Current Insights into the Antispasmodic and Analgesic Effects of Metamizole on the Gastrointestinal Tract
Brazilian authors published a review of available information on the mechanism of action of metamizole, its impact on gastrointestinal tract motility, its effect on the gastric mucosa, and its antispasmodic effects.
Classification of Metamizole
Metamizole (dipyrone) is currently classified as a non-opioid analgesic, although it was previously classified under nonsteroidal anti-inflammatory drugs. Along with its analgesic actions, it has demonstrated antipyretic and antispasmodic effects. It is a prodrug, with its pharmacological effects exhibited by its metabolites − 4-methyl-amino-antipyrin and 4-amino-antipyrin. The exact mechanism of action is not precisely known.
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Impact on Gastric Motility and Mucosa
In rats, metamizole leads to a delay in the emptying of liquid contents from the stomach. However, it seems that the change in gastric motility is not related to the risk of ulceration. Additionally, in humans, the impact of metamizole on slowing gastric emptying has not been demonstrated. Unlike non-selective nonsteroidal anti-inflammatory drugs, metamizole has shown in experimental studies to protect gastric mucosa and slow the development of gastric ulcers, which many of these drugs induce.
Antispasmodic Effects
Clinically, metamizole effectively alleviates colicky abdominal pain of biliary and intestinal origin. Studies in both humans and animals have shown the presence of β2 receptors in the smooth muscle cells of the bile duct walls and the activation of these receptors in the delay of gastric emptying induced by metamizole. Therefore, it is likely that these receptors contribute to the reduction of the spasm of the smooth muscle of the Oddi's sphincter, which metamizole induces.
In contrast, there is no evidence that metamizole affects the motility of the small and large intestines. Its clinical effects on colicky pain of intestinal origin are likely due to its analgesic action. Further studies are needed to clarify the antispasmodic effects of metamizole on the intestinal wall.
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Source: Collares E. F., Troncon L. E. A. Effects of dipyrone on the digestive tract. Braz J Med Biol Res 2019; 52 (2): e8103, doi: 10.1590/1414-431X20188103.
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