Diphenhydramine vs Cetirizine: what is the difference?
Diphenhydramine is a first generation antihistamine that reaches the brain and causes drowsiness, while cetirizine mostly stays out and sedates far less.
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. Aligned; 20 atoms differ, too many to mark as one group.
Side by side
| Diphenhydramine | Cetirizine | |
|---|---|---|
| Molecular weightCalculated PubChem | 255.35 g/molC17H21NO | 388.9 g/molC21H25ClN2O3 |
| Hydrogen-bond donorsCalculated PubChem | 0 | 1 |
| Where each turns upEditorial MoleculeFinder food and product lists |
| Not on our lists |
| Also sold asEditorial MoleculeFinder curated | Benadryl, ZzzQuil, Sominex | Zyrtec |
| FamilyEditorial MoleculeFinder curated | Over-the-counter medicines | Over-the-counter medicines |
| Everyday groupEditorial MoleculeFinder curated | OTC medicine | OTC medicine |
| Chemical groupsCalculated Found by rule (RDKit) | Aromatics, Ethers | Carboxylic Acids, Aromatics, Ethers, Halogenated |
| Hazard labelReported ECHA via PubChem | Warning | Warning |
| The supplier-filed hazard label's signal word, not a statement about ordinary use. | ||
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.
- 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.
- Also sold asfrom sourceMoleculeFinder curated
- Familyfrom sourceMoleculeFinder curated
- Everyday groupfrom sourceMoleculeFinder curated
- Chemical groupscomputedFound by rule (RDKit)Each group is found in the structure by a chemical pattern.
- Hazard labelfrom sourceECHA via PubChem
- ECHAfrom sourceAttributionSource: European Chemicals Agency, echa.europa.eu.
- Identifiersfrom sourcePubChemPubChem CID 3100 (Diphenhydramine) and 2678 (Cetirizine).
In more detail
These are the first and second generation antihistamines. Both block the H1 histamine receptor, which is what stops the itching and sneezing of an allergic response. Diphenhydramine is small and fat-soluble enough to cross the blood-brain barrier freely, which is why it causes strong drowsiness and why it is sold as a sleep aid as well as an allergy medicine. Cetirizine carries a carboxylic acid that keeps it largely out of the brain, so it is much less sedating while blocking the same receptor in the body. Cetirizine also lasts far longer, which is why it is a once-daily product and diphenhydramine is not.
Sources and notes
- The paragraphfrom sourceMoleculeFinder comparison notes
Questions
- What is the difference between Diphenhydramine and Cetirizine?
- Diphenhydramine is a first generation antihistamine that reaches the brain and causes drowsiness, while cetirizine mostly stays out and sedates far less.
- Is Diphenhydramine bigger than Cetirizine?
- Cetirizine is the heavier molecule, 388.9 g/mol against 255.35 g/mol for Diphenhydramine. Diphenhydramine is C17H21NO and Cetirizine is C21H25ClN2O3.
Sources and notes
- The answersfrom sourceMoleculeFinderThe first is the pair's answer line; the others are read off the table above.