How Long Does Alfentanil Stay in Your System?

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Alfentanil is an analog of fentanyl. Fentanyl is a powerful synthetic opioid that’s considered to be up to 80 times more potent than morphine. Alfentanil is a fast-acting medication that has roughly one-tenth the potency of fentanyl. Alfentanil’s maximum respiratory depressant and analgesic effects can take effect within one to two minutes of administration. Alfentanil is used in surgery as an anesthetic.

The terminal elimination half-life of alfentanil is, on average, 90 to 111 minutes, with a broader range of 50 to 150 minutes. This is significantly faster than fentanyl, which has an elimination half-life of 475 minutes.

How Long Does Alfentanil Stay in Your System?

Alfentanil is administered intravenously as a narcotic analgesic for short operative procedures. It may also be used in longer duration procedures during periods of exceptionally painful stimuli. Patients must be closely monitored during and after surgery for respiratory depression. Alfentanil is best-suited for inpatient procedures in which controlled ventilation and endotracheal intubation are used.

Complications can be severe and life-threatening when alfentanil is mixed with other opioids, benzodiazepines, and anti-anxiety medications. Several other drugs, including many used to treat infections, can inhibit the body’s ability to metabolize alfentanil. Alfentanil is excreted in breast milk. Breastfeeding should be avoided in the first 24 hours following the drug’s administration.

Alfentanil use is tightly regulated in the United States as a Schedule II substance. Fentanyl analogs like alfentanil have been responsible for the deaths of hundreds of people in the former Soviet republics and Europe beginning in the early 2000s. Since then, new derivatives of fentanyl continue to appear.

Alfentanil is incredibly dangerous to take recreationally. The minimum lethal dose of alfentanil varies dramatically according to each patient’s unique metabolism. When the drug is taken outside of a hospital setting, it has a substantially higher overdose rate.

How Long Does Alfentanil Stay in Your System?

When alfentanil is distributed on the black market, people often mix it with other opioids, benzodiazepines, alcohol, and various other central nervous system depressants. The concomitant use of these drugs can lead to severely depressed respiratory and circulatory function. The risk of lethal overdose is high when alfentanil is mixed with these substances.

Monoamine oxidase inhibitors (MAO inhibitors) should be avoided within two weeks leading up to alfentanil use. MAO inhibitors are a third-line treatment for depression and are contraindicated for a wide range of substances. Several anti-anxiety medications should also be avoided when taking alfentanil. Selective serotonin reuptake inhibitors (SSRIs) and selective serotonin/norepinephrine reuptake inhibitors (SNRIs) are contraindicated for alfentanil use. Combining these anxiolytics with alfentanil can result in toxic serotonin overload and death.

Alfentanil achieves its analgesic effects by binding to opioid receptor sites in the body that regulate pain response. By binding to and activating these receptors, alfentanil reduces the patient’s perception of pain. The patient’s return to consciousness typically occurs rapidly once alfentanil use is discontinued.

Common side effects of alfentanil use include respiratory and cardiovascular depression, increased muscular tone, thoracic muscular rigidity (common), bradycardia (slow heart rate), euphoria, and constricted pupils. Symptoms tend to be more prominent in doses exceeding 120 micrograms/kg.

Alfentanil has a rapid elimination time. For most patients, the terminal elimination half-life of alfentanil is between 90 and 111 minutes, although alfentanil’s half-life can range from 50 to 150 minutes for certain individuals. The sequential distribution half-lives of alfentanil are one and 14 minutes.

The activity of alfentanil during surgery can be prolonged by continuous infusion. Prolonged administration increases plasma concentrations of the drug. The elimination half-life of alfentanil remains unaltered once a steady state has been reached.

Several factors influence how long alfentanil remains in the body. Obese patients and individuals with hepatic (liver), and renal (kidney) malfunction experience reduced clearance rates. Doses should be titrated individually for obese patients throughout the procedure.

Chronic liver disease can decrease plasma protein concentrations and reduce clearance rates, leading to more pronounced and longer-lasting clinical effects. Kidney malfunction is less influential but can still increase plasma free fraction of alfentanil. Doses are typically reduced to one-third in elderly patients due to reduced clearance.

Alfentanil is thoroughly metabolized by the liver, leaving only one percent of the active drug to be excreted in the urine. Approximately 70% to 80% of alfentanil’s metabolites are eliminated in the urine. Alfentanil is eliminated from the blood plasma at an average clearance rate of 356 L/min. As with most substances, alfentanil may remain at testable levels in hair follicles for up to 90 days following administration.

Introducing synthetic opioids to the body carries with it the potential for dependency. If you have questions or concerns about the addictive potential of opiates, The Recovery Village is available to provide answers. Call us 24/7 at 855-548-9825 or visit online at