Withdrawal of the long-acting beta blocker bopindolol is not associated with beta-adrenoceptor supersensitivity

beta-Adrenoceptor sensitivity after abrupt withdrawal of long-term therapy (5-12 months) with bopindolol (1-2 mg/day), a long-acting beta-adrenoceptor blocking agent with intrinsic sympathomimetic activity, was assessed in five patients with uncomplicated essential hypertension. The chronotropic dose 25 of isoproterenol (CD 25), plasma concentrations of catecholamines, triiodothyronine and thyroxin, plasma renin activity and aldosterone, hemoglobin, hematocrit and oxyhemoglobin dissociation were measured on the last day of bopindolol administration and 1, 2, 3, 6, and 13 days after abrupt replacement by placebo tablets. The chronotropic dose 25 of isoproterenol (microgram/m2) was greater than 25.6 in all patients on the last day of bopindolol therapy. On day 1 in patients who had been taking 2 mg/day of bopindolol, CD 25 remained greater than 25.6 but fell to 12.1 in the one patient who had been taking 1 mg/day. On day 2, CD 25 was 10.19 +/- 2.97 and felt gradually to the lowest value of 3.76 +/- 1.19 on day 13. Throughout the study, plasma concentrations of catecholamines, triiodothyronine and thyroxin, and oxyhemoglobin dissociation remained unchanged. Plasma renin activity and plasma aldosterone, which were suppressed during bopindolol therapy, rose during placebo, coinciding with a fall in hemoglobin and hematocrit. No subjective symptoms of increased beta-adrenoceptor-mediated functions were reported by the patients throughout the whole study period. Therefore, hypersensitivity of beta-adrenoceptor-mediated responses was not demonstrated within the first 13 days after sudden withdrawal of bopindolol.