West London NHS Trust

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Real world data evaluation of prescribing practices and safety data for metformin prophylaxis in patients prescribed anti-psychotic medication – retrospective cohort study. Extension Request

This is a retrospective study of patients who are prescribed antipsychotics. The main aim of the study will be to establish the prevalence, efficacy, and safety of prophylactic prescribing of metformin in individuals taking antipsychotics who do not have type 2 diabetes. The cohort will include all patients prescribed antipsychotics who do not have type 2 diabetes from 1 January 2015 to 1st December 2019. Retrospective follow up data for this cohort will be collected to evaluate real world prescribing in this cohort of patients. This cohort will be further split into individuals taking antipsychotics that are categorised as: 1.) High risk of weight gain 2.) Moderate risk of weight gain 3.) Low risk of weight gain 4.) Unspecified risk of weight gain Within this cohort two groups will be identified and compared: 1. Those prescribed metformin 2. Those not prescribed metformin As patients in this cohort will not have type 2 diabetes, it can be inferred that any prescription of metformin will be prophylactic in nature, to prevent the development of type 2 diabetes or to prevent or treat antipsychotic induced weight gain. This will enable the evaluation of the following: 1. The prevalence of prophylactic prescribing in this cohort 2. The safety of metformin prescribing in the cohort. The two groups (metformin prohylaxis versus no metformin) will be compared on these clinical outcome measures and evaluate the effectiveness and safety of metformin prophylaxis. Outcome measures: 1. Development of Type 2 diabetes 2. BMI 3. HBA1c 4. All-cause mortality 5. Hospitalization for heart failure 7. Major adverse cardiovascular events (MACE) outcomes 8. Number of consultations per year 9. Number of in-patient hospitalizations per person-year 10. Length of hospital stay 11. End stage renal disease 12. Dialysis for renal disease 13. Percutaneous coronary interventions 14. Bone fractures 15. Diabetic ketoacidosis 16. Severe hypoglycaemia 17. Lower limb amputation Scientific justification: Individuals who are prescribed antipsychotic medication are at higher risk of excessive weight gain and developing type 2 diabetes mellitus. Excessive weight gain and obesity are known to be linked to increased cardiovascular and cerebrovascular mortality, morbidity and are an increasing public health concern. Certain antipsychotics, such as clozapine and olanzapine, are known to pose a particularly elevated risk of weight gain. However, these medications are also often the most effective in treating psychotic symptoms. Metformin is prescribed as a treatment for type 2 diabetes mellitus and can be used to prevent or delay the onset of diabetes in individuals at high risk of the disease. Additionally, several studies have also indicated that metformin can be effective in preventing or treating weight gain in individuals taking antipsychotics. Despite this evidence, the use of metformin to prevent or treat weight gain is not common practice in many clinical settings in which antipsychotics are used. Thus there is a need to gather real-world data on the efficacy and safety of prophylactic use of metformin in individuals with psychosis, in order to inform prescribers.

15/04/2021

TRE