Caffeine vs Theophylline: what is the difference?

How they differ

Theophylline is caffeine minus one methyl group, C7H8N4O2 against C8H10N4O2, and the two sit in the same alkaloid family for that reason. Both block adenosine, but theophylline also relaxes airway muscle strongly enough that it was used as an asthma medicine for most of the twentieth century, which caffeine never was. It stays in the body longer, a half-life near 8 hours against caffeine's 5. Tea carries both, with caffeine dominant and theophylline in traces, so a cup does not deliver a medicinal amount of either. Their reported oral LD50 values are close, 192 mg/kg in rats for caffeine and 332 mg/kg in mice for theophylline, which is a reminder that the gap between the two is about what they do rather than about how toxic they are.

Side by side

Structural similarity 0.46 of 1, computed as a Morgan fingerprint Tanimoto coefficient. It measures shape, not effect.

Common questions

What is the difference between Caffeine and Theophylline?

Theophylline is caffeine minus one methyl group, C7H8N4O2 against C8H10N4O2, and the two sit in the same alkaloid family for that reason. Both block adenosine, but theophylline also relaxes airway muscle strongly enough that it was used as an asthma medicine for most of the twentieth century, which caffeine never was. It stays in the body longer, a half-life near 8 hours against caffeine's 5.

Is Caffeine bigger than Theophylline?

Caffeine is the heavier molecule, 194.19 g/mol against 180.16 g/mol for Theophylline. Caffeine is C8H10N4O2 and Theophylline is C7H8N4O2.

Which has the lower reported LD50, Caffeine or Theophylline?

Caffeine, at 192 mg/kg (oral, rat), against 332 mg/kg (oral, mouse) for Theophylline. An LD50 is one acute animal measurement, and the two here were not necessarily measured in the same species, so it is a data point rather than a ranking of how dangerous either is to a person.