Are there any medications to treat unintended weight loss?

There are no medications specifically designed to increase body weight. However, several medications are known to cause weight gain as a “side effect.”

Mirtazapine, for example, is a modern antidepressant that, in addition to stabilizing mood, leads to weight gain. As a kind of “dual effect,” mirtazapine can be prescribed to patients experiencing weight loss and low mood in order to deliberately (and in consultation with the patient) achieve the side effect of weight gain. With mirtazapine, a weight gain of three to four kilograms—or at least weight stabilization—is realistic.

In rare cases, the psychiatric medication olanzapine—which was originally developed to treat schizophrenia—may be used. This medication is associated with significant weight gain (up to 10 kg in psychiatric patients). The weight gain caused by olanzapine results from neurohormonal changes and an increase in appetite. In addition to the psychiatric medications mirtazapine (an antidepressant) and olanzapine (an antipsychotic), cannabis-based medications have been reported to have a beneficial effect on appetite and weight gain.

Overall, medications that promote weight gain are an important treatment option used in specialized medical care for people with ALS, usually in combination with other nutritional support measures.