RESUMO
INTRODUCTION: Use of kratom has outpaced systematic study of its effects, with most studies reliant on retrospective self-report. METHODS: We aimed to assess acute effects following kratom use in adults who use regularly, and quantify alkaloids in the products, urine, and plasma. Between July and November 2022, 10 adults came to our clinic and orally self-administered their typical kratom dose; blinding procedures were not used. Physiological measures included blood pressure, respiratory rate, heart rate, pulse oximetry, temperature, and pupil diameter. Subjective outcomes included Subjective Opioid Withdrawal Scale, Addiction Research Center Inventory, and Drug Effects Questionnaire. Psychomotor performance was also assessed. RESULTS: Participants were 6 men and 4 women, mean age 41.2 years. Nine were non-Hispanic White; 1 was biracial. They had used kratom for 6.6 years (SD, 3.8 years) on average (2.0-14.1). Sessions were 190.89 minutes on average (SD, 15.10 minutes). Mean session dose was 5.16 g (median, 4.38 g; range, 1.1-10.9 g) leaf powder. Relative to baseline, physiological changes were minor. However, pupil diameter decreased (right, b = -0.70, P < 0.01; left, b = -0.73, P < 0.01) 40-80 minutes postdose and remained below baseline >160 minutes. Subjective Opioid Withdrawal Scale pre-dosing was mild (5.5 ± 3.3) and decreased postdose (b = [-4.0, -2.9], P < 0.01). Drug Effects Questionnaire "feeling effects" increased to 40/100 (SD, 30.5) within 40 minutes and remained above baseline 80 to 120 minutes (b = 19.0, P = 0.04), peaking at 72.7/100; 6 participants rated euphoria as mild on the Addiction Research Center Inventory Morphine-Benzedrine-scale. Psychomotor performance did not reliably improve or deteriorate postdosing. CONCLUSIONS: Among regular consumers, we found few clinically significant differences pre- and post-kratom dosing. Alkaloidal contents in products were within expected ranges.