Efficacy of a 1% malic acid spray for xerostomia treatment: A systematic review and meta‐analysis

Objectives To assess the efficacy of topical sialogogue spray containing malic acid 1% for treating xerostomia. Methods We searched PubMed, Cochrane Library, Embase, ClinicalTrials.gov and Web of Science databases. Literature search, screening, study selection, data collection, data extraction and assessment of bias risk were independently conducted by two reviewers. The study appraisal was performed by Cochrane Collaboration's tool for assessing bias risk. The systematic review registration number was PROSPERO‐CRD42021241322. All statistical analyses were performed using Review Manager version 5.4. Results Five original articles involving 244 patients with xerostomia who received topical sialogogue spray (malic acid 1%) or placebo for two weeks were included in this review. Based on the questionnaire survey, the topical sialogogue spray (malic acid 1%) improved the symptoms of dry mouth significantly better than the placebo, which was reflected in the Dry Mouth Questionnaire (DMQ), Xerostomia Inventory (XI) and Visual Analogue Scale (VAS) scores. Regarding the increase in unstimulated and stimulated saliva flow rates, the intervention group was also better than the placebo group after a two‐week course of treatment. Conclusions Although the included studies are limited, our results show that topical sialogogue spray (malic acid 1%) is an effective method for the treatment of xerostomia. Additional randomised controlled trials in the future are needed to provide high‐quality evidence of this therapy and to improve clinical practice guidelines.