thioridazine (Rx)

Brand and Other Names:Mellaril
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Dosing & Uses


Dosage Forms & Strengths


  • 10mg
  • 25mg
  • 50mg
  • 100mg


Initial 50-100 mg PO q8hr, THEN

200-800 mg/day PO divided q6-12hr

Depressive Disorders

25 mg PO q8hr; may titrate to effect (20-200 mg/day)

Renal Impairment

Dose adjustment not necessary in dialysis

Hepatic Disease

Initiate treatment at lower dose and titrate to effect (monitor)

Other Indications & Uses

Psychotic disorders, geriatric psychoneurotic manifestations, pediatric behavioral disorders

Dosage Forms & Strengths


  • 10mg
  • 25mg
  • 50mg
  • 100mg


<2 years: Safety and efficacy not established

2-12 years: 0.5-3 mg/kg/day divided q8hr PO, no more than 3 mg/kg/day  

>12 years: Initial 50-100 mg PO q8hr; titrate to 200-800 mg/day PO divided q6-12hr

Potential toxic dose <6 years old: 3 mg/kg

Initiate treatment at lower dose and titrate to effect (monitor)


Initial 50-100 mg PO q8hr, THEN

200-800 mg/day PO divided q6-12hr

Debilitated patients: Initiate treatment at lower dose

Depressive disorders

25 mg PO q8hr; may titrate to effect (20-200 mg/day)



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            Adverse Effects

            Frequency Not Defined

            EPS (muscle stiffness, dystonia, parkinsonism, tardive dyskinesia, akathisia) (60%)

            NMS (infrequent but serious)


            Anticholinergic effects

            Weight gain


            Erectile dysfunction









            Cerebral edema


            Orthostatic hypotension



            Lens opacities (prolonged use)





            Blood dyscrasia

            ECG changes





            Ejaculatory disorder

            Seizure (rare)

            Priapism (rare)

            Cholestatic jaundice (rare)



            Black Box Warnings

            Patients with dementia-related psychosis who are treated with antipsychotic drugs are at an increased risk of death as shown in short-term controlled trials; the deaths appeared to be either cardiovascular (eg, heart failure, sudden death) or infectious (eg, pneumonia) in nature; this drug is not approved for the treatment of patients with dementia-related psychosis

            Shown to prolong QTc interval in a dose-related manner; drugs with this potential have been associated with Torsades de pointes type arrhythmias and sudden death; due to potential for significant, possibly life-threatening, proarrhythmic effects, therapy should be reserved for use in treatment of schizophrenic patients who fail to show acceptable response to adequate courses of treatment with other antipsychotic drugs, either because of insufficient effectiveness or inability to achieve effective dose due to intolerable adverse effects from those drugs


            Documented hypersensitivity to phenothiazines

            Coadministration with cytochrome P450 2D6 isozyme inhibitors (eg, fluoxetine and paroxetine) and certain other drugs (eg, 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 extreme degree

            Patients in comatose state

            Severe CNS depression

            Severe hyper-/hypotensive heart disease


            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, 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 (eg, 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 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


            • 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 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 > 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 occurrence of Torsades de pointes (eg, 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 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 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 syndrome and thereby may possibly mask underlying disease process; effect that symptomatic suppression has upon long-term course of syndrome is unknown
            • Given these considerations, antipsychotics should be prescribed in a manner that is most likely to minimize occurrence of tardive dyskinesia; chronic antipsychotic treatment should generally be reserved for patients who suffer from 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 (eg, 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 clinical presentation includes both serious medical illness (eg, 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 patient requires antipsychotic drug treatment after recovery from NMS, 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 (eg, fluoxetine and paroxetine), and certain other drugs (eg, fluvoxamine, propranolol, and pindolol) appear to appreciably inhibit 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 Torsades de pointes type arrhythmias
            • Such an increased risk may result also from additive effect of coadministering 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 & Lactation


            Use during pregnancy only if potential benefit justifies potential risk to fetus

            Neonates exposed to antipsychotic drugs, during 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


            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 not recommended

            Pregnancy Categories

            A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

            B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

            C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

            D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

            X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

            NA: Information not available.



