What is the mechanism of Metamizole Sodium?

Metamizole sodium, also known as dipyrone, is a non-opioid analgesic and antipyretic medication frequently used for its potent pain-relieving and fever-reducing properties. Despite its widespread use in many countries, the precise mechanism by which metamizole sodium exerts its effects is not fully understood. However, several hypotheses have been put forward based on available research.

One of the primary mechanisms of action proposed for metamizole sodium is its ability to inhibit the synthesis of prostaglandins. Prostaglandins are lipid compounds that play a significant role in the process of inflammation and the sensation of pain. Metamizole sodium is thought to inhibit the enzyme cyclooxygenase (COX), which is crucial for the conversion of arachidonic acid to prostaglandins. However, metamizole sodium appears to selectively inhibit COX-3, an enzyme variant found in the brain, rather than the more commonly discussed COX-1 and COX-2 enzymes. This selective inhibition could explain its strong central analgesic effects without causing significant gastrointestinal side effects typically associated with non-steroidal anti-inflammatory drugs (NSAIDs).

In addition to its role in inhibiting prostaglandin synthesis, metamizole sodium may also exert its analgesic effects through interactions with the endogenous opioid system. There is evidence suggesting that the drug may increase the levels of beta-endorphins, which are natural pain-relieving peptides in the body. This interaction could amplify the overall analgesic effect of metamizole sodium.

Another interesting aspect of metamizole sodium’s mechanism involves its antipyretic properties. Fever is typically caused by the action of pyrogens, which elevate the set point of the hypothalamic thermoregulatory center. Metamizole sodium appears to lower this set point, thereby reducing fever. This effect is believed to be mediated by the inhibition of prostaglandin E2 synthesis within the hypothalamus.

Furthermore, recent research has pointed towards the involvement of metamizole sodium in modulating neurotransmitter release. The drug has been shown to influence the release of certain neurotransmitters such as serotonin and endocannabinoids, which play a role in pain perception and modulation. This could provide an additional explanation for its analgesic and antipyretic effects.

Metamizole sodium also has a unique property of being effective in treating visceral pain, which is pain originating from internal organs. This type of pain is usually resistant to many other analgesics. The exact mechanism behind this specific action is still under investigation, but it is believed to involve both central and peripheral pathways.

It is important to note that while metamizole sodium is effective, it is not without risks. One of the most significant concerns is its potential to cause agranulocytosis, a condition where the number of white blood cells drops dangerously low, leading to a compromised immune system. This severe side effect has led to the withdrawal or restriction of the drug in several countries.

In conclusion, metamizole sodium is a multifaceted drug with a complex mechanism of action that includes inhibition of prostaglandin synthesis, interaction with the endogenous opioid system, modulation of neurotransmitter release, and effects on the hypothalamic thermoregulatory center. While it offers potent analgesic and antipyretic effects, its use must be carefully monitored due to potential severe side effects. Further research is needed to fully elucidate its mechanisms and optimize its therapeutic use.