Safety of Obesity Medicines: Lessons Learned from Withdrawn Drugs

Safety of Obesity Medicines: Lessons Learned from Withdrawn Drugs

Obesity is a global health concern affecting millions worldwide, leading to various chronic conditions and reducing overall quality of life. To combat this epidemic, pharmaceutical companies have developed and marketed several obesity medicines. While these medications have provided hope for many individuals struggling with weight management, there have been instances where the safety of certain drugs has been called into question, leading to their withdrawal from the market. This article explores the importance of safety in obesity medicines and provides examples of drugs withdrawn due to safety concerns.

The Need for Safe Obesity Medicines

Developing effective obesity medications is crucial in addressing the complex nature of weight management. These drugs are designed to supplement lifestyle changes, such as diet and exercise, to help individuals achieve and maintain a healthy weight. However, the safety of these medicines must always be a top priority. Adverse effects and potential risks associated with obesity medications can have severe consequences for patients, making it essential to evaluate their safety profile before and after market approval thoroughly.

Withdrawn Obesity Medicines: Learning from Past Mistakes

Fen-Phen (fenfluramine/phentermine):

One of the most well-known examples of withdrawn obesity medicines is Fen-Phen. This combination drug, containing fenfluramine and phentermine, was approved in the 1990s and rapidly gained popularity. However, reports of serious heart valve damage and pulmonary hypertension emerged, leading to its withdrawal in 1997. The Fen-Phen case highlighted the importance of post-marketing surveillance and reinforced the need for rigorous, long-term safety studies.

Rimonabant (Acomplia):

Rimonabant, marketed under the brand name Acomplia, was approved in some countries as an anti-obesity drug. It works by blocking cannabinoid receptors in the brain, reducing appetite and cravings. However, concerns regarding psychiatric side effects, including depression and suicidal ideation, led to its withdrawal from the market in 2008. The case of Rimonabant underscored the significance of monitoring psychiatric effects during clinical trials and post-marketing surveillance.

Sibutramine (Meridia):

Sibutramine, sold under Meridia, was an appetite suppressant approved for weight management. However, cardiovascular risks associated with the drug, including an increased risk of heart attacks and strokes, prompted its withdrawal in 2010. The discontinuation of Sibutramine highlighted the importance of ongoing safety monitoring and evaluation even after initial approval.

Recent Safety Concerns with Obesity Drugs:

In 2022, the European Medicines Agency’s safety committee (PRAC) recommended the withdrawal of European Union marketing authorizations for amfepramone obesity medicines. This decision followed a review that revealed inadequate effectiveness of measures aimed at restricting the use of these medicines for safety reasons. The review found that patients were using the medications longer than the recommended maximum duration of 3 months. Such prolonged usage increases the risk of serious side effects, including pulmonary arterial hypertension and dependency.

In 2023, Pfizer announced the discontinuation of its experimental obesity and diabetes pill, lotiglipron, due to elevated levels of liver enzymes observed in patients participating in mid-stage clinical studies. As a result, the company has shifted its focus to another oral obesity drug, danuglipron, which is currently undergoing a fully enrolled phase two clinical trial.

Lessons Learned

These recent incidents serve as valuable lessons in ensuring the safety of obesity drugs. The recommendations to withdraw amfepramone obesity medicines highlight the importance of implementing more effective measures to restrict their usage, particularly concerning the duration of treatment. This is crucial to minimize the potential risks associated with long-term use, such as pulmonary arterial hypertension and dependency.

Pfizer’s decision to discontinue lotiglipron underscores the significance of closely monitoring drug safety during clinical studies. Identifying elevated liver enzymes in patients prompted the company to prioritize patient well-being and redirect its efforts toward developing a safer alternative in the form of danuglipron.

Ensuring Safety in Obesity Medicines

The examples mentioned above highlight the critical need for stringent safety evaluation throughout the lifecycle of obesity medicines. Implementation of several measures is necessary to ensure the safety of these medications. 

Thorough Clinical Trials: 

Obesity medications should undergo rigorous clinical trials evaluating their effectiveness and safety. Long-term studies should be conducted to monitor potential adverse effects that may emerge over time.

Post-Marketing Surveillance: 

Active surveillance systems should be in place to monitor the safety of obesity medicines once they are approved and made available to the public. This helps to identify any previously unknown adverse effects or rare complications.

Communication and Patient Education: 

Healthcare providers should communicate the potential risks and benefits of obesity medications to patients, enabling them to make informed decisions. Patients must know the importance of regular follow-ups and reporting any concerning symptoms.

Regulatory Scrutiny: 

Regulatory bodies should maintain strict oversight and thoroughly assess obesity medicines before approving them. Additionally, they should continuously review safety data and take prompt action if potential risks emerge.


Developing safe and effective obesity medicines is crucial in addressing the global obesity epidemic. However, drug withdrawals due to safety concerns serve as a reminder of the paramount importance of safety. Withdrawn obesity medicines highlight the need for robust clinical trials, post-marketing surveillance, effective communication, and regulatory scrutiny. Pharmacovigilance plays a pivotal role in ensuring the safety of obesity medicines. While clinical trials assess safety and efficacy before market approval, comprehensive post-marketing surveillance is equally vital to monitor a more extensive population’s adverse effects and unforeseen risks. Active pharmacovigilance involves monitoring scientific literature, databases, and safety reports to identify potential safety signals and emerging evidence related to obesity medicines. This proactive approach allows regulatory authorities and healthcare professionals to take timely actions to protect patient safety, such as updating prescribing information or withdrawing drugs if necessary.

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