Carvedilol Phosphate

1 INDICATIONS AND USAGE Carvedilol phosphate extended-release capsules are an alpha-/beta-adrenergic blocking agent indicated for the treatment of: mild to severe chronic heart failure. ( 1.1 ) left ventricular dysfunction following myocardial infarction in clinically stable patients. ( 1.2 ) hypertension ( 1.3 ) 1.1 Heart Failure Carvedilol phosphate extended-release capsules are indicated for the treatment of mild-to-severe chronic heart failure of ischemic or cardiomyopathic origin, usually in addition to diuretics, ACE inhibitors, and digitalis, to increase survival and, also, to reduce the risk of hospitalization [see Drug Interactions (7.4) , Clinical Studies (14.1) ]. 1.2 Left Ventricular Dysfunction following Myocardial Infarction Carvedilol phosphate extended-release capsules are indicated to reduce cardiovascular mortality in clinically stable patients who have survived the acute phase of a myocardial infarction and have a left ventricular ejection fraction of less than or equal to 40% (with or without symptomatic heart failure) [see Clinical Studies (14.2) ]. 1.3 Hypertension Carvedilol phosphate extended-release capsules are indicated for the management of essential hypertension [see Clinical Studies (14.3 , 14.4) ] . It can be used alone or in combination with other antihypertensive agents, especially thiazide-type diuretics [see Drug Interactions (7.2) ] .

2 DOSAGE AND ADMINISTRATION Carvedilol phosphate extended-release capsules are intended for once-daily administration. Patients controlled with immediate-release carvedilol tablets alone or in combination with other medications may be switched to carvedilol phosphate extended-release capsules based on the total daily doses shown in Table 1. Table 1. Dosing Conversion Daily Dose of Immediate-Release Carvedilol Tablets Daily Dose of Carvedilol Phosphate Extended-Release Capsules* 6.25 mg (3.125 mg twice daily) 10 mg once daily 12.5 mg (6.25 mg twice daily) 20 mg once daily 25 mg (12.5 mg twice daily) 40 mg once daily 50 mg (25 mg twice daily) 80 mg once daily * When switching from carvedilol 12.5 mg or 25 mg twice daily, a starting dose of carvedilol phosphate extended-release capsules 20 mg or 40 mg once daily, respectively, may be warranted for elderly patients or those at increased risk of hypotension, dizziness, or syncope. Subsequent titration to higher doses should, as appropriate, be made after an interval of at least 2 weeks. Carvedilol phosphate extended-release capsules should be taken once daily in the morning with food. Carvedilol phosphate extended-release capsules should be swallowed as a whole capsule. Carvedilol phosphate extended-release capsules and/or its contents should not be crushed, chewed, or taken in divided doses. Alternative Administration The capsules may be carefully opened and the beads sprinkled over a spoonful of applesauce. The applesauce should not be warm because it could affect the modified-release properties of this formulation. The mixture of drug and applesauce should be consumed immediately in its entirety. The drug and applesauce mixture should not be stored for future use. Absorption of the beads sprinkled on other foods has not been tested. Take with food. Do not crush or chew capsules. Individualize dosage and monitor during up-titration. ( 2 ) Heart failure: Start at 10 mg once daily and increase to 20 mg, 40 mg, and then 80 mg once daily over intervals of at least 2 weeks. Maintain lower doses if higher doses are not tolerated. ( 2.1 ) Left ventricular dysfunction following myocardial infarction: Start at 20 mg once daily and increase to 40 mg then 80 mg once daily after intervals of 3 to 10 days. A lower starting dose or slower titration may be used. ( 2.2 ) Hypertension: Start at 20 mg once daily and increase if needed for blood pressure control to 40 mg then 80 mg once daily over intervals of 1 to 2 weeks. ( 2.3 ) Elderly patients (greater than 65 years of age): When switching from higher doses of immediate-release carvedilol to carvedilol phosphate extended-release capsules, a lower starting dose should be considered to reduce the risk of hypotension and syncope. ( 2.5 ) 2.1 Heart Failure DOSAGE MUST BE INDIVIDUALIZED AND CLOSELY MONITORED BY A PHYSICIAN DURING UP-TITRATION. Prior to initiation of carvedilol phosphate extended-release capsules, it is recommended that fluid retention be minimized. The recommended starting dose of carvedilol phosphate extended-release