After oral administration of dimethyl fumarate delayed-release capsules, dimethyl fumarate undergoes rapid presystemic hydrolysis by esterases and is converted to its active metabolite, monomethyl fumarate (MMF). Dimethyl fumarate is not quantifiable in plasma following oral administration of dimethyl fumarate delayed- release capsules. Therefore all pharmacokinetic analyses related to dimethyl fumarate delayed-release capsules were performed with plasma MMF concentrations. Pharmacokinetic data were obtained in subjects with multiple sclerosis and healthy volunteers.
Absorption
The median Tmax of MMF is 2 to 2.5 hours. The peak plasma concentration (Cmax) and overall exposure (AUC) increased approximately dose proportionally in the dose range studied (120 mg to 360 mg). Following administration of dimethyl fumarate delayed- release capsules 240 mg twice a day with food, the mean Cmax of MMF was 1.87 mg/L and AUC was 8.21 mg.hr/L in MS patients.
A high-fat, high-calorie meal did not affect the AUC of MMF but decreased its Cmax by 40%. The Tmax was delayed from 2.0 hours to 5.5 hours. In this study, the incidence of flushing was reduced by approximately 25% in the fed state.
Distribution
The apparent volume of distribution of MMF varies between 53 and 73 L in healthy subjects. Human plasma protein binding of MMF is 27 to 45% and independent of concentration.
Metabolism
In humans, dimethyl fumarate is extensively metabolized by esterases, which are ubiquitous in the gastrointestinal tract, blood, and tissues, before it reaches the systemic circulation. Further metabolism of MMF occurs through the tricarboxylic acid (TCA) cycle, with no involvement of the cytochrome P450 (CYP) system. MMF, fumaric and citric acid, and glucose are the major metabolites in plasma.
Elimination
Exhalation of CO2 is the primary route of elimination, accounting for approximately 60% of the dimethyl fumarate delayed-release capsules dose. Renal and fecal elimination are minor routes of elimination, accounting for 16% and 1% of the dose respectively. Trace amounts of unchanged MMF were present in urine.
The terminal half-life of MMF is approximately 1 hour and no circulating MMF is present at 24 hours in the majority of individuals. Accumulation of MMF does not occur with multiple doses of dimethyl fumarate delayed-release capsules.
Specific Populations
Body weight, gender, and age do not require dosage adjustment.
No studies have been conducted in subjects with hepatic or renal impairment. However, neither condition would be expected to affect exposure to MMF and therefore no dosage adjustment is necessary.
Drug Interaction Studies
No potential drug interactions with dimethyl fumarate or MMF were identified in in vitro CYP inhibition and induction studies, or in P-glycoprotein studies. Single doses of interferon beta-1a or glatiramer acetate did not alter the pharmacokinetics of MMF. Aspirin, when administered approximately 30 minutes before dimethyl fumarate delayed-release capsules, did not alter the pharmacokinetics of MMF.
Oral Contraceptives
The coadministration of dimethyl fumarate with a combined oral contraceptive (norelgestromin and ethinyl estradiol) did not elicit any relevant effects in oral contraceptives exposure. No interaction studies have been performed with oral contraceptives containing other progestogens.
Vaccines
A randomized, open-label study examined the concomitant use of dimethyl fumarate delayed-release capsules and several non-live vaccines in adults 27-55 years of age with relapsing forms of MS (38 subjects undergoing treatment with dimethyl fumarate delayed-release capsules at the time of vaccination and 33 subjects undergoing treatment with non-pegylated interferon at the time of vaccination). Concomitant exposure to dimethyl fumarate delayed-release capsules, did not attenuate antibody responses to tetanus toxoid-containing vaccine, pneumococcal polysaccharide, and meningococcal vaccines relative to antibody responses in interferon-treated patients. The impact of these findings on vaccine effectiveness in this patient population is unknown. The safety and effectiveness of live or live-attenuated vaccines administered concomitantly with dimethyl fumarate delayed-release capsules, have not been assessed.