Thioridazine (Mellaril) - Uses, Dose, MOA, Brands, Side effects

Thioridazine (Mellaril) is a typical antipsychotic drug that is nowadays rarely used to treat psychosis and schizophrenia.

Thioridazine (Mellaril) Uses:

  • Schizophrenia:

    • Thioridazine (Mellaril) is an anti-psychotic drug that is not commonly used as a first-line of treatment in patients with psychosis or schizophrenia.
    • It is indicated only if the person has failed a trial of at least two antipsychotic drugs due to either intolerable side effects or because of a lack of efficacy.

Thioridazine (Mellaril) Dose in Adults

Thioridazine (Mellaril) Dose in the treatment of Schizophrenia:

  • It is administered orally in a dose of 50 to 100 mg three times a day initially. The dose is then gradually increased in increments at weekly intervals up to a maximum dose of 800 mg per day.
  • The usual dose is 300 mg per day given in two to four divided doses.
  • Discontinuation of therapy:

    • The drug should be tapered off before discontinuing it completely. Slow tapering is advised to avoid withdrawal symptoms such as gastrointestinal symptoms, headache, and lack of sleep.
    • In certain situations, abrupt withdrawal may be advised when the drug has to be discontinued primarily because of adverse drug reactions or intolerable side effects.
    • It is important to monitor the patient while discontinuing the drug so as to avoid the recurrence of the disease.
  • Switching antipsychotics:

    • Antipsychotics, like other neuropsychiatric symptoms, maybe either switched to another antipsychotic drug by slowly reducing the dose of one and building the dose of the new antipsychotic drug. It can also be abruptly discontinued and the new antipsychotic drug may be started at full dose.
    • Occasionally, when the risks of recurrence are very high, it is best to maintain the patient on one antipsychotic while slowly increasing the dose of the other. Once the new antipsychotic drug is in the therapeutic dose range, the first antipsychotic may be slowly tapered off.
    • Most psychiatrists prefer the overlapping method rather than abruptly discontinuing the medicines.

Thioridazine (Mellaril) Dose in Children

Note: It is best to use second-generation antipsychotic medicines when treating children with behavioral problems and schizophrenia.

Thioridazine (Mellaril) Dose in the treatment of Schizophrenia, refractory:

Note: It is important to keep the following points in mind when using thioridazine in children with schizophrenia:

  • Use the lowest effective dose
  • Use second-generation antipsychotics preferably
  • Use it only if the child has been given a trial of at least two antipsychotic medicines.
  • Children 6 years of age or older:

    • It is given in a dose of 0.5 mg/kg/day orally in 2 to 3 divided doses. The maximum initial dose is 50 mg/dose. The dose is then gradually titrated until either a clinical response is achieved or up to a maximum daily dose of 3 mg/kg/day.

Thioridazine (Malleril) Pregnancy Risk Category: N

  • Even though case reports involving maternal thioridazine use in pregnancy have published some outcome information, the majority of information is available for phenothiazines.
  • After maternal use of phenothiazines, newborn infants have experienced jaundice and hypo- or hyperreflexia.
  • The use of antipsychotics during pregnancy's third trimester can lead to abnormal muscle movements and withdrawal symptoms in newborns after delivery.
  • The newborn can experience agitation, feeding disorders, hypotonia, and hypertonia as well as respiratory distress, somnolence, and tremor.
  • These symptoms may be self-limiting or may require hospitalization. To reduce the risk of EPS, use the lowest effective maternal dose when it is necessary. 
  • Thioridazine has been linked to increased prolactin levels, which can lead to amenorrhea among women and impotence among men. Thioridazine may cause false pregnancy tests.

Use of Thioridazine while breastfeeding

  • It is unknown if breast milk contains thioridazine. 
  • Infants who have been exposed to antipsychotic drugs should be closely monitored for any signs of adverse reactions.
  • Routine monitoring of serum concentrations in infants is not recommended.

Dose in Kidney Disease:

There are no dosage adjustments provided in the manufacturer’s labeling.

Dose in Liver disease:

There are no dosage adjustments provided in the manufacturer’s labeling; use with caution (hepatic metabolism).

Side effects of Thioridazine (Mellaril):

  • Cardiovascular:

    • ECG Changes
    • Hypotension
    • Orthostatic Hypotension
    • Peripheral Edema
    • Prolonged QT Interval On ECG
    • Torsades De Pointes
  • Central Nervous System:

    • Confusion (Sundowning)
    • Disruption Of Temperature Regulation (Martinez 2002)
    • Drowsiness
    • Drug-Induced Parkinson Disease
    • Extrapyramidal Reaction
    • Headache
    • Hyperactive Behavior
    • Lethargy
    • Psychotic Reaction
    • Restlessness
    • Seizure
    • Tardive Dyskinesia (Lehman 2004)
  • Dermatologic:

    • Dermatitis
    • Hyperpigmentation (Lehman 2004)
    • Pallor
    • Skin Photosensitivity
    • Skin Rash
    • Urticaria
  • Endocrine & Metabolic:

