Half-Life Comparison: Carvedilol vs Metoprolol
Carvedilol has a substantially longer elimination half-life (7-10 hours) compared to metoprolol tartrate (3-4 hours), though metoprolol's half-life can extend to 7-9 hours in poor CYP2D6 metabolizers. 1, 2
Metoprolol Half-Life
- The mean elimination half-life of metoprolol is 3 to 4 hours in extensive metabolizers 1
- In poor CYP2D6 metabolizers (approximately 8% of Caucasians), the half-life extends to 7 to 9 hours 1
- The pharmacokinetics differ based on formulation: metoprolol tartrate has a shorter duration of action compared to metoprolol succinate extended-release 3
- During hemodialysis, metoprolol demonstrates an elimination half-life of 2.9 hours (with metabolites at 5 hours) 4
Carvedilol Half-Life
- The apparent mean terminal elimination half-life of carvedilol generally ranges from 7 to 10 hours 2
- Carvedilol exhibits stereoselective pharmacokinetics, with R(+)-carvedilol having a half-life of 5 to 9 hours and S(-)-carvedilol having 7 to 11 hours 2
- After oral administration, the half-life is 6.4 hours, which is longer than the 2.4 hours observed after intravenous administration, suggesting absorption-dependent kinetics 5
- During hemodialysis, carvedilol shows an elimination half-life of 4.6 hours 4
Clinical Implications of Half-Life Differences
- Carvedilol is considered an inherently long-acting beta-blocker, while metoprolol's duration depends on the specific salt and formulation used 3
- Despite the longer half-life of carvedilol, both drugs produce similar 24-hour heart rate control when dosed appropriately (metoprolol tartrate 50 mg twice daily vs carvedilol 25 mg twice daily) 6
- The longer half-life of carvedilol may contribute to more sustained beta-blockade throughout the dosing interval 3
Special Population Considerations
Renal Impairment
- Metoprolol's half-life does not differ clinically in patients with renal failure, as the drug is primarily hepatically metabolized 1
- Carvedilol plasma concentrations increase 40-50% in patients with moderate to severe renal impairment, though the half-life remains similar 2, 7
Hepatic Impairment
- Metoprolol's elimination half-life is considerably prolonged in hepatic impairment (up to 7.2 hours depending on severity) 1
- Carvedilol levels increase 4 to 7-fold in patients with severe liver impairment (cirrhosis), making it contraindicated in this population 2
Elderly Patients
- Elderly patients show slightly higher metoprolol plasma concentrations due to decreased metabolism and hepatic blood flow, though this is not clinically significant 1
- Carvedilol plasma levels average about 50% higher in elderly patients compared to young subjects 2
- In elderly hypertensive patients, carvedilol's pharmacokinetic parameters (peak levels, time to maximum concentration, AUC, half-life) do not differ significantly between those >65 years and those 35-50 years 8