Evidence suggest that if an antipsychotic is not showing benefit by 1-4 weeks, it is unlikely to work for that patient. Antipsychotics may differ in the initial time period required to show early benefit, for example , risperidone and haloperidol may show benefits early on ( 1-2 weeks) where as olanzapine may take upto 4 weeks.
After starting the medication, if by two weeks , there is no response ( early non response)- patients and clinicians will be asking the question: In early non responders, what is the best strategy?
Kotaro Hatta & Hiroto Ito review the evidence for different strategies when faced with early non response in acute psychosis.
1. “Switching or staying” after early non response? The first RCT on this ( switching vs staying. Kinon et al) , showed that switching to risperidone in early non-responders to olanzapine at week 2 resulted in a small but significantly greater reduction in PANSS total score. There are not many studies at present to make any conclusions regarding this.
2. Augmenting ? Adding another agent after initial nonresponse was addressed in very few studies. Available results do not suggest that this is effective.
3. Dose escalation? There are no good quality studies addressing this issue in acute phase treatment . In chronic resistant schizophrenia high dose olanzapine was similar in efficacy to clozapine in one study.
Comments: It is unclear what is the best strategy when initial antipsychotic is not showing any benefit by two weeks. Clinicians and patients can get frustrated, but there is not enough information available to make any decisions. Continuing the same antipsychotic up to 4 weeks in sufficient doses and then switching appears to be the best given we do not have enough evidence to support other strategies for non response by two weeks.
Hatta K, Ito H. Clin Psychopharmacol Neurosci. 2014 Apr;12(1):1-7.