capsule is 10 mg once daily for 2 weeks. Patients who tolerate a dose of 10 mg once daily may have their dose increased to 20 mg, 40 mg, and 80 mg over successive intervals of at least 2 weeks. Patients should be maintained on lower doses if higher doses are not tolerated. Patients should be advised that initiation of treatment and (to a lesser extent) dosage increases may be associated with transient symptoms of dizziness or lightheadedness (and rarely syncope) within the first hour after dosing. Thus, during these periods, they should avoid situations such as driving or hazardous tasks, where symptoms could result in injury. Vasodilatory symptoms often do not require treatment, but it may be useful to separate the time of dosing of carvedilol phosphate extended-release capsules from that of the ACE inhibitor or to reduce temporarily the dose of the ACE inhibitor. The dose of carvedilol phosphate extended-release capsules should not be increased until symptoms of worsening heart failure or vasodilation have been stabilized. Fluid retention (with or without transient worsening heart failure symptoms) should be treated by an increase in the dose of diuretics. The dose of carvedilol phosphate extended-release capsules should be reduced if patients experience bradycardia (heart rate less than 55 beats per minute). Episodes of dizziness or fluid retention during initiation of carvedilol phosphate extended-release capsules can generally be managed without discontinuation of treatment and do not preclude subsequent successful titration of, or a favorable response to, carvedilol phosphate extended-release capsules. 2.2 Left Ventricular Dysfunction following Myocardial Infarction DOSAGE MUST BE INDIVIDUALIZED AND MONITORED DURING UP-TITRATION. Treatment with carvedilol phosphate extended-release capsules may be started as an inpatient or outpatient and should be started after the patient is hemodynamically stable and fluid retention has been minimized. It is recommended that carvedilol phosphate extended-release capsules be started at 20 mg once daily and increased after 3 to 10 days, based on tolerability, to 40 mg once daily, then again to the target dose of 80 mg once daily. A lower starting dose may be used (10 mg once daily) and/or the rate of up-titration may be slowed if clinically indicated (e.g., due to low blood pressure or heart rate, or fluid retention). Patients should be maintained on lower doses if higher doses are not tolerated. The recommended dosing regimen need not be altered in patients who received treatment with an IV or oral beta-blocker during the acute phase of the myocardial infarction. 2.3 Hypertension DOSAGE MUST BE INDIVIDUALIZED. The recommended starting dose of carvedilol phosphate extended-release capsule is 20 mg once daily. If this dose is tolerated, using standing systolic pressure measured about one hour after dosing as a guide, the dose should be maintained for 7 to 14 days, and then increased to 40 mg once daily if needed, based on trough blood pressure, again using standing systolic pressure one hour after dosing as a guide for tolerance. This dose should also be maintained for 7 to 14 days and can then be adjusted upward to 80 mg once daily if tolerated and needed. Although not specifically studied, it is anticipated the full antihypertensive effect of carvedilol phosphate extended-release capsules would be seen within 7 to 14 days as had been demonstrated with immediate-release carvedilol. Total daily dose should not exceed 80 mg. Concomitant administration with a diuretic can be expected to produce additive effects and exaggerate the orthostatic component of carvedilol action. 2.4 Hepatic Impairment Carvedilol phosphate extended-release capsules should not be given to patients with severe hepatic impairment [see Contraindications (4) ] . 2.5 Geriatric Use When switching elderly patients (aged 65 years or older) who are taking the higher doses of immediate-release carvedilol tablets (25 mg twice daily) to carvedilol phosphate extended-release capsules, a lower starting dose (40 mg) of carvedilol phosphate extended-release capsules are recommended to minimize the potential for dizziness, syncope, or hypotension [see Dosage and Administration (2) ] . Patients who have switched and who tolerate carvedilol phosphate extended-release capsules should, as appropriate, have their dose increased to after an interval of at least 2 weeks [see Use in Specific Populations (8.5) ] .

