Why are beta blockers contraindicated in cocaine use?

[Daitong]

I understand that "unopposed α-adrenergic receptor agonist activity"...

But what does that mean? Cocaine blocks reuptake of adrenergics (NE/E), but I'm having trouble thicking about what that has to do with beta blockers, and how they even affect one another.

Thanks!

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[Phloston]

If you block beta-receptors then your catecholamines have to bind to alpha receptors instead (alpha 1 effects are much more salient and faster than alpha 2). You'll cause vasoconstriction and increased BP by giving a beta-blocker when catecholamines are floating around.

In cocaine use associated with sympathetic symptoms (e.g., tachycardia, mydriasis), the first step is an ECG. If normal, you want to give a benzo (lorazepam) first-line; if that doesn't work add an alpha-blocker (phentolamine).

Cocaine increases the risk of coronary vasospasm and coronary artery thrombus. If ECG shows signs of ischaemia (e.g., ST-T-wave changes), the next best step is coronary angiography to rule out thrombus. In either event, if ischaemia is present, in addition to the lorazepam, give nitrates or dihydropyridine CCB, PLUS aspirin.

That info is from UWorld Step 3 just fyi.

 

[Daitong]

You should teach at HMS...

 

[2xA]

Would this apply to a B1 specific blocker like metoprolol?

 

[deleted500612]

Would this apply to a B1 specific blocker like metoprolol?

Yes, remember that B1 specific beta blockers are not exclusively B1, they are simply more selective for B1 but still have mild B2 antagonistic effects.