Naltrexone is a medication used to manage alcohol use disorder and opioid use disorder. It works by blocking the euphoric feelings associated with these substances. Available as an oral tablet or extended-release injectable, it helps reduce cravings and prevent relapse as part of a comprehensive treatment plan.
Naltrexone and Weight: The Direct Answer
Naltrexone, when used alone, is generally not associated with significant weight gain. Some of its common side effects, such as nausea, vomiting, stomach pain, cramping, and loss of appetite, could lead to weight loss. The manufacturer has reported both weight gain and increased appetite as infrequent adverse events with oral naltrexone.
Naltrexone is approved for weight management when combined with bupropion (Contrave). This combination is prescribed for adults with obesity or those who are overweight with at least one weight-related health condition. Clinical trials for Contrave have shown an average weight loss ranging from 3.7% to 8.1% over 56 weeks, compared to placebo.
How Naltrexone May Influence Weight
Naltrexone functions as an opioid antagonist, blocking opioid receptors in the brain. These receptors play a role in the brain’s reward system and appetite regulation. By blocking them, naltrexone can reduce the pleasure or reward associated with eating, especially highly palatable foods. This action may decrease food intake and cravings for some individuals.
When naltrexone is combined with bupropion (Contrave), their effects are thought to be synergistic. Bupropion is believed to stimulate pro-opiomelanocortin (POMC) cells in the hypothalamus, leading to increased alpha-MSH production. Alpha-MSH contributes to decreased food intake and increased energy expenditure. Naltrexone, by blocking beta-endorphin’s inhibitory effect on these POMC cells, further enhances this pathway, potentially reducing appetite and increasing metabolism.
Other Factors Affecting Weight During Treatment
Weight changes during naltrexone treatment can be influenced by factors beyond the medication’s direct pharmacological effects. For individuals recovering from alcohol or opioid use disorder, lifestyle and health status changes are common. Quitting alcohol, for instance, can lead to weight gain as the body adjusts metabolically, and individuals may replace alcohol with comfort foods or sugary drinks. Increased appetite and fluid retention can also contribute to this weight change.
Recovery from opioid use can also result in weight gain. Chronic opioid use can lead to irregular eating patterns, nausea, and vomiting, often resulting in unintentional weight loss. As recovery progresses, appetite can normalize, and the body begins to heal, which may lead to weight restoration.
Other medications prescribed for co-occurring health conditions, such as certain antidepressants, antipsychotics, or diabetes medications, are known to cause weight gain. Therefore, any weight changes observed during naltrexone treatment might be a complex interplay of the medication’s direct effects, the body’s recovery process from substance use, and the influence of other prescribed drugs.