Mechanism of Action
COREG is a racemic mixture in which nonselective β-adrenoreceptor
blocking activity is present in the S(-) enantiomer and α1-adrenergic
blocking activity is present in both R(+) and S(-) enantiomers at equal
potency. COREG has no intrinsic sympathomimetic activity.
Pharmacodynamics
Heart Failure
The basis for the beneficial effects of COREG in heart failure is not established.
Two placebo-controlled studies compared the acute
hemodynamic effects of COREG to baseline measurements in 59 and 49 patients
with NYHA class II-IV heart failure receiving diuretics, ACE inhibitors, and
digitalis. There were significant reductions in systemic blood pressure,
pulmonary artery pressure, pulmonary capillary wedge pressure, and heart rate.
Initial effects on cardiac output, stroke volume index, and systemic vascular resistance
were small and variable.
These studies measured hemodynamic effects again at 12 to 14
weeks. COREG significantly reduced systemic blood pressure, pulmonary artery
pressure, right atrial pressure, systemic vascular resistance, and heart rate,
while stroke volume index was increased.
Among 839 patients with NYHA class II-III heart failure
treated for 26 to 52 weeks in 4 US placebo-controlled trials, average left
ventricular ejection fraction (EF) measured by radionuclide ventriculography
increased by 9 EF units (%) in patients receiving COREG and by 2 EF units in
placebo patients at a target dose of 25-50 mg twice daily. The effects of
carvedilol on ejection fraction were related to dose. Doses of 6.25 mg twice
daily, 12.5 mg twice daily, and 25 mg twice daily were associated with
placebo-corrected increases in EF of 5 EF units, 6 EF units, and 8 EF units,
respectively; each of these effects were nominally statistically significant.
Left Ventricular Dysfunction Following Myocardial Infarction
The basis for the beneficial effects of COREG in patients
with left ventricular dysfunction following an acute myocardial infarction is
not established.
Hypertension
The mechanism by which β-blockade produces an
antihypertensive effect has not been established.
β-adrenoreceptor blocking activity has been
demonstrated in animal and human studies showing that carvedilol (1) reduces
cardiac output in normal subjects; (2) reduces exercise- and/or
isoproterenol-induced tachycardia; and (3) reduces reflex orthostatic
tachycardia. Significant β-adrenoreceptor blocking effect is usually seen
within 1 hour of drug administration.
α1-adrenoreceptor blocking activity has been
demonstrated in human and animal studies, showing that carvedilol (1)
attenuates the pressor effects of phenylephrine; (2) causes vasodilation; and
(3) reduces peripheral vascular resistance. These effects contribute to the
reduction of blood pressure and usually are seen within 30 minutes of drug
administration.
Due to the α1-receptor blocking activity of carvedilol,
blood pressure is lowered more in the standing than in the supine position, and
symptoms of postural hypotension (1.8%), including rare instances of syncope,
can occur. Following oral administration, when postural hypotension has occurred,
it has been transient and is uncommon when COREG is administered with food at
the recommended starting dose and titration increments are closely followed
[see DOSAGE AND ADMINISTRATION].
In hypertensive patients with normal renal function,
therapeutic doses of COREG decreased renal vascular resistance with no change
in glomerular filtration rate or renal plasma flow. Changes in excretion of
sodium, potassium, uric acid, and phosphorus in hypertensive patients with
normal renal function were similar after COREG and placebo.
COREG has little effect on plasma catecholamines, plasma
aldosterone, or electrolyte levels, but it does significantly reduce plasma
renin activity when given for at least 4 weeks. It also increases levels of
atrial natriuretic peptide.
Pharmacokinetics
COREG is rapidly and extensively absorbed following oral
administration, with absolute bioavailability of approximately 25% to 35% due
to a significant degree of first-pass metabolism. Following oral
administration, the apparent mean terminal elimination half-life of carvedilol
generally ranges from 7 to 10 hours. Plasma concentrations achieved are
proportional to the oral dose administered. When administered with food, the
rate of absorption is slowed, as evidenced by a delay in the time to reach peak
plasma levels, with no significant difference in extent of bioavailability.
Taking COREG with food should minimize the risk of orthostatic hypotension.
Carvedilol is extensively metabolized. Following oral
administration of radiolabelled carvedilol to healthy volunteers, carvedilol
accounted for only about 7% of the total radioactivity in plasma as measured by
area under the curve (AUC). Less than 2% of the dose was excreted unchanged in
the urine. Carvedilol is metabolized primarily by aromatic ring oxidation and
glucuronidation. The oxidative metabolites are further metabolized by
conjugation via glucuronidation and sulfation. The metabolites of carvedilol
are excreted primarily via the bile into the feces. Demethylation and hydroxylation
at the phenol ring produce 3 active metabolites with β-receptor blocking
activity. Based on preclinical studies, the 4'-hydroxyphenyl metabolite is
approximately 13 times more potent than carvedilol for β-blockade.
