Large Doses of Antipsychotics May Increase Tardive Dyskinesia Risks: Study

Researchers found that side effects of Thorazine may increase the risk tardive dyskinesia as higher doses of the antipsychotic are used

A new study indicates that taking high doses of Thorazine and other first-generation antipsychotic drugs may increase a person’s risk of developing involuntary muscle movements.

According to findings recently published in the Journal of Clinical Psychopharmacology, patients developed a condition known as tardive dyskinesia when they took doses of antipsychotic drugs above the recommended amount, or when they took the maximum dose.

Tardive Dyskinesia

Tardive dyskinesia is a neurological disorder that causes involuntary movements, like rocking back and forth, frowning, chewing movements and rapid eye blinking.

Health experts do not know what causes tardive dyskinesia, but data from prior studies has suggested that side effects of first-generation antipsychotic medications, such as Thorazine, Haldol and Prolixin, may contribute to the risk.

Research published in 2022 indicated that the second-generation antipsychotic Risperdal increased a person’s risk of developing tardive dyskinesia, even at low doses. Other research indicates taking some antidepressants and anti-nausea medications like Reglan also increase the risk of tardive dyskinesia.

Roughly 4 million people in the United States take antipsychotic medications to treat conditions like schizophrenia and bipolar disorder. While the drugs are highly necessary for conditions like that, they may put many people at risk of developing the condition.

Tardive dyskinesia is treated by decreasing the dose of the drugs that may cause the condition, or by stopping use of the drug completely. While there are some medications, like Austedo, to help control the symptoms, there is no cure.

In this new study, Japanese researchers examined data on more than 58,000 patients 15 years and older who were diagnosed with schizophrenia, depression or bipolar disorder,and were prescribed first-generation antipsychotics, including Thorazine. They were compared with control patients.

The average daily Thorazine dose was 75 mg/d, but patients also took doses of Thorazine higher than 75 mg, up to 300 mg.

Patients taking more than 75 mg of Thorazine had a significantly higher risk of developing tardive dyskinesia, the researchers concluded.

The data indicates that the risk increased based on the dose. The higher the dose of Thorazine, the higher the risk of developing tardive dyskinesia. The risk was seen after patients immediately began taking a higher dose or after the most recent maximum dose, as well as in patients who had been taking the medication for a while.

This type of correlation is often referred to as a causal connection and is strong evidence that the drug is actually the cause of the involuntary movements and not a coincidental association, the researchers indicated.

The researchers concluded it is important to weigh the risks of using first-generation antipsychotics against the benefits and the possibility patients may develop tardive dyskinesia. They also emphasized the need for doctors to closely monitor patients when prescribing first-generation antipsychotic drugs like Thorazine.