Table 1.
Classification, Potency, and Characteristics of Opioids and Opioid Antagonists
| Opioid | Type | Morphine 10 mg SC Equivalence | Comments |
|---|---|---|---|
| Naturally derived | |||
| Codeine | Agonist | 60 orally | Prodrug of morphine |
| Morphine | Agonist | 10 SC or IM | |
| Semisynthetic | |||
| Hydrocodone | Agonist | 1 IM, 2 orally | |
| Hydromorphone | Agonist | 1.3 SC | |
| Oxycodone | Agonist | 5 orally | |
| Oxymorphone | Agonist | 1 SC | |
| Naloxone | Antagonist | Nonanalgesic | Short-acting antagonist (0.5 h) |
| Naltrexone | Antagonist | Nonanalgesic | Very-long-acting antagonist (24 h) |
| Buprenorphine | Partial agonist | 0.3 IM | Medication-assisted therapy requires 6-16 mg/d (contains naloxone) |
| Synthetic | |||
| Fentanyl | Agonist | 0.75 IM | Very short acting (<1 h) |
| Loperamide | Agonist | Nonanalgesic | Antidiarrheal, abuse, P-glycoprotein substrate |
| Meperidine | Agonist | 75 SC or IM | Seizures caused by metabolite accumulation |
| Methadone | Agonist | 10 IM | Very long acting (24 h) |
| Tramadol | Agonist | 50-100 orally | Seizures possible with therapeutic dosing |
| Methylnaltrexone | Antagonist | Nonanalgesic | Peripherally acting antagonist; reverses opioid-induced constipation |
IM, intramuscularly; SC, subcutaneously.
Goldfrank's Toxicologic Emergencies 11e, Nelson et al 2019.