The epidemiology and phenomenology of non-antipsychotic-induced dystonia: a hybrid systematic-narrative review.

Background: Medication-induced dystonia (MID) is a movement disorder (MD), characterized by involuntary sustained or intermittent muscle contractions, causing abnormal, often repetitive, movements, postures, or both. Although MID is commonly associated with the use of antipsychotics, it also occurs with many other medications widely used in clinical practice.

Methods: A systematic literature search (from inception to November 2023), using the PubMed and Embase databases, was conducted without language restriction for articles reporting on MID in people without pre-existing MDs, and this for all potentially relevant non-antipsychotic medications. A narrative synthesis of the available evidence was undertaken.

Results: MID is common (1 to 10%) with certain antiemetics. Selective serotonin reuptake inhibitors and the antiepileptics valproate, carbamazepine, and lamotrigine are rarely (0.01 to 0.1%) or very rarely (<0.01%) associated with MID. All other medications are very rarely (<0.01%) associated with MID or have a risk that cannot be precisely estimated. The actual rate of dystonic reactions with most non-antipsychotic agents remains unknown, owing to misdiagnosis and underreporting in the scientific literature. In general, MID seems to occur more often in children and adolescents, even with a single low dose, and with polymedication. In most cases, MID is acute in onset (occurring within hours to days) and involves the head and neck.

Conclusions: Although MID is most common with dopamine receptor-blocking antiemetics, many other medications may also produce dystonic reactions, particularly in children and adolescents. Although such incidents remain rare, there are indications that MID is underreported for many classes of medications.