Continuous Dopamine D₂ Receptor Blockade and Long-Term Outcome in First-Episode Schizophrenia

It is not known what proportion of patients experience relapse in first-episode schizophrenia despite continuous dopamine D₂ receptor blockade and whether breakthrough psychosis is attributable to long-term use of D₂-blocking antipsychotics. Using data from a Finnish nationwide cohort, the authors sought to test the hypothesis that the incidence of breakthrough psychosis is accelerated among previously relapse-free patients receiving continuous D₂ antagonist treatment beyond 5 years.

All persons age 45 years or younger with first-episode schizophrenia were identified from the nationwide registry of inpatient care for the years 1996-2014. The primary outcome was a severe relapse leading to hospitalization among those treated continuously with long-acting injectable (LAI) antipsychotics. The secondary outcome was the incidence rate ratio (IRR) of relapse during years 2-10, using year 1 as the reference.

A total of 305 patients initiated ensured LAI use during the first 30 days of follow-up. Kaplan-Meier analysis showed that during the 10-year follow-up, their cumulative probability of relapse was 45% (95% CI=35-57). The annual relapse incidence per person-year decreased from 0.26 (95% CI=0.20-0.35) during the first year to 0.05 (95% CI=0.01-0.19) during the fifth year, corresponding to an IRR of 0.18 (95% CI=0.04-0.74). During years 6-10, only four relapses occurred during 128 person-years, corresponding to an IRR of 0.12 (95% CI=0.03-0.33) compared with year 1.

About 40%-50% of patients with first-episode schizophrenia will relapse despite continuous D₂ blockade, apparently due to non-dopaminergic elements of the pathophysiology of the illness, as the results show that long-term dopamine receptor blockade is not associated with an increased risk of breakthrough psychosis.