Reports of adverse events following the use of Wegovy and Mounjaro have reached 1,780 in Korea as prescriptions for the weight-loss drugs have surged, government data showed Friday.
The data, submitted to ruling Democratic Party of Korea Rep. Kwon Chil-seung, showed 944 reports involving Wegovy from its Korean launch in October 2024 through March this year.
The annual breakdown was 49 in 2024, 672 in 2025 and 223 in the first three months of 2026.
“Adverse-event reports alone cannot establish a causal relationship with a medicine,” Kwon said. “But with the growing use of obesity drugs and the accumulation of a substantial number of reports, closer oversight is needed.”
Mounjaro, launched in Korea in August 2025, was associated with 836 reports over the same period: 345 last year and 491 in the first quarter of this year.
Including 518 reports involving Saxenda between 2024 and March 2026, the combined number for the three injectable obesity drugs reached 2,298.
Frequently reported symptoms included vomiting, diarrhea, injection-site pain, headaches and indigestion. The ministry stressed that an adverse-event report records a health problem observed after a drug was used and does not by itself prove a causal link.
Use of the medications has expanded rapidly. Mounjaro was prescribed about 1.84 million times through July this year, compared with 394,365 prescriptions in 2025, when it was available for only the final five months of the year.
Wegovy recorded 482,071 prescriptions through July, following 828,209 in 2025. The figures represent prescription records, not the number of individual patients.
Wegovy contains semaglutide, while Mounjaro contains tirzepatide, which acts on both GIP and GLP-1 receptors. Saxenda contains liraglutide.
All three are prescription medicines that reduce appetite and are administered by injection.
The boom has also fueled demand for products obtained outside authorized channels. Separate Korea Customs Service data released Thursday showed that authorities intercepted 5,030 attempts to bring obesity drugs into the country illegally through August, more than four times the 1,189 cases recorded in all of 2025.
Tests on nine suspected counterfeit Mounjaro products sent from India found inconsistent levels of tirzepatide and unidentified impurities in some samples. The products had also been shipped without the required cold chain, customs officials said.
shwang9@heraldcorp.com
