Cholinergic Toxicity, Myasthenic Crisis and Cholinergic Crisis

00:01 So let's talk about other issues in cholinomimetic toxicity. Let's talk about nicotine.

00:07 Think about what a person looks like or feels like when they first start smoking.

00:12 First-time smokers who are exposed to new high levels of nicotine can become quite nauseous.

00:18 Obviously you become acclimated to it and you don't feel that way later and you actually become addicted to nicotine.

00:24 Exposure to Malathion and parathion, it really only is relevant at very high doses.

00:29 Remember that these are prodrugs. So, they have to be metabolized to an active state.

00:35 Now that happens much more in insects than it does in humans.

00:38 So, when we talk about general use of Malathion and parathion that's safe for humans.

00:46 But when you get exposed to very toxic levels where you're super concentrated, then you may have toxic levels accumulate in the human.

00:55 Other aspects of cholinomimetic toxicity can be certain medicines like pyridostigmine, neostigmine, physostigmine. Here's an image of pyridostigmine.

01:06 Now, let's look at the differences between myasthenic crisis and a cholinergic crisis.

01:13 They're slightly different. The myasthenic crisis causes destruction of the acetylcholine receptor.

01:20 So there is an increase in heart rate and an increase in blood pressure.

01:26 Bowel and bladder incontinence.

01:29 There's an absent cough reflex and an absent swallow reflex.

01:33 Edrophonium gives temporary relief and the acetyl, that's because it's an acetylcholinesterase inhibitor.

01:41 So there's more acetylcholine in the synaptic cleft that overcomes the lower numbers of the acetylcholine receptors that have been destroyed.

01:51 That's why Edrophonium works in myasthenic crisis.

01:55 Atropine doesn't help these symptoms. Now let's talk about a cholinergic crisis.

02:02 A cholinergic crisis is when you have excess acetylcholine.

02:06 An example is sarin gas. You have a decrease in blood pressure.

02:10 You have abdominal cramps, nausea, vomiting and diarrhea.

02:16 You have blurred vision you have pallor.

02:19 You have some twitching in the face.

02:22 Edrophonium does not help in this case but actually may precipitate either a cholinergic crisis and subacute patients or worsen the cholinergic crisis through an over dosage of the acetylcholine.

02:38 And atropine here will improve symptoms.

02:41 So you can see the difference between myasthenic crisis and cholinergic crisis.

02:45 The difference is, and the important knowledge that edrophonium works in one and doesn't in another.

02:51 And atropine will work in another and not in one.

02:55 Okay. That's a tough topic, you did well.

02:58 Go write your exam and show them what you know.