Renal Impairment in Multiple Sclerosis Patients Prescribed Dalfampridine Extended Release

The use of dalfampridine extended release (D-ER) to treat multiple sclerosis (MS) is not related to the prevalence of renal impairment, according to findings published in the December 2014 issue of Therapeutics and Clinical Risk Management.

Researchers from Acorda Therapeutics in Ardsley, New York conducted a retrospective study of nearly 2,000 patients in order to characterize the prescribing of twice daily dalfampridine extended release (D-ER) 10 mg tablet treatment in MS patients. Most patients were mostly women (72 percent) and generally aged between 45-64 years, and were pulled from the Medco pharmacy benefit management (PBM) between January 1, 2009 and September 15, 2012. MS patients were required to have an MS diagnosis for at least a year prior to the index period, and 704 patients had a year of continuous enrollment prior to their initial D-ER prescription and were matched with D-ER naïve patients.

D-ER has been proven to improve walking in patients with MS, but has also been linked to moderate or severe renal impairment of history of seizure. And, the researchers noted, since the incidence of seizure is related to the dose, patients are urged not to exceed maximum daily doses.

Just 22 of the 704 patients prescribed D-ER had a seizure related diagnostic code prior to the initial D-ER prescription, which totaled an estimated seizure prevalence of 31 per 1,000. That rate was higher at 47 out of 1,000 patients in the population of D-ER naïve patients, but the difference between cohorts was not statistically relevant, the researchers say.

The seizure rate in prescribed D-ER women was 28 per 1,000 and 40 per 1,000 male patients. In D-ER naïve patients, the rate rose to 51 out of 1,000 female patients and dropped to 38 per 1,000 for male patients. The researchers said these differences were not statistically significant.

Renal impairment was higher in D-ER naïve patients (51 per 1,000 patients) than in those prescribed D-ER (43 per 1,000 patients), though, again, the researchers noted this was not statistically significant. Renal impairment was lower in women than men from the preindex period, though it was similar in women regardless of D-ER prescription status. Men’s rates of renal impairments were lower when patients were prescribed D-ER (50 per 1,000 patients) compared to D-ER naïve patients (73 per 1,000 patients).

“D-ER is commonly prescribed to older MS patients who may have advanced disease,” the authors concluded. “Although the prescribing of anti epileptics prior to D-ER initiation was substantial, these medications are commonly used for the treatment of MS-related pain. Seizure and renal impairment rates among D-ER-naïve patients were consistent with those in published literature, yet the rates among D-ER users during the 12 month period preceding D-ER initiation were slightly lower than the rates among D-ER-naïve patients, which could suggest that the risk minimization messages were somewhat effective.”