Worst Pills, Best Pills

An expert, independent second opinion on more than 1,800 prescription drugs, over-the-counter medications, and supplements

Drug Profile

Do NOT stop taking this or any drug without the advice of your physician. Some drugs can cause severe adverse effects when they are stopped suddenly.

Do Not Use [what does this mean?]
Generic drug name: thioridazine (thye oh RID a zeen)
Brand name(s): MELLARIL
GENERIC: not available FAMILY: Traditional or Typical Antipsychotics
Find the drug label by searching at DailyMed.

Alternative Treatment [top]

Safety Warnings For This Drug [top]

FDA BLACK BOX WARNING

MELLARIL (thioridazine HCl) has been shown to prolong the QTc interval in a dose-related manner, and drugs with this potential, including Mellaril, have been associated with torsades de pointes–type arrhythmias and sudden death. Due to its potential for significant, possibly life-threatening, proarrhythmic effects, Mellaril should be reserved for use in the treatment of schizophrenic patients who fail to show an acceptable response to adequate courses of treatment with other antipsychotic drugs, either because of insufficient effectiveness or the inability to achieve an effective dose due to intolerable adverse effects from those drugs.

Increased Mortality in Elderly Patients with Dementia-Related Psychosis

Elderly patients with dementia-related psychosis treated with antipsychotic drugs are at an increased risk of death. Analyses of seventeen placebo-controlled trials (modal duration of 10 weeks), largely in patients taking atypical antipsychotic drugs, revealed a risk of death in drug-treated patients of between 1.6 to 1.7 times the risk of death in placebo-treated patients. Over the course of a typical 10-week controlled trial, the rate of death in drug-treated patients was about 4.5%, compared to a rate of about 2.6% in the placebo group. Although the causes of death were varied, most of the deaths appeared to be either cardiovascular (e.g., heart failure, sudden death) or infectious (e.g., pneumonia) in nature. Observational studies suggest that, similar to atypical antipsychotic drugs, treatment with conventional antipsychotic drugs may increase mortality. The extent to which the findings of increased mortality in observational studies may be attributed to the antipsychotic drug as opposed to some characteristic(s) of the patients is not clear. Thioridazine hydrochloride is not approved for the treatment of patients with dementia-related psychosis.

Product Warnings

Ask a doctor or pharmacist before use if you are taking antibiotics.

When using this product, tiredness, drowsiness or dizziness may occur. Be careful driving or operating machinery.

Stop using and ask a doctor if symptoms get worse, diarrhea lasts more than two days or you get abdominal swelling or bulging. These may be signs of a serious condition.

If pregnant or breast-feeding, ask a health care professional before use.

Older adults are especially sensitive to the harmful anticholinergic effects of this drug. Drugs in this family should not be used unless absolutely necessary.

Mental Effects: confusion, delirium, short-term memory problems, disorientation and impaired attention.

Physical Effects: dry mouth, constipation, difficulty urinating (especially for a man with an enlarged prostate), blurred vision, decreased sweating with increased body temperature, sexual dysfunction and worsening of glaucoma.

Facts About This Drug [top]

Thioridazine (MELLARIL) required extensive new safety warnings, including a black-box warning, in its professional product labeling or package insert in July 2000 because of life-threatening heart rhythm disturbances and death associated with the use of the drug. The only FDA-approved use for thioridazine is now “the management of schizophrenic patients who fail to respond adequately to treatment with other antipsychotic drugs.”[1]

We have listed thioridazine as a Do Not Use drug because...

Thioridazine (MELLARIL) required extensive new safety warnings, including a black-box warning, in its professional product labeling or package insert in July 2000 because of life-threatening heart rhythm disturbances and death associated with the use of the drug. The only FDA-approved use for thioridazine is now “the management of schizophrenic patients who fail to respond adequately to treatment with other antipsychotic drugs.”[1]

We have listed thioridazine as a Do Not Use drug because there are a number of safer antipsychotic drugs available on the market. There is simply no longer any reason to expose patients to the risk of thioridazine.

On September 8, 2005, Health Canada, an agency similar to the U.S. Food and Drug Administration (FDA), announced that the sale of thioridazine would be halted by September 30, 2005 because of safety concerns.[2]

Health Canada received reports of three deaths between 2000 and 2005 possibly related to thioridazine. The most recent death occurred in February 2005. This is a significant number because Canada has about one-tenth the population of the U.S.

Thioridazine causes an adverse effect known as QT prolongation, a change in the electrical activity of the heart that can lead to a fatal heart rhythm disturbance called torsades de pointes, resulting in sudden death. QT prolongation can be detected only by an electrocardiogram (EKG or ECG). Torsades de pointes is a French phrase that means “twisted point,” which describes the appearance of this rhythm disturbance on the EKG tracing.

Thioridazine is now contraindicated in combination with other drugs that can prolong the QT prolongation and in patients who have a long QT interval on an EKG without using any drugs (this is called "congenital long QT syndrome"). The only extensive list of drugs that cause QT prolongation is maintained by the University of Arizona Health Sciences Center: http://www.torsades.org. Furthermore, thioridazine is also contraindicated in patients with a history of heart rhythm disturbances.

A number of drugs are now contraindicated with the use of thioridazine because they can inhibit one of a group of liver enzymes known as cytochrome P450 that metabolize, or break down, thioridazine. If this enzyme is inhibited, increased blood levels of thioridazine can result, leading to a greater risk of a heart rhythm disturbance.

last reviewed January 31, 2021