Dronedarone 400 mg · Tablets

The mechanism of action of dronedarone is unknown. Dronedarone has antiarrhythmic properties belonging to all four Vaughan-Williams classes, but the contribution of each of these activities to the clinical effect is unknown.

Dronedarone is extensively metabolized and has low systemic bioavailability; its bioavailability is increased by meals. Its elimination half-life is 13 to 19 hours.

Absorption — Because of presystemic first pass metabolism the absolute bioavailability of dronedarone without food is low, about 4%. It increases to approximately 15% when dronedarone is administered with a high fat meal. After oral administration in fed conditions, peak plasma concentrations of dronedarone and the main circulating active metabolite (N-debutyl metabolite) are reached within 3 to 6 hours. After repeated administration of 400 mg twice daily, steady state is reached within 4 to 8 days of treatment and the mean accumulation ratio for dronedarone ranges from 2.6 to 4.5. The steady-state Cmax and exposure of the main N-debutyl metabolite is similar to that of the parent compound. The pharmacokinetics of dronedarone and its N-debutyl metabolite both deviate moderately from dose proportionality: a doubling in dose results in approximately 2.5 to 3.0-fold the Cmax and AUC.

Distribution — The in vitro plasma protein binding of dronedarone and its N-debutyl metabolite is >98% and not saturable. Both compounds bind mainly to albumin. After intravenous (IV) administration the volume of distribution at steady state is about 1400 L.

Metabolism — Dronedarone is extensively metabolized, mainly by CYP3A. The initial metabolic pathway includes N-debutylation to form the active N-debutyl metabolite, oxidative deamination to form the inactive propanoic acid metabolite, and direct oxidation. The metabolites undergo further metabolism to yield over 30 uncharacterized metabolites. Monoamine oxidases contribute partially to the metabolism of the active metabolite of dronedarone.

Excretion/Elimination — In a mass balance study with orally administered dronedarone (14C-labeled) approximately 6% of the labeled dose was excreted in urine, mainly as metabolites (no unchanged compound excreted in urine), and 84% was excreted in feces, mainly as metabolites. Dronedarone and its N-debutyl active metabolite accounted for less than 15% of the resultant radioactivity in the plasma.

After IV administration the plasma clearance of dronedarone ranges from 130 to 150 L/h. The elimination half-life of dronedarone ranges from 13 to 19 hours.

Drug Interactions — Dronedarone is metabolized primarily by CYP3A and is a moderate inhibitor of CYP3A and CYP2D6. Dronedarone has no significant potential to inhibit CYP1A2, CYP2C9, CYP2C19, CYP2C8 and CYP2B6. It has the potential to inhibit P-glycoprotein (P-gp) transport. Dronedarone inhibits in vivo the tubular secretion of creatinine a substrate of the organic cation transporter (OCT2) [see Warnings and Precautions (5.9)].

In vitro dronedarone and the metabolites SR35021 and SR90154 show no significant potential to inhibit the organic anion transporters OAT1 and OAT3 or the organic cation transporter OCT1. However, in vitro data indicate that SR90154 is likely to inhibit the organic anion transporting polypeptides (OATP1B1, OATP1B3) in vivo.

Pharmacokinetic measures indicating the magnitude of these interactions are presented in Figure 1 (impact of coadministered drugs on dronedarone) and Figure 2 (impact of dronedarone on coadministered drugs).