    • Amenorrhea
    • Galactorrhea Not Associated With Childbirth
    • Weight Gain (Lehman 2004)
  • Gastrointestinal:

    • Constipation
    • Diarrhea
    • Nausea
    • Parotid Gland Enlargement
    • Vomiting
    • Xerostomia
  • Genitourinary:

    • Breast Engorgement
    • Inhibited Ejaculation
    • Priapism
    • Sexual Difficulty (La Torre 2013)
    • Sexual Disorder (La Torre 2013)
  • Hematologic & Oncologic:

    • Agranulocytosis
    • Leukopenia
  • Ophthalmic:

    • Blurred Vision
    • Corneal Opacity (Lehman 2004)
    • Retinitis Pigmentosa
  • Respiratory:

    • Nasal Congestion

Contraindications to Thioridazine (Mellaril):

  • Severe CNS depression;
  • Severe hyper/hypotensive cardiac disease;
  • Coma.
  • In combination with other drugs known to prolong QTc intervals, CYP2D6 inhibits (fluoxetine, paroxetine, and/or fluvoxamine, propranolol, or pindolol);
  • In patients with congenital long QT syndrome or a history of cardiac arrhythmias.
  • Patients with a genetic defect leading to decreased activity of CYP2D6

Warnings and Precautions

  • Arrhythmias: [US Boxed Warning]:

    • It has been demonstrated that it prolongs the QTc interval in dose-related ways; this could potentially lead to Torsades De Pointes or sudden death.
    • Patients with schizophrenia should not be given thioridazine if they have not responded to other antipsychotic drugs.
    • Patients with bradycardia and hypokalemia may be at greater risk of sudden death or torsades-de-pointes.
    • Patients who have symptoms such as dizziness, palpitations or syncope should be referred to a Holter monitor and a cardiac exam.
    • Patients with QTc greater than 500 msec should be stopped from receiving therapy.
  • Anticholinergic effects

    • It may cause constipation, xerostomia, and blurred vision.
    • Thioridazine is a neuroleptic with a higher potency than other neuroleptics.
  • Blood dyscrasias:

    • Clinical trials have reported leukopenia, neutropenia, and/or agranulocytosis (sometimes deadly) in postmarketing reports.
    • The presence of risk factors, such as low WBC, or a history of drug-induced neurotoxicity, should prompt periodic blood counts assessment.
    • Stop treatment immediately if blood dyscrasias develop or absolute neutrophil count is below 1,000/mm³.
  • CNS depression:

    • CNS depression can lead to mental or physical impairments.
    • Patients should be cautious about driving, operating machinery, and other tasks that require mental alertness.
  • Esophageal dysmotility/Aspiration:

    • Antipsychotic use has been linked to esophageal dysmotility, aspiration, and increased risk with age.
    • Patients at high risk of aspiration pneumonia (i.e. Alzheimer's disease) should be treated with caution, especially patients over 75 years old.
  • Extrapyramidal symptoms:

    • Extrapyramidal symptoms (EPS) may include pseudoparkinsonism and acute dystonic reactions.
    • Higher doses of antipsychotics and use by males (and younger patients) can increase the risk of dystonia (and other EPS).
    • The following factors are associated with higher vulnerability to tardive dyskinesia: older age, female gender, postmenopausal status, and Parkinson's disease symptoms.
    • You may consider discontinuing therapy if you experience tardive dyskinesia symptoms.
  • Hyperprolactinemia:

    • Hyperprolactinemia is a condition that results in an increase in prolactin levels.
    • The clinical significance of hyperprolactinemia for patients with breast cancer or other prolactin-dependent tumors is not known.
  • Neuroleptic malignant syndrome (NMS):

    • This may be due to NMS. Monitor for changes in mental status, fever, the rigidity of the muscles, and/or other signs that could indicate NMS.
    • After recovery from NMS, it is important to carefully consider reintroduction. If an antipsychotic agent was resumed, be sure to monitor for NMS.
  • Ocular effects

    • Patients who take more than the recommended doses of this medication may develop pigmentary retinopathy. This is characterized by a decrease in visual acuity and brownish-colored vision.
    • Patients who consume 600 mg or more of this medication should have their eyes examined at least once a month.
  • Orthostatic hypotension

    • May cause orthostatic hypotension; use with caution in patients at risk of this effect or in those who would not tolerate transient hypotensive episodes (cerebrovascular disease, cardiovascular disease, hypovolemia, or concurrent medication use which may predispose to hypotension/bradycardia).
  • Temperature regulation

    • It is possible to have impaired core body temperature regulation.
    • Be careful with heat exposure, strenuous exercise, heat, dehydration and any concomitant anticholinergic medication (Kwok 2005; Martinez2002).
  • Cardiovascular disease

    • Patients with severe cardiovascular disease should be cautious. Patients with QTc intervals >450 msec should not be initiated.
  • Dementia: [US Boxed Warning]

