Efficacy of combined administration of Baekhogainsam-Tang and low-dose pilocarpine on frequent intractable xerostomia: Study protocol for a randomized controlled trial.

Background: Intractable xerostomia is defined as the subjective perception of dry mouth and persistent salivary gland hypofunction. Pilocarpine is an approved salivary sialagogue that is frequently prescribed for the treatment of intractable xerostomia; however, it often exhibits more side effects at high-doses and limited effectiveness at low-doses. Baekhogainsam-Tang (BIT) is a common herbal formula used by patients complaining of sore throats and thirst. It seems that BIT can compensate for the insufficient effect of low-dose pilocarpine. However, no clinical trials have studied the efficacy of combined administration of BIT and low-dose pilocarpine for intractable xerostomia. We aim to assess the non-inferior efficacy and fewer side effects of combined administration of BIT and low-dose pilocarpine compared with the administration of high-dose pilocarpine.

Methods: A randomized, open-label, parallel-group, multi-center trial will be conducted. A total of 120 patients with Sjogren's syndrome having an unstimulated salivary flow rate (SFR) ≤0.1 mL/min or who have undergone radiotherapy to the head and neck with an unstimulated SFR ≤0.25 mL/min will be recruited competitively. They will be randomly allocated to either the experimental or control groups. The experimental group will receive BIT herbal granules three times and pilocarpine (2.5-mg) four times daily; meanwhile, the control group will receive only 5-mg pilocarpine four times daily for 12 weeks. The primary outcome is unstimulated SFR after 12 weeks of treatment. Secondary outcomes are stimulated SFR after 12 weeks of medication, as well as differences and mean percentage changes in unstimulated and stimulated SFR, visual analog scale, salivary scintigraphy, and questionnaires for both oral symptoms and quality of life during the clinical trial. An independent T test or Mann-Whitney U test will be performed to compare values between the two groups. The Paired T test or Wilcoxon signed-rank test will be performed to compare intragroup continuous values.

Conclusion: This trial will be significant evidence on the efficacy and safety of combined use of BIT and low-dose pilocarpine to treat intractable xerostomia.

Clinical Trial Registration: The Clinical Research Information Service of the Republic of Korea (ISRCTN, KCT0005982). Registered on 10 February 2021.