Pregnancy Category: C
Pharmacologic: opioid agonists
ClassificationTherapeutic: anesthetic adjuncts
Pharmacologic: opioid agonists
Analgesic adjunct used to maintain anesthesia with barbiturate/nitrous oxide/oxygen.Analgesic (continuous IV infusion) with nitrous oxide/oxygen while maintaining general anesthesia.Primary induction anesthetic when endotracheal intubation and mechanical ventilation are required.
Binds to opiate receptors in the CNS, altering the response to and perception of pain while causing generalized-CNS-depression.
Relief of moderate to severe pain.
Absorption: Following IV administration, absorption is essentially complete.
Distribution: Does not penetrate adipose tissue. Crosses placenta, enters breast milk.
Metabolism and Excretion: >95% metabolized by the liver.
Half-life: 60–130 min (↓ in children).
Time/action profile (analgesia and respiratory depression)
|IV||immediate||1–1.5 min||5–10 min†|
Contraindicated in: Hypersensitivity; Known intolerance.
Use Cautiously in: Debilitated, geriatric or severely ill patients; Diabetes; Severe pulmonary or hepatic disease; CNS tumors; Increased intracranial pressure; Head trauma; Adrenal insufficiency; Undiagnosed abdominal pain; Hypothyroidism; Alcoholism; Cardiac disease (arrhythmias); Obstetric / Lactation / Pediatric: Safety not established; Geriatric: Older patients may be more susceptible to side effects.
Adverse Reactions/Side Effects
Central nervous system
Ear, Eye, Nose, Throat
- blurred vision
- respiratory depression
- bradycardia (most frequent)
- hypotension (most frequent)
- tachycardia (most frequent)
- nausea (most frequent)
- vomiting (most frequent)
- thoracic muscle rigidity (most frequent)
- skeletal muscle rigidity
Drug-Drug interactionalcohol, antihistamines, antidepressants, and other sedative/hypnotics —concurrent use ↑ CNS depression.MAO inhibitors should be avoided for 14 days before use.Cimetidine orerythromycin may ↑ duration of recovery.Concurrent use with benzodiazepines, antihypertensives, alcohol, or diuretics may ↑ risk of hypotension.Nalbuphine, buprenorphine, butorphanol, or pentazocine may ↓ analgesia.Concurrent use of protease inhibitor antiretrovirals may ↑ risk of CNS depression.Naltrexone and naloxone will block all effects of alfentanil.Concommitant use of kava, valerian, can ↑ CNS depression.
Route/DosageIncremental Injection (Duration of Anesthesia <30 min)—Induction Period
Intravenous (Adults) 8–20 mcg/kg.Incremental Injection (Duration of Anesthesia <30 min)—Maintenance Period
Intravenous (Adults) 3–5 mcg/kg every 5–20 min or 0.5–1 mcg/kg/min (total dose 8–40 mcg/kg).Incremental Injection (Duration of Anesthesia 30–60 min)—Induction Period
Intravenous (Adults) 20–50 mcg/kg.Incremental Injection (Duration of Anesthesia 30–60 min)—Maintenance Period
Intravenous (Adults) 5–15 mcg/kg every 5–20 min (up to total dose of 75 mg/kg).Continuous Infusion (Duration of Anesthesia >45 min)—Induction
Intravenous (Adults) 50–75 mcg/kg.Continuous Infusion (Duration of Anesthesia >45 min)—Maintenance
Intravenous (Adults) 0.5–3 mcg/kg/min (average rate 1–1.5 mcg/kg/min). Infusion rate should be decreased by 30–50% after first hour of maintenance. If lightening occurs, infusion rate may be increased up to 4 mcg/kg/min or boluses of 7 mcg/kg may be administered.Pediatric dose (unlabeled)
Intravenous (Children) Induction—12.5–50 mcg/kg initially, followed by supplemental doses of 10–15 mcg or infusion at 0.5–1.5 mcg/kg/min.Anesthetic Induction (Duration of Anesthesia >45 min)
Intravenous (Adults) 130–245 mcg/kg followed by 0.5–1.5 mcg/kg/min or general anesthesia.Monitored Anesthesia Care (MAC)—Induction
Intravenous (Adults) 3–8 mcg/kg.Monitored Anesthesia Care (MAC)—Maintenance
Intravenous (Adults) 3–5 mcg/kg every 5–20 min or 0.25–1 mcg/kg/min (total dose 3–40 mg/kg).
Injection: 500 mcg/mL in 2-, 5-, 10-, and 20-mL ampules
- Assess vital signs, especially respiratory status and ECG, frequently during and following administration. Notify health care professional immediately of significant changes. Postoperative pain may require treatment relatively early in recovery period due to short duration of alfentanil.
- Lab Test Considerations: May cause elevated serum amylase and lipase concentrations. Symptoms of toxicity include respiratory depression, hypotension, arrhythmias, bradycardia, and asystole. Atropine may be used to treat bradycardia. If respiratory depression persists after surgery, prolonged mechanical ventilation may be required. If an opioid antagonist is required to reverse respiratory depression or coma, naloxone (Narcan) is the antidote. Dilute the 0.4-mg ampule of naloxone in 10 mL of 0.9% NaCl and administer 0.5 mL (0.02 mg) by direct IV push every 2 min. For children and patients weighing <40 kg, dilute 0.1 mg of naloxone in 10 mL of 0.9% NaCl for a concentration of 10 mcg/mL and administer 0.5 mcg/kg every 1–2 min. Titrate dose to avoid withdrawal, seizures, and severe pain. Administration of naloxone in these circumstances, especially in cardiac patients, has resulted in hypertension and tachycardia, occasionally causing left ventricular failure and pulmonary edema.
Potential Nursing DiagnosesAcute pain (Indications)
Disturbed sensory perception(visual, auditory) (Side Effects)
Ineffective breathing pattern (Side Effects)
- high alert: Accidental overdose of opioid analgesics has resulted in fatalities. Before administering, clarify all ambiguous orders; have second practitioner independently check original order, dose calculations and infusion pump programming.
- Benzodiazepines may be administered before alfentanil to reduce induction dose requirements and decrease time to loss of consciousness; may also increase the risk of hypotension.
- Administer small volumes for direct IV use undiluted via tuberculin syringe for accuracy.
- Rate: Administer slowly over 90 sec–3 min; may reduce incidence and severity of muscle rigidity, bradycardia, or hypotension. Neuromuscular blocking agents may be administered concurrently to decrease muscle rigidity.
- Continuous Infusion: Diluent: Dilute 20 mL of alfentanil (500 mcg/mL solution) with 230 mL of 0.9% NaCl, D5W, D5/0.9% NaCl, or lactated Ringer’s solution. Concentration: 40 mcg/mL.
- Rate: See Route and Dosage section.
- Discontinue IV infusion at least 10–15 min before the end of surgery.
- Discuss the use of anesthetic agents and sensations to expect with patient before surgery.
- Alfentanil may cause drowsiness and dizziness. Advise patient to call for assistance when ambulating.
- Advise patient to change position slowly to minimize orthostatic hypotension.
- After outpatient surgery, instruct patients to avoid alcohol or other CNS depressants for 24 hr after the administration of alfentanil.
- General quiescence.
- Reduced motor activity.
- Pronounced analgesia.
alfentanilA potent, short-acting opioid analgaesic and fentanyl analogue which is 10-fold stronger than morphine. It is an OP3 mu agonist.
Mechanism of action
Modulation of the sympathetic response to endotracheal intubation and surgical stimulation.
Profound respiratory depression and skeletal muscle rigidity.