Thioridazine

Reviewed on 7/19/2022

What Is Thioridazine and How Does It Work?

Thioridazine is a prescription medication used to treat the symptoms of Schizophrenia and Depressive Disorders. 

  • Thioridazine is available under the following different brand names: Mellaril

What Are Side Effects Associated with Using Thioridazine?

Common side effects of Thioridazine include:

  • drowsiness,
  • dry mouth,
  • blurred vision,
  • nausea,
  • vomiting,
  • constipation,
  • diarrhea,
  • breast swelling or discharge,
  • changes in the menstrual periods, and
  • swelling in the hands or feet

Serious side effects of Thioridazine include:

  • hives,
  • difficulty breathing,
  • swelling of the face, lips, tongue, or throat,
  • chewing,
  • lip-smacking,
  • frowning,
  • tongue movement,
  • blinking or eye movement,
  • tremor,
  • drooling,
  • trouble swallowing,
  • problems with balance or walking,
  • headache with chest pain and severe dizziness,
  • fainting,
  • fast or pounding heartbeats,
  • confusion,
  • slurred speech,
  • seizure,
  • sudden weakness,
  • ill-feeling,
  • fever,
  • chills,
  • sore throat,
  • swollen gums,
  • painful mouth sores,
  • pain when swallowing,
  • skin sores,
  • cold or flu symptoms,
  • cough,
  • little or no urination,
  • decreased night vision,
  • tunnel vision,
  • watery eyes,
  • increased sensitivity to light,
  • very stiff (rigid) muscles,
  • high fever,
  • sweating,
  • confusion,
  • fast or uneven heartbeats,
  • tremors, and
  • light-headedness

Rare side effects of Thioridazine include:

  • none

Seek medical care or call 911 at once if you have the following serious side effects:

  • Severe headache, confusion, slurred speech, arm or leg weakness, trouble walking, loss of coordination, feeling unsteady, very stiff muscles, high fever, profuse sweating, or tremors;
  • Serious eye symptoms such as sudden vision loss, blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights;
  • Serious heart symptoms include fast, irregular, or pounding heartbeats; fluttering in the chest; shortness of breath; sudden dizziness, lightheartedness, or passing out.

This is not a complete list of side effects and other serious side effects or health problems that may occur as a result of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.

SLIDESHOW

Schizophrenia: Symptoms, Types, Causes, Treatment See Slideshow

What Are Dosages of Thioridazine?

Adult and pediatric dosage

Tablet

  • 10 mg
  • 25 mg
  • 50 mg
  • 100 mg

Schizophrenia

Adult and geriatric dosage

  • Initial 50-100 mg orally every 8 hours, THEN
  • 200-800 mg/day orally divided every 6-12 hours

Pediatric dosage

  • Children below 2 years: Safety and efficacy not established
  • 2-12 years: 0.5-3 mg/kg/day divided every 8 hours orally, no more than 3 mg/kg/day  
  • Children above 12 years: Initial 50-100 mg orally every 8 hours; titrate to 200-800 mg/day orally divided every 6-12 hours
  • Potential toxic dose for children below 6 years old: 3 mg/kg

Depressive Disorders

Adult and geriatric dosage

  • 25 mg orally every 8 hours; may titrate to effect (20-200 mg/day)

Dosage Considerations – Should be Given as Follows: 

  • See “Dosages”

What Other Drugs Interact with Thioridazine?

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

  • Thioridazine has severe interactions with at least 54 other drugs.
  • Thioridazine has serious interactions with at least 125 other drugs.
  • Thioridazine has moderate interactions with at least 311 other drugs.
  • Thioridazine has minor interactions with at least 70 other drugs.

This information does not contain all possible interactions or adverse effects. Visit the RxList Drug Interaction Checker for any drug interactions. Therefore, before using this product, tell your doctor or pharmacist about all your products. Keep a list of all your medications with you and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions or concerns.

What Are Warnings and Precautions for Thioridazine?

