RESUMO
Background and Purpose: Sphenopalatine ganglion (SPG) electrical stimulation has been studied in the setting of acute ischemic stroke to enhance collateral flow. Capsaicin poses an alternative to chemically stimulate the sphenopalatine ganglion. Therefore, the objective of this study was to determine the safety and effect of increasing doses of capsaicin upon serial transcranial Doppler markers of cerebral blood flow. Methods: We performed serial transcranial Doppler testing in 30 healthy volunteers divided into 5 equal groups. Capsaicin doses ranged from 33 to 165 µMol. We recorded peak systolic and end-diastolic velocities in the middle cerebral artery, arterial pressure, and perceived pungency in 5-minute intervals up to 20 minutes. We then calculated the mean velocity, the pulsatility index, and the cerebral blood flow index. Results: The participants' median age was 21 years (range, 5 years); all reported consumption of capsaicin in their diets. After and during the study, none reported side effects. Perceived pungency peaked at 5 minutes, and by the 20-minute mark, none perceived any pungency. All the tested doses produced the same pattern, consisting of augmentation of the middle cerebral artery mean velocity with the pulsatility index's diminution. The effects peaked between the 5- and the 10-minute measurements and then returned to basal levels except for the 66-µMol doses, which produced a sustained effect. We found no correlation between perceived pungency and dose, but the middle cerebral artery mean velocity was strongly correlated with the dose administered. Conclusions: This study provides evidence supporting the safety and tolerability of oral capsaicin in a population of healthy volunteers. Capsaicin appears to produce effects similar to those of sphenopalatine ganglion electrical stimulation. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT04545892.
