Out of several treatments tested, the drug pilocarpine gave the most significant improvement in dry mouth following radiotherapy for head and neck cancer. Less dry mouth and increased salivary flow were twice as likely after taking pilocarpine than after a dummy pill.
Dry mouth from radiotherapy impairs quality of life. Although people can try simple measures at home, such as sucking ice cubes, they may wish to discuss pilocarpine treatment with their GP. Side effects from this medication are usually short-lived but if they are troublesome other options are available, though not supported by such good evidence as pilocarpine.
Why was this study needed?
Every day in the UK, 31 people are diagnosed with a type of head and neck cancer. Radiotherapy, a common treatment, often causes dry mouth. This can lead to mouth discomfort, a change in taste, dental disease and problems speaking, chewing and swallowing.
Several treatments are available. Chewing gum and sucking sweets or ice are thought to stimulate saliva production. Artificial saliva can be given as a lozenge, spray or gel. Drugs, such as pilocarpine, have been available to stimulate saliva production for many years but can cause side effects including sweating, blurred vision and nausea.
This review aimed to systematically compare all available treatments for a dry mouth and reduced salivation after radiotherapy for head and neck cancer.
What did this study do?
This systematic review included 20 randomised controlled trials, three from the UK. Trials compared treatments with each other or a placebo among 1,732 adults with a dry mouth after radiotherapy. Interventions replaced or aimed to stimulate saliva production. They included mouth gels, toothpaste, acupuncture, laser therapy, herbal compounds, artificial saliva and two drugs – pilocarpine and cevimeline.
The trials of drugs were of high quality so we can be confident in these results. However, the trials of non-drug treatments had a high risk of certain bias because the person and assessor knew which treatment they were having. They were also mostly small trials of between 20 and 38 participants, so conclusions from these should be treated with caution.
What did it find?
- People taking a pilocarpine tablet were twice as likely to have an improvement in sensation of a dry mouth. Defined as 25mm or more on a visual analogue scale from 0 to 100mm. This level of improvement was reported by 63/140 people (45%) on pilocarpine compared to 36/140 people (26%) on placebo, (odds ratio [OR] 2.37, 95% confidence interval [CI] 1.43 to 3.94, two trials).
- There was also an improvement in salivary flow 60 minutes after taking oral pilocarpine for 89/129 people (69%) compared to 65/132 people (49%) on placebo, (OR 2.27, 95% CI 1.37 to 3.76, two trials).
- Acupuncture did not increase salivary flow rate (mean difference 0.00, 95% CI ‑0.02 to 0.03). However, these trials were small with a total of 50 participants.
- There was insufficient evidence on the effect of biotene gel, toothpaste, mouthcare systems, herbal medicine, humidifiers or laser therapy.
What does current guidance say on this issue?
Guidelines from the British Association of Head and Neck Oncologists (2016) state that pilocarpine may be offered as one option to improve radiation-induced dry mouth following radiotherapy to people with evidence of some intact salivary function. The recommended dose is 5 to 10mg per day.
What are the implications?
In recent years radiotherapy has been better targeted, and lower doses have been used, however, dry mouth is still an unpleasant and common side effect of treatment to the head and neck.
Pilocarpine remains an option in the treatment for persistent dry mouth after radiotherapy.
Though there was no robust evidence of the effectiveness of the other interventions, this does not mean that they aren’t useful. Given the limited number trial on these options, it is possible that they may still be worth trying. Some simple measures, like sucking ice or using saliva substitutes might be more appropriate for milder symptoms.
Citation and Funding
Mercadante V, Al Hamad A, Lodi G, et al. Interventions for the management of radiotherapy-induced xerostomia and hyposalivation: A systematic review and meta-analysis. Oral Oncol. 2017;66:64-74.
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
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