| Indication |
For the management of postoperative pain and the maintenance of general anesthesia. |
| Pharmacodynamics |
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. |
| Absorption |
For intravenous injection or infusion only. |
| Volume of distribution |
|
| Protein binding |
92% |
| Metabolism |
The liver is the major site of biotransformation. |
| Route of elimination |
Only 1.0% of the dose is excreted as unchanged drug; urinary excretion is the major route of elimination of metabolites. |
| Half life |
90-111 minutes |
| Clearance |
|
| Toxicity |
Symptoms of overexposure include characteristic rigidity of the
skeletal muscles, cardiac and respiratory depression, and narrowing of
the pupils. |
