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In hypothyroidism, formulation of levothyroxine therapy may influence adherence rates
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Patients with hypothyroidism prescribed levothyroxine therapy were more likely to adhere to treatment at 1 year when prescribed specific formulations of the drug, according to an analysis of claims data published in Current Medical Research and Opinion.
Levothyroxine remains the standard treatment for hypothyroidism and is available in tablet, soft gel and oral solution formulations, Zsolt Hepp, PharmD, MS, associate director of U.S. health economics and outcomes research analytics at AbbVie, Chicago, and colleagues wrote in the study background. Both the American Thyroid Association and the American Association of Clinical Endocrinologists recommend a consistent levothyroxine preparation for patients to minimize variability between refills.
“Among hypothyroidism patients in the US, the adherence to thyroid hormone replacement therapy is poor,” Hepp told Endocrine Today. “With only half of the patients staying adherent to their treatment after 1 year, there is room for improvement in this population. Our study also showed that some formulations of levothyroxine seem to be associated with better adherence. The reason for this is not known and the results need to be replicated and confirmed but there seems to be a clear trend for some branded products being associated with higher levels of adherence in this study population.”
In a retrospective study, Hepp and colleagues analyzed insurance claims data from 580,331 patients with at least one diagnosis of hypothyroidism who initiated any levothyroxine formulation from 1 year before diagnosis date to 1 year after the diagnosis date (73.94% women; mean age, 52 years). Data were taken from Truven’s Health Analytics MarketScan Commercial Claims and Encounters database from 2000 to March 2016, which includes medical claims linked to outpatient prescription drug claims and person-level enrollment information.
Researchers focused on adherence to levothyroxine by comparing Synthroid (Abbott Laboratories) with all other formulations, including Levoxyl (Pfizer), Tirosint (Akrimax Pharmaceuticals), Unithroid (Jerome Stevens Pharmaceuticals) and generic levothyroxine at 6 and 12 months. Additionally, likelihood of remaining adherent at 1 year was examined for each branded formulation vs. generic levothyroxine, calculated using proportion of days covered. Patients were defined as adherent if they achieved a proportion of days covered threshold of at least 80%. Researchers used analysis of variance to compare differences between formulations and logistic regression analysis to compare adherence to generic levothyroxine relative to each individual drug.
Within the cohort, 67.93% were prescribed generic levothyroxine and 25.05% were prescribed Synthroid as their index medication.
Researchers found that adherence fell between 6 and 12 months after diagnosis. At 6 months after initiation of therapy, 59.7% were adherent to levothyroxine, falling to 48.1% at 12 months. Compared with all other formulations of levothyroxine, use of Synthroid was associated with higher rates of adherence at 6 months (64.6% vs. 58.1%) and 12 months (53.2% vs. 46.4%).
Using generic levothyroxine as the reference group, researchers found that patients who initiated Tirosint or Unithroid therapy were 35% and 21% less likely to be adherent, respectively (P < .0001), whereas patients prescribed Levoxyl or Synthroid were 20% and 44% more likely to be adherent, respectively (P < .0001).
“I believe our study highlighted two areas of need for further research. First, research should focus on ways of improving adherence in this population. There is a clear opportunity to improve adherence and thereby improve care for patients suffering from hypothyroidism. Secondly, our work generated some hypotheses that formulation of levothyroxine may affect adherence which needs to be further explored. Both questions could be answered by doing some primary research with patients and physicians to identify drivers of adherence and find ways to help patients stay adherent to their medications.”
– by Regina Schaffer
For more information:
Zsolt Hepp , PharmD, MS, can be reached at 1 N Waukegan Rd., North Chicago, Il 60064; email: zsolthepp@gmail.com.
Disclosures: AbbVie supported this study and participated in the study design, data collection, analysis and interpretation. All study authors are employees of or consultants for AbbVie.
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