Alfentanil

Article Author:
Rajat Moman
Article Editor:
Steve Bhimji
Updated:
11/29/2017 9:36:27 PM
PubMed Link:
Alfentanil

Indications

Alfentanil is short-acting opioid analgesic that is commonly compared to fentanyl, a medication that is ubiquitous in the hospital setting along with remifentanil and sufentanil. It is approved by the FDA as an anesthetic agent in adults and children 12 years and older who are undergoing general anesthesia and monitored anesthesia care. The use of alfentanil is limited to certain settings and situations; much of the literature surrounds its use in the operating room for surgical procedures, for procedural sedation, and during rapid sequence intubation. Because of its short half-life, its use outside of these settings is limited.

 In a randomized, controlled clinical trial in patients who underwent abdominal hysterectomy, alfentanil administered by the epidural route was found to be equivalent to the intravenous route for control of postoperative pain. In this study, the same doses were used: a loading dose of 15 micrograms/kg followed by an infusion of 18 micrograms/kg/hour. Both routes had similar rates of analgesia; however, analgesia occurred earlier in the intravenously treated group. Of note, the only vital sign abnormalities reported were in the intravenous group, respiratory depression was observed after administration of the loading dose, and mean plasma concentration was higher in the intravenous group at 60 minutes.

A randomized, double-blind, three-arm trial to study the pharmacokinetics and pharmacodynamics of alfentanil, fentanyl, and sufentanil given with propofol in total intravenous anesthesia for patients undergoing coronary artery bypass surgery was performed. The investigators reported mean times for a decrease in plasma concentration and mean time until endotracheal tube extubation. All three drugs, alfentanil, fentanyl, and sufentanil, took similar amounts of time to decrease to a 50% plasma concentration after administration (102, 92, and 69 minutes, respectively). Alfentanil and sufentanil decreased to an 80% plasma concentration faster than fentanyl (310 and 329 compared to 494 minutes, respectively). Patients who received alfentanil or sufentanil had a shorter time until endotracheal extubation than fentanyl.

One prospective observational study investigated the incidence of adverse respiratory outcomes in the use of alfentanil with propofol for procedural sedation in the emergency department. Outcome measures were airway and respiratory events leading to intervention including increasing supplemental oxygen, bag-valve-mask use, airway repositioning, and stimulation to induce breathing. Visual analog scales were used to assess the depth of analgesia, recall, and patient satisfaction. They found that the visual analog scale for the recall of the procedure was high, suggesting high recall and awareness during sedation with alfentanil. They found a comparable incidence of minor respiratory complications when compared to the known published rates of propofol despite sedation, with alfentanil being lighter than propofol.

A randomized, single-blinded, clinical trial investigating the optimal dose of alfentanil to the blunt hemodynamic response from rapid sequence induction and intubation was performed in patients undergoing elective surgery. Rocuronium and thiopental were the other agents administered for induction. Primary outcomes were the hemodynamic variables: arterial blood pressure and heart rate. Data were analyzed by the average hemodynamic response to finding the minimal (less than 10%) average response post-endotracheal intubation by alfentanil dose. Doses of greater than 40 micrograms/kg and greater than 50 micrograms/kg were needed to minimize hemodynamic response in arterial blood pressure and heart rate, respectively. Of note, one patient did require a vasopressor bolus after rapid sequence induction and intubation.

A randomized, controlled, double-blinded study of patients who suffered trauma and required rapid sequence induction and intubation in the emergency department examined the hemodynamic effects of alfentanil, fentanyl, and sufentanil and found no statistically significant differences in heart rate or systolic blood pressure at three, five, and ten minutes after intubation.

Mechanism of Action

Alfentanil is a tetrazole derivative of fentanyl. It is about one-eighth as potent as fentanyl and has an onset approximately three times faster than fentanyl. Because of alfentanil’s short half-life, it is not an ideal agent to intermittently bolus intravenously or for intermittent administration intramuscularly for the management of acute pain, such as in the emergency department setting. Instead, opioids such as fentanyl, morphine, and hydromorphone predominate in the management of acute pain in this fashion because of their longer duration of action. Like other opioids, alfentanil exerts its effects by binding to the mu receptor. Whenever considering using alfentanil, or other opioid medications, it is important to assess the risks and benefits of opioid medications weighed against those of non-opioid analgesics or to consider utilizing the multimodal analgesic approach. The clinician should consider if the use of non-opioid medications like acetaminophen, non-steroidal anti-inflammatory medications, topical medications, ketamine, intravenous lidocaine, and the like are appropriate and safe for their patient.

Administration

Alfentanil is about one-eighth as potent and its onset is approximately three times faster than fentanyl. Because of alfentanil’s short half-life, it is not an ideal agent for intermittent bolus intravenously or for intermittent administration intramuscularly for the management of acute pain, such as in the emergency department setting. Instead, opioids such as fentanyl, morphine, and hydromorphone predominate in the management of acute pain in this setting because of their longer duration of action. Like other opioids, alfentanil exerts its effects by binding to the mu receptor. Whenever considering using alfentanil or other opioid medications, it is important to assess the risks and benefits of opioid medications weighed against those of nonopioid analgesics or to consider utilizing the multimodal analgesic approach. The clinician should consider if the use of non-opioid medications like acetaminophen, non-steroidal anti-inflammatory medications, topical medications, ketamine, or intravenous lidocaine is appropriate and safe for their patient.

Adverse Effects

Adverse effects of alfentanil include hypertension, tachycardia, nausea, and vomiting. More serious adverse effects are bradyarrhythmia, cardiac dysrhythmia, hypotension, chest wall rigidity, apnea, and respiratory depression. Of note, in those with a history of seizures, alfentanil administration can lead to focal activation of the cerebral cortex and cause seizure-like activity. Additionally, one must be vigilant regarding adverse effects that are common to all opioid medications; these include somnolence, depression of respiratory drive, nausea, vomiting, urinary retention, ileus, constipation, opioid-induced hyperalgesia, opioid dependence, and visceral hypersensitivity syndrome.

Contraindications

Contraindications to alfentanil include a history of seizures because it can cause focal activation of the cerebral cortex and cause seizure-like activity. Alfentanil should be avoided in those with hypersensitivity to the drug or its components or intolerance to opioids. As with all opioid medications, avoid use in elderly patients who have a history of falls or fractures.

Monitoring

Monitor vital signs for signs or symptoms of cardiorespiratory depression including bradycardia, asystole, arrhythmia, hypotension, or respiratory arrest.