Overdose and treatment: Over dosage would cause severe hypotension, bradycardia or asystole. The half-life of adenosine in blood is very short (< 10 seconds), and side effects (when they occur) would quickly resolve. Administration of IV aminophylline or theophylline may be needed. Pharmacokinetic evaluation indicates that methyl xanthines are competitive antagonists to adenosine and that therapeutic concentrations of theophylline block its exogenous effects.