Opioid Agents Comparison Table (Clinical Pharmacist Focus)
| Feature | Naloxone | Naltrexone | Buprenorphine | Nalbuphine |
|---|---|---|---|---|
| Pharmacologic Class | Opioid antagonist | Opioid antagonist | Partial μ-agonist + κ-antagonist | κ-agonist + partial μ-antagonist |
| Mechanism of Action (MoA) | Competitive antagonist at μ, κ, δ opioid receptors → rapidly reverses opioid respiratory depression | Competitive antagonist at μ-opioid receptors (long-acting) → blocks euphoric effects & reduces cravings | Partial μ-opioid agonist (ceiling effect on respiratory depression) + κ-antagonist → maintenance therapy for OUD, analgesia | κ-agonist provides analgesia; μ-antagonism can precipitate withdrawal in opioid-dependent patients |
| Primary Clinical Use | Emergency reversal of opioid overdose | Opioid Use Disorder (relapse prevention), alcohol use disorder | OUD maintenance therapy; opioid withdrawal suppression; analgesia at low doses | Moderate–severe pain (post-op, labor analgesia), opioid alternative |
| Onset of Action | IV/IM/IN: 1–2 min (IN slightly slower) | PO: 1 hr; IM/ER injection peak ~2 hrs | SL film/tablet: 15–60 min; IV: 5–10 min | IV: 2–3 min; IM: 15 min |
| Duration | 30–90 min (shorter than most opioids → redosing often required) | ~24 hr (PO 50 mg) or ~1 month (IM ER Vivitrol®) | 6–12 hrs (SL) → long receptor occupancy (slow dissociation) | 3–6 hrs |
| Formulations | IV, IM, SQ, Intranasal spray (Narcan®, Kloxxado®) | PO tablets (Revia®) • IM monthly ER injection (Vivitrol®) | SL tablets/films (Subutex®, Suboxone® [+ naloxone]) • Depot (Sublocade®) | IV, IM |
| Adult Dosing (Typical Practice) | OD reversal: 0.4–2 mg IV q2–3 min until breathing; IN: 4 mg single spray, repeat q2–3 min | OUD: 50 mg PO daily; 380 mg IM monthly | OUD induction: 2–4 mg SL, titrate to 8–16 mg/day; Maintenance: 8–24 mg/day; Sublocade® 300 mg monthly ×2 then 100 mg monthly | Pain: 10 mg IM/IV q3–6 hr PRN; Max 160 mg/day |
| Pediatric Dosing (Quick Note) | 0.1 mg/kg IV (max 2 mg), repeat PRN | Not typically used < 18 yrs | Used in adolescents ≥ 16 yr for OUD | Weight-based IM/IV 0.1 mg/kg |
| Metabolism | Hepatic (UGT2B7) | Hepatic → 6-β-naltrexol | Hepatic (CYP3A4) | Hepatic |
| Renal Adjustment | No | Not required, caution hepatic failure | Not required, caution severe liver impairment | Avoid or reduce dose in renal impairment |
| Liver Considerations | Safe in liver disease | Contraindicated in acute hepatitis / LFTs ≥3× ULN | Can ↑ LFTs; monitor baseline + periodic AST/ALT | Hepatic impairment increases effect; reduce dose |
| Withdrawal Risk | Will precipitate immediate withdrawal in opioid-dependent patients | Can precipitate withdrawal if opioids still present | Lower risk due to partial agonist, but induction requires COWS ≥12 to avoid precipitation | Yes – μ-antagonism can trigger withdrawal |
| Analgesic Value | ❌ None | ❌ None | ✔ Yes (partial agonist) | ✔ Yes |
| Respiratory Depression | Reversal only | None | Ceiling effect → safer than full agonists | Risk present, but lower than morphine |
| Clinical Pearls (Pharmacist Tips) | • Overdose may require repeated dosing or infusion due to short t½ • Avoid excessive boluses → may cause violent withdrawal • Educate community patients on IN spray use |
• Test opioid-free ≥7–10 days before starting (use naloxone challenge if unsure) • Preferred in highly motivated patients already detoxed • Useful in AUD dual-benefit |
• Use COWS protocol for induction • Suboxone® (buprenorphine/naloxone) prevents diversion via parenteral misuse • Long-acting depot improves adherence |
• Good post-op analgesic when avoiding μ-agonists (obstetrics) • Avoid in OUD patients — will precipitate withdrawal • Ceiling effect limits overdose risk |
| Role in Harm-Reduction / OUD Programs | First-line community overdose kit | Relapse-prevention after abstinence | First-line maintenance therapy (with methadone) | No role in OUD treatment |