6 ADVERSE REACTIONS The safety profile of carvedilol phosphate extended-release capsules were similar to that observed for immediate-release carvedilol. Most common adverse events seen with immediate-release carvedilol. ( 6.1 ): Heart failure and left ventricular dysfunction following myocardial infarction (greater than or equal to 10%): Dizziness, fatigue, hypotension, diarrhea, hyperglycemia, asthenia, bradycardia, weight increase. Hypertension (greater than or equal to 5%): Dizziness. To report SUSPECTED ADVERSE REACTIONS, contact AvKARE at 1-855-361-3993 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared with rates in the clinical trials of another drug and may not reflect the rates observed in practice. Carvedilol has been evaluated for safety in subjects with heart failure (mild, moderate, and severe), in subjects with left ventricular dysfunction following myocardial infarction, and in hypertensive subjects. The observed adverse event profile was consistent with the pharmacology of the drug and the health status of the subjects in the clinical trials. Adverse events reported for each of these populations reflecting the use of either carvedilol phosphate extended-release capsules or immediate-release carvedilol are provided below. Excluded are adverse events considered too general to be informative, and those not reasonably associated with the use of the drug because they were associated with the condition being treated or are very common in the treated population. Rates of adverse events were generally similar across demographic subsets (men and women, elderly and non-elderly, blacks and non-blacks). Carvedilol phosphate extended-release capsules have been evaluated for safety in a 4-week (2 weeks of immediate-release carvedilol and 2 weeks of carvedilol phosphate extended-release capsules) clinical trial (n = 187) which included 157 subjects with stable mild, moderate, or severe chronic heart failure and 30 subjects with left ventricular dysfunction following acute myocardial infarction. The profile of adverse events observed with carvedilol phosphate extended-release capsules in this small, short-term trial was generally similar to that observed with immediate-release carvedilol. Differences in safety would not be expected based on the similarity in plasma levels for carvedilol phosphate extended-release capsules and immediate-release carvedilol. Heart Failure The following information describes the safety experience in heart failure with immediate-release carvedilol. Carvedilol has been evaluated for safety in heart failure in more than 4,500 subjects worldwide of whom more than 2,100 participated in placebo-controlled clinical trials. Approximately 60% of the total treated population in placebo-controlled clinical trials received carvedilol for at least 6 months and 30% received carvedilol for at least 12 months. In the COMET trial, 1,511 subjects with mild-to-moderate heart failure were treated with carvedilol for up to 5.9 years (mean: 4.8 years). Both in U.S. clinical trials in mild-to-moderate heart failure that compared carvedilol in daily doses up to 100 mg (n = 765) with placebo (n = 437), and in a multinational clinical trial in severe heart failure (COPERNICUS) that compared carvedilol in daily doses up to 50 mg (n = 1,156) with placebo (n = 1,133), discontinuation rates for adverse experiences were similar in carvedilol and placebo subjects. In placebo-controlled clinical trials, the only cause of discontinuation greater than 1% and occurring more often on carvedilol was dizziness (1.3% on carvedilol, 0.6% on placebo in the COPERNICUS trial). Table 2 shows adverse events reported in subjects with mild-to-moderate heart failure enrolled in U.S. placebo-controlled clinical trials, and with severe heart failure enrolled in the COPERNICUS trial. Shown are adverse events that occurred more frequently in drug-treated subjects than placebo-treated subjects with an incidence of greater than 3% in subjects treated with carvedilol regardless of causality. Median trial medication exposure was 6.3 months for both carvedilol and placebo subjects in the trials of mild-to-moderate heart failure and 10.4 months in the trial of subjects with severe heart failure. The adverse event profile of carvedilol observed in the long-term COMET trial was generally similar to that observed in the U.S. Heart Failure Trials. Table 2. Adverse Events (%) Occurring More