Mesoridazine (Serentil)

Naomi Carr
Author: Naomi Carr Medical Reviewer: Amy Shelby Last updated:

Mesoridazine, also known as Serentil, is an antipsychotic medication, classified as a phenothiazine, typically used to treat schizophrenia. A number of risks and fatalities have been reported due to the use of this medication, and it has since been discontinued in the US.

Mesoridazine brand names

  • Serentil (discontinued)

What is mesoridazine prescribed for?

Mesoridazine was prescribed to treat schizophrenia, but is no longer produced or prescribed in the US, due to the reports of several serious side effects and fatalities related to abnormal and irregular heart rhythms. [1] 

If you are still taking a mesoridazine prescription, you may wish to speak to your doctor or healthcare provider about changing your medication.

Mesoridazine can only be prescribed if at least two other antipsychotic drugs have been used to treat the condition with no success. [2] It has been found to be especially helpful in the reduction of anxiety and agitation seen in schizophrenic patients. [1] 

How does mesoridazine work?

Mesoridazine is a dopamine antagonist, which means that it blocks dopamine receptors, reducing the amount of active dopamine in the brain. This results in a decrease of hyperactivity and impulsiveness, and relief of symptoms such as anxiety and agitation. [1][3]

How is mesoridazine usually taken?

Mesoridazine has historically been available as a tablet and a liquid. Tablets were produced in 10mg, 25mg, 50mg, and 100mg strengths, to be swallowed whole. The liquid was produced as 25mg per mL, to be diluted with water or a non-caffeinated soft drink, such as orange juice.

A prescription of mesoridazine will likely begin on a low dose, around 50mg given 2-3 times per day, with the dose gradually increasing over a matter of weeks, in order to find the most effective dose, which is generally 100-400mg.

However, it has been found that the higher the dose, the greater the risk of heart abnormalities. There is also evidence to suggest that these abnormalities would entirely dissipate within two weeks after stopping the medication. [2]

If you are prescribed any liquid medication, it is important that you use an appropriate implement to measure your dose, such as a syringe or a marked spoon made specifically for this purpose.

How long does mesoridazine stay in your system?

Mesoridazine may take several weeks to build up a therapeutic level in your body. Similarly, it may take several weeks for the medication to be completely out of your system.

Mesoridazine side effects

When you begin any medication, it is common to experience some adverse effects or allergic reactions. While many side effects will naturally decrease in the first week or two, some may continue or become problematic. If this occurs, you should consult your doctor immediately, as you may need an altered dose or a different medication.

Common side effects of mesoridazine include:

  • Upset stomach, including nausea, vomiting, constipation, or diarrhea
  • Pink urine (although unusual, this is not harmful)
  • Drowsiness
  • Dry mouth
  • Restlessness
  • Increase in appetite or weight
  • Headaches

Your medication may cause more serious side effects, at which point you should consult your doctor immediately.

Serious side effects of mesoridazine include:

  • Blurred vision
  • Dizziness or fainting
  • Seizures
  • Shaking
  • Muscle spasms or pain
  • Uncontrollable mouth, jaw, or tongue movements
  • Difficulties breathing or rapid breathing
  • Rash
  • Yellowing of the skin or eyes

Mesoridazine was reported to cause several heart issues, some resulting in sudden death, leading to its discontinuation.

If you are still taking this medication and experience any chest pain or irregularities in your heartbeat, contact your doctor immediately and cease taking this medication. You may need to call 911 if the side effects are severe.

Mesoridazine precautions

Mesoridazine has been discontinued due to the number of severe risks associated with the medication and the number of fatalities reported.

Always discuss with your doctor any past or present physical and mental health conditions that you have experienced, prior to beginning any new medications.

If you have any condition that slows the central nervous system, mesoridazine and other phenothiazines are not safe for you to take.

Tell your doctor about all medications you are currently taking or plan to take (including vitamins and dietary supplements), as they may cause adverse reactions.

Mesoridazine interactions

Medications and substances that have a depressant effect on the central nervous system, such as opiates, street drugs, alcohol, anesthetics, tranquilizers, and other antipsychotic agents, should not be taken with mesoridazine or other phenothiazines, as these drug interactions may result in fatality.

Mesoridazine storage

Always keep all medications out of reach of children.

Store medication in its original packaging, in airtight containers, and at room temperature (never above 86º F).

If you need to dispose of medication that has expired or is no longer needed, contact a medical professional to ensure it is disposed of appropriately. Never flush medications down the toilet or casually deposit them in a garbage bin, as this can create unnecessary risks.

What to do if you overdose on mesoridazine

If you overdose on mesoridazine, call Poison Control on 1-800-222-1222, a medical professional, or 911. Mesoridazine overdose may cause severe or fatal heart irregularities. Other symptoms of mesoridazine overdose include confusion, drowsiness, muscle rigidity or pain, difficulty breathing, or vomiting.

Frequently asked questions about mesoridazine

What are the alternative medications to mesoridazine that are still available?

There are several available medications for the treatment of schizophrenia, classified as first generation or typical antipsychotics and second generation or atypical antipsychotics. Mesoridazine is a first generation antipsychotic medication.

Second generation, or atypical, antipsychotic medications have been found to cause fewer side effects, while better treating the symptoms of schizophrenia. [4][5] Medications within this category include clozapine, chlorpromazine, quetiapine, and olanzapine.

Discuss alternative medications with your doctor, who will inform you of the potential side effects and effectiveness of these treatments, so that you can make an informed decision about which medication may be right for you. Some people may need to try various antipsychotic treatments before finding one that works well, as people tend to have different responses to medications. [6][7] 

  1. Mesoridazine. MedlinePlus. Retrieved from
  2. Novartis Pharmaceuticals Corporation. (2001). Serentil.Access Data FDA. Retrieved from
  3. National Center for Biotechnology Information. (2005, updated 2022). Compound summary for CID 4078, Mesoridazine. PubChem. Retrieved from
  4. Jackson, J.W., VanderWeele, T.J., Blacker, D., & Schneeweiss, S. (2015). Mediators of first- versus second-generation antipsychotic-related mortality in older adults. Epidemiology (Cambridge, Mass.), 26(5), 700–709. Retrieved from
  5. Meltzer, H.Y., & Gadaleta, E. (2021). Contrasting typical and atypical antipsychotic drugs. Perspectives in psychopharmacology, 19(1), 3-13. Retrieved from
  6. The Centre for Addiction and Mental Health. (n.d). Antipsychotic medications. CAMH. Retrieved from
  7. Vardanyan, R.S., & Hruby, V.J. (2006). Antipsychotics (Neuroleptics). In Elsevier. Synthesis of essential drugs(pp. 83-101). Retrieved from
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Naomi Carr
Author Naomi Carr Writer

Naomi Carr is a writer with a background in English Literature from Oxford Brookes University.

Published: Nov 22nd 2022, Last edited: Oct 24th 2023

Amy Shelby
Medical Reviewer Amy Shelby M.S. Counseling Psychology

Amy Shelby is a medical reviewer with a B.A. in Psychology from Northwestern and an M.S. in Psychology from Chatham University.

Content reviewed by a medical professional. Last reviewed: Nov 23rd 2022