They commonly cause dryness of the mouth and may cause nausea, blurred vision, increased heart rate, constipation, and urinary retention in men with enlarged prostates. People with glaucoma should use these drugs cautiously. Anticholinergics may even cause significant mental problems, including memory loss, confusion, and hallucinations, which can mimic schizophrenia. They also interact with alcohol and antihistamines. Most experts oppose the routine use of anti-parkinsonism drugs for schizophrenia and recommend them only for patients who cannot be monitored regularly and for those who need very high doses of powerful antipsychotic drugs and are at risk for severe side effect.
Experts recommend they be withdrawn after three or four months if possible.
If symptoms recur, the drugs can be reinstituted. It should be noted that withdrawal from anticholinergics can cause depression that can exacerbate schizophrenia. In one study, it safely improved not only the neuroleptic side effects but also symptoms of psychosis. Side effects include headache, fatigue, constipation, and dry mouth. Vitamin B6 may help relieve these symptoms.