Prospective analysis of the medicine possession ratio of antidepressants in the private health sector of South Africa, 2006 – 2011

Abstract

Background. Major depressive disorder (MDD) is a disabling mental illness with high morbidity and mortality rates. Inadequate treatment efficacy, unfavourable side-effect profiles and consequent shortfalls in compliance are major stumbling blocks in its treatment. Noncompliance data in low- to middle-income countries are lacking. Objective. To investigate the prevalence of antidepressant (AD) non-compliance in the private healthcare sector of South Africa (SA). Methods. We conducted a prospective cohort study analysing AD medicine claims (N=35 175) for 14 135 patients, obtained from a nationally representative pharmaceutical benefit management company, over a 6-year study period (1 January 2006 - 31 December 2011). The medicine possession ratio (MPR) was used as a proxy to determine compliance with AD medication. Only patients >18 years of age whose treatment had been initiated by a psychiatrist following an appropriate International Classification of Diseases (10th edition) (ICD- 10) diagnosis of a mood disorder were included. A patient was considered compliant if the MPR was between ≥80% and ≤110% over a >4-month treatment period. Results. After the first 4 months, only 34% of patients were compliant. A statistically significant association was found between active ingredient consumed and compliance (p<0.0001). Only 26.2% of patients who received amitriptyline-containing products were compliant, compared with 38.8% and 38.7% for venlafaxine and duloxetine, respectively. Conclusion. Compliance data collected from pharmacy claims provide a workable estimate of the broader clinical scenario they represent. Although differences between classes of AD were evident, non-compliance was found to be high in the private healthcare environment of SA, comparable with global trends.