Medications That Can Cause Weight Gain: What You Need to Know

1. Benadryl: The Surprising Weight Gain Culprit

Benadryl, an over-the-counter antihistamine commonly used to alleviate allergic reactions, is a surprising contributor to weight gain. Dr. Kati Forbes explains that histamine plays a role in appetite regulation. Antihistamines like Benadryl block histamine, which can interfere with the body’s "I’m full" signal, leading to overeating. Long-term or continued use exacerbates this effect, potentially resulting in unintended weight gain. This revelation is crucial for those considering regular use of such medications.

2. Paroxetine (Paxil): The Antidepressant with Weight Gain Side Effects

Paroxetine, known by the brand name Paxil, is an antidepressant that can cause significant weight gain. As a selective serotonin reuptake inhibitor (SSRI), it increases serotonin levels, but Forbes notes it’s particularly prone to causing weight gain. With increasing antidepressant use among young adults and teens, understanding these side effects is vital. Some studies indicate that up to 14% of U.S. adults take antidepressants, with weight gain often leading to discontinuation. Psychiatrists prefer alternatives to Paxil due to its adverse effects, including severe withdrawal symptoms.

3. Mirtazapine (Remeron): A Weight Gain-Inducing Antidepressant

Mirtazapine, or Remeron, prescribed for PTSD, insomnia, and depression, is another medication linked to weight gain. Forbes highlights its use as an appetite stimulant in veterinary medicine. Dr. James Kocsis notes that its antihistaminic properties cause sluggishness, contributing to weight gain. While effective, alternatives like trazodone may be preferable for those concerned about weight gain, offering similar benefits with fewer side effects.

4. Second-Generation Antipsychotics: Zyprexa and Seroquel

Second-generation antipsychotics, particularly Zyprexa and Seroquel, are known for significant weight gain, sometimes up to 30-50 pounds annually. These drugs affect neuropeptides involved in appetite control. Forbes attributes weight gain to antihistamine activity and serotonin receptor antagonism. Understanding these mechanisms helps patients and healthcare providers make informed decisions, balancing efficacy with potential side effects.

5. Dronabinol: A Synthetic THC for Appetite Stimulation

Dronabinol, a synthetic THC, is used to stimulate appetite in chemotherapy and HIV/AIDS patients. Its role in weight gain is direct, increasing appetite and calorie intake. While beneficial for certain conditions, it’s a clear contributor to weight gain, underscoring the complex relationship between medication and body weight. Patients using Dronabinol should be aware of this side effect, considering the benefits against potential weight gain.

6. Insulin: A Vital Hormone with Weight Gain Consequences

Insulin, crucial for glucose regulation, can lead to weight gain when cells absorb excess glucose, converting it into fat. Forbes distinguishes insulin from GLP-1 drugs like Ozempic, though both are injected and require refrigeration. While insulin is essential for diabetics, its side effects highlight the importance of monitoring and managing medication regimens to mitigate weight gain.

Each medication’s weight gain potential varies, but understanding these effects is key to making informed health decisions. Balancing therapeutic benefits with lifestyle considerations can help manage weight effectively, emphasizing the need for open dialogue between patients and healthcare providers.