    • Antipsychotics have a higher death rate than placebo for dementia-related psychosis in the elderly.
    • The majority of deaths were either from cardiovascular disease (eg heart failure, sudden death, etc.) or infectious diseases (eg pneumonia).
    • Patients with Parkinson's disease dementia or Lewy body dementia should be cautious due to the increased risk of adverse effects and increased sensitivity for extrapyramidal effects. Also, there is the possibility of irreversible cognitive decline or death.
    • The APA recommends that second-generation antipsychotics be preferred to first-generation antipsychotics for elderly patients with dementia-related schizophrenia.
    • This is because there is a greater risk of harm than second-generation antipsychotics.
    • Thioridazine has not been approved for the treatment of dementia-related psychosis.
  • Hepatic impairment

    • Patients with hepatic impairment should be cautious.
  • Seizure disorder:

    • Patients at high risk of seizures should be cautious; first-generation antipsychotics might lower the seizure threshold.

Thioridazine: Drug Interaction

Risk Factor C (Monitor therapy)

Acetylcholinesterase Inhibitors

May diminish the therapeutic effect of Anticholinergic Agents. Anticholinergic Agents may diminish the therapeutic effect of Acetylcholinesterase Inhibitors.

Acetylcholinesterase Inhibitors (Central)

May enhance the neurotoxic (central) effect of Antipsychotic Agents. Severe extrapyramidal symptoms have occurred in some patients.

Alcohol (Ethyl)

CNS Depressants may enhance the CNS depressant effect of Alcohol (Ethyl).

Alfuzosin

May enhance the hypotensive effect of Blood Pressure Lowering Agents.

Alizapride

May enhance the CNS depressant effect of CNS Depressants.

Amifampridine

Agents With Seizure Threshold Lowering Potential may enhance the neuroexcitatory and/or seizure-potentiating effect of Amifampridine.

Aminolevulinic Acid (Topical)

Photosensitizing Agents may enhance the photosensitizing effect of Aminolevulinic Acid (Topical).

Amphetamines

Antipsychotic Agents may diminish the stimulatory effect of Amphetamines.

Amphetamines

CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Amphetamines.

Antacids

May decrease the absorption of Antipsychotic Agents (Phenothiazines).

Anticholinergic Agents

May enhance the adverse/toxic effect of other Anticholinergic Agents.

Antimalarial Agents

May increase the serum concentration of Antipsychotic Agents (Phenothiazines).

Antipsychotic Agents (Second Generation [Atypical

Blood Pressure Lowering Agents may enhance the hypotensive effect of Antipsychotic Agents (Second Generation [Atypical]).

ARIPiprazole

CYP2D6 Inhibitors (Moderate) may increase the serum concentration of ARIPiprazole. Management: Monitor for increased aripiprazole pharmacologic effects. Aripiprazole dose adjustments may or may not be required based on concomitant therapy and/or indication. Consult full interaction monograph for specific recommendations.

Barbiturates

May enhance the hypotensive effect of Blood Pressure Lowering Agents.

Benperidol

May enhance the hypotensive effect of Blood Pressure Lowering Agents.

Beta-Blockers

Antipsychotic Agents (Phenothiazines) may enhance the hypotensive effect of Beta-Blockers. Beta-Blockers may decrease the metabolism of Antipsychotic Agents (Phenothiazines). Antipsychotic Agents (Phenothiazines) may decrease the metabolism of BetaBlockers. Exceptions: Atenolol; Levobunolol; Metipranolol; Nadolol.

Blood Pressure Lowering Agents

May enhance the hypotensive effect of HypotensionAssociated Agents.

Botulinum Toxin-Containing Products

May enhance the anticholinergic effect of Anticholinergic Agents.

Brexanolone

CNS Depressants may enhance the CNS depressant effect of Brexanolone.

Brexpiprazole

CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Brexpiprazole. Management: If brexpiprazole is to be used together with both a moderate CYP2D6 inhibitor and a strong or moderate CYP3A4 inhibitor, the brexpiprazole dose should be reduced to 25% of the usual dose.

Brimonidine (Topical)

May enhance the CNS depressant effect of CNS Depressants.

Brimonidine (Topical)

May enhance the hypotensive effect of Blood Pressure Lowering Agents.

Cannabidiol

May enhance the CNS depressant effect of CNS Depressants.

Cannabis

May enhance the CNS depressant effect of CNS Depressants.

Chloral Betaine

May enhance the adverse/toxic effect of Anticholinergic Agents.

Chlorphenesin Carbamate

May enhance the adverse/toxic effect of Antipsychotic Agents (Phenothiazines).

Chlorphenesin Carbamate

May enhance the adverse/toxic effect of CNS Depressants.

Clarithromycin

QT-prolonging Antipsychotics (Moderate Risk) may enhance the QTc-prolonging effect of Clarithromycin. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk.

CloBAZam

May increase the serum concentration of CYP2D6 Substrates (High risk with Inhibitors).

CloZAPine

CYP2D6 Inhibitors (Moderate) may increase the serum concentration of CloZAPine.

CloZAPine

QT-prolonging Antipsychotics (Moderate Risk) may enhance the QTc-prolonging effect of CloZAPine. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk.

