Thioridazine: Chemical Formula, Indications, Mechanism of Action, Dosage, Side Effects, Warnings and Interactions

It is an antipsychotic drug previously used to treat schizophrenia and psychosis.

Due to concerns about cardiotoxicity and high-dose retinopathy, this drug is now less prescribed and used primarily for refractory cases.

Thioridazine was initially introduced in 1959 for the treatment of psychosis.

Thioridazine is usually given after other antipsychotic medications have been tried without success.

Chemical formula

  • C21H26N2S2HCl.


The presentation is in tablets of 10, 25, 50, and 100 mg.


Thioridazine is used to treat schizophrenia.

Mechanism of action

Thioridazine blocks postsynaptic D1 and D2 dopamine receptors in the brain; blocks the alpha-adrenergic effect.


It depresses the release of hypothalamic and pituitary hormones and is believed to push the reticular activation system, affecting basal metabolism, body temperature, wakefulness, vasomotor tone, and emesis.


For the treatment of schizophrenia, a starting dose of 50 to 100 mg, orally every 8 hours, is generally recommended. Increasing the amount from 200 to 800 mg, orally divided every 6 to 12 hours a day.

For depressive disorders, the recommended dose is 25 mg orally every 8 hours.

Side effects

Common side effects can include:

  • Drowsiness.
  • Dry mouth, blurred vision.
  • Nausea, vomiting, constipation , diarrhea.
  • Swelling or discharge from the breasts.
  • Changes in menstrual periods.
  • Swelling in the hands or feet

Stop using thioridazine and call your doctor at once if you have:

  • Uncontrollable muscle movements in the face (chewing, smacking the lips, frowning, moving the tongue, blinking, or moving the eyes).
  • Shaking, drooling, trouble swallowing, trouble balancing, or walking.
  • Headache.
  • Confusion, slurred speech.
  • Sudden weakness or feeling, fever, chills, sore throat, swollen gums, painful mouth sores, pain when swallowing, skin sores, cold or flu symptoms, cough.
  • Dizziness or severe headaches
  • Presence of oliguria or anuria.
  • Decreased night vision, tunnel vision, watery eyes, and increased sensitivity to light.
  • Allergic reaction with the presence of swelling of the face, mouth, tongue, or throat and difficulty breathing.
  • Seizures

Warnings and Contraindications

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

You should not use thioridazine if:

  • You have heart disease, high blood pressure, or a heart rhythm disorder.
  • You have had or have breast cancer.
  • You have liver or kidney disease.
  • Severe asthma, emphysema, or some other breathing problem.
  • You have a history of seizures.
  • He has Parkinson’s disease.
  • Tumor in the adrenal gland.
  • You have an enlarged prostate or urination problems.
  • You have low levels of calcium in your blood (hypocalcemia).
  • You have glaucoma.
  • If you have ever had a severe side effect while using thioridazine or another phenothiazine.

The longer you take thioridazine, the more movement disorders are likely to develop, such as uncontrollable muscle movements of the lips, tongue, eyes, face, arms, or legs, which may not be reversible in the long run.

This side effect occurs more often in women and older adults.

Tell your doctor if you are pregnant or plan to become pregnant while using this medicine, as antipsychotic medication can affect the fetus in the last three months of gestation.

If you become pregnant while taking thioridazine, do not stop taking it without your doctor’s advice. It is not known whether thioridazine passes into breast milk. So you should inform your doctor if you are breastfeeding a baby.

Avoid driving vehicles or operating machinery, or doing any activity that requires alertness.

Try not to get up too quickly from a sitting or lying position to avoid a fall, as you may feel dizzy.

While using thioridazine, you may need frequent blood tests. You may need to check your heart function with an EKG.

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


Thioridazine can cause a life-threatening heart rhythm disorder, mainly if you use certain medications simultaneously.

Many medications should not be taken together with thioridazine, including certain antibiotics, antidepressants, and heart or blood pressure medications.

Other antipsychotic medications and medications to treat migraine or certain narcotic pain medications prevent or treat nausea and vomiting, cancer, malaria, or AIDS.