Common Orthostatic hypotension (sudden lowering of blood pressure on standing), Sleepiness, Dryness in mouth, Abnormality of voluntary movements, Parkinsonism, Weight gain, Akathisia, Dystonia, Constipation.

Expert advice for Multizine Tablet

Take precautions as long term use of thioridazine may cause neuroleptic malignant syndrome (characterized by extreme body temperature, muscle rigidity, altered mental status) and tardive dyskinesia (disorder resulting in involuntary, repetitive body movements).
You may be at risk of developing hypotension (low blood pressure) during the treatment with thioridazine if you are a female or an elderly or alcoholic patient.
Tell your doctor if you are suffering from narrow-angle glaucoma (increased pressure inside the eyes that causes visual problem), prostatic hypertrophy (enlargement of organ called prostate), heart disease or epilepsy.
You should undergo regular eye examinations if you are receiving thioridazine for long term or in high doses or if you have liver disease.
Do not drive or operate machinery as thioridazine may impair the mental and/or physical abilities.
Tell your doctor if you are or planning to become pregnant or are breastfeeding.