De mest almindelige bivirkninger (observeret hos flere end 1 ud af 10 patienter) er insomni (søvnbesvær), forstoppelse, kvalme, svedudbrud, hovedpine samt abstinenssymptomer.
The most common side-effects (seen in more than 1 patient in 10) are insomnia (difficulty sleeping), constipation, nausea (feeling sick), sweating, headache, and withdrawal syndrome.