Customs authorities are tightening clearance checks and enforcement as overseas shipments of obesity drugs such as Mounjaro and Wegovy surge into South Korea. Tests on some of the seized products found inconsistent levels of active ingredients and unidentified impurities.
Seizures of obesity drugs brought in from abroad jumped to 1,189 in 2025 from four in 2024, the Korea Customs Service said on the 17th. Through August this year, 5,030 cases were caught — 4.2 times last year's full-year total in just eight months.
Over the past three years, 6,223 cases involving obesity drugs were seized in total. By route, international mail accounted for the most at 4,961 cases, followed by travelers' hand-carried goods at 1,232 and express cargo at 30.
Seizures extend beyond obesity drugs to illegal pharmaceuticals broadly. The customs agency has caught about 60,000 cases of illegal medicines over the past three years, including roughly 21,000 through August this year.
The Korea Customs Service manages clearance of incoming pharmaceuticals together with the Ministry of Food and Drug Safety. Products that the drug ministry flags to customs as hazardous can enter the country only if they meet set requirements, such as a recommendation letter exempting them from import requirement verification.
Mounjaro and Wegovy are both on the list of hazardous medicines the ministry has reported to customs.
Customs officials identify such products through X-ray screening and physical inspection of packages. When the required import conditions are not met, clearance is suspended and the goods are returned or destroyed. If a separate legal violation such as smuggling is confirmed, investigation and punishment follow under the relevant laws.
The agency also links on-site customs inspections with component analysis by its Central Customs Laboratory to block drugs and illegal medicines that could threaten public safety at the border.
As part of that work, researchers at the Central Customs Laboratory and the College of Pharmacy at Chung-Ang University recently ran a detailed analysis of the ingredients and quality of Mounjaro products shipped from India and seized at the clearance stage.
The laboratory measured the content of tirzepatide, Mounjaro's active ingredient, using a method developed by the National Institute of Food and Drug Safety Evaluation. The Chung-Ang University team focused on impurities, a key measure in pharmaceutical quality control.
The tests found wide variation in active-ingredient content from product to product. Some products also contained multiple unidentified impurities that could not be pinned down.
Taken together, the results showed the products fell short of the quality and safety standards required of pharmaceuticals.
Distribution was also a problem. The products were shipped without the refrigerated "cold chain" system needed to maintain drug quality, the investigation found.
Mounjaro must in principle be refrigerated at 2 to 8 degrees Celsius. It requires strict quality control, including consistent temperatures not only during manufacturing but also in transport and storage.
The products in question were later confirmed as counterfeits after appraisal by the trademark holder.
"This analysis found that active-ingredient content varied from product to product and that unidentified impurities were present," said Na Dong-hee, a professor at Chung-Ang University's College of Pharmacy. "Injectable drugs in particular require strict manufacturing and quality control, including sterility as well as management of active ingredients and impurities, so buying and using products of unverified origin and quality on one's own can be dangerous."
Ensuring sterility means managing the manufacturing, packaging and storage of drugs and injectables so that microbes such as bacteria and fungi neither enter nor survive in the product.
"Attempts to illegally bring in various medicines including obesity drugs are increasing, so we will strengthen clearance inspections across each route — travelers, international mail and express cargo — and respond firmly to illegal acts such as smuggling," said Lee Jin-hee, head of the customs clearance bureau at the Korea Customs Service.
"We will link on-site customs inspections more closely with expert analysis by the Central Customs Laboratory to thoroughly block drugs, illegal medicines and other goods that threaten public health and safety from entering the country at the border stage," Lee added.
