REMIFENTANIL

​

Remifentanil is an important drug in the field of anesthesia for several reasons. It is a potent, ultra-short-acting synthetic opioid analgesic. Its unique pharmacokinetic and pharmacodynamic properties make it a valuable tool in various clinical settings. Some of the key reasons for its importance include:

​

1. Rapid onset and offset: Remifentanil has an extremely rapid onset of action (typically within 1-2 minutes) and a short duration of action due to its rapid metabolism by plasma esterases. This allows for precise control of analgesia and makes it well-suited for procedures requiring rapid changes in anesthetic depth or for those with an unpredictable duration.

2. Predictable pharmacokinetics: Remifentanil's pharmacokinetics are relatively unaffected by factors such as age, weight, renal or hepatic function, making it more predictable compared to other opioids. This enables anesthesiologists to titrate the drug more effectively for individual patients.

3. Excellent analgesic properties: Remifentanil provides effective analgesia for various surgical procedures, reducing the need for additional analgesic medications and improving patient comfort.

4. Facilitation of fast-track anesthesia: Due to its rapid elimination, patients receiving remifentanil often have a quicker recovery from anesthesia, which can facilitate early mobilization, enhance postoperative recovery, and shorten hospital stays.

5. Utility in monitored anesthesia care: Remifentanil can be used for sedation and analgesia in monitored anesthesia care (MAC), where patients require varying levels of sedation while maintaining spontaneous ventilation.

​​

​

Here are the main steps in remifentanil's mechanism of action:

​

1. Binding to opioid receptors: Remifentanil primarily acts on mu-opioid receptors, which are G-protein-coupled receptors found throughout the central and peripheral nervous systems. It can also bind to other opioid receptor subtypes (such as delta and kappa receptors) but with lower affinity.

2. Activation of opioid receptors: Upon binding to the mu-opioid receptors, remifentanil activates the receptors, leading to the inhibition of adenylate cyclase. This results in a decrease in intracellular cyclic AMP (cAMP) levels.

3. Modulation of ion channels: The activation of mu-opioid receptors by remifentanil also causes the opening of potassium channels and the closing of voltage-gated calcium channels. The opening of potassium channels leads to hyperpolarization of the cell membrane, reducing the neuron's excitability. The closing of calcium channels inhibits the release of neurotransmitters, including substance P, which is involved in pain transmission.

4. Inhibition of pain transmission: The overall effect of remifentanil's action on opioid receptors is the inhibition of pain transmission in the central nervous system. This results in analgesia, sedation, and a reduced perception of pain.

                                     

​

                                                                                           Key points about Remifentanil

​

• Selective Mu-1 and Mu-2 agonist.

 

• 75-100 times more potent than morphine.

 

• Rapid onset and offset of action.

 

• Unique opioid because of its ester linkage which makes it susceptible to hydrolysis by nonspecific plasma and tissue esterases to inactive metabolites.

 

• Small volume of distribution and rapid clearance.

 

• Ideal when rapid recovery is desirable.

 

• Good choice for short procedures of intense stimulation.

 

• Pharmacokinetics unchanged by renal or hepatic function.

 

• May be associated with acute opioid tolerance.

 

• Hyperalgesia may occur after exposure to high doses.

 

• Context-sensitive half-time is independent of duration of infusion and estimated to be around 4 minutes.

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

 

​​

​​