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Opioids
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Classification
Classification by receptor affinity
- Opioid Agonists - Morphine, Codeine, Meperidine, Fentanyl, Sufentanil, Remifentanil, Methadone, Tramadol
- Opioid Agonist/Antagonists & Partial Agonists - Pentazocine, Nalbuphine, Butorphanol, Buprenorphine
- Opioid Antagonists - Nalorphine, Naloxone, Naltrexone, Naltrindole, Nalmefene
Classification by Exogenous Opioids Strength
According to the strength or potency based on the plasma concentrations at which they exert their effects. C50 or the plasma concentration causing a 50% effect.
- Strong Opioids include fentanyl, sufentanil, and remifentanil
- Weak opioids include codeine and tramadol
- Intermediate group includes morphine, methadone, oxycodone, and buprenorphine
Classification by synthetic process
- Naturally occurring compounds - Morphine, Codeine, Thebaine, Papaverine
- Semi-synthetic compounds - Diamorphine (heroin), Dihydromorphone, Buprenorphine, Oxycodone
- Synthetic compounds - Pethidine, Fentanyl, Methadone, Alfentanil, Remifentanil, Tapentadol
Pharmacology
| Mu | Delta | Kappa | |
| Mu1 - Analgesia
Mu2 - Sedation, vomiting, respiratory depression, pruritis, euphoria, anorexia, urinary retention, physical dependence. |
Analgesia, spinal analgesia | Analgesia, sedation, dyspnoea, psychomimetic effects, miosis, respiratory depression, euphoria, dysphoria, dyspnoea | |
| Endogenous Peptides | |||
|---|---|---|---|
| Enkephalins | Agonist | Agonist | |
| B-Endorphin | Agonist | Agonist | |
| Dynorphin A | Agonist | Agonist | |
| Agonists | |||
| Morphine | Agonist | Weak Agonist | |
| Codeine | Weak Agonist | Weak Agonist | |
| Fentanyl | Agonist | ||
| Meperidine | Agonist | Agonist | |
| Methadone | Agonist | ||
| Antagonists | |||
| Naloxone | Antagonist | Weak Antagonist | Antagonist |
| Naltrexone | Antagonist | Weak Antagonist | Antagonist |
