Antacids and anticholinergics in the treatment of duodenal ulcer

Anticholinergic agents are most often divided into tertiary and quaternary ammonium compounds. Tertiary ammonium agents are fully and rapidly absorbed. Quaternary ammonium agents are slowly and incompletely absorbed, but do not cross the blood-brain barrier, or do so to a very limited degree, and have a very low rate of central nervous system side-effects. There are probably subclasses of cholinergic receptors, and anticholinergic agents have different affinities for these. Anticholinergics can decrease the basal acid secretion as well as secretion stimulated by histamine, pentagastrin, insulin or food. Combined therapy with antacids and anticholinergics will give a more long-lasting decrease in acidity than with either drug alone. The reported controlled studies with anticholinergic agents suggest that they can induce healing of duodenal ulcer to the same degree as cimetidine but at the cost of more frequent side-effects. Except for the studies on pirenzepine there are, however, too few studies in which anticholinergics have been compared with histamine H2-receptor antagonists; thus the place of anticholinergics in the treatment of an active duodenal ulcer is not clear. In doses of not less than 100 mg daily, pirenzepine is a candidate-drug for the short-term treatment of duodenal ulcer. At these doses, side-effects of dry mouth and visual disturbance are, however, rather frequent, and more serious side-effects such as urinary retention do also occur. More studies with both the conventional anticholinergics and pirenzepine, with emphasis not only on the desired effects but also on side-effects, are needed before anticholinergics can be taken into consideration as alternatives to histamine H2-receptor antagonists for healing and maintenance treatment. There is some evidence that long-term treatment with anticholinergic agents can decrease recurrences and complications of peptic ulcer disease. Even if there are some encouraging reports on the combination of anticholinergics and antacids, we need more such studies with lower doses of antacids and lower doses of anticholinergics before this combination therapy can be regarded as an equally good alternative to histamine H2-receptor antagonists for ulcer healing and symptom relief.