Acebutolol is well tolerated in properly selected patients. Most adverse reactions have been mild, not required discontinuation of therapy, and tended to decrease as duration of treatment increases. The following table shows the frequency of treatment-related side effects derived from controlled clinical trials in patients with hypertension, angina pectoris, and arrhythmia. These patients received acebutolol, propranolol, or hydrochlorothiazide as monotherapy, or placebo. The following selected (potentially important) side effects were seen in up to 2% of acebutolol patients: Cardiovascular: hypotension, bradycardia, heart failure. Central Nervous System: anxiety, hyper/hypoesthesia, impotence. Dermatological: pruritus. Gastrointestinal: vomiting, abdominal pain. Genitourinary: dysuria, nocturia. Liver and Biliary System: A small number of cases of liver abnormalities (increased SGOT, SGPT, LDH) have been reported in association with acebutolol therapy. In some cases increased bilirubin or alkaline phosphatase, fever, malaise, dark urine, anorexia, nausea, headache, and/or other symptoms have been reported. In some of the reported cases, the symptoms and signs were confirmed by rechallenge with acebutolol. The abnormalities were reversible upon cessation of acebutolol therapy. Musculoskeletal: back pain, joint pain. Respiratory: pharyngitis, wheezing. Special Senses: conjunctivitis, dry eye, eye pain. Autoimmune: In extremely rare instances, systemic lupus erythematosus has been reported. The incidence of drug-related adverse effects (volunteered and solicited) according to acebutolol dose is shown below. (Data from 266 hypertensive patients treated for 3 months on a constant dose.) POTENTIAL ADVERSE EFFECTS In addition, certain adverse effects not listed above have been reported with other β-blocking agents and should also be considered as potential adverse effects of acebutolol. Central Nervous System: Reversible mental depression progressing to catatonia (an acute syndrome characterized by disorientation for time and place), short-term memory loss, emotional lability, slightly clouded sensorium, and decreased performance (neuropsychometrics). Cardiovascular: Intensification of AV block (see Contraindications). Allergic: Erythematous rash, fever combined with aching and sore throat, laryngospasm, and respiratory distress. Hematologic: Agranulocytosis, nonthrombocytopenic, and thrombocytopenic purpura. Gastrointestinal: Mesenteric arterial thrombosis and ischemic colitis. Miscellaneous: Reversible alopecia and Peyronie’s disease. The oculomucocutaneous syndrome associated with the β-blocker practolol has not been reported with acebutolol during investigational use and extensive foreign clinical experience.