Thioridazine is an antipsychotic medication sometimes prescribed for people who have been diagnosed with schizophrenia, approved by the Food and Drug Administration for this purpose. [1] Thioridazine carries a high risk of adverse side effects so anyone taking it is advised to remain under close supervision from their medical team. Because of this risk, Thioridazine is only recommended if someone has already tried at least two other antipsychotic drugs which have not been effective for them. [2]

Thioridazine brand names

Thioridazine was commonly known in the US by the brand name Mellaril; however, this medication was withdrawn by its manufacturer across the world in 2005 because of the side effects people taking it were experiencing. [3] Some non-brand name versions of the medication remain available.

Other names Thioridazine is known as include:

  • Mallorol
  • Malloryl
  • Meleril
  • Mellaril-S
  • Mellerets
  • Mellerette
  • Melleretten
  • Melleril
  • Novoridazine
  • Orsanil
  • Ridazin
  • Ridazine
  • Sonapax
  • Thioril
  • Aldazine [4]

What is Thioridazine prescribed for?

This type of antipsychotic drug is primarily used to treat the positive symptoms of schizophrenia, which include hallucinations, delusions, and disorganized thoughts. [5] Although not approved for this use, this drug can also be used to treat depressive disorders and behavioral disorders in children. [6]

Similarly, although not approved by the Food and Drug Administration for this use, some people take Thioridazine for the symptoms of dementia, but there is an increased risk of adverse side effects for older people who take this drug.

How does Thioridazine work?

In simple terms, Thioridazine calms down unusual brain activity by blocking dopamine receptors. Dopamine is a neurotransmitter, or brain chemical, that is responsible for a large number of functions and feelings including pleasure, excitement, motivation, movement and memory.

The drug also has an impact on muscarinic receptors, which are related to the functioning of the nervous system. This is why Thioridazine can cause side effects like a dry mouth and constipation, because the regulation of these functions through the nervous system is impacted.

How is Thioridazine usually taken?

Thioridazine is usually taken between two and four times a day and it is recommended that you try to take your doses at roughly the same time each day. It is taken orally, in a tablet which can come in anything from 10 mg to up to 200 mg strength. Generally, clinicians will start you on the lowest possible dose and monitor its impact before progressing to a higher dosage in strength and frequency.

Because Thioridazine is a powerful medication, it is very important to stick to your treatment regime and to continue to take it at the same intervals and at the same strength, even if you are feeling better than you were, feeling worse than usual or even feeling completely well. If you want to come off the medication, you should seek advice from your doctor before proceeding.

If you miss a dose and remember soon after, try to take it as soon as you can. If you only remember near to the time your next dose is due, skip it. Do not take two doses in quick succession because of the risk of overdosing.

Because of the way Thioridazine interacts with other medications and even vitamins, it is advisable to carry a list with you of which medications you take in case a clinician needs to see it before making a medical decision, especially in an emergency.

Thioridazine side effects

Thioridazine is only recommended for people who have already tried at least two other similar antipsychotic drugs but did not find them effective, because there are other medications designed to have similar benefits while carrying a lower risk of adverse side effects.

One of the most serious side effects of Thioridazine is that it can lead to the development of an irregular heartbeat, which can lead to death. It is recommended that clinicians wanting to prescribe this medication consult with a psychiatrist to see if there is any other option before proceeding with it.

Another key risk that Thioridazine carries is that it can make people feel suicidal, which also increases their risk of death. Using Thioridazine over a long period of time, or at high strengths, can also lead to someone developing a permanent movement disorder, with women and older people at highest risk of this adverse effect.

Common adverse effects of Thioridazine include:

  • Feeling tired or drowsy and having blurred vision, all of which can impact your ability to work, especially if you carry out manual labor.
  • Feeling sick a lot of the time, and throwing up frequently.
  • Changes in bowel movements, including constipation and diarrhea, and difficulty urinating.
  • Changes in appetite, which can lead to weight gain or loss.
  • A change in the way your skin looks, including darker eyes and paler skin on the rest of your body.
  • Parkinsonism - this includes various symptoms commonly associated with Parkinson’s diseases including tremors, body stiffness, a shuffling walk and unusual body movements that might be very slow or restless. [7]
  • Parts of your body swelling up including your limbs, feet, hands and ankles.
  • A change in breast size, including swelling, breast milk production or breast discharge and changes in menstruation for women.
  • Reduced libido and difficulty with sexual functioning for men.

Unusual adverse effects include:

  • Changes to your heartbeat, including a fast, pounding and jumpy heartbeat.
  • Feeling lightheaded or fainting.
  • Sweating a lot or developing a fever or skin rash.
  • Feeling very confused about who you or the people around you are and what is going on.
  • Having trouble with swallowing food or drink, feeling tight in your throat, struggling to breathe, your tongue sticking out of your mouth or moving a lot.
  • Facial movements that are out of control, particularly around the mouth and jaw.
  • Temporary blindness or seeing everything with a colored tint on it.
  • An erection that continues for many hours.
  • A yellow tinge to the skin and/or the eyes.

If you or someone you know is experiencing any of these symptoms, you should seek help immediately, either by calling the poison control helpline at 1-800-222-1222, or by calling 911.

Thioridazine interactions and precautions

Interactions

Not only does Thioridazine carry a high risk of adverse side effects, it is also highly interactive with other medications and substances.

