To Örebro University

Introduction: Baclofen is the first line drug choice for spasticity; a common MS feature influencing function and quality of life. Its prescription and discontinuation patterns among persons with MS (pwMS) are described incompletely.

Objective & Aim: To characterize baclofen prescription patterns in a nationwide cohort study of people with prevalent (pMS) and incident (iMS) MS.

Method: Data was linked from the Swedish MS register and national health registers for PwMS aged 18-65 years at diagnosis. Baclofen initiation was identified using the Prescription Drug Register excluding prescriptions from 1 July 2005—30 June 2006 (1st year of the register) and before MS diagnosis, to identify new prescriptions. Follow-up was from first dispensation until discontinuation, 31 Dec 2014 or death. Discontinuation was defined as no renewed prescription within gaps of 90, 150, or 180 days from last dispensation. Failure functions were plotted and Cox regression estimated hazard ratios.

Results: A total of 188 (10%) of iMS (N=1826) and 628 (19%) of pMS (N=3519) received a new baclofen prescription. Discontinuation among iMS and pMS was similar using different time gaps: 49% (CI 0.42-0.57) iMS and 51% (CI 0.48-0.56) pMS discontinued within 150 days and approx. 90% discontinued overall. Approx. 65%  of  individuals  discontinued  within  1-year  and  80%  by  2-years.  iMS  with progressive  course  were  treated  for  longer than relapsing course, and though similar among pMS differences between courses were less evident. Stratifying by EDSS (0-2.5, 3.0-5.5 and 6+) at baclofen initiation showed that PwMS with higher EDSS persisted longer than EDSS 0-2.5 but discontinuation  was  high  among  all groups.  Cox  regression  showed  EDSS associated with discontinuation, with iMS of EDSS 3-5.5 and 6+ 72% (CI 0.44-1.16) and 61% (CI 0.35-1.05); pMS 78% (CI 0.59-1.03) and 65% (CI 0.49-0.85) less likely to discontinue. No other MS characteristics (duration, age, course, sex, diagnosis/onset  age),  depression  or seizures  were  associated.  Though  not  statistically significantly associated, females and those with a progressive course were less likely to discontinue.

Conclusions: Baclofen  has  similarly  high  discontinuation  rates  among  patients with  iMS  and  pMS,  possibly  reflecting  low tolerability  or  efficacy.  Only increased  disability  indicated  by  higher  EDSS  was  associated  with  longer baclofen  persistence  highlighting the need for more tolerable and efficacious pharmacological treatments for spasticity in PwMS.