Acute withdrawal symptoms, including nausea, vomiting and insomnia, have very rarely been described after abrupt cessation of high doses of antipsychotic drugs. Relapse may also occur and gradual withdrawal is advisable. Caution is advised in liver disease, renal failure, cardiovascular disease, epilepsy, and conditions predisposing to epilepsy and convulsions. An approximately 3-fold increased risk of cerebrovascular adverse events has been seen in randomized placebo-controlled clinical trials in the dementia population with some atypical antipsychotics. The mechanism for this increased risk is not known. Benperidol should be used with caution in risk factors for stroke. Patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption should not take this medicine as it contains lactose. As with other neuroleptics, cases of QT interval prolongation may occur. Absence of the following risk factors for onset of this type of arrhythmia should be verified prior to administration: cardiac disease, family history of sudden death and/or QT prolongation, uncorrected electrolyte disturbances, history of QT interval prolongation, ventricular arrhythmias or torsade de pointes. Concomitant neuroleptics should be avoided.