Page 15 - RxExam's Naplex Theory Review Part-1

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Drug Interactions with Propafenone:

Quinidine Concomitant administration of quinidine (50 mg TID) with 150 mg
immediate release propafenone TID decreased the clearance of
propafenone by 60%.

Digoxin Concomitant use of propafenone and digoxin increased steady-
state serum digoxin exposure (AUC) in patients by 60 to 270%, and
decreased the clearance of digoxin by 31 to 67%. Plasma digoxin
levels of patients receiving Propafenone should be monitored and
digoxin dosage adjusted as needed.

Lidocaine Concomitant use of propafenone and lidocaine has been reported
to increase the risks of central nervous system side effects of
lidocaine (e.g. seizure).

Warfarin The concomitant administration of propafenone and warfarin
increased warfarin plasma concentrations at steady state by 39% in
healthy volunteers and prolonged the prothrombin time in patients
taking warfarin.

Rifampin Concomitant administration of rifampin and propafenone in
extensive metabolizers decreased the plasma concentrations of
propafenone by 67%.

Drug Interactions with Moricizine:

Cimetidine May increase the toxic effects of Moricizine by inhibiting its
metabolism.

Theophylline May decrease the serum concentration of theophylline by
enhancing its renal clearance and metabolism.

Class III Antiarrhythmic Agents:

Dose Special Notes

Amiodarone Loading dose: 1. Amiodarone (Cordarone) is indicated for the treatment of recurrent
(Tablet) 800 to 1600 mg ventricular fibrillation and ventricular tachycardia.
(Injection) PO per day for 3
to 4 weeks. 2. Pulmonary toxicity has been reported with Amiodarone when given
in doses that exceed 400 mg/day for a prolonged period of time.
Maintenance
dose:
400 mg PO per 3. It causes hypothyroidism as well as hyperthyroidism.
day.
4. It has the longest half-life (about 45 to 50 days) among all available
antiarrhythmic agents.

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