Sertraline-induced acute mandibular dystonia

To the Editor

Although extra-pyramidal side effects are traditionally associated with antipsychotics, they can also be precipitated by other medications including antidepressants. Serotonin-specific reuptake inhibitors (SSRIs) have been reported to cause akathisia, dyskinesias, dystonias, Parkinsonism and bruxism (Ranjan et al., 2006).

We present a 48-year-old Caucasian man with a history of treatment-resistant schizophrenia, amphetamine abuse and opioid dependence, who was hospitalised for a psychotic exacerbation of his illness. ¹ Following the re-introduction of his usual regimen of olanzapine depot 300 mg IMI monthly, his florid persecutory delusions and thought disorder abated. On admission he exhibited orobuccal tardive dyskinesia with prominent puckering of his lips secondary to two decades of antipsychotic use. Collateral history confirmed that this movement disorder was chronic and stable.

During his admission we commenced sertraline for comorbid social anxiety. After approximately 3 weeks, the dose was doubled from 25 to 50 mg daily, at which point he complained of rapid onset of jaw stiffness. These symptoms were distressing and made eating and drinking difficult. He was observed by nursing staff to require the use of his hand to close his mouth when chewing.

On examination, the patient demonstrated jaw hypertonicity preventing mandibular closure. There was no bruxism, and no neck or limb dystonias. Vital signs were unremarkable, and blood chemistry was normal. A speech pathology review identified deficits in chewing, but not swallowing. We diagnosed an acute mandibular dystonia.

A dietary regimen of thickened fluids was charted. Oral benztropine 2 mg was administered without improvement. We discontinued the sertraline, and within 72 hours his symptoms began to lessen. Near-complete resolution of the dystonia followed within the week: a response to the withdrawal of the medication consistent with other reported cases (Raveendranathan and Rao, 2015).

Acute mandibular dystonia is a rare but important complication of sertraline. The mechanism is believed to involve the inhibitory effects of serotonergic inputs on dopaminergic pathways in the striatum. By comparison, the related phenomenon of SSRI-induced bruxism is considered to be a variant of akathisia arising from dopamine hypofunction in the mesocortical pathway (Uvais et al., 2016).

This case highlights the need for caution when prescribing SSRIs to patients with pre-existing movement disorders, especially where polypharmacy is a feature.