Table 4.

	Morphine	Fentanyl	Alfentanil	Sufentanil	Remifentanil
Pharmacodynamics	μ 1, μ 2, κ and Δ agonists
Elimination t 1/2 (h)	3	3.7	1.5	2.2	0.25
Distribution t 1/2	3–11 min	10–30 min	15 min	5 min	1 min
Neuroprotective effects	May increase ICP	Minimal effect beyond the analgesic effect on CBF and CMRO2
Pharmacokinetics	Onset 6 min Peak effect 20 min (IV) 30% protein bound Hepatically metabolised to active metabolites Renal clearance	95% protein bound High lipid solubility 75% first pass pulmonary uptake Hepatically metabolised to active metabolites Renal clearance	Onset Peak 90 s Duration 5–10 min 90% protein bound Hepatically metabolised Renal clearance	Hepatically metabolised Renal clearance	Peak 60 s Small Vd Rapid clearance Rapid ester hydrolysis by plasma esterases to inactive metabolite (Independent of renal & hepatic function)
Advantages	Lower cost Relative haemodynamic stability Hypnotic agent sparing Analgesic properties	Lower cost Relative haemodynamic stability Hypnotic agent sparing Analgesic properties	Relative haemodynamic stability Hypnotic agent sparing Analgesic properties	Relative haemodynamic stability Hypnotic agent sparing Analgesic properties	Very rapid onset/offset Less nausea Relative haemodynamic stability Hypnotic agent sparing Analgesic properties
Disadvantages and major side effects			Hypotension Bradycardia Respiratory depression Cough reflex suppression Seizures Rigidity Constipation Spasm sphincter of Oddi Nausea Pruritis
Dosage	0.05–0.1 mg/kg/hr	Induction: 1–3 mcg/kg Maintenance: 0.5–2 mcg/kg/h	Induction: 10–50 mcg/kg Infusion: 0.5–1 mcg/kg/min	Induction: 4 mcg/kg	Bolus: 1 mcg/kg Infusion: 0.0125–1 mcg/kg/min
Appropriate uses in TBI	Long term analgesia Palliation	Co-Induction agent Continuous infusion Palliation	Co-Induction agent	Co-Induction agent	Co-Induction agent Continuous infusion infusion