In clinical trials, the most common side effects of Banzel were headache, dizziness, fatigue and sleepiness, double vision and tremor (trembling). The percent of people who had these side effects is given below, for people taking the highest dose (3200 mg/day). Side effects tended to be less for people on lower dosages. Some people had more than one side effect. Not all of the side effects may have been caused by Banzel, because people, for example, get headaches or fatigue for other reasons, and all patients in the trials also were taking other medicines.

Headache 27%
Dizziness 19%
Fatigue 16%
Nausea 12%
Sleepinesse 11%
Diplopia 9%
Tremor 6%
Vision Blurred 6%
Vomiting 5%
Ataxia (staggering) 4%
Abdominal pain 3%
Anxiety 3%
Constipation 3%
Stomach burning 3%
Back pain 3%
Vertigo (spinning dizziness) 3%

Patients taking Banzel have a small change of experiencing an allergic reaction known as the hypersensitivity syndrome, with fever, rash, fluid accumulation, swollen lymph nodes, liver injury and confusion.

Laboratory abnormalities: Intermediate

Blood tests sometimes show abnormalities in patients taking Banzel. White blood counts were lowered in about 4% of people, though usually not to levels that would increase risk for infections. Electrocardiograms (a heart test) showed shortening of the QT intervals in some patients, which reflects an effect on conduction of the electrical signals through the heart. People who have the “Short QT syndrome” should not take Banzel.