Compared to carvedilol, the 3 active metabolites exhibit
weak vasodilating activity. Plasma concentrations of the active metabolites are
about one-tenth of those observed for carvedilol and have pharmacokinetics
similar to the parent.
Carvedilol undergoes stereoselective first-pass metabolism
with plasma levels of R(+)-carvedilol approximately 2 to 3 times higher than
S(-)-carvedilol following oral administration in healthy subjects. The mean
apparent terminal elimination half-lives for R(+)-carvedilol range from 5 to 9
hours compared with 7 to 11 hours for the S(-)-enantiomer.
The primary P450 enzymes responsible for the metabolism of
both R(+) and S(-)-carvedilol in human liver microsomes were CYP2D6 and CYP2C9
and to a lesser extent CYP3A4, 2C19, 1A2, and 2E1. CYP2D6 is thought to be the
major enzyme in the 4'- and 5'-hydroxylation of carvedilol, with a potential
contribution from 3A4. CYP2C9 is thought to be of primary importance in the
O-methylation pathway of S(-)-carvedilol.
Carvedilol is subject to the effects of genetic polymorphism
with poor metabolizers of debrisoquin (a marker for cytochrome P450 2D6)
exhibiting 2- to 3-fold higher plasma concentrations of R(+)-carvedilol
compared to extensive metabolizers. In contrast, plasma levels of
S(-)-carvedilol are increased only about 20% to 25% in poor metabolizers,
indicating this enantiomer is metabolized to a lesser extent by cytochrome P450
2D6 than R(+)-carvedilol. The pharmacokinetics of carvedilol do not appear to
be different in poor metabolizers of S-mephenytoin (patients deficient in
cytochrome P450 2C19).
Carvedilol is more than 98% bound to plasma proteins,
primarily with albumin. The plasma-protein binding is independent of
concentration over the therapeutic range. Carvedilol is a basic, lipophilic
compound with a steady-state volume of distribution of approximately 115 L,
indicating substantial distribution into extravascular tissues. Plasma
clearance ranges from 500 to 700 mL/min.
Specific Populations
Heart Failure
Steady-state plasma concentrations of carvedilol and its
enantiomers increased proportionally over the 6.25 to 50 mg dose range in
patients with heart failure. Compared to healthy subjects, heart failure
patients had increased mean AUC and Cmax values for carvedilol and its
enantiomers, with up to 50% to 100% higher values observed in 6 patients with
NYHA class IV heart failure. The mean apparent terminal elimination half-life
for carvedilol was similar to that observed in healthy subjects.
Geriatric
Plasma levels of carvedilol average about 50% higher in the
elderly compared to young subjects.
Hepatic Impairment
Compared to healthy subjects, patients with severe liver
impairment (cirrhosis) exhibit a 4- to 7-fold increase in carvedilol levels.
Carvedilol is contraindicated in patients with severe liver impairment.
Renal Impairment
Although carvedilol is metabolized primarily by the liver,
plasma concentrations of carvedilol have been reported to be increased in
patients with renal impairment. Based on mean AUC data, approximately 40% to
50% higher plasma concentrations of carvedilol were observed in hypertensive
patients with moderate to severe renal impairment compared to a control group
of hypertensive patients with normal renal function. However, the ranges of AUC
values were similar for both groups. Changes in mean peak plasma levels were
less pronounced, approximately 12% to 26% higher in patients with impaired
renal function.
Consistent with its high degree of plasma protein-binding,
carvedilol does not appear to be cleared significantly by hemodialysis.
Drug-Drug Interactions
Since carvedilol undergoes substantial oxidative metabolism,
the metabolism and pharmacokinetics of carvedilol may be affected by induction
or inhibition of cytochrome P450 enzymes.
Amiodarone
In a pharmacokinetic study conducted in 106 Japanese patients with heart failure,
coadministration of small loading and maintenance doses of amiodarone with carvedilol
resulted in at least a 2-fold increase in the steady-state trough concentrations
of S(-)-carvedilol [see DRUG INTERACTIONS].
Cimetidine
In a pharmacokinetic study conducted in 10 healthy male
subjects, cimetidine (1,000 mg/day) increased the steady-state AUC of
carvedilol by 30% with no change in Cmax [see DRUG INTERACTIONS].
