The Hidden Dangers of Illegal Weight-Loss Pens

A 42-year-old administrative assistant from Belo Horizonte has been hospitalized in critical condition since December following severe complications from an unauthorized weight-loss pen. Kellen Oliveira Bretas Antunes used the medication, which was brought from Paraguay, without medical guidance or prescription.

Her ordeal began with intense abdominal pain that required immediate hospitalization. Over the following weeks, her condition deteriorated significantly, developing into neurological alterations. Doctors suspect she may have developed a syndrome capable of compromising her muscles, movements, speech, and the function of various organs.

Experts explain that such severe health evolution is common when products do not adhere to basic pharmaceutical standards. Laboratory analyses of weight-loss pens sold outside regulated networks have repeatedly identified substances that differ entirely from what the medication should contain.

According to Dr. Maria Fernanda Barca, an endocrinologist from the University of São Paulo’s School of Medicine, lab results from similar cases have revealed:

• Solutions with purity levels far below acceptable standards
• Vials lacking minimum sterility requirements
• Raw materials of unknown origin
• Attempts to mimic industrial concentration without technical precision
• The presence of sibutramina, a substance banned for injectable use

Many of the damages begin at the production chain. These pens are manufactured in environments that do not follow basic hygiene norms, using cheap and untraceable raw materials. Super-concentrated vials sold to multiple patients further amplify the risk of contamination.

The disparity between legitimate medication and illegal alternatives is stark. Dr. Clayton Macedo, an endocrinologist at the Hospital Israelita Albert Einstein, confirms the gravity of the situation. In independent tests, vials sold as tirzepatida—the active ingredient in Mounjaro—showed purity levels between 7% and 14%. The actual medication requires 99% purity.

“It is another substance. It is an unstable compound. It does not behave like tirzepatida and cannot generate the expected therapeutic effect.”

While Brazilian law permits the compounding of tirzepatida, ANVISA enforces strict conditions: proven purity of ingredients, total traceability, sterile environments, and production strictly on demand for a single patient. When these criteria are ignored, the preparation is irregular. If the product lacks tirzepatida entirely or contains undeclared ingredients, it is considered a forgery.

The illegal market operates in two prohibited zones: lack of traceability and lack of sterility. For the consumer, this difference is invisible; for the body, it is decisive. Ivete de Freitas, a 69-year-old retiree, experienced a different side of this market. Despite having a legitimate prescription for Mounjaro, she was tempted by a lower price offered by a friend importing from Argentina.

Minutes after applying the substance, her body was covered in red patches. “It looked like measles; it rose from her waist to her neck. At night it got worse,” she described. She continued four more applications before stopping as the symptoms intensified. Her doctor confirmed the situation could have been much more severe. Dr. Barca notes that other common reactions include psychotic outbreaks and diverticulitis, with a risk of death in serious cases.

When tirzepatida does not follow pharmaceutical standards, the body is the first to react. The molecule is sensitive and requires high purity and a sterile environment. Without these, effects can be immediate or cumulative.

Violent gastrointestinal reactions are the most frequent, including persistent vomiting, incapacitating nausea, intense diarrhea, dehydration, and abrupt drops in blood pressure. These are not side effects of the original drug but results of impurities, inadequate solvents, or thermal degradation of the molecule.

The risk of infection also increases. Solutions made without sterility can introduce bacteria into the subcutaneous tissue, causing abscesses, local inflammation, fever, and systemic infection. Chemical composition changes can lead to neurological and cardiovascular issues such as intense dizziness, palpitations, tachycardia, arrhythmia, and blood pressure spikes.

Furthermore, the risk of incorrect dosing is silent. Counterfeit products may deliver concentrations far above or below what is necessary. High concentrations can provoke hypoglycemia and sudden malaise, while low concentrations simply do not work, leading patients to dangerously increase the dose on their own.

The manufacturer of Mounjaro, Eli Lilly, has taken a firm stance against the illegal market. The company states it does not produce, commercialize, or authorize the manufacture of the medication in compounding pharmacies, nor the sale of bulk, fractionated, or refilled products.

According to the company, any liquid solution sold as tirzepatida outside official channels must be considered counterfeit. In recent analyses, the company identified clandestine ampoules containing unknown substances, impurities, a complete absence of tirzepatida, and mixtures with other active ingredients such as undeclared stimulants.

Eli Lilly emphasizes that the chemical and microbiological integrity of these products cannot be guaranteed. There is no quality control, sterility, cold chain, or traceability of raw material origins. The legitimate Mounjaro is distributed only in sealed, traceable, single-use disposable pens via prescription.

The case of Kellen Oliveira Bretas Antunes serves as a grave warning about the unregulated pharmaceutical market. The pursuit of weight loss through unauthorized channels carries risks that extend far beyond ineffectiveness, potentially leading to permanent organ damage or death.

Consumers must understand that traceability and sterility are not bureaucratic formalities but essential safety barriers. The absence of these safeguards in illegal products creates a direct pathway for toxins, bacteria, and incorrect dosages into the human body.

Ultimately, the financial savings offered by the black market are insignificant compared to the potential cost of a lifetime of medical complications or the loss of life itself. Medical supervision remains the only safe path for managing weight and diabetes.