Theophylline Interactions

Caffeine and theophylline are closely related methylxanthines that share the CYP1A2 metabolic pathway and act on the same adenosine receptors. Taking them together can slow theophylline clearance and add to its stimulant and cardiovascular effects, which matters because theophylline has a very narrow safety margin.

Combustion products in tobacco smoke induce the liver enzyme CYP1A2, speeding up how fast the body clears theophylline. Smokers therefore tend to need more theophylline to stay in range, and stopping smoking can reverse this within days and push levels into a toxic range unless the dose is reviewed.