Other medications that interact with Thioridazine include (brand names in brackets):

  • Amiodarone (Cordarone), sotalol (Betapace, Betapace AF) and dofetilide (Tikosyn) - used to treat heartbeat abnormalities
  • Disopyramide (Norpace) - a heart medication
  • Erythromycin (E.E.S., E-Mycin, Erythrocin) and moxifloxacin (Avelox) - used to treat bacterial infections
  • Fluoxetine (Prozac, Sarafem), paroxetine (Paxil, Pexeva) and fluvoxamine (Luvox) - used to treat depression
  • Pimozide (Orap) - another antipsychotic drug
  • Pindolol (Visken) and propranolol (Inderal) - used to treat high blood pressure

It is also important to check whether you might be allergic to Thioridazine before starting to take it. If you have had an allergic reaction to chlorpromazine, fluphenazine, perphenazine, prochlorperazine (Compro), promethazine (Phenergan), or trifluoperazine, you should not take Thioridazine.

This medication can also interact with other things you are taking like vitamins, or medication for Parkinson’s disease, sleeping medication or sedatives and medication used to treat IBS, asthma, malaria, cancer and HIV. This is why it is crucial to talk honestly with your doctor about other conditions you have and medications you are taking before starting to take Thioridazine.

Precautions

Other factors that can put you at greater risk while taking Thioridazine include:

  • Any personal or family history of seizures or breast cancer.
  • Being over the age of 65.
  • Any personal history of difficulty urinating or having an enlarged prostate if you are a man.

You should take particular care when taking Thioridazine if you fulfill any of these criteria. Be sure to talk with your doctor about whether this is the best medication for you.

Other considerations

Other things to think about before starting to take Thioridazine include:

  • Whether you have any planned surgery coming up, as your doctor will likely advise you to wait until after it is completed to start on the medication.
  • Whether you are pregnant, likely to be pregnant or trying to become pregnant. Taking this medication in the third trimester of pregnancy can have a significant impact on both the mother and unborn child - causing breathing difficulties in the former and withdrawal symptoms in the latter when they are born. If you are trying to become pregnant, taking Thioridazine can impact the results of pregnancy tests. It is advisable to take a test before starting a course of this medication.
  • If you are breastfeeding, taking this medication can create feeding problems for you and your child, so is considered inadvisable.
  • How often you drink alcohol, as it does not interact well with this medication.

Your medical team should suggest regular tests as a precaution if you are taking Thioridazine. This might include electrocardiographs or ECGs (sometimes called an EKG) to check your heart, and eye exams, because it can pigment your eyes irreversibly. [8]

Thioridazine storage

The best way to store Thioridazine is in the container in which it was given to you, at room temperature, away from extreme heat and moisture. A dark cupboard that is not in the bathroom and does not have direct sunlight onto it is a good option, if you have one.

It is also important to make sure this medication is out of reach of other people, particularly children, and that the container is closed properly, because of the risk of adverse side effects.

If you need to get rid of Thioridazine tablets, it is recommended that you do this through a medicine take back programme. Do not give this medication to other people or flush it down the toilet.

What to do if you overdose on Thioridazine

If you overdose on Thioridazine, you should call the poison control helpline at 1-800-222-1222 immediately, or ring 911, especially if you or the person you are with is having difficulty breathing or is having a seizure.

Things to look out for that are signs of an overdose include:

  • Experiencing an unusually fast or slow heartbeat.
  • Feeling confused or agitated, and being very restless.
  • Feeling very drowsy or sleepy.
  • Having very slow or out of character bodily movements.
  • Having a seizure.
  • Having an unusually high or low body temperature.
  • Going into a coma or losing consciousness.
  • Having dilated eye pupils.
  • Struggling with constipation, to urinate, to see or to breathe.
  • Having a very dry mouth or a blocked nose.

You can also access more information to help determine whether someone is having an overdose at https://www.poisonhelp.org/help.

Resources:

  1. National Library of Medicine. (2006). Thioridazine. Retrieved December 19, 2022, from https://www.ncbi.nlm.nih.gov/books/NBK501922/
  2. Xiang, Y.T., Chiu, H.F., Ungvari, G.S., Correll, C.U., Lai, K.Y. et al. (2015). QTc prolongation in schizophrenia patients in Asia: clinical correlates and trends between 2004 and 2008/2009. Human Psychopharmacology, 30(2), 94-99.
    DOI: 10.1002/hup.2458
  3. Purhonen, M., Koponen, H., Tiihonen, J., & Tanskanen, A. (2012). Outcome of patients after market withdrawal of thioridazine: A retrospective analysis in a nationwide cohort. Pharmacoepidemiology & Drug Safety, 21(11), 1227-1231. https://doi.org/10.1002/pds.3346
  4. Drugbank Online. (2005). Thioridazine. Retrieved December 19, 2022, from: https://go.drugbank.com/drugs/DB00679
  5. Brunton, L. L., Chabner, B., Knollmann, B.C. (2011). Goodman & Gilman's the pharmacological basis of therapeutics. McGraw-Hill.
  6. Feinberg, S.M., Fariba, K.A., & Saadabadi, A. (2022). Thioridazine. National Library of Medicine. Retrieved December 19, 2022, from: https://www.ncbi.nlm.nih.gov/books/NBK459140/
  7. Euwema, M.S., & Swanson, T.J. (2022). Deadly single dose agents. National Library of Medicine. Retrieved December 19, 2022, from https://pubmed.ncbi.nlm.nih.gov/28722879/
  8. Scott, A.W. (1963). Retinal pigmentation in a patient receiving thioridazine. JAMA Ophthalmology, 70(6), 775-778. doi:10.1001/archopht.1963.00960050777009