Orally dissolving pilocarpine tablets for xerostomia in advanced cancer: A pilot N-of-1 feasibility study

Background: Xerostomia is a common and difficult symptom experienced by patients with cancer. Pilocarpine is a cholinergic agent that stimulates salivation.

Aim: To assess the feasibility of conducting a N-of-1 trial to determine the efficacy of pilocarpine orally dissolving tablets in patients with xerostomia.

Design: Double-blind, crossover, placebo-controlled N-of-1 trials of 5 mg pilocarpine tablets vs placebo. Each trial consisted of three 6-day cycles containing pilocarpine (3 days) and placebo (3 days) in random order.

Setting/participants: Participants with advanced cancer and xerostomia (scoring >3 on an 11-point numerical rating scale) from any cause, were recruited from an inpatient and outpatient palliative care unit in Brisbane, Australia.

Results: Eighteen people were recruited in 17 months. Nine withdrew, seven before or during the first 4 days. Three withdrew due to unacceptable side effects. Two participants met the definition of response (⩾2 point reduction in mean scores active vs placebo cycles). When assessing individual cycles, 15 out of 27 cycles (56%) met the definition of response. More people reported at least one mild episode during pilocarpine than placebo of nausea (6 vs 3), vomiting (3 vs 0) and sweating (3 vs 2). About 48% of adverse event classifications were reported in placebo cycles only.

Conclusion: Recruitment to an N-of-1 trial for xerostomia is feasible but attrition was high (50%). Early dropout may have been due to the trial length, complexity, appropriateness or number of questionnaires. Adverse events were generally mild. Two of 10 participants were considered to have benefited from pilocarpine warranting ongoing treatment.