Efficacy of olanzapine and ziprasidone for the treatment of schizophrenia: a systematic review

Olanzapine abuse

Olanzapine is a thienobenzodiazepine that blocks especially the serontonin (5-hydroxytryptamine [5-HT]) 5-HT2A and the dopamine D2 receptors as well as muscarinic (M1), histamine (H1), 5-HT2C, 5-HT3 to 5-HT6, adrenergic (α(l)), and D4 receptors. This case report presents an olanzapine abuse. A 48-year-old, primary school graduate, married woman applied to psychiatry clinic with tachycardia, insomnia, and anxiety complaints. In psychiatric evaluations, it was determined that these complaints have been continuing for 15 years at intervals and that she has been using citalopram 40 mg/day and olanzapine 50 mg/day for the last 3 years. As diabetes mellitus was diagnosed in follow-ups, interruption of olanzapine treatment was planned. The patient stated that she started taking the medicine again upon discomfort, increase in anxiety, dysphoria, insomnia, and nervousness, which started just after olanzapine was interrupted. She said that she was feeling dense stress when she did not take the medicine, and she thought that this situation would recover only by taking that medicine and hence she could not discontinue the medicine. In addition to medications with obvious abuse potential such as benzodiazepines and methylphenidate, and other stimulants, abuse of a number of commonly prescribed psychiatric medications has been reported. There are only 2 cases of olanzapine abuse in literature.

Randomized controlled study of the T-type calcium channel antagonist MK-8998 for the treatment of acute psychosis in patients with schizophrenia

OBJECTIVE

This study aimed to evaluate whether the T-type calcium channel antagonist MK-8998 was effective in treating acute psychosis in patients with schizophrenia.

METHODS

This was a randomized, double-blind, parallel-group study. After a placebo lead-in, acutely psychotic inpatients with schizophrenia were randomized to 4 weeks of MK-8998 12/16 mg daily (N = 86), olanzapine 10/15 mg daily (N = 47), or placebo (N = 83). The primary efficacy measure was score on the Positive and Negative Syndrome Scale (PANSS).

RESULTS

Out of 216 randomized patients, 158 completed the 4-week study: MK-8998 = 58 (67.4%), olanzapine = 38 (80.9%), and placebo = 62 (74.7%). The mean changes from baseline in PANSS score at week 4 for MK-8998 and olanzapine were not significantly different from placebo: MK-8998-placebo difference = -0.6 [95% confidence interval (CI): -7.0, 5.8], p = 0.9; olanzapine-placebo difference = -4.3 [95% CI: -11.7, 3.1), p = 0.3. A responder rate analysis (≥20% improvement from baseline in PANSS score) suggested an advantage of olanzapine over placebo (odds ratio = 2.20 [95% CI: 0.95, 5.09], p = 0.07) but no effect of MK-8998 over placebo (odds ratio = 1.28 [95% CI: 0.62, 2.64], p = 0.5). Treatments were generally well tolerated, but more patients reported adverse events for MK-8998 (47.7%) and olanzapine (48.9%) than placebo (37.3%).

CONCLUSIONS

MK-8998 was not effective in treating acutely psychotic inpatients with schizophrenia, as measured by PANSS score at week 4. Because of the limited efficacy of the active comparator, we cannot exclude the possibility that T-type calcium channel antagonists could prove to be effective in schizophrenia.

The role of histaminergic H1 and H3 receptors in food intake: a mechanism for atypical antipsychotic-induced weight gain?

