Acebutolol is a cardioselective beta blocker with ISA (Intrinsic Sympathomimetic Activity, see article on Pindolol). It is therefore more suitable than non cardioselective beta blockers, if a patient with Asthma bronchiale or chronic obstructive lung disease (COLD) needs treatment with a beta blocker. In doses lower than 800mg daily its constricting effects on the bronchial system and smooth muscle vessels are only 10% to 30% of those observed under Propranolol treatment. But there is experimental evidence that the cardioselective properties diminish at doses of 800mg/day or more. The drug has lipophilic properties, this means that it crosses the Blood Brain Barrier. Acebutolol has no negative impact on serum lipids (cholesterol and triglycerides), in particular no HDL decrease has been observed. In this regard it is unlike to many other beta blockers which have this unfavourable property. The drug works in hypertensive patients with high or normal and low renin plasma concentrations, although acebutolol may be more efficient in patients with high or normal renin plasma concentrations. It seems that in clinical relevant concentrations a membrane stabilizing effect does not play an important role.

Pharmacokinetics

Acebutolol is well absorbed from the GI tract, but undergoes substantial first-pass-metabolization, leading to a bioavailability of only 35% to 50%. Peak plasma levels of acebutolol are reached within 2 to 2,5 hours after oral dosing, those of the active main metabolite diacetolol after 4 hours. Acebutolol has a halflife of 3 to 4 hours, diacetolol one of 8 to 13 hours. Acebutolol undergoes extensive hepatic metabolization resulting in the desbutyl amine acetolol which is readily converted into diacetolol. Diacetolol is as aktive as acebutolol (equipotency) and appears to have the same pharmakologic profile. Geriatric patients tend to have higher peak plasma levels of both acebutolol and diacetolol and a slightly prolonged excretion. Excretion is substantially prolonged in patients with renal impairment; a dose reduction may be needed. Liver cirrhosis does not seem to alter the pharmakokinetic profile of parent drug and metabolite.

Uses

hypertension
angina pectoris, including instable angina
ventricular and atrial cardiac arrhythmias
acute myocardial infarction in high risk patients

Contraindications and Precautions

See article on Propranolol. Acebutolol may be suitable in patients with Asthma bronchiale or COLD.

Side Effects

See article on Propranolol. The development of ANA (Anti-Nuclear-Antibodies) has been found in 10 to 30% of patients under treatment with acebutolol. A systemic disease with arthralgic pain and myalgias has been developed in 1%. A lupus erythematosus like syndrome with skin rash and multiforme organ involvement is even less frequent. The incidence of both ANA and symptomatic disease under acebutolol is higher than under Propranolol. Female patients develop these symptoms more likely than male patients. Also, a few cases of hepatotoxicity with increased liver enzymes (ALT, AST) have been seen. Altogether, 5 to 6% of all patients treated have to discontinue acebutolol due to intolerable side effects. The treatment should be, if possible, discontinued gradually in order to avoid a withdrawal syndrome with increased frequency of angina and even precipitation of myocardial infarction.

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Safe beta blockers in patients with reactive airway disease - Tips from Other Journals
From American Family Physician, 3/1/03 by Richard Sadovsky

Beta blockers are widely used in the management of cardiac conditions and thyrotoxicosis, and to reduce perioperative complications. Asthma and chronic obstructive pulmonary disease (COPD) have been classic contraindications to the use of beta blockers because of their potential for causing bronchospasm. The identification of cardioselective beta blockers that have significantly greater affinity for [beta.sup.1] receptors than for [beta.sub.2] receptors offers a subgroup of beta blockers that are less likely to cause bronchospasm. Salpeter and associates analyzed data from randomized, blinded, placebo-controlled trials to evaluate the effect of cardioselective beta blockers on patients with reactive airway disease, including asthma or COPD with a reversible component. Eligible studies could use oral or intravenous dosing given as a single dose or as continuous treatment. Of the 29 studies included in this meta-analysis, 19 studied single-dose treatment in a total of 240 patients. The cardioselective beta blockers without intrinsic sympathomimetic activity that were used in the study included atenolol, metoprolol, bisoprolol, and practolol. Those with intrinsic sympathomimetic activity included celiprolol, acebutolol, and xamoterol. In the group that received a single dose of a beta blocker, there was a 7.46 percent reduction in forced expiratory volume in one second ([FEV.sub.1]), which reversed after administration of a beta agonist. None of the studies demonstrated increased respiratory symptoms among patients. In the 10 studies involving 141 participants who received continuous cardioselective beta-blocker treatment, no participant had a significant drop in [FEV.sub.1] or developed new symptoms.

The authors conclude that cardioselective beta blockers can be used safely in patients with reactive airway disease. The first dose of a cardioselective beta blocker may cause a small drop in FEV1, but continuous therapy over a few days to weeks, especially with agents without intrinsic sympathomimetic activity, was not associated with significant [FEV.sub.1] changes, symptoms, or beta-agonist inhaler use.

In the same journal, Epstein agrees that cardioselective beta blockers are safe in patients with mild to moderate reactive airway disease. These medications clearly can decrease mortality among patients with acute coronary syndromes, congestive heart failure, select arrhythmias, and hypertension. Drugs should be started at a low dosage and titrated upward. Care is necessary in patients with severe asthma or ongoing bronchospasms.

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