Carvedilol (Page 4 of 9)

6.2 Postmarketing Experience

The following adverse reactions have been identified during post-approval use of carvedilol. 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.

7 DRUG INTERACTIONS

7.1 CYP2D6 Inhibitors and Poor Metabolizers

Interactions of carvedilol with potent inhibitors of CYP2D6 isoenzyme (such as quinidine, fluoxetine, paroxetine, and propafenone) have not been studied, but these drugs would be expected to increase blood levels of the R(+) enantiomer of carvedilol [see Clinical Pharmacology (12.3)]. Retrospective analysis of side effects in clinical trials showed that poor 2D6 metabolizers had a higher rate of dizziness during up-titration, presumably resulting from vasodilating effects of the higher concentrations of the α-blocking R(+) enantiomer.

7.2 Hypotensive Agents

Patients taking a β-blocker and a drug that can deplete catecholamines (e.g., reserpine and monoamine oxidase inhibitors) should be observed closely for signs of hypotension and/or severe bradycardia.

Concomitant administration of clonidine with a β-blocker may cause hypotension and bradycardia. When concomitant treatment with a β-blocker and clonidine is to be terminated, the β-blocker should be discontinued first. Clonidine therapy can then be discontinued several days later by gradually decreasing the dosage.

7.3 Cyclosporine

Modest increases in mean trough cyclosporine concentrations were observed following initiation of carvedilol treatment in 21 renal transplant subjects suffering from chronic vascular rejection. In about 30% of subjects, the dose of cyclosporine had to be reduced in order to maintain cyclosporine concentrations within the therapeutic range, while in the remainder no adjustment was needed. On the average for the group, the dose of cyclosporine was reduced about 20% in these subjects. Due to wide interindividual variability in the dose adjustment required, it is recommended that cyclosporine concentrations be monitored closely after initiation of carvedilol therapy and that the dose of cyclosporine be adjusted as appropriate.

7.4 Digitalis Glycosides

Both digitalis glycosides and β-blockers slow atrioventricular conduction and decrease heart rate. Concomitant use can increase the risk of bradycardia. Digoxin concentrations are increased by about 15% when digoxin and carvedilol are administered concomitantly. Therefore, increased monitoring of digoxin is recommended when initiating, adjusting, or discontinuing carvedilol [see Clinical Pharmacology (12.5)].

7.5 Inducers/Inhibitors of Hepatic Metabolism

Rifampin reduced plasma concentrations of carvedilol by about 70% [see Clinical Pharmacology (12.5)]. Cimetidine increased AUC by about 30% but caused no change in Cmax [see Clinical Pharmacology (12.5)].

7.6 Amiodarone

Amiodarone, and its metabolite desethyl amiodarone, inhibitors of CYP2C9 and P-glycoprotein, increased concentrations of the S(-) enantiomer of carvedilol by at least 2 fold [see Clinical Pharmacology (12.5)]. The concomitant administration of amiodarone or other CYP2C9 inhibitors such as fluconazole with carvedilol may enhance the β-blocking activity, resulting in further slowing of the heart rate or cardiac conduction. Patients should be observed for signs of bradycardia or heart block, particularly when one agent is added to pre-existing treatment with the other.

7.7 Calcium Channel Blockers

Conduction disturbance (rarely with hemodynamic compromise) has been observed when carvedilol is co-administered with diltiazem. As with other β-blockers, if carvedilol is administered with calcium channel blockers of the verapamil or diltiazem type, it is recommended that ECG and blood pressure be monitored.

7.8 Insulin or Oral Hypoglycemics

β-blockers may enhance the blood-sugar-reducing effect of insulin and oral hypoglycemics. Therefore, in patients taking insulin or oral hypoglycemics, regular monitoring of blood glucose is recommended [see Warnings and Precautions (5.6)].

7.9 Anesthesia

If treatment with carvedilol is to be continued perioperatively, particular care should be taken when anesthetic agents that depress myocardial function, such as ether, cyclopropane, and trichloroethylene, are used [see Overdosage (10)].

8 USE IN SPECIFIC POPULATIONS

8.1 Pregnancy

Risk Summary

Available data regarding use of carvedilol in pregnant women are insufficient to determine whether there are drug-associated risks of adverse developmental outcomes. There are risks to the mother and fetus associated with poorly controlled hypertension in pregnancy. The use of beta blockers during the third trimester of pregnancy may increase the risk of hypotension, bradycardia, hypoglycemia, and respiratory depression in the neonate [see Clinical Considerations]. In animal reproduction studies, there was no evidence of adverse developmental outcomes at clinically relevant doses [see Data]. Oral administration of carvedilol to pregnant rats during organogenesis resulted in post-implantation loss, decreased fetal body weight, and an increased frequency of delayed fetal skeletal development at maternally toxic doses that were 50 times the maximum recommended human dose (MRHD). In addition, oral administration of carvedilol to pregnant rabbits during organogenesis resulted in increased post-implantation loss at doses 25 times the MRHD [see Data].

The estimated background risk of major birth defects and miscarriage for the indicated populations are unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively.

Clinical Considerations

Disease-Associated Maternal and/or Embryo/Fetal Risk: Hypertension in pregnancy increases the maternal risk for pre-eclampsia, gestational diabetes, premature delivery, and delivery complications (e.g., need for cesarean section and post-partum hemorrhage). Hypertension increases the fetal risk for intrauterine growth restriction and intrauterine death. Pregnant women with hypertension should be carefully monitored and managed accordingly.

Fetal/Neonatal Adverse Reactions: Neonates of women with hypertension who are treated with beta-blockers during the third trimester of pregnancy may be at increased risk for hypotension, bradycardia, hypoglycemia, and respiratory depression. Observe newborns for symptoms of hypotension, bradycardia, hypoglycemia, and respiratory depression and manage accordingly.

Data

Animal Data: Studies performed in rats and rabbits given carvedilol during fetal organogenesis revealed increased post-implantation loss in rats at a maternally toxic dose of 300 mg per kg per day (50 times the MRHD as mg per m2) and in rabbits (in the absence of maternal toxicity) at doses of 75 mg per kg per day (25 times the MRHD as mg per m2). In the rats, there was also a decrease in fetal body weight at 300 mg per kg per day (50 times the MRHD as mg per m2) accompanied by an increased incidence of fetuses with delayed skeletal development. In rats, the no-effect level for embryo-fetal toxicity was 60 mg per kg per day (10 times the MRHD as mg per m2); in rabbits, it was 15 mg per kg per day (5 times the MRHD as mg per m2). In a pre-and post-natal development study in rats administered carvedilol from late gestation through lactation, increased embryo-lethality was observed at a maternally toxic dose of 200 mg per kg per day (approximately 32 times the MRHD as mg per m2), and pup mortality and delays in physical growth/development were observed at 60 mg per kg per day (10 times the MRHD as mg per m2) in the absence of maternal toxicity. The no-effect level was 12 mg per kg per day (2 times the MRHD as mg per m2). Carvedilol was present in fetal rat tissue.

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