Alfentanil

ALFENTA

What it isShort-acting mu-opioid agonist; anesthesia.

Why this oneA large unionized fraction at physiologic pH gives faster onset than fentanyl, while brief action suits short procedures.

What limits itRapid bolus can cause chest-wall rigidity. Respiratory depression and CYP3A4 interactions matter.

FDA-approved for

FDA dosing	Population	Target	Max
Analgesic adjunct — spontaneous/assisted ventilation	Adults	Induction 8-20 mcg/kg; maintenance 3-5 mcg/kg q5-20min or 0.5-1 mcg/kg/min	Total 8-40 mcg/kg
Analgesic adjunct — assisted/controlled ventilation (incremental)	Adults	Induction 20-50 mcg/kg; maintenance 5-15 mcg/kg q5-20min	Up to 75 mcg/kg
Anesthetic induction	Adults	Induction 130-245 mcg/kg; maintenance 0.5-1.5 mcg/kg/min
Monitored anesthesia care (MAC)	Adults	Induction 3-8 mcg/kg; maintenance 3-5 mcg/kg q5-20min or 0.25-1 mcg/kg/min	3-40 mcg/kg

Renal Undefined

Hepatic Undefined

Individualize and titrate to effect; base dose on lean body weight in obese patients (>20% above ideal weight)
Reduce dose in elderly or debilitated patients
Anesthetic induction doses: expect truncal rigidity — use a muscle relaxant; administer slowly over 3 minutes
Discontinue infusion at least 10-15 minutes before end of surgery
Not recommended in children under 12 years

Respiratory depression — ensure qualified personnel and resuscitation facilities
Skeletal muscle (truncal) rigidity
Bradycardia and hypotension

Pregnancy Pregnancy Category C. Embryocidal in animals at high/prolonged doses; use only if potential benefit justifies risk.

Lactation Undefined

⚠ BOXED WARNINGS

Principal riskRigidity with rapid bolus

Direct muscarinic antagonism0 / 4