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.

Caffeine vs Theophylline: what is the difference?

Theophylline is caffeine minus one methyl group, and theophylline also relaxes airway muscle strongly enough to have been a long-standing asthma medicine.

One methyl group apart.

CaffeineC8H10N4O2Highlighted: the extra methyl group and its nitrogen.

TheophyllineC7H8N4O2Highlighted: the same nitrogen, with a hydrogen instead.

Sources and notes

The sentence under the titlefrom sourceMoleculeFinder comparison notesThe pair's answer line.
The two drawingscomputedMoleculeFinder rule (RDKit MCS)Drawn the same way round on the skeleton they share; the amber marks where the two differ.
The captionfrom sourceMoleculeFinder curated
What is highlightedfrom sourceMoleculeFinder curatedOne line under each drawing, written from the atoms the amber marks.
Structural similaritycomputedRDKit Morgan/Tanimoto0.46 of 1, a Morgan fingerprint Tanimoto coefficient. It measures shape, not effect.

Side by side

	Caffeine	Theophylline
Molecular weightCalculated PubChem	194.19 g/molC8H10N4O2	180.16 g/molC7H8N4O2
Hydrogen-bond donorsCalculated PubChem	0	1
Half-life in the bodyEditorial MoleculeFinder curated	about 5 h	about 8 h
Where each turns upEditorial MoleculeFinder food and product lists	CoffeeAbout 95 mg per 8 oz cupNaturally present Energy drinksAbout 80 mg per 250 ml canAdded by the maker TeaAbout 47 mg per 8 oz cupNaturally present Soft drinksAdded by the maker Also on our chocolate and cocoa lists	CoffeeNaturally present TeaNaturally present CocoaNaturally present
FamilyEditorial MoleculeFinder curated	Plant alkaloids, Stimulants	Plant alkaloids, Stimulants
Everyday groupEditorial MoleculeFinder curated	Food & flavor	Plant
Hazard labelReported ECHA, EU CLP Regulation, Safe Work Australia via PubChem; ECHA, EU CLP Regulation, HSDB via PubChem	Warning	Danger
The supplier-filed hazard label's signal word, not a statement about ordinary use.
Oral LD50Measured HSDB via PubChem	192 mg/kgpure caffeine, rat, oral	332 mg/kgpure theophylline, mouse, oral
A single acute animal measure, here in two different species. It ranks nothing about human safety.

Sources and notes

Molecular weightcomputedPubChemComputed from the structure; the formula is under each weight.
Hydrogen-bond donorscomputedPubChemThe hydrogens on nitrogen or oxygen that each molecule can lend to a hydrogen bond, counted from its structure.
Half-life in the bodyfrom sourceMoleculeFinder curatedIn a typical adult: the time the body takes to clear half of it.
Where each turns upfrom sourceMoleculeFinder food and product listsEach amount is an editorial figure from our lists, not a measurement of any one product. Each mark is set by hand on the list, never inferred.
Familyfrom sourceMoleculeFinder curated
Everyday groupfrom sourceMoleculeFinder curated
Hazard labelfrom sourceECHA, EU CLP Regulation, Safe Work Australia via PubChem; ECHA, EU CLP Regulation, HSDB via PubChem
Oral LD50from sourceHSDB via PubChem
ECHAfrom sourceAttributionSource: European Chemicals Agency, echa.europa.eu.
EU CLP Regulationfrom sourceAttributionSource: EUR-Lex, Regulation (EC) No 1272/2008, © European Union.
Safe Work Australiafrom sourceAttributionSource: Safe Work Australia, Hazardous Chemical Information System, © Commonwealth of Australia, CC BY 4.0.
Identifiersfrom sourcePubChemPubChem CID 2519 (Caffeine) and 2153 (Theophylline).

In more detail

The formulas show that one 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 a standard asthma medicine for much of the twentieth century; caffeine's effect on the airways is weaker. 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.

Sources and notes

The paragraphfrom sourceMoleculeFinder comparison notes

Questions

What is the difference between Caffeine and Theophylline?: Theophylline is caffeine minus one methyl group, and theophylline also relaxes airway muscle strongly enough to have been a long-standing asthma medicine.
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.

Sources and notes

The answersfrom sourceMoleculeFinderThe first is the pair's answer line; the others are read off the table above.

Keep going

CaffeineIts structure, properties and sources, on its own page.TheophyllineIts structure, properties and sources, on its own page.CoffeeFollow caffeine from your cup to the sleepiness signal it blocks, then on to chocolate.