Oral pilocarpine: a review of its pharmacological properties and clinical potential in xerostomia

Abstract

Pilocarpine is a cholinergic agonist which stimulates salivary secretion both in individuals with normal salivary gland function and in those with impaired salivary flow (xerostomia or oral dryness). A rapid increase in salivary flow rate is observed following oral pilocarpine administration and peak levels are maintained for at least 1 to 2 hours. Mean salivary flow rates after administration of pilocarpine are 2- to 10-fold higher than after placebo, and no evidence of tolerance to the pharmacological effects of the drug has been observed during prolonged administration for up to 5 months. The clinical efficacy of oral pilocarpine in relieving symptoms of xerostomia (resulting from radiation therapy to the head and neck region or salivary gland dysfunction), including oral dryness and difficulty in chewing, swallowing and speaking, has been demonstrated in double-blind placebo-controlled clinical trials. In these studies, pilocarpine 5 to 10mg 3 times daily increased salivary flow and improved symptoms of xerostomia in a significantly higher percentage of patients than did placebo (54 versus 25% in one study). Preliminary findings indicate that administration of pilocarpine during radiation therapy may reduce the severity of xerostomia; however, this requires further investigation. The majority of patients receiving oral pilocarpine therapy for xerostomia experience adverse events (most commonly sweating); however, these are generally mild and tolerable in nature. Thus, pilocarpine is an effective agent for the treatment of xerostomia, increasing salivary flow and reducing symptom severity to a significantly greater extent than placebo. Further clinical trials should evaluate the potential beneficial effects of pilocarpine on the incidence of dental caries and oral candidiasis during prolonged therapy, its prophylactic efficacy during radiation therapy and its efficacy relative to that of other salivary stimulants.