Frequently with Immediate-Release Carvedilol than with Placebo in Subjects with Mild-to-Moderate Heart Failure (HF) Enrolled in U.S. Heart Failure Trials or in Subjects with Severe Heart Failure in the COPERNICUS Trial (Incidence Greater than 3% in Subjects Treated with Carvedilol, Regardless of Causality) Body System/ Adverse Event Mild-to-Moderate HF Severe HF Carvedilol (n = 765) Placebo (n = 437) Carvedilol (n = 1,156) Placebo (n = 1,133) Body as a Whole Asthenia 7 7 11 9 Fatigue 24 22 - - Digoxin level increased 5 4 2 1 Edema generalized 5 3 6 5 Edema dependent 4 2 - - Cardiovascular Bradycardia 9 1 10 3 Hypotension 9 3 14 8 Syncope 3 3 8 5 Angina pectoris 2 3 6 4 Central Nervous System Dizziness 32 19 24 17 Headache 8 7 5 3 Gastrointestinal Diarrhea 12 6 5 3 Nausea 9 5 4 3 Vomiting 6 4 1 2 Metabolic Hyperglycemia 12 8 5 3 Weight increase 10 7 12 11 BUN increased 6 5 - - NPN increased 6 5 - - Hypercholesterolemia 4 3 1 1 Edema peripheral 2 1 7 6 Musculoskeletal Arthralgia 6 5 1 1 Respiratory Cough increased 8 9 5 4 Rales 4 4 4 2 Vision Vision abnormal 5 2 - - Cardiac failure and dyspnea were also reported in these trials, but the rates were equal or greater in subjects who received placebo. The following adverse events were reported with a frequency of greater than 1% but less than or equal to 3% and more frequently with carvedilol in either the U.S. placebo-controlled trials in subjects with mild-to-moderate heart failure or in subjects with severe heart failure in the COPERNICUS trial. Incidence greater than 1% to less than or equal to 3% Body as a Whole: Allergy, malaise, hypovolemia, fever, leg edema. Cardiovascular: Fluid overload, postural hypotension, aggravated angina pectoris, AV block, palpitation, hypertension. Central and Peripheral Nervous System: Hypesthesia, vertigo, paresthesia. Gastrointestinal: Melena, periodontitis. Liver and Biliary System: SGPT increased, SGOT increased. Metabolic and Nutritional: Hyperuricemia, hypoglycemia, hyponatremia, increased alkaline phosphatase, glycosuria, hypervolemia, diabetes mellitus, GGT increased, weight loss, hyperkalemia, creatinine increased. Musculoskeletal: Muscle cramps. Platelet, Bleeding, and Clotting: Prothrombin decreased, purpura, thrombocytopenia. Psychiatric: Somnolence. Reproductive, male: Impotence. Special Senses: Blurred vision. Urinary System: Renal insufficiency, albuminuria, hematuria. Left Ventricular Dysfunction following Myocardial Infarction The following information describes the safety experience in left ventricular dysfunction following acute myocardial infarction with immediate-release carvedilol. Carvedilol has been evaluated for safety in survivors of an acute myocardial infarction with left ventricular dysfunction in the CAPRICORN trial which involved 969 subjects who received carvedilol and 980 who received placebo. Approximately 75% of the subjects received carvedilol for at least 6 months and 53% received carvedilol for at least 12 months. Subjects were treated for an average of 12.9 months and 12.8 months with carvedilol and placebo, respectively. The most common adverse events reported with carvedilol in the CAPRICORN trial were consistent with the profile of the drug in the U.S. heart failure trials and the COPERNICUS trial. The only additional adverse events reported in CAPRICORN in greater than 3% of the subjects and more commonly on carvedilol were dyspnea, anemia, and lung edema. The following adverse events were reported with a frequency of greater than 1% but less than or equal to 3% and more frequently with carvedilol: flu syndrome, cerebrovascular accident, peripheral vascular disorder, hypotonia, depression, gastrointestinal pain, arthritis, and gout. The overall rates of discontinuations due to adverse events were similar in both groups of subjects. In this database, the only cause of discontinuation greater than 1% and occurring more often on carvedilol was hypotension (1.5% on carvedilol, 0.2% on placebo). Hypertension Carvedilol phosphate extended-release capsules were evaluated for safety in an 8-week double-blind trial in 337 subjects with essential hypertension. The profile of adverse events observed with carvedilol phosphate extended-release capsules were generally similar to that observed with immediate-release carvedilol. The overall rates of discontinuations due to adverse events were similar between carvedilol phosphate extended-release capsules and