CNS Depressants

May enhance the adverse/toxic effect of other CNS Depressants.

Cobicistat

May increase the serum concentration of CYP2D6 Substrates (High risk with Inhibitors).

CYP2D6 Substrates (High risk with Inhibitors)

CYP2D6 Inhibitors (Moderate) may decrease the metabolism of CYP2D6 Substrates (High risk with Inhibitors). Exceptions: Tamoxifen.

Deutetrabenazine

May enhance the adverse/toxic effect of Antipsychotic Agents. Specifically, the risk for akathisia, parkinsonism, or neuroleptic malignant syndrome may be increased.

Diazoxide

May enhance the hypotensive effect of Blood Pressure Lowering Agents.

Dimethindene (Topical

May enhance the CNS depressant effect of CNS Depressants.

Doxylamine

May enhance the CNS depressant effect of CNS Depressants. Management: The manufacturer of Diclegis (doxylamine/pyridoxine), intended for use in pregnancy, specifically states that use with other CNS depressants is not recommended.

Dronabinol

May enhance the CNS depressant effect of CNS Depressants.

Droperidol

QT-prolonging Antipsychotics (Moderate Risk) may enhance the QTc-prolonging effect of Droperidol. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk.

Esketamine

May enhance the CNS depressant effect of CNS Depressants.

Fesoterodine

CYP2D6 Inhibitors may increase serum concentrations of the active metabolite(s) of Fesoterodine.

Flupentixol

QT-prolonging Antipsychotics (Moderate Risk) may enhance the QTc-prolonging effect of Flupentixol. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk.

Gastrointestinal Agents (Prokinetic)

Anticholinergic Agents may diminish the therapeutic effect of Gastrointestinal Agents (Prokinetic).

Glucagon

Anticholinergic Agents may enhance the adverse/toxic effect of Glucagon. Specifically, the risk of gastrointestinal adverse effects may be increased.

Guanethidine

Antipsychotic Agents may diminish the therapeutic effect of Guanethidine.

Haloperidol

QT-prolonging Antipsychotics (Moderate Risk) may enhance the QTc-prolonging effect of Haloperidol. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk.

Herbs (Hypotensive Properties

May enhance the hypotensive effect of Blood Pressure Lowering Agents.

HydrOXYzine

May enhance the CNS depressant effect of CNS Depressants.

Hypotension-Associated Agents

Blood Pressure Lowering Agents may enhance the hypotensive effect of Hypotension-Associated Agents.

Imatinib

May increase the serum concentration of CYP2D6 Substrates (High risk with Inhibitors).

Indoramin

CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Indoramin.

Itopride

Anticholinergic Agents may diminish the therapeutic effect of Itopride.

Kava Kava

May enhance the adverse/toxic effect of CNS Depressants.

Lithium

May enhance the neurotoxic effect of Antipsychotic Agents. Lithium may decrease the serum concentration of Antipsychotic Agents. Specifically noted with chlorpromazine.

Lormetazepam

May enhance the hypotensive effect of Blood Pressure Lowering Agents.

Lumefantrine

May increase the serum concentration of CYP2D6 Substrates (High risk with Inhibitors).

Magnesium Sulfate

May enhance the CNS depressant effect of CNS Depressants.

Melatonin

May enhance the adverse/toxic effect of Thioridazine.

Methylphenidate

Antipsychotic Agents may enhance the adverse/toxic effect of Methylphenidate. Methylphenidate may enhance the adverse/toxic effect of Antipsychotic Agents.

Metoprolol

CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Metoprolol.

MetyroSINE

CNS Depressants may enhance the sedative effect of MetyroSINE.

MetyroSINE

May enhance the adverse/toxic effect of Antipsychotic Agents.

Mianserin

May enhance the anticholinergic effect of Anticholinergic Agents.

Minocycline

May enhance the CNS depressant effect of CNS Depressants.

Mirtazapine

CNS Depressants may enhance the CNS depressant effect of Mirtazapine.

Molsidomine

May enhance the hypotensive effect of Blood Pressure Lowering Agents.

Nabilone

May enhance the CNS depressant effect of CNS Depressants.

Naftopidil

May enhance the hypotensive effect of Blood Pressure Lowering Agents.

Nebivolol

CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Nebivolol.

Nicergoline

May enhance the hypotensive effect of Blood Pressure Lowering Agents.

Nicorandil

May enhance the hypotensive effect of Blood Pressure Lowering Agents.

Nitroglycerin

Anticholinergic Agents may decrease the absorption of Nitroglycerin. Specifically, anticholinergic agents may decrease the dissolution of sublingual nitroglycerin tablets, possibly impairing or slowing nitroglycerin absorption.

Nitroprusside

Blood Pressure Lowering Agents may enhance the hypotensive effect of Nitroprusside.

OLANZapine

QT-prolonging Antipsychotics (Moderate Risk) may enhance the QTc-prolonging effect of OLANZapine. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk.

Ondansetron

May enhance the QTc-prolonging effect of QT-prolonging Antipsychotics (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk.

Panobinostat

May increase the serum concentration of CYP2D6 Substrates (High risk with Inhibitors).

