Brands, Medical Use, Clinical Data
- Opiate Agonists
Brands / Synonyms
Alfenta; Alfentanil; Alfentanilum [Inn-Latin]; Alfentanyl
For the management of postoperative pain and the maintenance of general anesthesia.
Alfentanil is a synthetic opioid analgesic. Alfentanil interacts predominately with the opioid mu-receptor. These mu-binding sites are discretely distributed in the human brain, spinal cord, and other tissues. In clinical settings, alfentanil exerts its principal pharmacologic effects on the central nervous system. Its primary actions of therapeutic value are analgesia and sedation. Alfentanil may increase the patient's tolerance for pain and decrease the perception of suffering, although the presence of the pain itself may still be recognized. In addition to analgesia, alterations in mood, euphoria and dysphoria, and drowsiness commonly occur. Alfentanil depresses the respiratory centers, depresses the cough reflex, and constricts the pupils.
Mechanism of Action
Opiate receptors are coupled with G-protein receptors and function as both positive and negative regulators of synaptic transmission via G-proteins that activate effector proteins. Binding of the opiate stimulates the exchange of GTP for GDP on the G-protein complex. As the effector system is adenylate cyclase and cAMP located at the inner surface of the plasma membrane, opioids decrease intracellular cAMP by inhibiting adenylate cyclase. Subsequently, the release of nociceptive neurotransmitters such as substance P, GABA, dopamine, acetylcholine and noradrenaline is inhibited. Opioids also inhibit the release of vasopressin, somatostatin, insulin and glucagon. Alfentanil's analgesic activity is, most likely, due to its conversion to morphine. Opioids close N-type voltage-operated calcium channels (OP2-receptor agonist) and open calcium-dependent inwardly rectifying potassium channels (OP3 and OP1 receptor agonist). This results in hyperpolarization and reduced neuronal excitability.
Symptoms of overexposure include characteristic rigidity of the skeletal muscles, cardiac and respiratory depression, and narrowing of the pupils.
Biotrnasformation / Drug Metabolism
The liver is the major site of biotransformation.
ALFENTA (alfentanil hydrochloride) is contraindicated in patients with known hypersensitivity to the drug or known
intolerance to other opioid agonists.
Both the magnitude and duration of central nervous system and cardiovascular effects may be enhanced when ALFENTA
is administered in combination with other CNS depressants such as barbiturates, tranquilizers, opioids, or inhalation
general anesthetics. Postoperative respiratory depression may be enhanced or prolonged by these agents. In such cases
of combined treatment, the dose of one or both agents should be reduced. Limited clinical experience indicates that
requirements for volatile inhalation anesthetics are reduced by 30 to 50% for the first sixty (60) minutes following
ALFENTA induction The concomitant use of erythromycin with ALFENTA can significantly inhibit ALFENTA clearance and
may increase the risk of prolonged or delayed respiratory depression.
Cimetidine reduces the clearance of ALFENTA. Therefore smaller ALFENTA doses will be required with prolonged
administration and the duration of action of ALFENTA my be extended.
Perioperative administration of drugs affecting hepatic blood flow or enzyme function may reduce plasma clearance
and prolong recovery.