Radiation-induced hyposalivation and its treatment with oral pilocarpine

The aim of this study was to determine the effects of radiation on the secretion of saliva from mucous salivary glands in comparison with serous salivary glands.

The minor salivary glands of the palate were used as an example of mucous glands, while the parotid glands were used as an example of a serous secretion organ. Serial flow rate measurements of the parotid and palatal glands were taken over a period of approximately 9 months in 13 patients who suffered from malignancies of the head and neck region. Twelve patients consented to take part in a second study in which salivary flow was stimulated by oral pilocarpine before and at the conclusion of radiotherapy and 7 months later. Complaints and symptoms were recorded at each time of measurement.

After radiotherapy, the secretory performance of the parotid glands dropped off rapidly and irreversibly. Salivary secretion from the palatal glands was not totally diminished as a result of radiation. Clinical complaints and histologic findings indicate a serious alteration of the tissues irradiated; however, residual secretion from the remaining parenchyma of the mucous glands still remains. Pilocarpine produced a clinically significant increase of salivary flow from the palatal glands before and 7 months after radiation. Secretory performance of the parotid glands could not be sufficiently increased by stimulation with pilocarpine after radiotherapy. Clinical side effects and risks for the treatment of symptomatic postradiation xerostomia with pilocarpine were minimal.

These findings emphasize the greater resistance and recoverability of the mucous secreting minor palatal glands in comparison with the serous secreting parotid glands. They also indicate the significant postradiation ability of the mucous secreting glands to be stimulated by pilocarpine.