Unclassified (Anti-Arrythmics) Flashcards
How does Adenosine work as an anti-arrythmic (even though it is technically a nucleoside)?
It’s a neuromodulator, it decreases SA and AV nodal activity by stimulating the Gi coupled receptors to decrease cAMP and the eventual phosphorylation cascade.
How do adenosine work?
Dephosphorylates the nodal cells (Na, K, and Ca) thereby closing the Na and Ca and opening the K, allowing for hyperpolarization and retard the progression back to resting pot.
When do we use Adenosine?
Drug of choice for paroxysmal supraventricular tachycardieas and AV nodal arrythmias.
What are the relavant PK of Adenosine?
It’s half life is less than 10 seconds and can only be administered via IV.
What is a big problem with the AE of Adenosine? Other side effects?
Bronchioles have Gq receptors to adenosine, which act like M3 receptors, and as a result Adenosine can induce bronchospasm and dyspnea. Other side effects include flushing and sedation.
What is a very important DDI of adenosine? What’s special about the class of Methylxanthines?
It is antagonized by methylxanthines (which includes caffiene and cocoa), like theophiline (used for COPD and asthema) and caffiene. Methylxanthines will however cause Ventricular tachycardieas.
What are the two drugs in this class of unclassified anti-arrythmic drugs?
Adenosine and magnesium
What is the purpose of administering Mg in terms of anti-arrythmics?
Since it is very similar to Ca in terms of size and shape but doesn’t have the same physiologic effects, administering Mg will attempt to compete with Ca and therefore reduce the effects of Ca.
What is a very important use of Magnesium?
For countering the torsades rhythm.
What drugs cause torsades?
K channel blockers, Anti-psychotics (Thioridazine) and TCA’s. Anti-muscurinic drugs. Basically anything that decreases K+ efflux.
