Amiodarone is potassium channel blocker but also voltage-gated Na+ channel blocker according to Pubchem. However, upon reading my notes I discovered

Amiodarone blocks potassium channels and block alpha and beta channels.

I think it must be alpha and beta receptors here, instead of channel. Pubchem proposes that there may beta-blocker-like properties in amiodarone. However, its alpha-like properties are obscure to me as I cannot find any sources. How is amiodarone working as alpha and beta blocker?

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    $\begingroup$ Are your notes a good source of reliable information? $\endgroup$ – anongoodnurse Jun 8 '15 at 21:17
  • $\begingroup$ hello again masi, my interstitial fluid & pharmacology friend... yes, the adrenergic receptors work via 2nd messenger not as ion channels... also as I understand it a lot of the class III antiarrhythmics have properties of all the other classes and class II are beta-blocker... so this is confirmation of your source... like you I also have no information about alpha blockade as this is irrelevant to it's effects as an antiarrhythmic... my source is my memory from med school, even less reliable than your notes.... $\endgroup$ – Jasand Pruski Jun 9 '15 at 2:51

Amiodarone inhibits sodium, potassium and calcium currents. Its major antiarrhythmic properties are thought to be related to prolongation of the action potential duration. Amiodarone also exerts an antiadrenergic effect by non competitively inhibiting alpha- and beta-receptors (Ghuran & Camm, 2000).

Alpha blockers relax certain muscles and help small blood vessels remain open by antagonizing norepinephrine's tightening effects on the muscles in the walls of smaller arteries and veins, which improves blood flow and lowers blood pressure (Mayo Clinic). Beta blockers decrease the effects of epinephrine (adrenaline), reducing heart rate and reducing its force, thereby reducing blood pressure. Beta blockers also help blood vessels open up to improve blood flow (Mayo Clinic).

Alpha-adrenergic receptors and Beta-adrenergic receptors are G-protein coupled receptors (Wallukat, 2002). Hence, they do not form channels and your notes are incorrect. The ion currents are mediated by channels, though.

- Ghuran & Camm, J Clin Basic Cardiol (2000); 3: 206
- Wallukat, Herz (2002); 27(7): 683-90


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