Cholinergic Receptor Inhibiting Drugs

Question 1

Which of the classes of cholinergic receptor inhibiting drugs is most often used in practice and why?

Answer 1

Anti-muscarinic drugs; they are the most selective and have fewer unwanted side effects

Question 2

What are the general effects of anti-muscarinic drugs?

Answer 2

SNS stimulation (PNS is blocked or dampened), except in CNS where the effect is sedating. Also reduction in sweating and salivation.

Question 3

What is the use of atropine?

Answer 3

Induce mydriasis (dilation) or cycloplegia (loss of accommodation)

Question 4

What is the use of scopolamine?

Answer 4

Prevent or reduce motion sickness

Question 5

What is the use of dicyclomine?

Answer 5

Treatment of spastic colon (slows that shit down)

Question 6

What is the use of tropicamide?

Answer 6

Induce mydriasis (dilation) or cycloplegia (loss of accommodation); shorter acting than atropine

Question 7

What is the use of tolterodine?

Answer 7

Treatment of transient cystitis, postop bladder spasms, and incontinence

Question 8

What is the use of benztropine?

Answer 8

Treatment of manifestations of Parkinson’s

Question 9

What are the two anti muscarinic drugs used to induce bronchodilation in asthma or COPD, and which is longer acting?

Answer 9

Ipratropium, tiotropium (longer acting)

Question 10

Which penetrates the CNS better, tertiary or quaternary amines?

Answer 10

Tertiary (atropine, scopolamine, dicyclomine, tropicamide, tolterodine, benztropine)

Question 11

What are the general side effects of antimuscarinic drugs?

Answer 11

Hot as a JGL, dry as a bone, blind as a bat, red as a beet, mad as a hatter

Question 12

What receptors do ganglionic blocker effect?

Answer 12

Nicotinic (Nn). Rarely used because both PNS and SNS ganglia are blocked

Question 13

You’re in the middle of nowhere, and you stumble upon a guy who tripped and landed on a tree branch, which he proceeds to pull out. He learns that you’re a med student and begs you to do exploratory surgery to repair his wounds. What do you really wish you had in your bag with you?

Answer 13

A surgical attending and hexamethonium (to minimize bleeding). Hexamethonium would also be helpful in a hypertensive crisis.

Question 14

Name two drugs that act at the NMJ to block Nm. Which is nondepolarizing, and which is depolarizing? What is their MOA?

Answer 14

NDP: tubocurarine (true antagonist)

DP: succinylcholine (super agonist)

Question 15

You’re shadowing in the ED and a patient comes in with a compound tib-fib fracture. The attending asks you to help with the reduction, but they have to get the screaming patient to relax their muscles first; which drug will they most likely use and why?

Answer 15

Succinylcholine, which produces paralysis within one minute. The drug is rapidly cleared within 5-10 mins.

Question 16

You’re on your psych rotation and your patient that has severe depression has just been recommended electroconvulsive therapy by the attending. You don’t want the patient to be struggling during the whole procedure, so you recommend a drug to relax the patient. What did you recommend?

Answer 16

Tubocurarine, producing motor weakness followed by flaccid paralysis (lasts 30-60 mins)

Question 17

You’re on your PM&R peds elective and a patient with a history of cerebral palsy comes in to outpatient clinic. You notice severe spasticity in the adductor muscles of the legs, to the point where the legs are crossing and interfering with the child’s gait. What does the attending recommend for the severe localized spasticity and how does this treatment work?

Answer 17

Botulinum toxin A injection. Works at the NMJ to degrade SNAP25 and inhibit vesicle fusion and subsequent release of ACh. Overall effect: decreased ACh in the synapse.