placebo. Table 3. Adverse Events (%) Occurring More Frequently with Carvedilol Phosphate Extended-Release Capsules than with Placebo in Patients with Hypertension (Incidence Greater than or Equal to 1% in Patients Treated with Carvedilol, Regardless of Causality) Adverse Event Carvedilol Phosphate Extended-Release Capsules (n = 253) Placebo (n = 84) Nasopharyngitis 4 0 Dizziness 2 1 Nausea 2 0 Edema peripheral 2 1 Nasal congestion 1 0 Paresthesia 1 0 Sinus congestion 1 0 Diarrhea 1 0 Insomnia 1 0 The following information describes the safety experience in hypertension with immediate-release carvedilol. Carvedilol has been evaluated for safety in hypertension in more than 2,193 subjects in U.S. clinical trials and in 2,976 subjects in international clinical trials. Approximately 36% of the total treated population received carvedilol for at least 6 months. In general, carvedilol was well tolerated at doses up to 50 mg daily. Most adverse events reported during carvedilol therapy were of mild to moderate severity. In U.S. controlled clinical trials directly comparing carvedilol monotherapy in doses up to 50 mg (n = 1,142) with placebo (n = 462), 4.9% of carvedilol subjects discontinued for adverse events versus 5.2% of placebo subjects. Although there was no overall difference in discontinuation rates, discontinuations were more common in the carvedilol group for postural hypotension (1% versus 0). The overall incidence of adverse events in U.S. placebo-controlled trials was found to increase with increasing dose of carvedilol. For individual adverse events this could only be distinguished for dizziness, which increased in frequency from 2% to 5% as total daily dose increased from 6.25 mg to 50 mg as single or divided doses. Table 4 shows adverse events in U.S. placebo-controlled clinical trials for hypertension that occurred with an incidence of greater than or equal to 1% regardless of causality and that were more frequent in drug-treated patients than placebo-treated subjects. Table 4. Adverse Events (% Occurrence) in U.S. Placebo-Controlled Hypertension Trials with Immediate-Release Carvedilol (Incidence Greater than or Equal to 1% in Patients Treated with Carvedilol, Regardless of Causality)* Adverse Event Carvedilol (n = 1,142) Placebo (n = 462) Cardiovascular Bradycardia Postural hypotension Peripheral edema 2 2 1 - - - Central Nervous System Dizziness Insomnia 6 2 5 1 Gastrointestinal Diarrhea 2 1 Hematologic Thrombocytopenia 1 - Metabolic Hypertriglyceridemia 1 - * Shown are events with rate greater than 1% rounded to nearest integer. Dyspnea and fatigue were also reported in these studies, but the rates were equal or greater in subjects who received placebo. The following adverse events not described above were reported as possibly or probably related to carvedilol in worldwide open or controlled trials with carvedilol in subjects with hypertension or heart failure. Incidence greater than 0.1% to less than or equal to 1% Cardiovascular: Peripheral ischemia, tachycardia. Central and Peripheral Nervous System: Hypokinesia. Gastrointestinal: Bilirubinemia, increased hepatic enzymes (0.2% of hypertension patients and 0.4% of heart failure patients were discontinued from therapy because of increases in hepatic enzymes) [see Adverse Reactions (6.2) ]. Psychiatric: Nervousness, sleep disorder, aggravated depression, impaired concentration, abnormal thinking, paroniria, emotional lability. Respiratory System: Asthma [see Contraindications (4) ] . Reproductive, male: Decreased libido. Skin and Appendages: Pruritus, rash erythematous, rash maculopapular, rash psoriaform, photosensitivity reaction. Special Senses: Tinnitus. Urinary System: Micturition frequency increased. Autonomic Nervous System: Dry mouth, sweating increased. Metabolic and Nutritional: Hypokalemia, hypertriglyceridemia. Hematologic: Anemia, leukopenia. The following events were reported in less than or equal to 0.1% of subjects and are potentially important: Complete AV block, bundle branch block, myocardial ischemia, cerebrovascular disorder, convulsions, migraine, neuralgia, paresis, anaphylactoid reaction, alopecia, exfoliative dermatitis, amnesia, GI hemorrhage, bronchospasm, pulmonary edema, decreased hearing, respiratory alkalosis, increased BUN, decreased HDL, pancytopenia, and atypical lymphocytes. Laboratory Abnormalities Reversible elevations in serum transaminases (ALT or AST) have been