Peginterferon Alfa-2b

May decrease the serum concentration of CYP2D6 Substrates (High risk with Inhibitors). Peginterferon Alfa-2b may increase the serum concentration of CYP2D6 Substrates (High risk with Inhibitors).

Pentamidine (Systemic)

May enhance the QTc-prolonging effect of QT-prolonging Antipsychotics (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk.

Pentoxifylline

May enhance the hypotensive effect of Blood Pressure Lowering Agents.

Pholcodine

Blood Pressure Lowering Agents may enhance the hypotensive effect of Pholcodine.

Phosphodiesterase 5 Inhibitors

May enhance the hypotensive effect of Blood Pressure Lowering Agents.

Pitolisant

CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Pitolisant.

Porfimer

Photosensitizing Agents may enhance the photosensitizing effect of Porfimer.

Prostacyclin Analogues

May enhance the hypotensive effect of Blood Pressure Lowering Agents.

QT-prolonging Antidepressants (Moderate Risk)

QT-prolonging Antipsychotics (Moderate Risk) may enhance the QTc-prolonging effect of QT-prolonging Antidepressants (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk.

QT-prolonging Class IC Antiarrhythmics (Moderate Risk)

May enhance the QTc-prolonging effect of QT-prolonging Antipsychotics (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk.

QT-prolonging Kinase Inhibitors (Moderate Risk)

QT-prolonging Antipsychotics (Moderate Risk) may enhance the QTc-prolonging effect of QT-prolonging Kinase Inhibitors (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk.

QT-prolonging Miscellaneous Agents (Moderate Risk)

May enhance the QTc-prolonging effect of QT-prolonging Antipsychotics (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Exceptions: Domperidone.

QT-prolonging Moderate CYP3A4 Inhibitors (Moderate Risk)

May enhance the QTc-prolonging effect of QT-prolonging Antipsychotics (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk.

QT-prolonging Quinolone Antibiotics (Moderate Risk)

May enhance the QTc-prolonging effect of QT-prolonging Antipsychotics (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk.

QUEtiapine

QT-prolonging Antipsychotics (Moderate Risk) may enhance the QTc-prolonging effect of QUEtiapine. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk.

Quinagolide

Antipsychotic Agents may diminish the therapeutic effect of Quinagolide.

Quinagolide

May enhance the hypotensive effect of Blood Pressure Lowering Agents.

Ramosetron

Anticholinergic Agents may enhance the constipating effect of Ramosetron.

RisperiDONE

QT-prolonging Antipsychotics (Moderate Risk) may enhance the QTc-prolonging effect of RisperiDONE. QT-prolonging Antipsychotics (Moderate Risk) may increase the serum concentration of RisperiDONE. Specifically, thioridazine may increase concentrations of risperidone. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk.

Rufinamide

May enhance the adverse/toxic effect of CNS Depressants. Specifically, sleepiness and dizziness may be enhanced.

Selective Serotonin Reuptake Inhibitors

CNS Depressants may enhance the adverse/toxic effect of Selective Serotonin Reuptake Inhibitors. Specifically, the risk of psychomotor impairment may be enhanced.

Serotonin Modulators

May enhance the adverse/toxic effect of Antipsychotic Agents. Specifically, serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotic Agents may enhance the serotonergic effect of Serotonin Modulators. This could result in serotonin syndrome. Exceptions: Nicergoline.

Serotonin Reuptake Inhibitor/Antagonists

Antipsychotic Agents (Phenothiazines) may enhance the adverse/toxic effect of Serotonin Reuptake Inhibitor/Antagonists. Specifically, this may be manifest as symptoms consistent with serotonin syndrome or neuroleptic malignant syndrome. Serotonin Reuptake Inhibitor/Antagonists may enhance the hypotensive effect of Antipsychotic Agents (Phenothiazines).

Tamsulosin

CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Tamsulosin.

Tetrabenazine

May enhance the adverse/toxic effect of Antipsychotic Agents.

Tetrahydrocannabinol

May enhance the CNS depressant effect of CNS Depressants.

Tetrahydrocannabinol and Cannabidiol

May enhance the CNS depressant effect of CNS Depressants.

Thiazide and Thiazide-Like Diuretics

Anticholinergic Agents may increase the serum concentration of Thiazide and Thiazide-Like Diuretics.

Thiopental

Antipsychotic Agents (Phenothiazines) may enhance the adverse/toxic effect of Thiopental.

Topiramate

Anticholinergic Agents may enhance the adverse/toxic effect of Topiramate.

Trimeprazine

May enhance the CNS depressant effect of CNS Depressants.

Verteporfin

Photosensitizing Agents may enhance the photosensitizing effect of Verteporfin.

Voriconazole

May enhance the QTc-prolonging effect of QT-prolonging Antipsychotics (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk.

Risk Factor D (Consider therapy modification)

Amifostine

Blood Pressure Lowering Agents may enhance the hypotensive effect of Amifostine. Management: When amifostine is used at chemotherapy doses, blood pressure lowering medications should be withheld for 24 hours prior to amifostine administration. If blood pressure lowering therapy cannot be withheld, amifostine should not be administered.