Digoxin
Following concomitant administration of carvedilol (25 mg
once daily) and digoxin (0.25 mg once daily) for 14 days, steady-state AUC and
trough concentrations of digoxin were increased by 14% and 16%, respectively,
in 12 hypertensive patients [see DRUG INTERACTIONS].
Glyburide
In 12 healthy subjects, combined administration of
carvedilol (25 mg once daily) and a single dose of glyburide did not result in
a clinically relevant pharmacokinetic interaction for either compound.
Hydrochlorothiazide
A single oral dose of carvedilol 25 mg did not alter the
pharmacokinetics of a single oral dose of hydrochlorothiazide 25 mg in 12
patients with hypertension. Likewise, hydrochlorothiazide had no effect on the
pharmacokinetics of carvedilol.
Rifampin
In a pharmacokinetic study conducted in 8 healthy male
subjects, rifampin (600 mg daily for 12 days) decreased the AUC and Cmax of
carvedilol by about 70% [see DRUG INTERACTIONS].
Torsemide
In a study of 12 healthy subjects, combined oral
administration of carvedilol 25 mg once daily and torsemide 5 mg once daily for
5 days did not result in any significant differences in their pharmacokinetics
compared with administration of the drugs alone.
Warfarin
Carvedilol (12.5 mg twice daily) did not have an effect on
the steady-state prothrombin time ratios and did not alter the pharmacokinetics
of R(+)- and S(-)-warfarin following concomitant administration with warfarin
in 9 healthy volunteers.
Clinical Studies
Heart Failure
A total of 6,975 patients with mild to severe heart failure
were evaluated in placebo-controlled studies of carvedilol.
Mild-to-Moderate Heart Failure
Carvedilol was studied in 5 multicenter, placebo-controlled
studies, and in 1 active-controlled study (COMET study) involving patients with
mild-to-moderate heart failure.
Four US multicenter, double-blind, placebo-controlled
studies enrolled 1,094 patients (696 randomized to carvedilol) with NYHA class
II-III heart failure and ejection fraction ≤ 0.35. The vast majority were
on digitalis, diuretics, and an ACE inhibitor at study entry. Patients were
assigned to the studies based upon exercise ability. An Australia-New Zealand double-blind, placebo-controlled study enrolled 415 patients (half randomized
to carvedilol) with less severe heart failure. All protocols excluded patients
expected to undergo cardiac transplantation during the 7.5 to 15 months of
double-blind follow-up. All randomized patients had tolerated a 2-week course
on carvedilol 6.25 mg twice daily.
In each study, there was a primary end point, either
progression of heart failure (1 US study) or exercise tolerance (2 US studies meeting enrollment goals and the Australia-New Zealand study). There were many
secondary end points specified in these studies, including NYHA classification,
patient and physician global assessments, and cardiovascular hospitalization.
Other analyses not prospectively planned included the sum of deaths and total
cardiovascular hospitalizations. In situations where the primary end points of
a trial do not show a significant benefit of treatment, assignment of
significance values to the other results is complex, and such values need to be
interpreted cautiously.
The results of the US and Australia-New Zealand trials were
as follows:
Slowing Progression of Heart Failure: One US multicenter study
(366 subjects) had as its primary end point the sum of cardiovascular mortality,
cardiovascular hospitalization, and sustained increase in heart failure medications.
Heart failure progression was reduced, during an average follow-up of 7 months,
by 48% (p = 0.008).
In the Australia-New Zealand study, death and total
hospitalizations were reduced by about 25% over 18 to 24 months. In the 3
largest US studies, death and total hospitalizations were reduced by 19%, 39%,
and 49%, nominally statistically significant in the last 2 studies. The
Australia-New Zealand results were statistically borderline.
Functional Measures: None of the multicenter studies had NYHA
classification as a primary end point, but all such studies had it as a secondary
end point. There was at least a trend toward improvement in NYHA class in all
studies. Exercise tolerance was the primary end point in 3 studies; in none
was a statistically significant effect found.
Subjective Measures: Health-related quality of life, as measured
with a standard questionnaire (a primary end point in 1 study), was unaffected
by carvedilol. However, patients' and investigators' global assessments showed
significant improvement in most studies.
Mortality: Death was not a pre-specified end point in any study,
but was analyzed in all studies. Overall, in these 4 US trials, mortality was
reduced, nominally significantly so in 2 studies.
