Increased incidence of dyskinesias and other behavioral effects of re-exposure to neuroleptic treatment in social colonies of Cebus apella monkeys.

RATIONALE

Typical neuroleptic medications are still administered to as many as 40% of patients receiving antipsychotic treatment in the US. Intermittent administration or interruption of long-term neuroleptic medication for schizophrenia may increase the incidence of human tardive dyskinesias, and similarly may produce increasingly marked motor side-effects, parkinsonism, and other behavioral pathologies in non-human primates.

OBJECTIVES AND METHODS

Given these similarities, we addressed the issue of prolonged and intermittent typical neuroleptic treatment and dopaminergic function during a 5-year, multi-phase study with social colonies of Cebus apella monkeys. In the previously reported phase 1, we examined the effects of 48 weeks of exposure to, followed by withdrawal from, fluphenazine decanoate (FPZ). Phase 3 reported here examined the effects of 18 weeks of re-exposure to FPZ in these same monkeys, 91 weeks after discontinuation of their phase 1 FPZ treatment.

RESULTS

Analysis of blood plasma FPZ indicated levels of 0.22+/-0.08 ng/ml for the six injections during the re-exposure period (n=54), comparable to the 0.24+/-0.07 ng/ml levels measured during our original treatment with this dose. Acute dyskinesias and dystonias increased by 300% upon re-exposure to FPZ; 15 of 18 FPZ-treated animals exhibited oral-buccal dyskinesias and all exhibited torticollis or retrocollis. Retreatment with FPZ was also associated with highly significant reductions in Self- and Environment-Directed Behavior and Directed Affiliation, effects similar to those seen during the original phase 1 FPZ treatment. Although FPZ re-treatment was associated with a significant reduction in Directed Aggression (an effect that was more robust than that observed during phase 1), in phase 3, we again observed an increase in Directed Aggression during early drug discontinuation when animals were in a stress-inducing situation.

CONCLUSIONS

These results both support our phase 1 conclusion that typical neuroleptic medications may contribute to negative symptoms of schizophrenia and provide additional evidence for the possibility of increased aggression in stressful situations when medication is discontinued. Additionally, the results indicate that intermittent treatment with typical neuroleptics may dramatically increase the incidence of dystonias and dyskinesias.