Hypersalivation is a major side-effect of clozapine in patients with treatment-resistant schizophrenia.

We investigated the efficacy of topical anticholinergic formulation sofpironium bromide gel for improving hypersalivation in patients with treatment-resistant schizophrenia receiving clozapine.

A double-blind, controlled crossover study was conducted with sofpironium bromide gel and a placebo gel to treat clozapine-induced hypersalivation in 16 patients with treatment-resistant schizophrenia. Patients were randomly divided between groups A and B (each n = 8). Group A was treated with sofpironium bromide gel for 6 weeks, followed by a 2-week washout period and 6 weeks of placebo gel, after which they were observed for another 2 weeks. In contrast, group B was treated with placebo gel for 6 weeks, followed by a 2-week washout period, 6 weeks of sofpironium bromide gel and a 2-week observation period. One-minute saliva volume, objective salivation ratings (Drooling Severity and Frequency Scale and Nocturnal Hypersalivation Rating Scale) and subjective salivation ratings (Visual Analogue Scale) were assessed every 2 weeks.

All patients completed the trials. Three patients reported mild, spontaneously resolved skin itching. Compared with baseline values, the 1-min saliva volumes of both groups were significantly decreased by approximately 30% at the second week of sofpironium bromide gel treatment (P < 0.001), and significantly decreased by >40% at the fourth and sixth weeks of treatment (P < 0.001). The effects were maintained for over 2 weeks even after the treatment was discontinued.

We suggest that sofpironium bromide gel is effective in treating clozapine-induced hypersalivation in patients with treatment-resistant schizophrenia.