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Thioridazine Side Effects

Medically reviewed by Last updated on Sep 23, 2020.

In Summary

More frequently reported side effects include: syncope, akathisia, constipation, dizziness, drowsiness, epithelial keratopathy, increased serum prolactin, nasal congestion, retinitis pigmentosa, sedated state, star-shaped cataract, urinary retention, visual disturbance, hypohidrosis, and xerostomia. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to thioridazine: oral tablet


  • An unsafe heartbeat that is not normal (long QT on ECG) has happened with this drug. Sudden deaths have rarely happened in people taking this drug. Talk with the doctor.
  • This drug must only be used when other drugs cannot be used or have not worked. Talk with your doctor to be sure that the benefits of this drug are more than the risks.
  • There is a higher chance of death in older adults who take this drug for mental problems caused by dementia. Most of the deaths were linked to heart disease or infection. This drug is not approved to treat mental problems caused by dementia.

What are some side effects that I need to call my doctor about right away?

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

  • Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
  • Trouble controlling body movements, twitching, change in balance, trouble swallowing or speaking.
  • A heartbeat that does not feel normal.
  • Dizziness or passing out.
  • Chest pain or pressure or a fast heartbeat.
  • Shakiness, trouble moving around, or stiffness.
  • Feeling confused.
  • Mood changes.
  • Seizures.
  • Swelling in the arms or legs.
  • Change in eyesight.
  • Feeling very sleepy.
  • Feeling very tired or weak.
  • Restlessness.
  • Pale skin.
  • Enlarged breasts.
  • Nipple discharge.
  • Sex problems like lowered interest in sex or ejaculation problems.
  • Period (menstrual) changes.
  • Some people may get a severe muscle problem called tardive dyskinesia. This problem may lessen or go away after stopping this drug, but it may not go away. The risk is greater with diabetes and in older adults, especially older women. The risk is greater with longer use or higher doses, but it may also occur after short-term use with low doses. Call your doctor right away if you have trouble controlling body movements or problems with your tongue, face, mouth, or jaw like tongue sticking out, puffing cheeks, mouth puckering, or chewing.
  • A very bad and sometimes deadly health problem called neuroleptic malignant syndrome (NMS) may happen. Call your doctor right away if you have any fever, muscle cramps or stiffness, dizziness, very bad headache, confusion, change in thinking, fast heartbeat, heartbeat that does not feel normal, or are sweating a lot.

What are some other side effects of this drug?

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.

You may report side effects to the FDA at 1-800-332-1088. You may also report side effects at

For Healthcare Professionals

Applies to thioridazine: oral concentrate, oral suspension, oral tablet

Nervous system

Frequency not reported: Lethargy, drowsiness, pseudoparkinsonism, extrapyramidal symptoms, headache, hyperactivity, akathisia, motor restlessness, dystonic reactions, opisthotonos, tremor, akinesia, tardive dyskinesia, neuroleptic malignant syndrome[Ref]

Drowsiness has been reported to subside with continuation of therapy or a reduction in dosage.[Ref]


ECG changes are predicted to be reversible and are likely due to altered repolarization.[Ref]

Frequency not reported: Pallor, peripheral edema, edema, dose-related QT prolongation, Torsades de pointes, arrhythmia, polymorphic ventricular tachycardia/fatal polymorphic ventricular tachycardia, hypotension, cardiac arrest, ECG changes, bifid T/U wave, depression and inversion of the T wave[Ref]


Frequency not reported: Restlessness, nocturnal confusion, psychotic reactions, agitation, altered libido, excitement, bizarre dreams, aggravation of psychoses, toxic confusional states[Ref]


Frequency not reported: Dermatitis, urticarial skin eruptions, urticaria, photosensitivity, erythema, exfoliative dermatitis, contact dermatitis, angioneurotic edema, progressive skin pigmentation[Ref]


Frequency not reported: Dry mouth, constipation, nausea, vomiting, diarrhea, parotid swelling, obstipation, paralytic ileus[Ref]


Frequency not reported: Galactorrhea, breast engorgement, lactation, menstrual abnormalities/amenorrhea, urinary retention, urinary incontinence, inhibition of ejaculation

Postmarketing reports: Priapism[Ref]


Frequency not reported: Agranulocytosis, leukopenia, eosinophilia, thrombocytopenia, anemia, aplastic anemia, pancytopenia[Ref]


Frequency not reported: Blurred vision, miosis, oculogyric crises, progressive conjunctival pigmentation, discoloration of exposed sclera and cornea, stellate/irregular-shaped opacities of anterior lens and cornea[Ref]


Frequency not reported: Sudden death, fever, hyperpyrexia, skin-eye syndrome[Ref]


Frequency not reported: Trismus, torticollis, muscular rigidity, systemic lupus erythematosus-like syndrome[Ref]


Frequency not reported: Nasal stuffiness, laryngeal edema, asthma[Ref]


Frequency not reported: Jaundice, biliary stasis[Ref]


Frequency not reported: Gynecomastia, false positive pregnancy tests[Ref]


Frequency not reported: Anorexia, weight gain[Ref]


1. "Product Information. Mellaril (thioridazine)." Sandoz Pharmaceuticals Corporation, East Hanover, NJ.

Further information

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

Some side effects may not be reported. You may report them to the FDA.