Premedication and adherence to disease modifying therapy of multiple sclerosis : A retrospective cohort study with pharmacy claims data in Germany

BACKGROUND Chronic diseases like multiple sclerosis (MS) require long term therapy with strict adherence to gain benefit. The objective of this study was to find out (a) what kind of premedication patients had been prescribed and (b) whether premedication related to the long-term adherence to the therapy with disease modifying drugs (DMDs).

METHODS This retrospective cohort study is based on data between 2002 to 2009 from the healthcare claims database of the “GIDE”- German Institute for Drug Use Evaluation, including patient data of all statutory health insurers. Medication profiles of 52,516 MS patients were identified, which fulfilled inclusion criteria: i) having no DMD prescription 12 months before index date, ii) could be observed over a 24- month period after starting therapy with DMDs and iii) could still be found in the database after 12- month- follow up. Adherence to DMDs was expressed as medication possession ratio and as persistence - not having a defined gap in the medication profile or complete dropout. The association between premedication and non-adherence to DMDs was analyzed using the logistic- respectively Cox-regression model.

RESULTS Within 12 months before starting therapy with DMDs, 85.4% of the MS- patients received at least one physician-prescribed drug. The most common drugs were painkillers (56.8%), antihypertensives (36.9%), glucocorticoids (33.3%), antiulcerants (31.1%), thyroid disease medications (23.3%), and antidepressants (21.9%). Adherence to DMDs defined as medication possession ratio over 24 months was significantly higher in patients with premedication with glucocorticoids (OR 1.37; CI(99%): 1.30-1.45), painkillers (OR: 1.16; CI(99%): 1,10-1,22) or antiulcerants (OR 1.10; CI(99%): 1.05-1.15), whereas it was significantly lower in patients getting muscle relaxants (OR:0.91; CI(99%):0.86-0.99) or respiratory disease medications (OR:0.92; CI(99%): 0.87-0.99). No association could be seen between antidepressant use and non-adherence to DMDs. The results were confirmed if persistence was used to define adherence to DMDs.

DISCUSSION In general, premedication had a low impact on adherence to DMDs (Nagelkerke R-Square=0.015). Prescription of glucocorticoids before starting DMD therapy seems to ameliorate adherence. According to guidelines, glucocorticoids should be given if disease activity increases (i.e. a relapse or a progession occurs). One may speculate if such an experience motivates patients to adhere to DMDs. Furthermore, our results indicate that a history of antidepressant prescriptions is not a contraindication for starting therapy with DMDs in MS.