Morphine vs Fentanyl: what is the difference?
Morphine and fentanyl bind the same opioid receptor, but synthetic fentanyl reaches the brain in minutes and acts at a small fraction of the amount.
Sources and notes
- The sentence under the titlefrom sourceMoleculeFinder comparison notesThe pair's answer line.
- The two drawingscomputedMoleculeFinder rule (RDKit MCS)Each molecule's own drawing, as its page shows it. The common core, 7 of 25 atoms, is too small to align on.
Side by side
| Morphine | Fentanyl | |
|---|---|---|
| Molecular weightCalculated PubChem | 285.34 g/molC17H19NO3 | 336.5 g/molC22H28N2O |
| Hydrogen-bond donorsCalculated PubChem | 2 | 0 |
| FamilyEditorial MoleculeFinder curated | Opioids, Non-opioid painkillers | Opioids |
| Everyday groupEditorial MoleculeFinder curated | Prescription medicine | Prescription medicine |
| Chemical groupsCalculated Found by rule (RDKit) | Alcohols, Aromatics, Phenols, Ethers | Aromatics, Amides |
| Hazard labelReported ECHA via PubChem | Warning | Danger |
| The supplier-filed hazard label's signal word, not a statement about ordinary use. | ||
| Oral LD50Measured HSDB via PubChem | 335 mg/kgpure morphine, rat, oral | 18 mg/kgpure fentanyl, rat, oral |
| A single acute animal measure. 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
- Oral LD50from sourceHSDB via PubChem
- ECHAfrom sourceAttributionSource: European Chemicals Agency, echa.europa.eu.
- Identifiersfrom sourcePubChemPubChem CID 5288826 (Morphine) and 3345 (Fentanyl).
In more detail
The receptor is the mu-opioid receptor, and the enormous difference between them is how tightly and how easily they get there. Morphine is the natural alkaloid isolated from opium poppy in 1804, a rigid five-ring structure with two hydroxyl groups that make it relatively water-loving and slow to cross into the brain. Fentanyl is fully synthetic, much smaller in ring count, and far more fat-soluble, so it reaches the brain in minutes and acts at a small fraction of the amount. The reported oral LD50 values sit at 335 mg/kg in rats for morphine and 18 mg/kg in rats for fentanyl, a ratio that understates the difference in potency at ordinary exposures. That potency gap is the reason fentanyl dominates overdose statistics: the margin between a working amount and a fatal one is measured in units a kitchen scale cannot see.
Sources and notes
- The paragraphfrom sourceMoleculeFinder comparison notes
Questions
- What is the difference between Morphine and Fentanyl?
- Morphine and fentanyl bind the same opioid receptor, but synthetic fentanyl reaches the brain in minutes and acts at a small fraction of the amount.
- Is Morphine bigger than Fentanyl?
- Fentanyl is the heavier molecule, 336.5 g/mol against 285.34 g/mol for Morphine. Morphine is C17H19NO3 and Fentanyl is C22H28N2O.
- Which has the lower reported LD50, Morphine or Fentanyl?
- Fentanyl, at 18 mg/kg (oral, rat), against 335 mg/kg (oral, rat) for Morphine. 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.