Table 1.

Common opioid analgesics for ICU patients

Drug	Mechanism of action	Equivalent dose	Onset	Duration of analgesia	Common adverse reactions
Morphine	μ-opioid agonist (also with κ-opioid and δ-opioid agonist effects)	10 mg	15–60 min	4–5 h	Respiration depression, Nausea, Vomiting, Drowsiness, Constipation, Hypotension, Urinary retention, Itching
Fentanyl	μ-opioid agonist (also with κ-opioid agonist effects)	0.1 mg	< 1–2 min	1–1.5 h	Respiration depression, Nausea, Constipation, Skeletal-muscle rigidity
Sufentanil	μ-opioid agonist (also with κ-opioid agonist effects)	0.02 mg	within a few minutes	1–1.5 h	Respiratory depression, Nausea, Dizziness, Vomiting, Itching, Skeletal-muscle rigidity
Nalbuphine	μ-opioid antagonist (also with κ-opioid agonist effect)	10 mg	2–3 min	3–6 h	Nausea, Drowsiness, Sweating, Dry mouth, Dizziness. (nearly no psychotomimetic side effects)