guarana + caffeine medications
Guarana seeds contain roughly 2-4 times the caffeine concentration of coffee beans, and the caffeine in guarana adds directly to any caffeine-containing medication (e.g., Excedrin, Fioricet, Cafergot, Anacin, Esgic, NoDoz, Vivarin). The combined caffeine load can exceed safe single-dose thresholds, producing tachycardia, hypertension, jitteriness, GI upset, and insomnia.