Page 139 - pharma 1 theoretical updated MNU_Neat

Clinical pharmacy 2024/2025 Level 3 Pharm D Pharmacology 1 (PO 502)
 Contraindications:

1. With BBs: may aggravate HF, hypotension and AV block.

2. In digitalis toxicity:  AV block and  levels → toxicity.
3. Wolff Parkinson White syndrome:  refractory period of the accessory pathway →
 ventricular response → worsen the case.

5- Other antiarrhythmic drugs

Digoxin
+
+
➢ Digoxin inhibits the Na /K -ATPase pump, ultimately shortening the refractory
period in atrial and ventricular myocardial cells while prolonging the effective
refractory period and diminishing conduction velocity in the AV node.

Adenosine
➢ Adenosine is a naturally occurring nucleoside, but at high doses, the drug decreases
conduction velocity, prolongs the refractory period, and decreases automaticity in the

AV node.
➢ Drug of choice in acute paroxysmal supraventricular tachycardia-why?
 Brief duration (t 12 is less than 10 seconds)

 Less myocardial depression than others (verapamil & BBs)
 Available as an I.V solution → rapid onset.
 Adenosine is tolerated by most patients.

Magnesium
➢ Used for patients with digitalis-induced arrhythmias who were hypomagnesemic.
➢ The mechanisms of these effects are not known, but magnesium is recognized to
+
+
influence Na /K -ATPase, sodium channels, certain potassium channels and
calcium channels.
➢ Magnesium therapy appears to be indicated in patients with digitalis-induced

arrhythmias if hypomagnesemia is present.

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