British journal of clinical pharmacology
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Br J Clin Pharmacol · Jan 1979
Use of labetalol during hypotensive anaesthesia and in the management of phaeochromocytoma.
1 The circulatory effects of labetalol have been studied in 88 patients undergoing plastic surgery, 8 patients with carcinoma of the breast, 10 with carcinoma in the head and neck, and in 2 patients with phaeochromocytoma, each anaesthetized twice. 2 The use of labetalol intravenously produced hypotension and a bloodless operating field in patients undergoing plastic surgery and in those undergoing radical surgery for the removal of carcinoma. 3 Two patients with phaeochromocytoma pre-treated with oral labetalol before anaesthesia, had well controlled BPs and heart rates during surgery, although in one instance additional intravenous labetalol was required. 4 Pre-operative preparation of patients with phaeochromocytoma with labetalol seems to be simpler and safer than previous techniques involving drugs with separate alpha- and beta-adrenoceptor-blocking effects.
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Br J Clin Pharmacol · Jan 1979
Randomized Controlled Trial Comparative Study Clinical TrialA double-blind crossover comparison of pindolol, metoprolol, atenolol and labetalol in mild to moderate hypertension.
1 This study was designed to compare in a double-blind randomized crossover trial, atenolol, labetalol, metoprolol and pindolol. Considerable differences in dose (atenolol 138 +/- 13 mg daily; labetalol 308 +/- 34 mg daily; metoprolol 234 +/- 22 mg daily; and pindolol 24 +/-2 mg daily were required to produce similar antihypertensive effects. 3 The overall incidence of side-effects was similar with atenolol, metoprolol and pindolol but was slightly less with labetalol. Sleep disturbances and abnormal dreaming patterns were most frequent with pindolol. 4 There was a significantly greater fall in pulse rate during atenolol and metoprolol treatment periods.
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1 The circulatory effects of labetalol 25 mg intravenously in six patients during 1% halothane anaesthesia were studied. 2Labetalol caused a marked decrease in arterial pressure and a consistent but modest (20%) decrease in cardiac output. Heart rate was slowed and stroke volume did not change significantly. Central venous pressure increased and peripheral resistance decreased. 3 Increasing the halothane concentration of 3% led to marked myocardial depression as evidenced by reduced cardiac output and increased central venous pressure with increasing arterial hypotension. 4 Labetalol may be a suitable drug for controlling induced hypotension under general anaesthesia, although high concentrations of halothane should be used with care.
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A survey of one hundred patients submitted to autopsy has been carried out to assess the contribution of investigational procedures, surgery and drug therapy to death. In nineteen patients drug therapy, usually appropriate and necessary therapy, was thought to have contributed to death. In five patients failure to continue therapy properly contributed to death. The survey was not representative either of patients dying in hospital or in the community, but it suggests that a larger and more comprehensive survey should be undertaken.
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1 The disposition and metabolism of labetalol and either 14C- or 3H-labetalol has been studied in mouse, rat, rabbit, dog and man. 2 Radiolabelled labetalol was administered orally at doses of 100 mg/kg to the mouse, up to 50 mg/kg to the rat and rabbit, 20 mg/kg to the dog and 200 mg to man. From measurements of the total plasma radioactivity it was shown that labetalol was well absorbed by all the species. When the measurements of plasma radioactivity and labetalol concentrations were compared, it was found labetaol had been extensively metabolized by the first-pass effect in rat, rabbit and man. ⋯ This was probably formed through conjugation of glucuronic acid was the secondary alcohol group of labetalol. The major metabolite present in human urine was an unidentified conjugate of labetalol. Minor metabolites of labetalol present in rat, rabbit and dog urine were hydroxylabetalol and its glucuronyl conjugate.