Xanthines

There are three main xanthine derivatives. Theophylline and aminophylline are methylxanthines once widely used for the treatment of asthma, but now less commonly so. Caffeine is a trimethylxanthine closely related to theophylline. And theobromine, which is a plant extract.

The exact mechanism of toxicity is not known.

Theophylline

• inhibits phosphodiesterase at high levels, increasing intracellular cyclic adenosine monophosphate (cAMP).
• releases endogenous catecholamines
• stimulates beta-adrenergic receptors.
• And is an antagonist of adenosine receptors.

Caffeine

• acts primarily through inhibition of the adenosine receptor.
• In addition, with overdose there is beta-1 and beta-2 adrenergic stimulation secondary to release of endogenous catecholamines.

Shannon M, Amitai Y, Lovejoy FH Jr. Multiple dose activated charcoal for theophylline poisoning in young infants. Pediatrics 1987;80(3):368-70 PMID3627887
Henderson A, Wright DM, Pond SM. Management of theophylline overdose patients in the intensive care unit. Anaesth Intensive Care 1992;20(1):56-62 PMID1609943