Page 18 - RxExam's Naplex Theory Review Part-1

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Cimetidine It inhibits CYP3A4 and can increase serum amiodarone levels.

Cyclosporine Reported to produce persistently elevated plasma concentrations of
cyclosporine resulting in elevated creatinine, despite reduction in
dose of cyclosporine.

HMG-CoA reductase In combination with amiodarone, they may cause myopathy and/or
inhibitors rhabdomyolysis.

Digoxin Amiodarone taken concomitantly with digoxin increases the serum
digoxin concentration by 70% after one day. On initiation of oral
amiodarone, the need for digitalis therapy should be reviewed and
the dose should be reduced by approximately 50% or discontinued.

Warfarin Since the concomitant administration of warfarin with amiodarone
increases the prothrombin time by 100% after 3 to 4 days, the dose
of the anticoagulant should be reduced by one-third to one-half,
and prothrombin times should be monitored closely.

Drug Interactions with Dronedarone:

Digoxin Digoxin can potentiate the electrophysiologic effects of
dronedarone (such as decreased AV-node conduction). If digoxin
treatment is continued, halve the dose of digoxin, monitor serum
levels closely, and observe for toxicity.

Calcium channel Calcium channel blockers with depressant effects on the sinus and
blockers AV nodes could potentiate dronedarone's effects on conduction.

Beta-blockers May cause severe bradycardia.

Ketoconazole Repeated doses of ketoconazole, a strong CYP 3A inhibitor,
resulted in a 17-fold increase in dronedarone exposure and a 9-
fold increase in Cmax. Concomitant use of ketoconazole as well as
other potent CYP 3A inhibitors such as itraconazole, voriconazole,
ritonavir, clarithromycin, and nefazodone is contraindicated.

Grapefruit juice Grapefruit juice, a moderate inhibitor of CYP 3 A, resulted in a 3-
fold increase in dronedarone exposure and a 2.5-fold increase in
Cmax. Therefore, patients should avoid grapefruit juice beverages
while taking dronedarone.

Sirolimus, Tacrolimus Dronedarone can increase plasma concentrations of tacrolimus,
sirolimus, and other CYP 3 A substrates with a narrow therapeutic
range when given orally.

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