NEXTERONE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for NEXTERONE (NEXTERONE).
Class III antiarrhythmic agent; prolongs cardiac action potential duration by blocking potassium channels (IKr), primarily affecting the atria and ventricles.
| Metabolism | Primarily hepatic via CYP3A4 and CYP2D6; active metabolite desethylamiodarone; undergoes extensive hepatic metabolism with biliary excretion. |
| Excretion | Primarily hepatic metabolism; <1% excreted unchanged in urine. Biliary excretion of metabolites is significant, with approximately 30-40% eliminated in feces. Renal excretion accounts for ~15-20% of total clearance as metabolites. |
| Half-life | Terminal elimination half-life of 58 days (range 25-110 days) due to extensive tissue distribution and slow release from lipid stores. Steady-state concentrations require approximately 3-6 months of chronic dosing. |
| Protein binding | 99.4% bound, primarily to alpha1-acid glycoprotein and albumin. |
| Volume of Distribution | Extremely large, approximately 30-60 L/kg (range 20-100 L/kg), indicating extensive tissue accumulation, especially in adipose tissue, liver, and lungs. |
| Bioavailability | Oral bioavailability is approximately 20-60% (mean ~40%) due to extensive first-pass metabolism and variable absorption. |
| Onset of Action | Intravenous: Onset of antiarrhythmic effect occurs within 2-6 hours (mean 4 hours). Oral: Onset is delayed, typically 2-7 days after starting therapy, with maximal effects at 2-3 weeks. |
| Duration of Action | Duration of action after single IV dose: 24-48 hours. After chronic oral therapy (loading and maintenance), antiarrhythmic effects persist for weeks to months due to prolonged half-life; drug discontinuation may require monitoring for up to 6 months. |
Intravenous loading: 150 mg over 10 minutes, then 1 mg/min for 6 hours, followed by maintenance infusion of 0.5 mg/min. Oral: 400 mg twice daily for loading (total 1200 mg/day) for 7-10 days, then maintenance 200-400 mg once daily.
| Dosage form | INJECTABLE |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment (CrCl >30 mL/min). For severe renal impairment (CrCl <30 mL/min), use with caution; consider reducing maintenance infusion to 0.25 mg/min and monitor QT interval. |
| Liver impairment | Child-Pugh A: No adjustment. Child-Pugh B: Reduce dose by 25%. Child-Pugh C: Contraindicated. |
| Pediatric use | Not established; safety and efficacy have not been determined in pediatric patients. |
| Geriatric use | Start at lower end of dosing range; monitor for bradycardia, QT prolongation, and hypotension. Reduced clearance may necessitate lower maintenance doses. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for NEXTERONE (NEXTERONE).
| Breastfeeding | Amiodarone and its active metabolite desethylamiodarone are excreted in human milk at concentrations similar to or exceeding maternal plasma (M/P ratio ~0.5-1.0 for amiodarone; higher for metabolite). Potential for hypothyroidism, bradycardia, and QT prolongation in nursing infants. Breastfeeding is not recommended during treatment; if unavoidable, monitor infant thyroid function, heart rate, and ECG. |
| Teratogenic Risk | Pregnancy Category X. Amiodarone (active ingredient of NEXTERONE) can cause fetal harm when administered to a pregnant woman. Fetal exposure increases the risk of neonatal bradycardia, QT prolongation, hypothyroidism, goiter, neurodevelopmental abnormalities, and growth retardation. Use is contraindicated in pregnancy unless benefits outweigh risks and no alternative therapy is available. First trimester: highest risk for major malformations; second/third trimesters: risk of fetal thyroid dysfunction and cardiac effects. |
■ FDA Black Box Warning
WARNING: HEPATIC INJURY. NEXTERONE can cause severe hepatic injury, which can be fatal. Obtain hepatic function tests prior to and during therapy.
| Serious Effects |
["Hypersensitivity to amiodarone or any component","Severe sinus node dysfunction causing syncope (unless pacemaker present)","Second- or third-degree AV block (unless pacemaker present)","Cardiogenic shock"]
| Precautions | ["Hepatic toxicity (monitor LFTs)","Pulmonary toxicity (pneumonitis, fibrosis)","Thyroid dysfunction (hypo/hyperthyroidism)","Optic neuropathy/optic neuritis","Proarrhythmia (torsade de pointes)","Bradycardia and heart block","Hypotension (especially with IV use)","Photosensitivity and skin discoloration","Peripheral neuropathy"] |
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| Fetal Monitoring | Monitor maternal ECG, liver function, thyroid function, and pulmonary function periodically. Fetal monitoring: serial ultrasound for growth, thyroid gland size, amniotic fluid volume; fetal heart rate monitoring for bradycardia. Neonatal monitoring at birth: thyroid function, ECG, blood glucose, and neurologic assessment. |
| Fertility Effects | Reproductive toxicity studies in animals have shown impaired fertility at high doses. No adequate human data; potential for altered spermatogenesis or menstrual cycle disturbances. Unknown clinical significance in humans. |