Depot medications and the treatment of schizophrenia in community psychiatry

© 2005 Dr. Timothy John Robert LambertSince their introduction in the 1960s, depot antipsychotics have played a substantive role in the pharmacological management of patients with schizophrenia in Australia. During the 1990s, among radical changes to the structure and function of community services in the State of Victoria, a new generation of improved oral antipsychotics was introduced. The latter were anticipated to replace older antipsychotic medications. This thesis examines the impact these changes have had on depot prescribing in community psychiatric settings. It tests the hypothesis that due to widespread concerns over the consequences of non-adherence that frequently accompany the use of all oral antipsychotics, depot agents will maintain a key place in pharmacotherapy. The research is based on Australian data taken from community care teams in Victoria, complemented in one study with data from Western Australia. The prescribing patterns data indicate that between 1998 and 2003 substantial changes in the use of antipsychotics have occurred. The results show a rapid increase in second generation antipsychotics from 38 percent to 78 percent over the five year period of the study. Over the same time, first generation antipsychotics fell from 27 percent to 3 percent of prescriptions. Prescriptions of depot agents also fell, but by a much lesser amount, from 46 percent to 29 percent of prescriptions, a level close to the absolute level of non-adherence proposed in the literature. This supports a further hypothesis that depot antipsychotics use will stabilise at a level close to the absolute level of non-adherence. The findings also indicate that from the perspective of initially distinct prescribing practices in different services, there has been a convergence of prescribing trends towards a common level of use for each group of antipsychotic medications studied. Both depot and newer oral antipsychotics demonstrate a high degree of prescribing stability over time, which is found to be inversely related to the risk of admission for population of patients considered. The clinical application of depots is effected by factors relating to the Service, the range of medications available and, characteristics of the Patient. Four studies were undertaken to explore the likely impact of these influences on community prescribing. The first shows that community treatment orders are used with depot agents more than with other antipsychotics. This supports the hypothesis that involuntary treatment orders facilitate the instigation of depot antipsychotics in reluctant community-treated patients. The second study shows that fewer than 10 percent of patients meet non-adherence criteria of less than 75 percent adherence, that an inverse relationship exists between depot adherence and hospital admission and, a critical level of depot adherence of less than 85 percent is predictive of admission with respect to this population. These findings support the decision of clinicians who prescribe depots with the expectation they will lead to better adherence. The third and fourth studies examine the attitudes of mental health professionals and depot treated patients, respectively. Differences in critical attitudes towards depot antipsychotics between professionals and between services are described. Additionally, patient attitudes to depots, assessed through a pilot satisfaction survey, indicate that only a minority of patients (46 percent) are clearly dissatisfied with their depot medications. This is at odds with the negative attitudes towards depots found among many of the clinical staff. In conclusion, the thesis demonstrates that depot antipsychotics remain an important component of the pharmacotherapy of people with schizophrenia in community psychiatric settings in Victoria. For multi-disciplinary clinical care teams their utility lies in addressing non-adherence, and so preventing relapse and rehospitalisation, and the subsequent, often widespread, costs that ensue