Dopamine & Tachydysrthmias

[CWATT]

My pharmacology textbook identifies Dopamine as the precursor to Norepinephrine and suggests it has the same pharmacodynamic profile. To the best of my knowledge, we do not typically associate NorEpi as causing tachydysrthmias. Some internet-based sources suggest Dopamine shares equal probability of causing tachydysrthmias but neglects to mention NorEpi.

So what’s the story here? Is Dopamine the fall-guy for beta-1 agonists or is there actually something unique to its chemical structure that predisposes its use to tachydysrthmias.


Thank you,
- C

 

[DesertMedic66]

Dopamine is a chronotrope and acts on beta 1 receptors so you are going to have the increase in HR. Anytime you are increasing the HR you also run a risk of tachy rhythms.

Norepi has very little effect on HR because it primarily acts on alpha receptors which cause vasoconstriction and not chronotropy.

 

[Carlos Danger]

Arrythmogenicity with sympathomimetics is generally considered to correlate to increases in HR, so I think it primarily has to do with increased oxygen demand and / or issues with dromotropy. Dopamine causes less tachycardia than epi or isoproterenol, and is less prone to cause dysrhythmias. On the other hand, it causes more tachycardia than norepinephrine or dobutamine, and is thought to case more dysrhythmias.

But there may be more to it than that. Dopamine is a very "dirty" drug. It binds to lots of receptor subtypes and has all sorts of effects that we don't normally think too much about.