Rapifen

alfentanil

(al-fen-ta-nil) alfentanil,

Alfenta

(trade name),

Rapifen

(trade name)

Classification

Therapeutic: anesthetic adjuncts
Pharmacologic: opioid agonists
Pregnancy Category: C

Indications

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.

Action

Binds to opiate receptors in the CNS, altering the response to and perception of pain while causing generalized-CNS-depression.

Therapeutic effects

Relief of moderate to severe pain.Anesthesia.

Pharmacokinetics

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)

ROUTEONSETPEAKDURATION
IVimmediate1–1.5 min5–10 min†
†↓ in children

Contraindications/Precautions

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

  • dizziness
  • sleepiness

Ear, Eye, Nose, Throat

  • blurred vision

Respiratory

  • apnea
  • respiratory depression

Cardiovascular

  • bradycardia (most frequent)
  • hypotension (most frequent)
  • tachycardia (most frequent)
  • arrhythmias
  • hypertension

Gastrointestinal

  • nausea (most frequent)
  • vomiting (most frequent)

Musculoskeletal

  • thoracic muscle rigidity (most frequent)
  • skeletal muscle rigidity

Interactions

Drug-Drug interaction

alcohol, 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/Dosage

Incremental Injection (Duration of Anesthesia <30 min)—Induction PeriodIntravenous (Adults) 8–20 mcg/kg.Incremental Injection (Duration of Anesthesia <30 min)—Maintenance PeriodIntravenous (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 PeriodIntravenous (Adults) 20–50 mcg/kg.Incremental Injection (Duration of Anesthesia 30–60 min)—Maintenance PeriodIntravenous (Adults) 5–15 mcg/kg every 5–20 min (up to total dose of 75 mg/kg).Continuous Infusion (Duration of Anesthesia >45 min)—InductionIntravenous (Adults) 50–75 mcg/kg.Continuous Infusion (Duration of Anesthesia >45 min)—MaintenanceIntravenous (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)—InductionIntravenous (Adults) 3–8 mcg/kg.Monitored Anesthesia Care (MAC)—MaintenanceIntravenous (Adults) 3–5 mcg/kg every 5–20 min or 0.25–1 mcg/kg/min (total dose 3–40 mg/kg).

Availability

Injection: 500 mcg/mL in 2-, 5-, 10-, and 20-mL ampules

Nursing implications

Nursing assessment

  • 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 Diagnoses

Acute pain (Indications)
Disturbed sensory perception(visual, auditory) (Side Effects)
Ineffective breathing pattern (Side Effects)

Implementation

  • 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.
  • Intravenous Administration
  • 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.

Patient/Family Teaching

  • 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.

Evaluation/Desired Outcomes

  • General quiescence.
  • Reduced motor activity.
  • Pronounced analgesia.

alfentanil

A 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.
 
Cons
Profound respiratory depression and skeletal muscle rigidity.

Rapifen

A brand name for ALFENTANIL.