Cholinergic Antagonists

Question 1

What are the effects of cholinergic antagonists on the following:

1. Heart
2. Eye
3. GI
4. Resp
5. GU

Answer 1

1. increase HR, little effect on contractility
2. Mydriasis (dilation), inability to focus (cycloplegia)
3. Decreased motility
4. Bronchodilation, decrease secretions
5. Urinary retention

Question 2

What muscarinic antagonist when given in high doses, increases heart rate, but when given at low doses, slows heart rate?

Answer 2

Atropine (treats excess ACh)

Question 3

Describe how Pralidoxime (PAM) and atropine work as antidotes to nerve gas. Do they enter CNS?

Answer 3

PAM - regenerates ACh esterase, does not enter CNS

Atropine - muscarinic blocker, so blocks ACh action - enters CNS

Question 4

Ipratropium (**tropium)

Answer 4

Muscarinic blocker that prefers lungs

COPD, asthma - decreases secretions

Question 5

Theophylline (xanthines)

Answer 5

Inhibits cAMP PDE in lungs and thus converts AMP back to cAMP

Low therapeutic index

Bronchodilator

Question 6

Scopolamine

Answer 6

Muscarinic blocker that readily enters CNS

Transdermal patch

Prevent motion sickness

Question 7

What types of receptors do ganglionic blockers work on? What do they treat? Give two examples of drugs.

Answer 7

Nn (nicotinic receptors at the ganglia)

Treat hypertension

Mecamylamine, trimethaphan

Question 8

What types of receptors do neuromuscular junction blockers act on? What do they treat?

Answer 8

Nm (nicotinic receptors at neuromuscular junction)

Produce skeletal muscle relaxation

Question 9

How do you terminate effects of succinylcholine after surgery?

Answer 9

Wait! Only has a half life of < 1 minute

Question 10

What toxicity can result from overdose of cur drugs?

Answer 10

Respiratory paralysis

Question 11

How do you terminate effects of nondepolarizing NMJ blockers?

Answer 11

Administer a cholinesterase inhibitor along with a muscarinic antagonist

Muscarinic antagonist is so cardiac output does not rapidly decline

Question 12

What is malignant hyperthermia? What is the genetic inheritance pattern? What do you treat it with?

Answer 12

Rapid increase in temperature and rise in serum K+ levels in response to inhalational anesthetics (like halothane) or muscle relaxants (like succinylcholine).

Autosomal dominant

Question 13

Oxybutynin

Answer 13

Muscarinic, M3, blocker

Overactive bladder

Question 14

Glycopyrrolate (Robinul)

Answer 14

Muscarinic blocker

Reduce secretions prior to surgery

Question 15

Succinylcholine (Anectine)

Answer 15

Reversible, depolarizing NMJ blocker with very short half life

Relax skeletal muscles, especially during surgery

Question 16

Curare cur

Answer 16

Non-depolarizing NMJ blockers (does not open ion channel)

Relax skeletal muscles

Question 17

Gallamine (Flaxedil)

Answer 17

Non-depolarizing NMJ blockers (does not open ion channel)

Relax skeletal muscles

Question 18

Botulinum toxin (Botox)

Answer 18

Cleaves SNAP-25 protein required for docking of acetylcholine-containing vesicles; prevents acetylcholine release

Cosmetic use

1. Focal dystonia - local mvt disorder
2. Strabismus (eyes not aligned)
3. Cervical dystonia (head tilt)

Question 19

Dantrolene (Dantrium)

Answer 19

Inhibit release of Ca2+ from sarcoplasm to reduce muscle tone and heat production

Malignant hypertherima