            Mechanism of Action

            Piperazine phenothiazine agent; antagonist for the postsynaptic mesolimbic dopaminergic D2 receptors in the brain; decreases the release of hypothalamic and hypophyseal hormones


            Half-Life elimination: 24 hr

            Metabolism: Hepatic P450 enzyme CYP2D6

            Enzymes inhibited: CYP2D6

            Protein bound: 95%

            Duration: 4-5 days



            thioridazine oral
            100 mg tablet
            thioridazine oral
            25 mg tablet
            thioridazine oral
            10 mg tablet
            thioridazine oral
            50 mg tablet
            thioridazine oral
            100 mg tablet
            thioridazine oral
            10 mg tablet
            thioridazine oral
            25 mg tablet
            thioridazine oral
            50 mg tablet

            Copyright © 2010 First DataBank, Inc.


            Patient Handout

            Patient Education
            thioridazine oral



            COMMON BRAND NAME(S): Mellaril

            WARNING: Thioridazine rarely has caused very serious (possibly fatal) irregular heartbeat (QT prolongation in the EKG). It should be used only in patients who have not shown improvement with at least 2 other antipsychotic medications or who cannot tolerate other antipsychotic medications. This medication should not be used with other medications that can also cause a slow or irregular heartbeat. (See also Drug Interactions.)There may be a slightly increased risk of serious, possibly fatal side effects (such as heart failure, fast/irregular heartbeat, pneumonia) when this medication is used by older adults with dementia. This medication is not approved for the treatment of dementia-related behavior problems. Discuss the risks and benefits of this medication, as well as other effective and possibly safer treatments for dementia-related behavior problems, with the doctor.

            USES: This medication is used to treat certain mental/mood disorders (such as schizophrenia). This medication helps you to think more clearly, feel less nervous, and take part in everyday life. It can also help prevent suicide in people likely to harm themselves and reduce aggression and the desire to hurt others. It can help decrease your negative thoughts and hallucinations. Thioridazine belongs to a class of drugs known as phenothiazines.

            HOW TO USE: Take this medication by mouth with or without food as directed by your doctor, usually 2 to 4 times a day.Dosage is based on your medical condition and response to therapy. Once your condition improves and you are better for a while, your doctor may work with you to reduce your regular dose. This may be done over time. Do not stop your medication or lower your dose without talking with your doctor first. Some conditions may become worse when the drug is stopped abruptly. Your dose may need to be gradually reduced.Use this medication regularly in order to get the most benefit from it. To help you remember, use it at the same times each day.Tell your doctor if your condition lasts or gets worse.

            SIDE EFFECTS: Dizziness, lightheadedness, drowsiness, difficulty urinating, constipation, restlessness, headache, and blurred vision may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.Dizziness and lightheadedness can increase the risk of falling. Get up slowly when rising from a sitting or lying position.Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.Tell your doctor right away if you have any serious side effects, including: shakiness (tremors), mask-like facial expression, jerking movements while walking, signs of infection (such as sore throat that doesn't go away, fever), vision changes (such as vision loss, sudden difficulty seeing at night, brown-tinged vision).Get medical help right away if you have any very serious side effects, including: severe dizziness, fainting, slow heartbeat, seizures.Thioridazine may rarely cause a condition known as tardive dyskinesia. In some cases this condition may be permanent. Tell your doctor right away if you develop any unusual/uncontrolled movements (especially of the face, lips, tongue, arms or legs).In rare cases, thioridazine may increase your level of a certain chemical made by the body (prolactin). For females, this increase in prolactin may result in unwanted breast milk, missed/stopped periods, or difficulty becoming pregnant. For males, it may result in decreased sexual ability, inability to produce sperm, or enlarged breasts. If you develop any of these symptoms, tell your doctor right away.This medication may rarely cause a very serious condition called neuroleptic malignant syndrome (NMS). Get medical help right away if you have any of the following symptoms: fever, muscle stiffness/pain/tenderness/weakness, severe tiredness, severe confusion, sweating, fast/irregular heartbeat, dark urine, signs of kidney problems (such as change in the amount of urine).A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.In the US -Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

