Letter: Sclerosing peritonitis and practolol

The beta-adrenergic blocking agents and the treatment of glaucoma

The autonomic nervous system is divided into the parasympathetic and sympathetic systems, with three types of adrenergic receptors: alpha (smooth muscle contraction), beta1 (cardiac acceleration and fatty acid mobilization) and beta2 (smooth muscle relaxation). Substances affecting the function of the adrenergic system are the agonists or stimulators, which mimic the effects of endogenous norepinephrine or epinephrine, and antagonists or blockers, which block the receptors and prevent stimulation by the agonists. Autonomic stimulation in the eye mediates various changes which apparently affect outflow facility and rate of formation of aqueous humor. Alteration of either or both of these factors by autonomic agonists or antagonists may have a direct or an indirect effect on intraocular pressure. Beta-adrenergic blocking substances have been used to treat a variety of diseases. Some of the effects of these drugs are attributable to properties other than beta blockade, such as intrinsic sympathomimetic activity and local anaesthetic activity. Side effects of this class of drugs require caution in cases of congestive heart failure and in asthmatics. Autonomic agents used in the treatment of ocular hypertension and glaucoma include pilocarpine, a chilinergic agonist, epinephrine, an adrenergic agonist, and various beta adrenergic blockers or antagonists including propranolol, atenolol and timolol. The physico-chemical properties and pharmacokinetics of timolol are reviewed. Data showing a significant reduction in intraocular pressure as a result of ocular instillation of timolol are presented. Reduction of the rate of aqueous formation appears to be the mechanism of action. A low incidence of non-serious side effects is reported.

Sclerosing peritonitis due to practolol

Six patients developed intestinal obstruction from sclerosing peritonitis due to practolol. Complete surgical removal of the abnormal membrane appears to be necessary.

Practolol peritonitis

Barium examination of the small bowel revealed fixation, dilation, separation of bowel loops and delayed small intestinal transit in nine patients with practolol induced peritonitis. The diagnosis may be first suggested by this examination, and a history of prolonged therapy with beta-blocking agents should be sought in patients showing these changes where no other cause for them can be found. Symptoms may develop up to a year following cessation of therapy so that further cases may still come to light despite the withdrawal of practolol for long-term use. Small bowel barium examination is indicated in patients who have received practolol therapy and who develop suspicious alimentary symptoms.