholine

Pilocarpine is the only drug in this class still used to treat glaucoma today
o	Direct acting – mimics Ach
•	Opposite effects of the cholinergic antagonists (Mydriatics = ASHCT)

Question 3

Pilocarpine MOA

Answer 3

MOA
• Mimics Ach at the ciliary muscle and iris sphincter
• Thought that contraction of the ciliary muscle pulls on the scleral spur, widening the trabecular space
• Increases outflow through the trabecular meshwork
• Decreases IOP by 15-25%
o Works slightly better in blue eyes

Question 4

Pilocarpine Clinical Uses

Answer 4

1) Acute angle-closure glaucoma
o Note that ischemic iris is nonresponsive to pilocarpine at pressures >60 mmHg
o Must use another drug to lower IOP below 60 before using pilocarpine
2) Secondary glaucomas
o Drug of choice for pigmentary glaucoma
o Moves iris away from the lens zonules to prevent rubbing and pigment dispersion
3) Primary open angle glaucoma
o Historical medication
o Rarely used today due to development of safer, more effective drugs

Question 5

Pilocarpine Solution

Answer 5

Available in concentrations 0.5%, 1%, 2%, 3%, 4%, 6%

Dosing: q4h
• Bad for compliance
o Max effect achieved in a few days

Question 6

Pilocarpine 4% Gel

Answer 6

Dosing: ½ inch ribbon qhs
o Increased compliance
o Decreased complaints of side effects since they peak while patient sleeps
BUT
Increased risk of retinal detachment
o May combine with a drop in the afternoon if IOP is not lowered consistently through the day

Question 7

Ocusert Pilo-20/Ocusert Pilo-40

Answer 7

o Inserted into lower fornix
o Releases 20 or 40 ug/hour

Dosing: q7d
-Follows zero order kinetics
• Constant amount of drug delivered, released, and absorbed
• Release controlled by a polymer membrane to decrease systemic overload

Specific Side Effects
o Increased blur during first 12 hours after insertion
• Reduce complaints by inserting at night
o Possible foreign body sensation/discomfort
o May fall out of fornix
• Patient must monitor presence

Question 8

Pilocarpine Ocular Side Effects

Answer 8

1) Miosis

2) Accommodative spasm and blur
o Especially in patients

Question 9

Pilocarpine Systemic Side Effects

Answer 9

1) Brow ache
o Especially when beginning treatment
o Caused by miosis and accommodative spasm
o Minimized by starting at a low dose and working up

2) SLUDE
o Salivation, lacrimation, urination, defecation, emesis
o Parasympathetic-type effects
o Rare

3) Tremor

4) Heart
• Bradycardia
• Cardiac arrhythmia
• Hypotension

5) Lungs
• Bronchiolar spasm – rare
• Pulmonary edema

Question 10

Pilocarpine Contraindications

Answer 10

1) Patients may cause pupillary block

5) Severe asthma
o Respiratory effects

6) Concurrent use with succinylcholine
o An anesthetic – make sure surgeon or anesthesiologist knows if patient is taking this med