Atypical antipsychotics such as olanzapine and clozapine are effective at treating the multiple domains of schizophrenia, with a low risk of extra-pyramidal side-effects. However a major downfall to their use is metabolic side-effects particularly weight gain/obesity, which occurs by unknown mechanisms. The present paper explores the potential candidature of histaminergic neurotransmission in the mechanisms of atypical antipsychotic-induced weight gain, with a focus on the histaminergic H1 and H3 receptors. Olanzapine and clozapine have a high affinity for the H1 receptor, and meta-analyses show a strong correlation between risk of weight gain and H1 receptor affinity. In addition, olanzapine treatment decreases H1 receptor binding and mRNA expression in the rat hypothalamus. Furthermore, a complex role is emerging for the histamine H3 receptor in the control of hunger. The H3 receptor is a pre-synaptic autoreceptor that inhibits the synthesis and release of histamine, and a heteroreceptor that inhibits other neurotransmitters such as serotonin (5-HT), noradrenaline (NA) and acetylcholine (ACh), which are also implicated in the regulation of food intake. Thus, the H3 receptor is in a prime position to regulate food intake, both through its control of histamine and its influence on other feeding pathways. We proposed that a mechanism for atypical antipsychotic-induced weight gain may be partly through the H3 receptor, as a drug-induced decrease in H1 receptor activity may decrease histamine tone through the H3 autoreceptors, compounding the weight gain problem. In addition, atypical antipsychotics may affect food intake by influencing 5-HT, NA and ACh release via interactions with the H3 heteroreceptor.

Olanzapine and JL13 induce cross-tolerance to the clozapine discriminative stimulus in rats

We have previously shown that chronic treatment with clozapine induces tolerance to the clozapine discriminative stimulus in rats. The studies reported here extended this work to assess whether chronic treatment with the clozapine-like antipsychotics olanzapine and 5-(4-methylpiperazin-1-yl)-8-chloro-pyrido[2,3-b][1,5] benzoxazepine fumarate (JL13) induced cross-tolerance to clozapine. Two groups of rats were trained to discriminate clozapine (5 mg/kg, intraperitoneal). Training was suspended and the rats were treated with either olanzapine or JL13 at high doses (5 and 20 mg/kg, respectively). These doses were administered twice daily. The clozapine generalization curve was computed three times - before chronic drug treatment, after 10 days of chronic treatment, and after 16 drug-free days. Both olanzapine and JL13 induced cross-tolerance to the clozapine stimulus, shown by significant 3.4 and 3.9 fold parallel shifts to the right in the clozapine generalization curves. Cross-tolerance was lost spontaneously during the drug-free days after treatment as clozapine sensitivity returned to baseline. We interpret these findings as indicative of the development of pharmacodynamic cross-tolerance to clozapine. Possible neuroadaptive mechanisms involved in such cross-tolerance are discussed. The paradigm outlined here allows refinement of antipsychotic drug discrimination assays to identify common chronic effects of such drugs.

Aripiprazole-related tardive dyskinesia

The low prevalence of extrapyramidal symptoms associated with atypical antipsychotics has led to their widespread use during the past decade. Aripiprazole, the newest medication in this class, has been associated with extrapyramidal symptoms (eg, akathisia) and with improvement of tardive dyskinesia (TD), but to date it has not been associated with the development of TD. We report a case of TD associated with the use of aripiprazole 15 mg/day for 18 months for refractory depression. Symptoms of TD resolved within several weeks of discontinuation of aripiprazole.

Clinical trial design in schizophrenia: implications for clinical decisions

PURPOSE OF REVIEW

Results from clinical trials do not necessarily provide information for decisions in clinical practice. This review aims to present strengths and limitations of different methodological types of clinical trials and to offer an overview of how knowledge from clinical trails can be distilled for clinical practice. Selected key questions in the treatment of schizophrenia are presented, with a focus on the possibilities and restrictions of translating trial results into real-world practice.

RECENT FINDINGS

Randomized controlled trials are the gold standard for proving efficacy of a diagnostic or therapeutic procedure. They have a high degree of internal validity and a clear-cut message when conducted to good-quality standards but suffer from a lack of generalizability (external validity). Effectiveness studies evaluate effects of treatments under conditions approximating usual care. They may include patient-centred outcomes or health economic evaluations. According to the type of trial, specific problems arise in the interpretation of results. Typical examples are given for the treatment of acute exacerbations of schizophrenia, for relapse prevention and for the treatment of cognitive impairment.

SUMMARY

Clinical decisions have to be made upon the best knowledge. Therefore, well conducted studies addressing all major issues from all relevant perspectives are needed. The assessment of a treatment regimen for clinical utility requires both efficacy and effectiveness studies. An understanding of the design, analysis and conventions of both study types is essential for the interpretation of results and their translation to the clinical decision-making process.