(1) Dry mouth (
xerostomia) is a frequent complication of
radiation therapy for
cancers of the ear nose and throat. Local measures such as saliva substitutes and
anetholtrithione are either moderately effective, inadequately evaluated or little better than placebo. (2) Marketing authorization has been granted in France for an oral formulation of
pilocarpine, an old parasympathomimetic agent, in the treatment of
radiotherapy-induced
xerostomia. (3) According to the results of two double-blind trials,
pilocarpine (15-30 mg/day) improves symptoms in about 50 % of patients, compared to improvement in 25% of patients taking placebo. The
drug is slow to take effect and has little impact on daily life. It is not known whether
pilocarpine helps prevent the complications of
xerostomia. (4) Most adverse effects of
pilocarpine are due to its
parasympathomimetic effects, such as sweating, urinary frequency,
flushing,
rhinitis and
nausea.
Pilocarpine must therefore be used with caution in patients with
asthma, cardiac arrhythmia,
iridocyclitis, and
closed-angle glaucoma. (5) In France, this
pilocarpine formulation costs 18 times more than a preparation of
pilocarpine 2%
eye drops used orally (off licence). (6) In practice, patients needing symptomatic treatment of
xerostomia after
radiotherapy may benefit from oral
pilocarpine but, given its limited efficacy and its adverse effects, other local treatments should be tried first.