Anti-Parkinson Agents (Dopamine Agonist)

Antipsychotic Agents (First Generation [Typical]) may diminish the therapeutic effect of Anti-Parkinson Agents (Dopamine Agonist). Anti-Parkinson Agents (Dopamine Agonist) may diminish the therapeutic effect of Antipsychotic Agents (First Generation [Typical]). Management: Avoid concomitant therapy if possible and monitor for decreased effects of both agents when these combinations cannot be avoided. Atypical antipsychotics such as clozapine and quetiapine may be less likely to reduce the effects of antiParkinson agents.

Blonanserin

CNS Depressants may enhance the CNS depressant effect of Blonanserin.

Buprenorphine

CNS Depressants may enhance the CNS depressant effect of Buprenorphine. Management: Consider reduced doses of other CNS depressants, and avoiding such drugs in patients at high risk of buprenorphine overuse/self-injection. Initiate buprenorphine at lower doses in patients already receiving CNS depressants.

Chlormethiazole

May enhance the CNS depressant effect of CNS Depressants. Management: Monitor closely for evidence of excessive CNS depression. The chlormethiazole labeling states that an appropriately reduced dose should be used if such a combination must be used.

Chlorpheniramine

May enhance the arrhythmogenic effect of Thioridazine. Thioridazine may increase the serum concentration of Chlorpheniramine. Management: Avoid this combination when possible. If used, monitor closely for arrhythmia as well as general toxicity of chlorpheniramine.

Domperidone

QT-prolonging Agents (Moderate Risk) may enhance the QTc-prolonging effect of Domperidone. Management: Consider alternatives to this drug combination. If combined, monitor for QTc interval prolongation and ventricular arrhythmias. Patients with additional risk factors for QTc prolongation may be at even higher risk.

DOXOrubicin (Conventional

CYP2D6 Inhibitors (Moderate) may increase the serum concentration of DOXOrubicin (Conventional). Management: Seek alternatives to moderate CYP2D6 inhibitors in patients treated with doxorubicin whenever possible. One U.S. manufacturer (Pfizer Inc.) recommends that these combinations be avoided.

Eliglustat

CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Eliglustat. Management: Reduce the eliglustat dose to 84 mg daily. Avoid use of eliglustat in combination with a moderate CYP2D6 inhibitor and a strong or moderate CYP3A4 inhibitor.

Flunitrazepam

CNS Depressants may enhance the CNS depressant effect of Flunitrazepam.

HYDROcodone

CNS Depressants may enhance the CNS depressant effect of HYDROcodone. Management: Avoid concomitant use of hydrocodone and benzodiazepines or other CNS depressants when possible. These agents should only be combined if alternative treatment options are inadequate. If combined, limit the dosages and duration of each drug.

Iohexol

Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Iohexol. Specifically, the risk for seizures may be increased. Management: Discontinue agents that may lower the seizure threshold 48 hours prior to intrathecal use of iohexol. Wait at least 24 hours after the procedure to resume such agents. In nonelective procedures, consider use of prophylactic anticonvulsants.

Iomeprol

Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Iomeprol. Specifically, the risk for seizures may be increased. Management: Discontinue agents that may lower the seizure threshold 48 hours prior to intrathecal use of iomeprol. Wait at least 24 hours after the procedure to resume such agents. In nonelective procedures, consider use of prophylactic anticonvulsants.

Iopamidol

Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Iopamidol. Specifically, the risk for seizures may be increased. Management: Discontinue agents that may lower the seizure threshold 48 hours prior to intrathecal use of iopamidol. Wait at least 24 hours after the procedure to resume such agents. In nonelective procedures, consider use of prophylactic anticonvulsants.

Mequitazine

Antipsychotic Agents may enhance the arrhythmogenic effect of Mequitazine. Management: Consider alternatives to one of these agents when possible. While this combination is not specifically contraindicated, mequitazine labeling describes this combination as discouraged.

Methotrimeprazine

CNS Depressants may enhance the CNS depressant effect of Methotrimeprazine. Methotrimeprazine may enhance the CNS depressant effect of CNS Depressants. Management: Reduce adult dose of CNS depressant agents by 50% with initiation of concomitant methotrimeprazine therapy. Further CNS depressant dosage adjustments should be initiated only after clinically effective methotrimeprazine dose is established.

Obinutuzumab

May enhance the hypotensive effect of Blood Pressure Lowering Agents. Management: Consider temporarily withholding blood pressure lowering medications beginning 12 hours prior to obinutuzumab infusion and continuing until 1 hour after the end of the infusion.

Opioid Agonists

CNS Depressants may enhance the CNS depressant effect of Opioid Agonists. Management: Avoid concomitant use of opioid agonists and benzodiazepines or other CNS depressants when possible. These agents should only be combined if alternative treatment options are inadequate. If combined, limit the dosages and duration of each drug.