            PRECAUTIONS: Before taking thioridazine, tell your doctor or pharmacist if you are allergic to it; or to other phenothiazines (such as chlorpromazine); or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.Before using this medication, tell your doctor or pharmacist your medical history, especially of: nervous system problems (such as seizures, drug/alcohol overdose, severe drowsiness), blood pressure problems, certain blood problems (such as low white blood cell count), Parkinson's disease, low enzymes needed to remove drugs from the body (slow hydroxylator).Thioridazine may cause a condition that affects the heart rhythm (QT prolongation). QT prolongation can rarely cause serious (rarely fatal) fast/irregular heartbeat and other symptoms (such as severe dizziness, fainting) that need medical attention right away.The risk of QT prolongation may be increased if you have certain medical conditions or are taking other drugs that may cause QT prolongation. Before using thioridazine, tell your doctor or pharmacist of all the drugs you take and if you have any of the following conditions: certain heart problems (heart failure, slow heartbeat, QT prolongation in the EKG), family history of certain heart problems (QT prolongation in the EKG, sudden cardiac death).Low levels of potassium or magnesium in the blood may also increase your risk of QT prolongation. This risk may increase if you use certain drugs (such as diuretics/"water pills") or if you have conditions such as severe sweating, diarrhea, or vomiting. Talk to your doctor about using thioridazine safely.This drug may make you dizzy or drowsy. Alcohol or marijuana (cannabis) can make you more dizzy or drowsy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).Before having surgery, tell your doctor or dentist that you are taking this medication.This medication may make you more sensitive to the sun. Limit your time in the sun. Avoid tanning booths and sunlamps. Use sunscreen and wear protective clothing when outdoors. Tell your doctor right away if you get sunburned or have skin blisters/redness.Older adults may be more sensitive to the side effects of this drug, especially dizziness, lightheadedness, drowsiness, confusion, constipation, difficulty urinating, and QT prolongation (see above). Dizziness, lightheadedness, drowsiness, and confusion can increase the risk of falling.During pregnancy, this medication should be used only when clearly needed. Babies born to mothers who have used this drug during the last 3 months of pregnancy may rarely develop symptoms including muscle stiffness or shakiness, drowsiness, feeding/breathing difficulties, or constant crying. If you notice any of these symptoms in your newborn especially during their first month, tell the doctor right away.Since untreated mental/mood problems (such as schizophrenia, depression) can be a serious condition, do not stop taking this medication unless directed by your doctor. If you are planning pregnancy, become pregnant, or think you may be pregnant, immediately discuss with your doctor the benefits and risks of using this medication during pregnancy.It is not known whether this drug passes into breast milk. Consult your doctor before breast-feeding.

            DRUG INTERACTIONS: Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.Some products that may interact with this drug include: cabergoline, lithium, certain products used to treat chronic hepatitis C (asunaprevir, ombitasvir/paritaprevir/ritonavir), medications for Parkinson's disease (such as levodopa).Many drugs besides thioridazine may affect the heart rhythm (QT prolongation), including amiodarone, dofetilide, pimozide, procainamide, quinidine, sotalol, macrolide antibiotics (such as erythromycin), ziprasidone, among others. Before using thioridazine, report all medications you are currently using to your doctor or pharmacist.Other medications can affect the removal of thioridazine from your body, which may affect how thioridazine works. Examples include bupropion, cinacalcet, dacomitinib, duloxetine, mirabegron, pindolol, propranolol, rolapitant, terbinafine, certain SSRI antidepressants (such as fluoxetine, fluvoxamine, paroxetine), among others.Tell your doctor or pharmacist if you are taking other products that cause drowsiness such as opioid pain or cough relievers (such as codeine, hydrocodone), alcohol, marijuana (cannabis), drugs for sleep or anxiety (such as alprazolam, lorazepam, zolpidem), muscle relaxants (such as carisoprodol, cyclobenzaprine), or antihistamines (such as cetirizine, diphenhydramine).Check the labels on all your medicines (such as allergy or cough-and-cold products) because they may contain ingredients that cause drowsiness. Ask your pharmacist about using those products safely.

            OVERDOSE: If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center.

            NOTES: Do not share this medication with others.Lab and/or medical tests (such as eye exams, potassium levels, EKG) may be done while you are taking this medication. Keep all medical and lab appointments. Consult your doctor for more details.

            MISSED DOSE: If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.

            STORAGE: Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.

            Information last revised December 2022. Copyright(c) 2022 First Databank, Inc.

            IMPORTANT: HOW TO USE THIS INFORMATION: This is a summary and does NOT have all possible information about this product. This information does not assure that this product is safe, effective, or appropriate for you. This information is not individual medical advice and does not substitute for the advice of your health care professional. Always ask your health care professional for complete information about this product and your specific health needs.



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            Tier Description
            1 This drug is available at the lowest co-pay. Most commonly, these are generic drugs.
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