Contraindications

  • Documented hypersensitivity to phenothiazines
  • Coadministration with cytochrome P450 2D6 isozyme inhibitors (.g, fluoxetine and paroxetine) and certain other drugs (e.g., fluvoxamine, propranolol, and pindolol)
  • Patients who are known to have a genetic defect leading to reduced levels of activity of P450 2D6
  • Patients with hypertensive or hypotensive heart disease of the extreme degree
  • Patients in a comatose state
  • Severe CNS depression
  • Severe hyper-/hypotensive heart disease

Effects of drug abuse

  • None

Short-Term Effects

  • See “What Are Side Effects Associated with Using Thioridazine?”

Long-Term Effects

  • See “What Are Side Effects Associated with Using Thioridazine?”

Cautions

  • Avoid using in children with suspected Reye's syndrome
  • Hypotension may be particularly severe in patients with pheochromocytoma or mitral insufficiency
  • Depresses hypothalamic thermoregulatory mechanism; exposure to extreme temperatures may cause hypo- or hyperthermia
  • Leukopenia and/or agranulocytosis and convulsive seizures reported but infrequent; in schizophrenic patients with epilepsy, anticonvulsant medication should be maintained during treatment
  • Pigmentary retinopathy, which has been observed primarily in patients taking larger than recommended doses, is characterized by diminution of visual acuity, the brownish coloring of vision, and impairment of night vision; examination of the fundus discloses deposits of pigment; the possibility of this complication may be reduced by remaining within recommended limits of dosage
  • Where patients are participating in activities requiring complete mental alertness (.g, driving) it is advisable to administer the phenothiazines cautiously and to increase the dosage gradually
  • Female patients appear to have a greater tendency to orthostatic hypotension than male patients; administration of epinephrine should be avoided in the treatment of drug-induced hypotension as it may induce a reversed epinephrine effect on occasion; should a vasoconstrictor be required, the most suitable are levarterenol and phenylephrine
  • An increase in mammary neoplasms has been found in rodents after chronic administration of neuroleptic drugs; neither clinical studies nor epidemiologic studies conducted to date have shown an association between chronic administration of these drugs and mammary tumorigenesis; the available evidence is considered too limited to be conclusive at this time
  • Prolactin
    • Antipsychotic drugs elevate prolactin levels; the elevation persists during chronic administration; tissue culture experiments indicate that approximately one-third of human breast cancers are prolactin dependent in vitro, a factor of potential importance if the prescription of these drugs is contemplated in a patient with a previously detected breast cancer
    • Although disturbances such as galactorrhea, amenorrhea, gynecomastia, and impotence have been reported, the clinical significance of elevated serum prolactin levels is unknown for most patients
  • Proarrhythmic effects
    • Certain factors may increase the risk of Torsades de pointes and/or sudden death in association with the use of drugs that prolong the QTc interval, including bradycardia, hypokalemia, concomitant use of other drugs that prolong the QTc interval, presence of congenital prolongation of the QT interval, and for thioridazine, in particular, its use in patients with reduced activity of P450 2D6 or its coadministration with drugs that may inhibit P450 2D6 or by some other mechanism interfere with the clearance of thioridazine
    • Patients being considered for thioridazine treatment should have baseline ECG performed and serum potassium levels measured; serum potassium should be normalized before initiating treatment and patients with a QTc interval above 450 msec should not receive the therapy; may also be useful to periodically monitor ECG’s and serum potassium during thioridazine treatment, especially during a period of dose adjustment; therapy should be discontinued in patients who are found to have a QTc interval over 500 msec
    • Patients receiving therapy who experience symptoms that may be associated with the occurrence of Torsades de pointes (.g, dizziness, palpitations, or syncope) may warrant further cardiac evaluation; in particular, Holter monitoring should be considered
  • Tardive dyskinesia
    • Tardive dyskinesia, a syndrome consisting of potentially irreversible, involuntary, dyskinetic movements may develop in patients treated with antipsychotic drugs; it is impossible to rely upon prevalence estimates to predict, at the inception of antipsychotic treatment, which patients are likely to develop the syndrome; whether antipsychotic drug products differ in their potential to cause tardive dyskinesia is unknown
    • The risk of developing the syndrome and the likelihood that it will become irreversible are believed to increase as the duration of treatment and the total cumulative dose of antipsychotic drugs administered to the patient increase; syndrome can develop, although much less commonly, after relatively brief treatment periods at low doses
