[True and presumed contraindications of beta blockers. Peripheral vascular disease, diabetes mellitus, chronic bronchopneumopathy].

Traditional contraindications to beta-blockers are peripheral vascular diseases, diabetes mellitus, chronic obstructive pulmonary disease (COPD) and asthma. Recent data seem to show that rigorous application of these rules are not completely justified and indicate that many patients would be inappropriately excluded from the beneficial effects of this therapy. Appraisal of clear guidelines for a safe use of beta-blockers is thus mandatory for the clinician. A brief review of the effects of beta-adrenergic receptor blockade is offered. The therapy is aimed at blocking beta 1-receptors. On the other hand, the block of beta 2-receptors causes the well known side effects, i.e. vasoconstriction, delayed response to hypoglycemia in diabetic patients, bronchoconstriction. From the first compound, propranolol, with uniform action on beta 1 and beta 2-receptors, further generation of beta-blockers were subsequently developed: beta 1-selective, with intrinsic sympathomimetic activity, and with associated vasodilating "ancillary" property. Some favorable reduction in collateral effects has thus been obtained with new compounds, without reaching complete safety. Examination of exclusion criteria applied in clinical trials offers no useful indications because of their imprecise definition. Examination of the literature and a more accurate understanding of the diseases, traditionally considered contraindications, may help setting up a uniform and clear path: peripheral vascular disease: beta-blockers should be avoided only in those patients with vasospastic disorders, rest pain with severe peripheral vascular disease or nonhealing lesions. In patients with mild to moderate disease, beta-blockers can be prescribed, but careful surveillance for any changes in symptoms related to intermittent claudicatio should be achieved; diabetes mellitus: previous apprehension for the lessening reaction to hypoglycemia in patients treated with insulin has been retracted. Beta-blockers are not contraindicated in these patients. Some caution should be addressed when signs of autonomic disease are present or in patients with difficult glycemic control. Patients on oral long-acting antidiabetic drugs should not be neglected. The risk of prolonged and paucisymptomatic hypoglycemia while taking beta-blocker agents is somewhat more relevant than in patients treated regularly with insulin; COPD and asthma: confusion may arise if rigorous definition of these diseases and their severity is not applied following the guidelines of the American Thoracic Society. Because bronchial hyperreactivity seems the crucial factor in determining collateral effects to beta-blocker agents, agreement can be reached on the following statements. Beta-blockers are contraindicated a) when history of asthma is present, b) when COPD is moderate to severe, i.e. with FEV1 reduction < 50% of the predicted value, c) in patients on chronic bronchodilator treatment, d) in chronic airflow limitation with evidence of > or = 20% reversibility in airway obstruction in response to inhaled salbutamol. When FEV1 is > 50% of the predicted value, beta-blockers can be given, providing adequate control of stability of ventilatory conditions.