COMET Trial: In this double-blind trial, 3,029 patients with
NYHA class II-IV heart failure (left ventricular ejection fraction ≤ 35%)
were randomized to receive either carvedilol (target dose: 25 mg twice daily)
or immediate-release metoprolol tartrate (target dose: 50 mg twice daily). The
mean age of the patients was approximately 62 years, 80% were males, and the
mean left ventricular ejection fraction at baseline was 26%. Approximately 96%
of the patients had NYHA class II or III heart failure. Concomitant treatment
included diuretics (99%), ACE inhibitors (91%), digitalis (59%), aldosterone
antagonists (11%), and “statin” lipid-lowering agents (21%). The
mean duration of follow-up was 4.8 years. The mean dose of carvedilol was 42
mg per day.
The study had 2 primary end points: All-cause mortality and
the composite of death plus hospitalization for any reason. The results of
COMET are presented in Table 3 below. All-cause mortality carried most of the
statistical weight and was the primary determinant of the study size. All-cause
mortality was 34% in the patients treated with carvedilol and was 40% in the
immediate-release metoprolol group (p = 0.0017; hazard ratio = 0.83, 95%CI
0.74-0.93). The effect on mortality was primarily due to a reduction in
cardiovascular death. The difference between the 2 groups with respect to the
composite end point was not significant (p = 0.122). The estimated mean
survival was 8.0 years with carvedilol and 6.6 years with immediate-release
metoprolol.
Table 3 : Results of COMET
| End point |
Carvedilol
N = 1,511 |
Metoprolol
N = 1,518 |
Hazard ratio |
(95% CI) |
| All-cause mortality |
34% |
40% |
0.83 |
0.74 – 0.93 |
| Mortality + all hospitalization |
74% |
76% |
0.94 |
0.86 – 1.02 |
| Cardiovascular death |
30% |
35% |
0.80 |
0.70 – 0.90 |
| Sudden death |
14% |
17% |
0.81 |
0.68 – 0.97 |
| Death due to circulatory failure |
11% |
13% |
0.83 |
0.67 – 1.02 |
| Death due to stroke |
0.9% |
2.5% |
0.33 |
0.18 – 0.62 |
It is not known whether this formulation of metoprolol at any dose or this
low dose of metoprolol in any formulation has any effect on survival or hospitalization
in patients with heart failure. Thus, this trial extends the time over which
carvedilol manifests benefits on survival in heart failure, but it is not evidence
that carvedilol improves outcome over the formulation of metoprolol (TOPROL-XL®)
with benefits in heart failure.
Severe Heart Failure (COPERNICUS)
In a double-blind study (COPERNICUS), 2,289 patients with
heart failure at rest or with minimal exertion and left ventricular ejection
fraction < 25% (mean 20%), despite digitalis (66%), diuretics (99%), and ACE
inhibitors (89%) were randomized to placebo or carvedilol. Carvedilol was
titrated from a starting dose of 3.125 mg twice daily to the maximum tolerated
dose or up to 25 mg twice daily over a minimum of 6 weeks. Most subjects
achieved the target dose of 25 mg. The study was conducted in Eastern and
Western Europe, the United States, Israel, and Canada. Similar numbers of subjects
per group (about 100) withdrew during the titration period.
The primary end point of the trial was all-cause mortality,
but cause-specific mortality and the risk of death or hospitalization (total,
cardiovascular [CV], or heart failure [HF]) were also examined. The developing
trial data were followed by a data monitoring committee, and mortality analyses
were adjusted for these multiple looks. The trial was stopped after a median
follow-up of 10 months because of an observed 35% reduction in mortality (from
19.7% per patient year on placebo to 12.8% on carvedilol, hazard ratio 0.65,
95% CI 0.52 – 0.81, p = 0.0014, adjusted) (see Figure 1). The results of
COPERNICUS are shown in Table 4.
Table 4 : Results of COPERNICUS Trial in Patients With Severe
Heart Failure
| End point |
Placebo
(N = 1,133) |
Carvedilol
(N = 1,156) |
Hazard ratio
(95% CI) |
%
Reduction |
Nominal
p value |
| Mortality |
190 |
130 |
0.65
(0.52 – 0.81) |
35 |
0.00013 |
| Mortality + all hospitalization |
507 |
425 |
0.76
(0.67 – 0.87) |
24 |
0.00004 |
| Mortality + CV hospitalization |
395 |
314 |
0.73
(0.63 – 0.84) |
27 |
0.00002 |
| Mortality + HF hospitalization |
357 |
271 |
0.69
(0.59 – 0.81) |
31 |
0.000004 |
| Cardiovascular= CV; Heart failure = HF. |
Figure 1 : Survival Analysis for COPERNICUS (intent-to-treat)
The effect on mortality was principally the result of a
reduction in the rate of sudden death among patients without worsening heart
failure.
