Testing the effectiveness of pilocarpine drops for dry mouth in advanced cancer using aggregated n-of-1 trials: a pilot study

Abstract

Purpose : Dry mouth is a common and troublesome symptom in palliative care. Pilocarpine is a cholinergic agent that promotes salivation. We aimed to test the effectiveness of pilocarpine drops compared to placebo, for participants with advanced cancer, who experienced dry mouth.

Method : Aggregated n-of-1 trials for patients of specialist palliative care services with advanced cancer assessed as having a dry mouth. Each participant was offered three cycles of pilocarpine drops 4%, 6 mg tds (3 days) and placebo drops (3 days) in random order. Patients self-completed a diary using validated symptom and quality of life scores. The randomisation order was unmasked at the end of each person’s trial by a clinician independent of the trial to allow a treatment decision for individual patients to be made.

Results : Twenty people were recruited to this pilot study, of whom five completed the planned three cycles; 36 cycles of data were completed in total. 438 doses of pilocarpine were administered. Most withdrawals related to deteriorating condition, unacceptable toxicity, non-compliance with study procedures or withdrawal of consent. Overall, no clinical difference in relief of dry mouth was noted on two measures of dry mouth, and an oral health related quality of life scale.

Conclusion : The formulation of pilocarpine drops proved unacceptable to most participants. More work is required to determine an appropriate dose and method of delivery, then a retest of pilocarpine drops for this symptom.