Response limit of standard 6 mg adenosine in paroxysmal supraventricular tachycardia

Objective To investigate the efficacy of the standard 6 mg initial dose of adenosine for paroxysmal supraventricular tachycardia (PSVT) and identify clinical and demographic predictors of treatment failure in the emergency department (ED). Methods This prospective observational study included 182 adult patients diagnosed with PSVT and treated with a 6–12–18 mg adenosine protocol. The primary outcome was successful conversion to sinus rhythm (SR) after the initial 6 mg dose. Multivariable logistic regression, with covariates selected a priori on clinical and pharmacological grounds, identified independent predictors. Results SR was restored with the initial 6 mg dose in 106 (58.2%) patients. Univariate analysis identified higher body weight, height, weight-adjusted adenosine dose, male gender, active smoking, and higher serum sodium and calcium as factors associated with failure. In the multivariable model, gender and serum calcium were independent predictors of success: female patients were 2.70 times more likely to achieve SR than males (OR: 2.699; 95% CI: 1.246–5.849; *p* = 0.012), while higher calcium was associated with lower success (OR: 0.458; 95% CI: 0.259–0.808; *p* = 0.007). Weight-adjusted dose was not independently predictive ( *p* = 0.281), with no difference between male responders and non-responders ( *p* = 0.834). Conclusion The conventional “one-size-fits-all” 6 mg dose is frequently inadequate, particularly for male patients, who appear to face a dose–response threshold not overcome by standard dosing. Serum calcium was independently associated with treatment success, consistent with recent reports. These findings support transitioning toward personalized, weight- or gender-stratified adenosine dosing in PSVT management.