Naloxone vs Naltrexone: what is the difference?
Naloxone reverses an opioid overdose within minutes, while naltrexone survives the gut and lasts many hours; both block the same opioid receptor.
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; 5 atoms differ, too many to mark as one group.
- Structural similaritycomputedRDKit Morgan/Tanimoto0.75 of 1, a Morgan fingerprint Tanimoto coefficient. It measures shape, not effect.
Side by side
| Naloxone | Naltrexone | |
|---|---|---|
| Molecular weightCalculated PubChem | 327.4 g/molC19H21NO4 | 341.4 g/molC20H23NO4 |
| Hydrogen-bond donorsCalculated PubChem | 2 | 2 |
| FamilyEditorial MoleculeFinder curated | Opioid antagonist | Opioid antagonist |
| Everyday groupEditorial MoleculeFinder curated | OTC medicine | Prescription medicine |
| Chemical groupsCalculated Found by rule (RDKit) | Alcohols, Aromatics, Ketones, Phenols, Ethers | Alcohols, Aromatics, Ketones, Phenols, Ethers |
| Hazard labelReported ECHA via PubChem; ECHA, HSDB via PubChem | Danger | Danger |
| The supplier-filed hazard label's signal word, not a statement about ordinary use. | ||
| LD50Measured HSDB via PubChem | 90 mg/kgpure naloxone, mouse, intravenous | 1,450 mg/kgpure naltrexone, rat, 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.
- 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; ECHA, HSDB via PubChem
- LD50from sourceHSDB via PubChem
- ECHAfrom sourceAttributionSource: European Chemicals Agency, echa.europa.eu.
- Identifiersfrom sourcePubChemPubChem CID 5284596 (Naloxone) and 5360515 (Naltrexone).
In more detail
These two are constantly confused, they differ by one small chemical group, and what they are used for could hardly be less alike. Both are opioid antagonists: they occupy the mu-opioid receptor and switch nothing on, which displaces any opioid already there. Naloxone is poorly absorbed by mouth and acts within minutes when injected or sprayed into the nose, which is why it is the overdose reversal agent carried in emergency kits. Naltrexone survives the gut, lasts many hours, and is used to maintain a blocked receptor over time rather than to rescue anyone in an emergency. The structural difference is an allyl group on naloxone against a cyclopropylmethyl group on naltrexone, and the weights are 327.4 and 341.4.
Sources and notes
- The paragraphfrom sourceMoleculeFinder comparison notes
Questions
- What is the difference between Naloxone and Naltrexone?
- Naloxone reverses an opioid overdose within minutes, while naltrexone survives the gut and lasts many hours; both block the same opioid receptor.
- Is Naloxone bigger than Naltrexone?
- Naltrexone is the heavier molecule, 341.4 g/mol against 327.4 g/mol for Naloxone. Naloxone is C19H21NO4 and Naltrexone is C20H23NO4.
Sources and notes
- The answersfrom sourceMoleculeFinderThe first is the pair's answer line; the others are read off the table above.