Long-acting antipsychotics in bipolar disorder: linked to half the manic admissions

Design

Self-controlled case series from territory-wide electronic health records

Population

2,086 people with bipolar disorder in Hong Kong who used both injectable and oral antipsychotics

Primary outcome

Healthcare use, relapse admissions and safety events

Effect

Manic admissions aIRR 0.51 (0.44-0.59); EPS in first 90 days aIRR 2.95

This self-controlled case series used Hong Kong electronic health records from 2004 to 2023. Of 17,841 people with bipolar disorder, 2,086 had periods on both long-acting injectable and oral antipsychotics, so each person served as their own control.

Injectable periods were associated with fewer emergency visits (aIRR 0.85), fewer psychiatric admissions (aIRR 0.67, 0.61 to 0.74), about half as many manic admissions (aIRR 0.51, 0.44 to 0.59) and fewer mixed-episode admissions (aIRR 0.31). Depressive admissions did not fall (aIRR 1.34, 0.94 to 1.93), and there was no rise in cardiovascular or other medical admissions. Extrapyramidal symptoms were about three times as frequent in the first 90 days (aIRR 2.95, 1.40 to 6.22) but did not differ after that.

Injectables are often reserved for schizophrenia, with bipolar disorder an afterthought. These data support offering them to people with bipolar disorder whose relapses are mostly manic and driven by poor adherence. They will not prevent depressive relapse, so mood stabiliser and depression planning still matter.

• Consider a long-acting injectable for bipolar patients with repeated manic relapses linked to stopping oral medication.
• Do not expect an injectable to prevent depressive episodes; plan for those separately.
• Examine for extrapyramidal symptoms at each injection in the first three months.
• Discuss the option early, after a first manic admission, rather than after several.

Why it matters

Injectables are underused in bipolar disorder, and this ties them to fewer manic admissions, not depressive ones.

Don't overread it

This is observational; the self-controlled design removes fixed differences between people, not changes over time.

The statistics, in plain English

An incidence rate ratio of 0.51 means about half as many manic admissions per unit of time on injectables as on oral drugs in the same people. The depressive admission interval (0.94 to 1.93) crosses 1, so no difference was shown there, and a rise cannot be excluded.

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