This document summarizes several miscellaneous antiarrhythmic drugs: Adenosine terminates supraventricular tachycardias by inhibiting calcium channels and activating potassium channels. Magnesium sulfate is used to treat refractory ventricular arrhythmias. Digoxin controls ventricular response rate in atrial fibrillation by inhibiting the sodium-potassium pump and prolonging refractory periods. Atropine increases heart rate by blocking acetylcholine and is used to treat bradycardia.

1. 5.Miscellaneous
Antiarrhythmic Drugs

2. Miscellaneous Antiarrhythmic dugs
These are antiarrhythmic drugs that do not fit in the four classes
mentioned above. They include:
• Adenosine
• Digoxin
• Magnesium sulphate
• Atropine

3. Adenosine
• MOA
Activates adenosine receptors in the heart. Adenosine receptors are g
protein-coupled receptors that are present in the atria, AV node and
ventricles of the heart.
It binds to its receptors, which leads to activation of potassium channel
snd the inhibition of Calcium channels in the AV node. This results in
hyperpolarization of the AV node. As a result, the reentry circuit
responsible for SVT is interrupted and the heart rhythm returns to
normal sinus rhythm.

4. Pk of adenosine
• Adenosine is administered intravenously because it has a short half
life of a few seconds.
• Oral adenosine has a longer half life but is not effective in arrhythmia
treatment and can cause significant side effects.
• The short halflife of adenosine is the reason it is only used as an acute
medication of arrhythmia and not as a long term drug.

5. Side effects of adenosine
• Chest discomfort
• Diziness
• Nausea and vomiting
• Shortness of breath
• Flushing
Clinical use
• Acute termination of supraventricular tachycardias, including paroxysmal
supraventricular tachycardia(PSVT)

6. Magnesium Sulfate
• Mode Of Action
The mode of action is not fully understood but is believed to be related
to its ability to modulate ion channels and stabilize cell membranes.
• Side Effects of Magnesium Sulfate
Nausea and vomiting
Headache
Tachycardia and palpitations

7. • Pharmakokinetics of Magnesium sulfate
Administered intravenously
• Clinical use
• Management of torsades de pointes and refractory ventricular
arrhythmias.

8. Digoxin
• MOA
Digoxin inhibits the Na+/K+ ATPase pump, and shortening the refractory
period in atrial and ventricular myocardial cells while prolonging the
effective refractory period and diminishing conduction velocity in the AV
node. Digoxin is used to control ventricular response rate in atrial fibrillation
and flutter.
• Pharmacokinetics
Well absorbed orally with a bioavailability of 60-80%
Highly protein bound
Metabolised in the liver
Has a half-life of approximately 36-48 hours with normal renal function.

9. • Side effects of Digoxin
Nausea, vomiting, diarrhea
Loss of appetite
Dizziness and lightheadedness
Confusion or delirium
• Clinical use
Management of atrial fibrillation and heart failure

10. Atropine
• MOA
Blocks the action of acetylcholine, a neurotransmitter that slows heart
rate. By blocking this effect, atropine increases the heart rate which can
help to treat bradycardia or heart block
Atropine is administered intravenously and is used primarily in the
management of bradycardia and atrioventricular block.

11. Side Effects of Atropine
• Dry mouth
• Blurre vision
• Urinary retention
• Constipation
• Can cause tachycardia at higher doses