The hydrochloride salt form of alfentanil, an ultra short-acting, synthetic, opioid agonist with analgesic and local anesthesia enhancing activity.
Alfentanil hydrochloride primarily binds to and stimulates the opiate receptors in the central nervous system (CNS), thereby mimicking the actions of endogenous opioids. Stimulation of the mu-subtype opioid receptor stimulates the exchange of GTP for GDP on the G-protein complex and subsequently inhibits adenylate cyclase. This results in a decrease in intracellular cAMP and leads to a reduction in the release of various neurotransmitters.
The analgesic effect of alfentanil is likely due to the actions of its metabolite morphine, which induces opening of G-protein-coupled inwardly rectifying potassium (GIRK) channels and blocks the opening of N-type voltage-gated calcium channels, thereby resulting in hyperpolarization and reduced neuronal excitability.
Reference: National Cancer Institute. NCI Drug Dictionary. Internet. September 15, 2009. Available at http://www.cancer.gov/drugdictionary/?expand=All
Alfentanil and fentanyl are both highly lipid soluble with a far more rapid onset of action than morphine.
They may be used as infusions. Prolonged administration of alfentanil or fentanyl may result in sequestration of the drug to fat stores. This in turn may result in an extended period of recovery during which the drug is cleared from the body as it is returned to the vascular compartment from the fatty tissues prior to excretion renally, on cessation of administration.
1. PCA Analgesia for short procedures e.g. colonoscopy
2. Analgesia for palliative procedures e.g. percutaneous vertebroplasty
3. To reduce the propofol injection induced pain
Dose: at 5 mcg/kg, alfentanyl provides analgesia for the conscious, but sedated patient.
Shorter sedation times make alfentanyl more attractive than fentanyl and the side effects of cough as response to injection is lesser in comparison with fentanyl.
Reference: National Cancer Institute. NCI Drug Dictionary. Internet http://www.cancer.gov/drugdictionary?expand=A Accessed 15 Feb 2012. Pathan H and Williams J, Basic opioid pharmacology: an update. British Journal of Pain 2012 6: 11 3. Cho HB, Kwak HJ, Park SY, Kim JY. Acta Anaesthesiol Scand. 2010 Jul;54(6):717-20. Sesay M, Tauzin-Fin PJ Neurosurg Anesthesiol. Median effective infusion dose (ED50) of alfentanil for monitored anesthesia care of percutaneous vertebroplasty .