Investigations are intensifying into the safety of weight-loss medications, commonly known as “skinny pens,” as Brazil’s national health regulatory agency, Anvisa, investigates 65 reported deaths potentially linked to their use. The surge in reported adverse events and fatalities has prompted increased scrutiny of these drugs, particularly those containing semaglutide, liraglutide, and tirzepatide, and raised concerns about both legitimate pharmaceutical products and counterfeit versions circulating in the market.
The investigation, spanning from December 2018 to December 2025, represents a significant increase from previous reports. Earlier this month, Anvisa was investigating six deaths and had recorded 225 adverse events; those numbers have now risen to 65 deaths and 2,436 adverse events, according to reports confirmed by Brazilian media outlets. These adverse events range from common gastrointestinal issues like nausea and diarrhea to more severe complications, including reports of patients experiencing symptoms akin to imminent death. The growing number of cases underscores the potential risks associated with these medications, even as demand continues to climb.
The medications under scrutiny include Ozempic and Wegovy (both utilizing semaglutide, manufactured by Novo Nordisk), as well as versions containing liraglutida and tirzepatida – the active ingredient in Mounjaro. While initially approved for managing type 2 diabetes, these drugs have gained widespread off-label use for weight loss, fueling a booming market and, a rise in unregulated products. Anvisa emphasizes that its investigations focus on analyzing reported adverse events as part of its ongoing pharmacovigilance monitoring, rather than investigating individual deaths in isolation. The agency stated, “The value of notifications as evidence lies in the set of data that, when added together and analyzed globally, can indicate changes in the safety and efficacy profile of medications.”
The Rise of Unregulated “Skinny Pens” and Contraband
A significant portion of the safety concerns stems from the proliferation of unregulated versions of these medications. Anvisa reports that cases are arising from pens produced by unauthorized pharmacies and laboratories, as well as products smuggled from other South American countries and sold illegally. In January 2026, Brazilian police detained a criminal organization in Guarulhos with a shipment of counterfeit weight-loss pens valued at R$1 million, highlighting the scale of the illicit trade. The lack of quality control and oversight in these unregulated products poses a serious threat to public health, as their composition and dosage may be unknown or inconsistent.
The process of investigating these cases is complex and time-consuming, according to Anvisa. Determining a direct causal link between the medications and reported deaths is challenging, as underlying health conditions and the concurrent use of other medications can contribute to adverse outcomes. The agency’s investigations involve extensive clinical and scientific analysis to assess the potential role of these drugs in each case.
Pancreatitis and Other Adverse Reactions
On February 9th, Anvisa issued an alert regarding the risk of pancreatitis associated with the use of these weight-loss pens. Pancreatitis, an inflammation of the pancreas, is now recognized as a potential adverse reaction, and both pharmaceutical companies producing these medications have updated their product information accordingly. Eli Lilly, the manufacturer of Mounjaro (tirzepatida), states in its product labeling that pancreatitis is considered an uncommon adverse reaction. The company advises patients to consult with their healthcare provider if they experience symptoms of pancreatitis and to discontinue use of the medication if necessary.
Novo Nordisk, which markets Ozempic, Wegovy, and Saxenda, acknowledged that while the risk of pancreatitis is already noted in the approved product labels in Brazil, the number of reported cases has been increasing both nationally and internationally. The company emphasized the need to reinforce safety guidance for patients and healthcare professionals. These medications work by mimicking the effects of glucagon-like peptide-1 (GLP-1), a hormone that regulates blood sugar and appetite. While effective for weight management and diabetes control, GLP-1 receptor agonists can also have potential side effects, including nausea, vomiting, diarrhea, and, in rare cases, pancreatitis.
Understanding GLP-1 Receptor Agonists and Their Risks
GLP-1 receptor agonists, like semaglutide and tirzepatide, have become increasingly popular for both diabetes management and weight loss due to their ability to improve blood sugar control and promote feelings of fullness. However, their use is not without risk. Beyond pancreatitis, potential side effects can include gallbladder problems, kidney issues, and, in rare cases, thyroid tumors observed in animal studies. It’s crucial for individuals considering these medications to have a thorough discussion with their doctor about the potential benefits and risks, as well as any pre-existing health conditions that might increase their susceptibility to adverse effects.
Global Concerns and Regulatory Responses
The concerns surrounding these medications are not limited to Brazil. Regulatory agencies worldwide are monitoring the safety of GLP-1 receptor agonists and investigating reports of adverse events. The increasing demand for these drugs has also led to shortages in some regions, raising concerns about access for patients who genuinely need them for medical reasons. The World Health Organization (WHO) has not yet issued a formal statement specifically addressing the recent surge in adverse event reports, but continues to monitor the situation closely.
The Brazilian situation highlights the broader challenges of regulating the pharmaceutical market and combating the trade in counterfeit medications. Strengthening border controls, increasing public awareness about the risks of purchasing medications from unregulated sources, and enhancing collaboration between regulatory agencies are crucial steps in protecting public health. Anvisa’s ongoing investigation and its commitment to transparency are essential in addressing these concerns and ensuring the safe use of these medications.
Key Takeaways
- Anvisa is investigating 65 deaths potentially linked to the use of weight-loss pens containing semaglutide, liraglutide, and tirzepatide.
- The proliferation of unregulated and counterfeit versions of these medications poses a significant public health risk.
- Pancreatitis has been identified as a potential adverse reaction, and both Eli Lilly and Novo Nordisk have updated their product labeling accordingly.
- Patients considering these medications should discuss the potential benefits and risks with their healthcare provider.
Anvisa is expected to provide further updates on its investigation in the coming months. The agency continues to urge patients to report any suspected adverse events to its pharmacovigilance system. For more information on the safety of medications and to report adverse events, visit the Anvisa website: https://www.gov.br/anvisa/pt-br. We encourage readers to share their experiences and perspectives on this important issue in the comments below.