What is the adverse effect of rapid intravenous administration of theophylline?

Rapid intravenous administration of theophylline is associated with cardiac arrhythmias due to the drug's pharmacological effects on the cardiovascular system. Theophylline is a methylxanthine that acts as a bronchodilator but can also stimulate the central nervous system and heart. When administered too quickly, it can lead to increased heart rate, palpitations, and disturbances in cardiac rhythm. This risk is particularly significant in patients with underlying heart conditions or those on other medications that affect cardiac function.

Other effects such as nausea, headaches, and hypotension may occur as well, but they are typically not as directly linked to the pace of administration as cardiac arrhythmias. These side effects can arise from the overall pharmacological effects of theophylline and its dose but are less critical and severe than the risk of arrhythmias that can result from rapid infusion. Thus, cardiac arrhythmias represent the most dangerous and concerning adverse effect in this context.