When pharmacists switch from brand-name to generic drugs or between the same generics made by different manufacturers, this is thought may affect patient adherence to their medication. Therefore, Trotta and co-authors carried out a study to quantify the extent of switches between generic antidiabetics and to verify whether switching between different products of the same substance affects adherence [1].
Previous studies have suggested that generics substitution may confuse or make people suspicious when, for example, the names, colours, packaging, etc.; of their medication is changed [2, 3]. US Food and Drug Administration has even stated that generics should ‘look the same as the innovator as much as possible’ [4], and is carrying out a survey to investigate the effect of generics shape, colour, size [5].
This latest study included all elderly residents (≥ 75 years) of the Umbria Region of Italy who had received at least two prescriptions of antidiabetics in 2010 and 2011. Switching was defined as the dispensing of two different products of the same substance in a series of two prescriptions. Single and multiple switchers were identified according to the number of switches during 2011.
Switching was quantified for generics of the three antidiabetic drugs metformin, gliclazide and repaglinide, all of which had generics use ≥ 5%. The effect of switching on adherence, defined as the proportion of days in 2011 covered by prescriptions (Medication Possession Ratio, MPR), was estimated.
The results reported showed that among the 15,964 patients receiving antidiabetics (14.4% of the elderly population) the majority of diabetic patients (61.0%) did not switch during the year. The proportion of non-switchers was similar for the three substances, ranging from 62.5% with metformin to 57.9% with repaglinide.
Among the 9,211 patients that were prescribed at least one of the three generic antidiabetics studied, 23.3% experienced a single switch and 15.7% were multiple switchers. The proportion of multiple switchers increased with the number of prescriptions, reaching 26% among patients with ≥ 11 prescriptions.
With respect to adherence, the MPR was 62%, 62% and 72%, respectively, among non-switchers, single switchers and multiple switchers, with adherence data by intensity of switching being consistent for the three substances (metformin, repaglinide and gliclazide).
The authors therefore concluded that generics substitution of antidiabetic drugs in the elderly does not affect adherence.
Conflict of interest
The authors of the research paper [1] declared that there were no conflicts of interest.
Editor’s comment
Readers interested to learn more about generics substitution are invited to visit www.gabi-journal.net to view the following manuscripts published in GaBI Journal:
Generics substitution in primary care: summary of the Dutch community pharmacies guidelines
A review of patient perspectives on generics substitution: what are the challenges for optimal drug use
Readers interested in contributing a research or perspective paper to GaBI Journal – an independent, peer reviewed academic journal platform – please send us your submission here.
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References
1. Trotta F, Da Cas R, Maggini M, Rossi M, Traversa G. Generic substitution of antidiabetic drugs in the elderly does not affect adherence. Ann Ist Super Sanita. 2014;50(4):333-40.
2. GaBI Online - Generics and Biosimilars Initiative. Generic substitution causing confusion [www.gabionline.net]. Mol, Belgium: Pro Pharma Communications International; [cited 2015 Feb 20]. Available from: www.gabionline.net/Generics/Research/Generic-substitution-causing-confusion
3. Andersen ML, et al. [How do patients evaluate the newly introduced system of substituting prescriptions?] Ugeskr Laeger. 2000;162(45):6066-9. Danish.
4. GaBI Online - Generics and Biosimilars Initiative. FDA to release guidance on generic tablet size [www.gabionline.net]. Mol, Belgium: Pro Pharma Communications International; [cited 2015 Feb 20]. Available from: www.gabionline.net/Guidelines/FDA-to-release-guidance-on-generic-tablet-size
5. GaBI Online - Generics and Biosimilars Initiative. FDA to carry out survey into affect of generics shape, colour, size [www.gabionline.net]. Mol, Belgium: Pro Pharma Communications International; [cited 2015 Feb 20]. Available from: www.gabionline.net/Guidelines/FDA-to-carry-out-survey-into-affect-of-generics-shape-colour-size
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