Comparison of gargling and swabbing methods for delivering pre-procedural povidone-iodine mouthrinse: a randomised crossover trial

Povidone-iodine (PVP-I) mouthrinse is widely used as a pre-procedural antiseptic because of its broad-spectrum antimicrobial activity. Its effectiveness depends on maintaining sufficient iodine levels in saliva, enabling direct antimicrobial action within the oral cavity. However, the conventional gargling method may not be suitable for individuals with swallowing difficulties, limiting its practical application. This study aimed to compare salivary iodine concentrations achieved by two delivery methods—gargling and swabbing—using 0.2% PVP-I mouthrinse at specific post-application time intervals. A randomized crossover clinical trial was conducted in 25 healthy Thai adults aged 18–30 years. Participants received either gargling with 10 mL of 0.2% PVP-I or swabbing with 2 mL of 0.2% PVP-I for 1 min, followed by a 48-hour washout period before crossing over to the alternate intervention. Unstimulated saliva samples were collected at baseline and at 0, 5, 10, 20, 30, 60, and 120 min after mouthrinse application. Iodine concentrations were determined using inductively coupled plasma–mass spectrometry (ICP-MS). Differences in salivary iodine levels were analyzed using analysis of covariance (ANCOVA), with statistical significance set at p < 0.05. Baseline salivary iodine concentrations did not differ significantly between interventions (p = 0.579). Gargling produced significantly higher peak iodine concentrations than swabbing (2,774 ppm vs. 1,061 ppm; p < 0.001). Salivary iodine levels declined significantly over the first 20 min in both groups (p < 0.001), followed by similar clearance patterns over time. Throughout the 120-minute observation period, iodine concentrations achieved by both delivery methods remained above the the U.S. Centers for Disease Control and Prevention (CDC)-recommended threshold for viral inactivation (75–150 ppm). Both gargling and swabbing with 0.2% PVP-I resulted in immediate peak salivary iodine concentrations exceeding the CDC-recommended threshold for viral inactivation. While gargling achieved higher peak levels, swabbing maintained iodine concentrations above this threshold for the duration of observation. These findings suggest that swabbing may represent a feasible alternative delivery method in situations where gargling is not practical. Further studies evaluating direct antimicrobial outcomes and broader patient populations are warranted to clarify clinical effectiveness. ClinicalTrials.gov, NCT06272019. Registered on February 22, 2024.