Which of the following drugs can cause severe hematologic disorders?
A. digoxin (Lanoxin)
B. quinidine (Cardioquin)
C. disopyramide (Norpace)
D. procainamide (Pronestyl)
Correct Answer: D. procainamide (Pronestyl)
Pronestyl is known for this serious side effect. Associate Pronestyl with plasma — P and P. This drug is known for its hematologic side effects. Procainamide is known to cause certain blood dyscrasias. Procainamide as been known to cause bone marrow toxicity, leading to pancytopenia or agranulocytosis; this is usually due to hypersensitivity or varied immunologic mechanisms
Option A: Digoxin comes from the foxgloves plant known as Digitalis purpurea. It is a cardiotonic glycoside and belongs to the digitalis class. It increases the force of contraction of the heart by reversibly inhibiting the activity of the myocardial Na-K ATPase pump, an enzyme that controls the movement of ions into the heart. Digoxin has vagomimetic effects on the AV node.
Option B: Quinine is a derivative of the bark of the South American cinchona tree. Quinidine is a stereoisomer of quinine; it is a “class 1a antiarrhythmic drug” and also an antimalarial agent. Class 1a antiarrhythmic agents (for example – quinidine, procainamide, disopyramide, ajmaline) work by inhibiting the fast inward sodium current, depressing the phase 0 of the action potential hence dampening the excitability of cardiac muscles which in turn prolongs the action potential and decreases automaticity.
Option C: Despite rarely used now for heart rhythm abnormalities because of the availability of newer drugs that provided better efficacy and favorable side effect profiles, disopyramide is still the drug of choice for vagally mediated atrial fibrillation such as sleep-induced or atrial fibrillation in athlete groups. The effectiveness of disopyramide in these conditions is due to its anticholinergic activity that abolished parasympathetic tone.