Patients' global assessments, in which carvedilol-treated
patients were compared to placebo, were based on pre-specified, periodic
patient self-assessments regarding whether clinical status post-treatment
showed improvement, worsening or no change compared to baseline. Patients
treated with carvedilol showed significant improvements in global assessments
compared with those treated with placebo in COPERNICUS.
The protocol also specified that hospitalizations would be
assessed. Fewer patients on COREG than on placebo were hospitalized for any
reason (372 versus 432, p = 0.0029), for cardiovascular reasons (246 versus
314, p = 0.0003), or for worsening heart failure (198 versus 268, p = 0.0001).
COREG had a consistent and beneficial effect on all-cause
mortality as well as the combined end points of all-cause mortality plus
hospitalization (total, CV, or for heart failure) in the overall study
population and in all subgroups examined, including men and women, elderly and
non-elderly, blacks and non-blacks, and diabetics and non-diabetics (see Figure
2).
Figure 2 : Effects on Mortality for Subgroups in COPERNICUS
Left Ventricular Dysfunction Following Myocardial Infarction
CAPRICORN was a double-blind study comparing carvedilol and
placebo in 1,959 patients with a recent myocardial infarction (within 21 days)
and left ventricular ejection fraction of ≤ 40%, with (47%) or without
symptoms of heart failure. Patients given carvedilol received 6.25 mg twice
daily, titrated as tolerated to 25 mg twice daily. Patients had to have a
systolic blood pressure > 90 mm Hg, a sitting heart rate > 60 beats/minute,
and no contraindication to β-blocker use. Treatment of the index
infarction included aspirin (85%), IV or oral β-blockers (37%), nitrates
(73%), heparin (64%), thrombolytics (40%), and acute angioplasty (12%).
Background treatment included ACE inhibitors or angiotensin receptor blockers
(97%), anticoagulants (20%), lipid-lowering agents (23%), and diuretics (34%).
Baseline population characteristics included an average age of 63 years, 74%
male, 95% Caucasian, mean blood pressure 121/74 mm Hg, 22% with diabetes, and
54% with a history of hypertension. Mean dosage achieved of carvedilol was 20
mg twice daily; mean duration of follow-up was 15 months.
All-cause mortality was 15% in the placebo group and 12% in
the carvedilol group, indicating a 23% risk reduction in patients treated with
carvedilol (95% CI 2-40%, p = 0.03), as shown in Figure 3. The effects on
mortality in various subgroups are shown in Figure 4. Nearly all deaths were
cardiovascular (which were reduced by 25% by carvedilol), and most of these
deaths were sudden or related to pump failure (both types of death were reduced
by carvedilol). Another study end point, total mortality and all-cause
hospitalization, did not show a significant improvement.
There was also a significant 40% reduction in fatal or
non-fatal myocardial infarction observed in the group treated with carvedilol
(95% CI 11% to 60%, p = 0.01). A similar reduction in the risk of myocardial
infarction was also observed in a meta-analysis of placebo-controlled trials of
carvedilol in heart failure.
Figure 3 : Survival Analysis for CAPRICORN (intent-to-treat)
Figure 4 : Effects on Mortality for Subgroups in CAPRICORN
Hypertension
COREG was studied in 2 placebo-controlled trials that
utilized twice-daily dosing, at total daily doses of 12.5 to 50 mg. In these
and other studies, the starting dose did not exceed 12.5 mg. At 50 mg/day,
COREG reduced sitting trough (12-hour) blood pressure by about 9/5.5 mm Hg; at
25 mg/day the effect was about 7.5/3.5 mm Hg. Comparisons of trough to peak
blood pressure showed a trough to peak ratio for blood pressure response of
about 65%. Heart rate fell by about 7.5 beats/minute at 50 mg/day. In general,
as is true for other β-blockers, responses were smaller in black than
non-black patients. There were no age- or gender-related differences in
response.
The peak antihypertensive effect occurred 1 to 2 hours after
a dose. The dose-related blood pressure response was accompanied by a
dose-related increase in adverse effects [see ADVERSE REACTIONS].
Hypertension With Type 2 Diabetes Mellitus
In a double-blind study (GEMINI), COREG, added to an ACE inhibitor or angiotensin
receptor blocker, was evaluated in a population with mild-to-moderate hypertension
and well-controlled type 2 diabetes mellitus. The mean HbA1c at baseline was
7.2%. COREG was titrated to a mean dose of 17.5 mg twice daily and maintained
for 5 months. COREG had no adverse effect on glycemic control, based on HbA1c
measurements (mean change from baseline of 0.02%, 95% CI -0.06 to 0.10, p =
NS) [see WARNINGS AND PRECAUTIONS].
Last updated on RxList: 7/13/2009