Skip to main content

Does Fycompa cause weight gain?

Medically reviewed by Philip Thornton, DipPharm. Last updated on Nov 23, 2022.

Official answer


Weight gain is a common dose-related side effect of Fycompa (perampanel), a non-competitive AMPA glutamate receptor antagonist used to treat epilepsy. It occurs in about 4 percent of patients treated with an 8 mg or 12 mg dose of the drug. Monitoring for weight gain is recommended while being treated with Fycompa.

In a trial conducted in adults with partial-onset seizures, adults treated with Fycompa for 19 weeks gained more weight compared with adults who received placebo (2.5 lbs [1.1 kg] vs 0.7 lbs [0.3 kg]).

A total of 9.1 and 0.9 percent of Fycompa-treated adults gained at least 7 and 15 percent of their baseline (at the beginning of the study) body weight, respectively. This was more than the 4.5 and 0.2 percent of placebo recipients who gained at least 7 and 15 percent, respectively.

In a separate study conducted in adults and adolescents with primary generalized tonic-clonic seizures, a similar level of weight gain was observed.

Patients with mild-to-moderate intellectual disabilities also gain significantly more body weight while on Fycompa compared with patients with severe intellectual disabilities or no intellectual disabilities who took the drug, according to the results of a clinical study. This was thought to be because Fycompa-induced food intake was greater in patients with mild-to-moderate intellectual disability due to weaker behavioral control. The same body weight gains were not observed in patients with severe intellectual disability, which was likely due to their food intake being controlled by a caregiver.


Read next

Related medical questions

Drug information

Related support groups