Comparative Analysis of L-Carnitine and Coenzyme Q10 Adverse Reaction Reports Using the EudraVigilance Database: Implications for Health and Sports Supplementation

Background/Objectives: L-carnitine and Coenzyme Q10 (CoQ10) are widely used in health and sports supplementation settings to improve energy metabolism, reduce fatigue, and support recovery. Although generally perceived as safe, their safety profiles are mainly based on pre-marketing studies and selected clinical populations, while real-world pharmacovigilance evidence remains limited. This study aimed to evaluate and compare the adverse drug reaction (ADR) reporting patterns associated with L-carnitine and CoQ10 using the EudraVigilance database. Methods: A retrospective pharmacovigilance analysis was conducted using spontaneous individual case safety reports (ICSRs) retrieved from the EudraVigilance database. ADRs associated with L-carnitine and CoQ10 were analyzed and compared at the System Organ Class (SOC) level. Disproportionality analyses were performed using the reporting odds ratio (ROR) and proportional reporting ratio (PRR). Results: A total of 257 ICSRs for L-carnitine and 271 for CoQ10 were identified. Serious cases accounted for 34.2% of L-carnitine reports and 74.5% of CoQ10 reports. For L-carnitine, the most frequently reported SOC categories were gastrointestinal disorders, skin and subcutaneous tissue disorders, general disorders and administration site conditions, and nervous system disorders. For CoQ10, the most commonly reported SOC categories were general disorders and administration site conditions, nervous system disorders, investigations, and gastrointestinal disorders. Comparative disproportionality analysis showed higher reporting frequencies for CoQ10 in blood and lymphatic system disorders (ROR 3.04; PRR 2.99), musculoskeletal and connective tissue disorders (ROR 2.63; PRR 2.52). Conclusions: Real-world pharmacovigilance data suggest partially different ADR reporting patterns for L-carnitine and CoQ10 compared with those described in pre-marketing studies. CoQ10 was associated with a higher proportion of serious reports and greater disproportionality signals for selected SOC categories; however, these findings should be interpreted cautiously, as reporting patterns may be influenced by reporting bias, comorbidities, concomitant therapies, and differences in the populations using these compounds. Continuous pharmacovigilance monitoring and periodic reassessment of their benefit–risk profile remain essential given their widespread use in health and sports supplementation settings.