observed during treatment with carvedilol. Rates of transaminase elevations (2 to 3 times the upper limit of normal) observed during controlled clinical trials have generally been similar between subjects treated with carvedilol and those treated with placebo. However, transaminase elevations, confirmed by rechallenge, have been observed with carvedilol. In a long-term, placebo-controlled trial in severe heart failure, subjects treated with carvedilol had lower values for hepatic transaminases than subjects treated with placebo, possibly because carvedilol-induced improvements in cardiac function led to less hepatic congestion and/or improved hepatic blood flow. Carvedilol therapy has not been associated with clinically significant changes in serum potassium, total triglycerides, total cholesterol, HDL cholesterol, uric acid, blood urea nitrogen, or creatinine. No clinically relevant changes were noted in fasting serum glucose in hypertensive subjects; fasting serum glucose was not evaluated in the heart failure clinical trials. 6.2 Postmarketing Experience The following adverse reactions have been identified during post-approval use of carvedilol tablets or extended-release carvedilol capsules. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Blood and Lymphatic System Disorders Aplastic anemia. Immune System Disorders Hypersensitivity (e.g., anaphylactic reactions, angioedema, urticaria). Renal and Urinary Disorders Urinary incontinence. Respiratory, Thoracic and Mediastinal Disorders Interstitial pneumonitis. Skin and Subcutaneous Tissue Disorders Stevens-Johnson syndrome, toxic epidermal necrolysis, erythema multiforme.

12.3 Pharmacokinetics Absorption Carvedilol is rapidly and extensively absorbed following oral administration of immediate-release carvedilol tablets, with an absolute bioavailability of approximately 25% to 35% due to a significant degree of first-pass metabolism. Carvedilol phosphate extended-release capsules have approximately 85% of the bioavailability of immediate-release carvedilol tablets. For corresponding dosages [see Dosage and Administration (2) ] , the exposure (AUC, C max , trough concentration) of carvedilol as carvedilol phosphate extended-release capsules are equivalent to those of immediate-release carvedilol tablets when both are administered with food. The absorption of carvedilol from carvedilol phosphate extended-release capsules is slower and more prolonged compared to the immediate-release carvedilol tablet with peak concentrations achieved approximately 5 hours after administration. Plasma concentrations of carvedilol increase in a dose-proportional manner over the dosage range of carvedilol phosphate extended-release capsules 10 mg to 80 mg. Within-subject and between-subject variability for AUC and C max is similar for carvedilol phosphate extended-release capsules and immediate-release carvedilol. Effect of Food: Administration of carvedilol phosphate extended-release capsules with a high-fat meal resulted in increases (~20%) in AUC and C max compared with carvedilol phosphate extended-release capsules administered with a standard meal. Decreases in AUC (27%) and C max (43%) were observed when carvedilol phosphate extended-release capsules were administered in the fasted state compared with administration after a standard meal. Carvedilol phosphate extended-release capsules should be taken with food. In a trial with adult subjects, sprinkling the contents of the carvedilol phosphate extended-release capsule on applesauce did not appear to have a significant effect on overall exposure (AUC) compared with administration of the intact capsule following a standard meal, but did result in a decrease in C max (18%). Distribution 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. Metabolism and Excretion 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 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 beta-receptor blocking activity. Based on preclinical studies, the 4’-hydroxyphenyl metabolite is approximately 13 times more potent than carvedilol for beta-blockade. Compared with 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 of carvedilol phosphate extended-release capsules in healthy subjects. Apparent clearance is 90 L per h and 213 L per h for R(+)- and S(–)-carvedilol, respectively. 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 with 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).