Drug-Induced Movement Disorders

Why medicines cause movement problems

Movement is controlled by circuits deep in the brain (the basal ganglia) that rely on a balance of dopamine and acetylcholine. Drugs that block dopamine D2 receptors, especially first-generation antipsychotics, upset this balance. The resulting symptoms are called extrapyramidal side effects (EPS). See extrapyramidal symptoms.

Types of drug-induced movement disorders

Acute dystonia

Most common in young men and with high-potency antipsychotics such as haloperidol. Anti-nausea drugs such as metoclopramide and prochlorperazine can cause it after a single dose. It looks alarming but responds rapidly to treatment.

Akathisia

Akathisia is often mistaken for anxiety or worsening psychosis, which can lead to higher doses and more restlessness. It is distressing and has been linked to agitation and suicidal thoughts.

Drug-induced parkinsonism

It looks like Parkinson's disease but is more often symmetrical and comes on after a dopamine-blocking drug. It is the second most common cause of parkinsonism in older adults, and is often missed.

Tardive dyskinesia

"Tardive" means late. Tardive dyskinesia develops after months or years of exposure. Risk rises with duration, older age, female sex, diabetes and first-generation antipsychotics, but newer antipsychotics also carry risk. It may first appear or worsen when the drug is reduced or stopped.

Medicines that commonly cause them

• antipsychotics: haloperidol, chlorpromazine, fluphenazine, and to a lesser degree risperidone, olanzapine, aripiprazole and others. Clozapine and quetiapine have the lowest risk
• anti-nausea and gut drugs: metoclopramide (FDA boxed warning about tardive dyskinesia, with use advised for no more than 12 weeks), prochlorperazine, promethazine
• antidepressants: SSRIs occasionally cause akathisia or tremor
• mood stabilizers: lithium and valproate (tremor, parkinsonism)
• other drugs: calcium channel blockers flunarizine and cinnarizine (not available in the US), some anti-seizure drugs, amiodarone, stimulants and some antihistamines

Diagnosis

Diagnosis rests on the link between the medicine and the symptoms. A doctor will:

• take a detailed medication history, including recent dose changes and over-the-counter or anti-nausea drugs
• examine movements, tone, gait and tremor
• use rating scales such as the Abnormal Involuntary Movement Scale (AIMS), recommended at least yearly for people on long-term antipsychotics
• consider other causes, such as Parkinson's disease, Huntington's disease, Wilson disease in younger people, thyroid disease and dental problems
• occasionally order a DaTscan to distinguish drug-induced parkinsonism from Parkinson's disease

Treatment

General principles

• Reduce, stop or switch the causing drug where safely possible, in discussion with the prescriber. Never stop antipsychotics abruptly on your own.
• Choose medicines with lower movement risk when starting new treatment.

Specific treatments

• Acute dystonia: an injection of an anticholinergic (benztropine) or antihistamine (diphenhydramine) usually works within minutes. A short oral course prevents recurrence.
• Akathisia: lowering the dose, switching drug, or adding propranolol, mirtazapine or a benzodiazepine.
• Drug-induced parkinsonism: reduce or switch the drug. Symptoms usually resolve within weeks to months, though sometimes up to a year. Anticholinergics are sometimes used short-term but are avoided in older adults.
• Tardive dyskinesia: VMAT2 inhibitors (valbenazine and deutetrabenazine) are FDA-approved and reduce movements. Switching to clozapine may help. Anticholinergics can make it worse.
• Neuroleptic malignant syndrome: stop the drug and treat in hospital, often in intensive care.

Outlook

Acute dystonia and akathisia usually resolve quickly once treated. Drug-induced parkinsonism generally improves after the drug is stopped. Tardive dyskinesia may improve over time, but it can be persistent. VMAT2 inhibitors provide meaningful relief for many people.

Prevention

• use the lowest effective dose of dopamine-blocking drugs
• prefer agents with lower movement risk when possible
• limit metoclopramide to short-term use
• monitor regularly for early signs, especially in older adults and people on long-term treatment
• report any new movements, restlessness or stiffness promptly

Frequently asked questions

What are drug-induced movement disorders?

They are abnormal movements caused by medicines, most commonly drugs that block dopamine, such as antipsychotics and some anti-nausea drugs. They include muscle spasms, restlessness, Parkinson-like stiffness and slowness, tremor, and tardive dyskinesia.

What is tardive dyskinesia?

Tardive dyskinesia is a delayed movement disorder causing repetitive, involuntary movements, often of the mouth, lips, tongue and face, after months or years of taking dopamine-blocking drugs. It can persist after stopping the drug. VMAT2 inhibitor medicines can reduce the movements.

What is akathisia?

Akathisia is an intense feeling of inner restlessness with an urge to keep moving, such as pacing, rocking or shifting position. It is a side effect of antipsychotics and sometimes antidepressants. It is treated by lowering or changing the drug or adding medicines like propranolol.

Which medicines cause extrapyramidal side effects?

The most common are first-generation antipsychotics such as haloperidol, newer antipsychotics such as risperidone, and anti-nausea drugs such as metoclopramide and prochlorperazine. Lithium, valproate and some antidepressants can cause tremor or other movement effects.

Are drug-induced movement disorders permanent?

Most are not. Acute dystonia, akathisia and drug-induced parkinsonism usually improve when the drug is reduced or stopped. Tardive dyskinesia can be long-lasting or permanent in some people, which is why early detection and regular monitoring are important.