Review Question - QID 106840

The male is experiencing a dermatological side effect of amiodarone, which manifests as a blue-gray discoloration of the skin. Amiodarone prolongs phase 3 of the cardiac action potential.

Amiodarone is a class III antiarrhythmic that functions by blocking the potassium channel, thus prolonging phase 3 of the action potential as well as increasing the action potential duration, the effective refractory period, and the QT interval. Although a member of class III, amiodarone has class I-IV antiarrhythmic effects due to its ability to alter the lipid membrane. Amiodarone has many side effects, including pulmonary fibrosis, hepatotoxicity, hypo/hyperthyroidism, corneal deposits, photosensitivity, skin color changes, constipation, as well as neurologic and cardiovascular effects.

e Silva et al. discuss the side effect of skin hyperpigmentation due to amiodarone. The blue-gray discoloration of the skin results from the accumulation of lipofuscin in dermal macrophages. The degree of skin discoloration depends on the dosage and duration of use.

Siddoway reports on the use of amiodarone, an agent used to treat ventricular arrhythmias and atrial fibrillation. Although it is more effective than sotalol or propafenone for prevention of atrial fibrillation, care must be taken when using amiodarone on a long-term basis, as the side effects can be serious. Amiodarone is a strong inhibitor of the CYP hepatic system; thus, physicians should inquire if the patient is also taking commonly prescribed cardiac-related medications such as warfarin or digoxin. These agents may increase in concentration, as they are degraded by the same CYP system.

Figure A is a clinical picture showing the blue-gray discoloration of the skin due to amiodarone. Figure B is the action potential diagram. Illustration A shows the affected change in the action potential caused by amiodarone - prolongation of phase 3.

Incorrect Answers:
Answers 1-3,5: Amiodarone prolongs phase 3 of the action potential, not 0-2 or 4.