Thirty-five cases of adverse reactions to Mounjaro reported in first month of availability

Thirty-five cases of adverse reactions or serious side effects were reported in Korea within the first month of the release of Mounjaro (tirzepatide), a weight loss drug developed by Eli Lilly.

According to data submitted by the Korea Institute of Drug Safety and Risk Management to Democratic Party Rep. Seo Mi-hwa, a member of the National Assembly’s Health and Welfare Committee, a total of 35 cases of adverse reactions were reported from August to September, the first month of the drug’s availability in Korean pharmacies. Among the cases were four instances of diarrhea and one case of hypoglycemic shock, two reactions classified as serious adverse reactions.

Under Korea’s Regulations on the Safety of Pharmaceuticals and Related Products, serious adverse reactions include any medical occurrences that result in death, are life-threatening, require hospitalization or prolong existing hospitalization, cause permanent or significant disability or are otherwise considered medically significant and require treatment.

Other reported reactions included six cases of muscle pain, four of injection site bleeding, four of accidental underdosing, three of injection site pain, three of upper abdominal pain, three of indigestion, two of headaches, two of nausea, two of constipation and one of injection site erythema.

According to medical sources, tirzepatide is frequently associated with gastrointestinal issues such as diarrhea, upper abdominal pain and indigestion, as well as musculoskeletal disorders like muscle pain, and administration site conditions including bleeding at the injection site.

Along with Wegovy from Novo Nordisk, Mounjaro has secured a dominant position in Korea’s weight-loss drug market. However, concerns persist over adverse effects and misuse of such medications.

“There is rising demand for obesity drugs and growing concern about how they are prescribed,”  Seo said. “The Ministry of Food and Drug Safety must strengthen crackdowns on deceptive advertising through its cyber monitoring unit, while the Korea Institute of Drug Safety and Risk Management should conduct thorough analyses of adverse reaction reports.”

The institute noted, however, that adverse reactions reported to the agency do not necessarily establish a causal relationship with the drug. Therefore, the reported data alone is insufficient to confirm that Mounjaro was directly responsible for the reactions.

BY KIM JI-HYE [yoon.soyeon@joongang.co.kr]