Carvedilol should not be used in the case of the following diseases since there is a lack of experience in these situations: markedly reduce performance of the heart, labile or secondary (organically induced) high blood pressure, unstable angina pectoris, impulse conductions disturbances in the heart (complete bundle branch block), final stages of peripheral artery disease, impaired renal function (serum creatinine concentration > 1.8 mg/dl or creatinine clearance < 30 mL/min), recent heart attack (less than 6 months old), tendency to drop in blood-pressure lowering drugs (α1 receptor antagonists). Particularly close medical surveillance is required in diabetes mellitus patients with pronounced fluctuations in blood sugar levels and in the event of strict fasting. In older patients a sharper drop in blood pressure can occur after administration of the first dose of carvedilol. This applies especially to patients already taking diuretics. Diuretics should therefore be discontinued before beginning treatment with carvedilol. Drugs with β-blocking properties may trigger psoriasis vulgaris in isolated cases, cause the symptoms of this disease to deteriorate, or produce rashes resembling psoriasis (psoriasis form). Patients with personal of familiar history of psoriasis should only take drugs with β-blocking properties (e.g. carvedilol) after careful consideration of the benefit to risk ratio.
Treatment with carvedilol should not be stopped abruptly but must be gradually tapered all over a few days. This is particularly important in the case of patients with concomitant coronary artery disease (angina pectoris). Treatment of hypertension requires regular medical surveillance. Individual varying reactions can impair the ability to drive or operate machinery. This applies particularly when beginning the treatment or starting a new preparation and in conjuction with alcohol. During treatment with carvedilol the eyes must be examined regularly at 6-monthly intervals. Patients with mild to moderate occlusive vascular disease should be carefully monitored during initiation of therapy and β-blockers should be avoided in patients with severe occlusive vascular diease, particularly those with rest pain.
Carvedilol should only be used in patients with chronic obstructive pulmonary disease (COPD) with a bronchospastic component not receiving oral or inhaled medication if the potential benefit outweigh the potential risk. In patients with a tendency to bronchospasm, respiratory distress can occur as a result of a possible increase in airway resistance. Patient should be closely monitored during initiation and up-titration of carvedilol and the dose of carvedilol reduced if any evidence of bronchospasm is observed during treatment. Carvedilol, like other agents with beta-blocking properties may obscure the symptoms of thyrotoxicosis. Care should be taken in administering carvedilol to patients with a history of serious hypersensitivity reactions and in those undergoing desensitization therapy as beta-blockers may increase both the sensitivity towards allergens and the serious of anaphylactic reactions. In patients with pheochromocytoma, an alpha-blocking agent should be initiated prior to the use of any beta-blocking agent. Although carvedilol has both alpha and beta-blocking pharmacological activities, there is no experience with its use in this condition. Therefore, caution should be taken in administration of carvedilol to patients suspected of having pheochromocytoma. Agents with non-selective beta-blocking activity may provoke chest pain in patients with Prinzmetal's variant angina. There is no clinical experience with carvedilol in these patients, although the alpha-blocking activity of carvedilol may prevent such symptoms. However, caution should be taken in the administration of carvedilol to patients suspected of having Prinzmetal's variant angina. In patients suffering from peripheral circulatory disorders (Raynaud's phenomenon) there may be exacerbation of symptoms. Caution should be exercised in patients undergoing general surgery, because of the synergistic negative inotropic and hypotensive effects of carvedilol and anesthetic drugs. Carvedilol may induce bradycardia. If the pulse rate decreases to less than 55 beats per minute, the dosage of carvedilol should be reduced. In patients receiving concomitant therapy with calcium channel blockers of the verapamil or diltiazem-type, or other antiarrhythmic drugs, careful monitoring of ECG and blood is necessary.
Carvedilol should be used with caution in patients with labile or secondary hypertension until further clinical experience is available.