OxyCODONE

CNS Depressants may enhance the CNS depressant effect of OxyCODONE. Management: Avoid concomitant use of oxycodone and benzodiazepines or other CNS depressants when possible. These agents should only be combined if alternative treatment options are inadequate. If combined, limit the dosages and duration of each drug.

Perampanel

May enhance the CNS depressant effect of CNS Depressants. Management: Patients taking perampanel with any other drug that has CNS depressant activities should avoid complex and high-risk activities, particularly those such as driving that require alertness and coordination, until they have experience using the combination.

Pramlintide

May enhance the anticholinergic effect of Anticholinergic Agents. These effects are specific to the GI tract.

Secretin

Anticholinergic Agents may diminish the therapeutic effect of Secretin. Management: Avoid concomitant use of anticholinergic agents and secretin. Discontinue anticholinergic agents at least 5 half-lives prior to administration of secretin.

Sodium Oxybate

May enhance the CNS depressant effect of CNS Depressants. Management: Consider alternatives to combined use. When combined use is needed, consider minimizing doses of one or more drugs. Use of sodium oxybate with alcohol or sedative hypnotics is contraindicated.

Suvorexant

CNS Depressants may enhance the CNS depressant effect of Suvorexant. Management: Dose reduction of suvorexant and/or any other CNS depressant may be necessary. Use of suvorexant with alcohol is not recommended, and the use of suvorexant with any other drug to treat insomnia is not recommended.

Tamoxifen

CYP2D6 Inhibitors (Moderate) may decrease serum concentrations of the active metabolite(s) of Tamoxifen. Specifically, CYP2D6 inhibitors may decrease the metabolic formation of highly potent active metabolites. Management: Consider alternatives with less of an inhibitory effect on CYP2D6 activity when possible.

Tapentadol

May enhance the CNS depressant effect of CNS Depressants. Management: Avoid concomitant use of tapentadol and benzodiazepines or other CNS depressants when possible. These agents should only be combined if alternative treatment options are inadequate. If combined, limit the dosages and duration of each drug.

Zolpidem

CNS Depressants may enhance the CNS depressant effect of Zolpidem. Management: Reduce the Intermezzo brand sublingual zolpidem adult dose to 1.75 mg for men who are also receiving other CNS depressants. No such dose change is recommended for women. Avoid use with other CNS depressants at bedtime; avoid use with alcohol.

Risk Factor X (Avoid combination)

Aclidinium

May enhance the anticholinergic effect of Anticholinergic Agents.

Aminolevulinic Acid (Systemic)

Photosensitizing Agents may enhance the photosensitizing effect of Aminolevulinic Acid (Systemic).

Amisulpride

Antipsychotic Agents may enhance the adverse/toxic effect of Amisulpride. Management: Drugs listed as exceptions to this monograph are discussed in further detail in separate drug interaction monographs.

Amisulpride

May enhance the QTc-prolonging effect of QT-prolonging Antipsychotics (Moderate Risk).

Asunaprevir

May increase the serum concentration of Thioridazine.

Azelastine (Nasal)

CNS Depressants may enhance the CNS depressant effect of Azelastine (Nasal).

Bromopride

May enhance the adverse/toxic effect of Antipsychotic Agents.

Bromperidol

Blood Pressure Lowering Agents may enhance the hypotensive effect of Bromperidol. Bromperidol may diminish the hypotensive effect of Blood Pressure Lowering Agents.

Bromperidol

May enhance the CNS depressant effect of CNS Depressants.

Cimetropium

Anticholinergic Agents may enhance the anticholinergic effect of Cimetropium.

CYP2D6 Inhibitors

May increase the serum concentration of Thioridazine.

Dapoxetine

May enhance the arrhythmogenic effect of Thioridazine. Dapoxetine may increase the serum concentration of Thioridazine.

Dronedarone

Thioridazine may enhance the QTc-prolonging effect of Dronedarone.

Eluxadoline

Anticholinergic Agents may enhance the constipating effect of Eluxadoline.

FLUoxetine

May enhance the QTc-prolonging effect of Thioridazine. FLUoxetine may increase the serum concentration of Thioridazine.

FluvoxaMINE

May increase the serum concentration of Thioridazine.

Glycopyrrolate (Oral Inhalation)

Anticholinergic Agents may enhance the anticholinergic effect of Glycopyrrolate (Oral Inhalation).

Glycopyrronium (Topical)

May enhance the anticholinergic effect of Anticholinergic Agents.

Ipratropium (Oral Inhalation)

May enhance the anticholinergic effect of Anticholinergic Agents.

Levosulpiride

Anticholinergic Agents may diminish the therapeutic effect of Levosulpiride.

Metoclopramide

May enhance the adverse/toxic effect of Antipsychotic Agents.

Moclobemide

May increase the serum concentration of Thioridazine.

Orphenadrine

CNS Depressants may enhance the CNS depressant effect of Orphenadrine.

Oxatomide

May enhance the anticholinergic effect of Anticholinergic Agents.

Oxomemazine

May enhance the CNS depressant effect of CNS Depressants.

Paraldehyde

CNS Depressants may enhance the CNS depressant effect of Paraldehyde.

