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Chapter 14: Antiarrhythmic Drugs

A 76-year-old patient with rheumatoid arthritis and chronic heart disease is being considered for treatment with procainamide. She is already receiving digoxin, hydrochlorothiazide, and potassium supplements for her cardiac condition.

In deciding on a treatment regimen with procainamide for this patient, which of the following statements is most correct?

(A) A possible drug interaction with digoxin suggests that digoxin blood levels should be obtained before and after starting procainamide

(B) Hyperkalemia should be avoided to reduce the likelihood of procainamide toxicity

(C) Procainamide cannot be used if the patient has asthma because it has a β-blocking effect

(D) Procainamide cannot be used if the patient has angina because it has a β-agonist effect

(E) Procainamide is not active by the oral route

Hyperkalemia facilitates procainamide toxicity. Procainamide is active by the oral route and has a duration of action of 2–4 h (in the prompt-release form). Procainamide has no significant documented interaction with digoxin and no significant β-agonist or β-blocking action. The answer is B.

A 76-year-old patient with rheumatoid arthritis and chronic heart disease is being considered for treatment with procainamide. She is already receiving digoxin, hydrochlorothiazide, and potassium supplements for her cardiac condition.

If this patient should take an overdose and manifest severe acute procainamide toxicity with markedly prolonged QRS, which of the following should be given immediately?

(A) A calcium chelator such as EDTA

(B) Digitalis

(C) Nitroprusside

(D) Potassium chloride

(E) Sodium lactate

The most effective therapy for procainamide toxicity appears to be concentrated sodium lactate. This drug may (1) increase sodium current by increasing the sodium ion gradient and (2) reduce drug-receptor binding by alkalinizing the tissue. The answer is E.

A 57-year-old man is admitted to the emergency department with chest pain and a fast irregular heart rhythm. The ECG shows an inferior myocardial infarction and ventricular tachycardia. Lidocaine is ordered. When used as an antiarrhythmic drug, lidocaine typically

(A) Increases action potential duration

(B) Increases contractility

(C) Increases PR interval

(D) Reduces abnormal automaticity

(E) Reduces resting potential

Lidocaine reduces automaticity in the ventricles; the drug ...

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