    • There is no known treatment for established cases of tardive dyskinesia, although the syndrome may remit, partially or completely, if antipsychotic treatment is withdrawn; antipsychotic treatment itself, however, may suppress (or partially suppress) signs and symptoms of the syndrome and thereby may mask underlying disease process; an effect that symptomatic suppression has upon the long-term course of the syndrome is unknown
    • Given these considerations, antipsychotics should be prescribed in a manner that is most likely to minimize the occurrence of tardive dyskinesia; chronic antipsychotic treatment should generally be reserved for patients who suffer from a chronic illness that, is known to respond to antipsychotic drugs and for whom alternative, equally effective, but potentially less harmful treatments are not available or appropriate
    • In patients who do require chronic treatment, the smallest dose and shortest duration of treatment producing a satisfactory clinical response should be sought; the need for continued treatment should be reassessed periodically
    • If signs and symptoms of tardive dyskinesia appear in a patient on antipsychotics, drug discontinuation should be considered. However, some patients may require treatment despite the presence of the syndrome
    • It has been suggested that people who have demonstrated a hypersensitivity reaction (.g, blood dyscrasias, jaundice) to one may be more prone to demonstrate a reaction to others; physicians should carefully consider benefit versus risk when treating less severe disorders
  • Neuroleptic malignant syndrome
    • A potentially fatal symptom complex sometimes referred to as neuroleptic malignant syndrome (NMS) has been reported in association with antipsychotic drugs; clinical manifestations of NMS are hyperpyrexia, muscle rigidity, altered mental status, and evidence of autonomic instability (irregular pulse or blood pressure, tachycardia, diaphoresis, and cardiac dysrhythmias)
    • The diagnostic evaluation of patients with this syndrome is complicated; in arriving at a diagnosis, it is important to identify cases where the clinical presentation includes both serious medical illness (.g, pneumonia, systemic infection, etc.) and untreated or inadequately treated extrapyramidal signs and symptoms (EPS); other important considerations in the differential diagnosis include central anticholinergic toxicity, heat stroke, drug fever, and primary central nervous system (CNS) pathology
    • management of NMS should include immediate discontinuation of antipsychotic drugs and other drugs not essential to concurrent therapy, intensive symptomatic treatment and medical monitoring, and treatment of any concomitant serious medical problems for which specific treatments are available; there is no general agreement about specific pharmacological treatment regimens for uncomplicated NMS
    • If the patient requires antipsychotic drug treatment after recovery from NMS, the potential reintroduction of drug therapy should be carefully considered; the patient should be carefully monitored since recurrences of NMS have been reported
  • Drug interaction overview
    • Drugs that inhibit cytochrome P450 2D6 isozyme activity (.g, fluoxetine and paroxetine), and certain other drugs (.g, fluvoxamine, propranolol, and pindolol) appear to appreciably inhibit the metabolism of this drug; the resulting elevated levels of the drug would be expected to augment the prolongation of the QTc interval associated with thioridazine and may increase risk of serious, potentially fatal, cardiac arrhythmias, such as Torsade de Pointes type arrhythmias
    • Such an increased risk may result also from the additive effect of Coad ministering this drug with other agents that prolong the QTc interval; therefore, thioridazine is contraindicated with these drugs as well as in patients, comprising about 7% of the normal population, who are known to have a genetic defect leading to reduced levels of activity of P450 2D6

Pregnancy and Lactation

  • Use during pregnancy only if the potential benefit justifies the potential risk to the fetus
  • Neonates exposed to antipsychotic drugs, during the third trimester of pregnancy are at risk for extrapyramidal and/or withdrawal symptoms following delivery; there have been reports of agitation, hypertonia, hypotonia, tremor, somnolence, respiratory distress, and feeding disorder; these complications have varied in severity; while in some cases symptoms have been self-limited, in other cases neonates have required intensive care unit support and prolonged hospitalization
  • Lactation
    • Not known whether the drug is present in the milk; infants exposed to antipsychotic agents should be monitored for signs of adverse effects; routine monitoring of infant serum concentrations is not recommended

QUESTION

Schizophrenia is the most disabling mental illness. See Answer
References
https://reference.medscape.com/drug/thioridazine-342987#0

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