To examine initiation and prescribing patterns of metformin-glibenclamide and metformin-rosiglitazone fixed dose combination products within the Australian veteran population.
A retrospective observational study using Department of Veterans’ Affairs pharmacy claims data. We examined overall trends in the utilisation and proportion of patients who had been previously dispensed both, one, or none of the individual ingredient products before initiating combination products.
Of metformin-glibenclamide initiations, 9% involved a switch from metformin and glibenclamide as separate products, while 22% had used neither metformin nor a sulfonylurea. Thirty percent of metformin-rosiglitazone initiations involved a switch from both individual products, while in 10% neither metformin nor thiazolidinedione had been dispensed.
A minority of veterans started taking the combination products after being stabilised on the individual products; many had no prior history of oral hypoglycaemic use. This prescribing may lead to wastage if combination medications are poorly tolerated or, more importantly, may cause adverse events.
The number of Australians with type 2 diabetes mellitus has more than doubled in the past 2 decades and continues to increase.1 When oral antidiabetic monotherapy does not control blood glucose sufficiently, guidelines recommend intensifying therapy with a combination treatment regimen.2 However, polypharmacy may reduce adherence and increase the risk of medication errors.3 Fixed dose combination (FDC) products increase the simplicity of prescribing, decrease the number of required tablets (which may improve adherence), and under certain circumstances, decrease costs for the patient.4 However, there are potential disadvantages of FDC use, including lack of flexibility of dosing, difficulty ceasing only one component, and potential for patient confusion because of switching.4
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