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

Abstract
Background. Medication-induced dystonia (MID) is a movement disorder (MD), characterized
by involuntary sustained or intermittent muscle contractions, causing abnormal, often repeti-
tive, 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 polymedica-
tion. 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 under-
reported for many classes of medications.