Influence of intrinsic sympathomimetic activity on respiratory function during chronic beta blockade: comparison of propranolol and pindolol.

The long term effect of beta blockers and the influence of intrinsic sympathomimetic activity on respiratory function were assessed in patients with chronic stable angina pectoris randomised to receive treatment with propranolol (n = 21) or pindolol (n = 19) for one year. Forced expiratory volume in one second (FEV1) had fallen by a mean of 240 ml after one year (p less than 0.001) in those treated with propranolol compared with 120 ml in those treated with pindolol (p less than 0.05). The difference between the groups was significant (p less than 0.01). Vital capacity fell significantly only in those treated with propranolol (p less than 0.05 at one year). In those in whom the basal ratio of FEV1 to forced vital capacity was low (less than 70%) propranolol, but not pindolol, caused a significant (p less than 0.05) fall in FEV1 throughout treatment. Long term administration of pindolol has a less adverse effect on respiratory function than propranolol, which results in a progressive deterioration in respiratory function over one year.