Generic name: thioridazine [ THYE-oh-RID-a-zeen ]
Brand names: Mellaril, Mellaril-S
Dosage form: oral tablet (10 mg; 100 mg; 25 mg; 50 mg)
Drug class: Phenothiazine antipsychotics

Medically reviewed by Drugs.com on Aug 3, 2023. Written by Cerner Multum.

What is thioridazine?

Thioridazine is a phenothiazine (FEEN-oh-THYE-a-zeen) antipsychotic medicine that is used to treat schizophrenia.

Thioridazine is usually given after other treatments have failed.

Thioridazine may also be used for purposes not listed in this medication guide.

Thioridazine side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

High doses or long-term use of thioridazine can cause a serious movement disorder that may not be reversible. The longer you use thioridazine, the more likely you are to develop this disorder, especially if you are a woman or an older adult.

Thioridazine may cause serious side effects. Call your doctor at once if you have:

• uncontrolled muscle movements in your arms, legs, or face (chewing, lip smacking, frowning, tongue movement, blinking or eye movement);

• fast or pounding heartbeats, fluttering in your chest, shortness of breath, and sudden dizziness (like you might pass out);

• agitation, confusion;

• seizure (convulsions);

• decreased night vision, tunnel vision, watery eyes, increased sensitivity to light;

• little or no urinating;

• low white blood cell counts--fever, chills, mouth sores, skin sores, sore throat, cough, trouble breathing, feeling light-headed; or

• severe nervous system reaction--very stiff (rigid) muscles, high fever, sweating, confusion, fast or uneven heartbeats, tremors, feeling like you might pass out.

Common side effects of thioridazine may include:

• drowsiness;

• dry mouth, blurred vision;

• nausea, vomiting, constipation, diarrhea;

• breast swelling or discharge;

• changes in your menstrual periods; or

• swelling in your hands or feet.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Warnings

You should not use thioridazine if you have a heart rhythm disorder, a history of long QT syndrome, untreated or uncontrolled high blood pressure, very low blood pressure, or if you have drowsiness, slow breathing, weak pulse, or decreased alertness.

Thioridazine is not approved for use in older adults with dementia-related psychosis.

Thioridazine can cause a serious heart problem, especially if you also use certain other medicines for infections, asthma, heart problems, high blood pressure, depression, mental illness, cancer, malaria, or HIV. Tell your doctor about all your current medicines and any you start or stop using.

Before taking this medicine

You should not use thioridazine if you are allergic to it, or if you have:

• heart problems;

• long QT syndrome (in you or a family member);

• untreated or uncontrolled high blood pressure;

• very low blood pressure; or

• if you have drowsiness, slow breathing, weak pulse, or decreased alertness (such as after drinking alcohol or taking medicines that make you sleepy).

Thioridazine can cause a serious heart problem. Your risk may be higher if you also use certain other medicines. Your doctor may change your treatment plan if you also use:

• antibiotics;

• antidepressants;

• blood pressure medicine;

• cancer medicine;

• certain HIV/AIDS medicines;

• heart rhythm medicine;

• medicine to treat or prevent malaria; or

• other antipsychotic medicines.

Tell your doctor if you have ever had:

• heart problems, high blood pressure;

• slow heartbeats that have caused you to faint;

• breast cancer;

• liver or kidney disease;

• seizures;

• Parkinson's disease;

• enlarged prostate or urination problems;

• low levels of potassium in your blood (hypokalemia); or

• a serious side effect while using thioridazine or another phenothiazine.

Tell your doctor if you are pregnant or if you become pregnant. Taking antipsychotic medicine in the last 3 months of pregnancy may cause breathing problems, feeding problems, or withdrawal symptoms in the newborn.

It may not be safe to breastfeed while using thioridazine. Ask your doctor about any risk.

How should I take thioridazine?

Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose. Use the medicine exactly as directed.

You will need frequent medical tests. Your heart function may need to be checked using an electrocardiograph or ECG (sometimes called an EKG).

If you need surgery, tell the surgeon ahead of time that you are using thioridazine.

Store at room temperature away from moisture, heat, and light.

Thioridazine dosing information

Usual Adult Dose for Schizophrenia:

Initial dose: 50 to 100 mg orally 3 times a day
Maintenance dose: 200 to 800 mg/day, divided into 2 to 4 doses
Maximum dose: 800 mg/day

Comment: Once control is attained, the dose should be gradually lowered to determine the minimum effective maintenance dose.

Use: Patients with schizophrenia who have failed to respond to treatment with at least 2 other antipsychotic agents due to insufficient effectiveness or inability to achieve an effective dose due to intolerable side effects

Usual Pediatric Dose for Schizophrenia:

Initial dose: 0.5 mg/kg/day orally, in divided doses
Maximum dose: 3 mg/kg/day, in divided doses

Comment: The dose should be increased gradually until therapeutic effects are observed and/or the maximum dose is reached.

Use: Patients with schizophrenia who have failed to respond to treatment with at least 2 other antipsychotic agents due to insufficient effectiveness or inability to achieve an effective dose due to intolerable side effects

What happens if I miss a dose?

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking thioridazine?

Avoid driving or hazardous activity until you know how thioridazine will affect you. Dizziness or drowsiness can cause falls, accidents, or severe injuries.

Avoid getting up too fast from a sitting or lying position, or you may feel dizzy.

Avoid drinking alcohol. Dangerous side effects could occur.

What other drugs will affect thioridazine?

Taking thioridazine with other drugs that make you sleepy or slow your breathing can cause dangerous or life-threatening side effects. Ask your doctor before using opioid medication, a sleeping pill, a muscle relaxer, or medicine for anxiety or seizures.

Many drugs can affect thioridazine, and some drugs should not be used at the same time. Tell your doctor about all your current medicines and any medicine you start or stop using. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed here.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Medical Disclaimer

Copyright 1996-2024 Cerner Multum, Inc. Version: 18.01.