Pimozide

May enhance the QTc-prolonging effect of QT-prolonging Agents (Moderate Risk).

Piribedil

Antipsychotic Agents may diminish the therapeutic effect of Piribedil. Piribedil may diminish the therapeutic effect of Antipsychotic Agents. Management: Use of piribedil with antiemetic neuroleptics is contraindicated, and use with antipsychotic neuroleptics, except for clozapine, is not recommended.

Potassium Chloride

Anticholinergic Agents may enhance the ulcerogenic effect of Potassium Chloride. Management: Patients on drugs with substantial anticholinergic effects should avoid using any solid oral dosage form of potassium chloride.

Potassium Citrate

Anticholinergic Agents may enhance the ulcerogenic effect of Potassium Citrate.

QT-prolonging Agents (Highest Risk)

May enhance the QTc-prolonging effect of Thioridazine. Exceptions: Dronedarone; QuiNIDine.

QuiNIDine

Thioridazine may enhance the QTc-prolonging effect of QuiNIDine. QuiNIDine may increase the serum concentration of Thioridazine.

Revefenacin

Anticholinergic Agents may enhance the anticholinergic effect of Revefenacin.

Rolapitant

May increase the serum concentration of Thioridazine.

Saquinavir

May enhance the QTc-prolonging effect of Thioridazine.

Sulpiride

Antipsychotic Agents may enhance the adverse/toxic effect of Sulpiride.

Thalidomide

CNS Depressants may enhance the CNS depressant effect of Thalidomide.

Tiotropium

Anticholinergic Agents may enhance the anticholinergic effect of Tiotropium.

Umeclidinium

May enhance the anticholinergic effect of Anticholinergic Agents.

Monitoring parameters:

  • Mental status;
  • vital signs (as clinically indicated);
  • ECG (baseline, then periodic; do not initiate if QTc >450 msec);
  • weight, height, BMI, waist circumference (baseline; at every visit for the first 6 months; quarterly with stable antipsychotic dose);
  • CBC (as clinically indicated; monitor frequently during the first few months of therapy in patients with preexisting low WBC or history of drug-induced leukopenia/neutropenia);
  • electrolytes (baseline potassium; annually and as clinically indicated);
  • liver function (annually and as clinically indicated);
  • fasting plasma glucose level/HbA (baseline, then 1 yearly; in patients with diabetes risk factors or if gaining weight, repeat 4 months after starting antipsychotic, then yearly);
  • lipid panel (baseline; repeat every 2 years if the LDL level is normal; repeat every 6 months if the LDL level is >130 mg/dL);
  • changes in menstruation, libido, development of galactorrhea, erectile and ejaculatory function (at each visit for the first 12 weeks after the antipsychotic is initiated or until the dose is stable, then yearly);
  • abnormal involuntary movements or parkinsonian signs (baseline; repeat weekly until dose stabilized for at least 2 weeks after the introduction and for 2 weeks after any significant dose increase);
  • tardive dyskinesia (every 6 months; high-risk patients every 3 months);
  • visual changes (inquire yearly);
  • ocular examination (yearly in patients >40 years; every 2 years in younger patients).

How to administer Thioridazine (Mellaril)?

  • It can be administered orally with or without food.
  • To reduce the gastrointestinal side effects of the drug, it should be given with food or milk.

Mechanism of action of Thioridazine (Mellaril):

  • Thioridazine is a piperidine-phenothiazine that blocks postsynaptic dopaminergic and dopaminergic nerves in the brain.
  • It also acts at serotonin receptors, noradrenaline receptors, and histamine receptors.

Absorption is Rapid.

Protein binding: 96% to 99.3%.

Metabolism: It is metabolized in the liver primarily by sulphoxidation, demethylation (2%), and hydroxylation (limited) into its active metabolites mesoridazine and sulphoridazine.

Bioavailability is 25% to 33%

Half-life elimination is 5 to 27 hours.

Time to peak serum concentration: About 1 to 4 hours.

International Brand Names of Thioridazine:

  • Aldazine
  • Fialgin
  • Meleril
  • Mellerette
  • Melleril
  • Mellerzin
  • Melzin
  • Neubalon
  • Orsanil
  • Ridazin
  • Ridazine
  • Sequax
  • Simultan
  • Sonapax
  • Thinin
  • Thiomed
  • Thioridazin
  • Thioridazin prolongatum
  • Thioril
  • Thiosia
  • Thiozin
  • Thiozine
  • Winleril

Thioridazine Brand Names in Pakistan:

Thioridazine (Hcl) Suspension 10 Mg/5ml in Pakistan

Melleril Novartis Pharma (Pak) Ltd

 

Thioridazine (Hcl) Tablets 10 Mg in Pakistan

Melleril Novartis Pharma (Pak) Ltd

 

Thioridazine (Hcl) Tablets 25 Mg in Pakistan

Melleril Novartis Pharma (Pak) Ltd

 

Thioridazine (Hcl) Tablets 100 Mg in Pakistan

Melleril Novartis Pharma (Pak) Ltd