Section 04 · Monograph

Monomethyl fumarate

Reviewed Nov 2026FDA label

BafiertamNrf2 activator

Indications

Treatment of relapsing forms of multiple sclerosis (MS) in adults, including clinically isolated syndrome, relapsing-remitting disease, and active secondary progressive diseaseFDA-labeled

Monomethyl fumarate (MMF) is the active metabolite common to dimethyl fumarate and diroximel fumarate
Exact therapeutic mechanism in MS is not fully understood; MMF activates the Nrf2 (nuclear factor erythroid 2-related factor 2) pathway involved in the cellular antioxidative stress response
MMF also functions as a nicotinic acid receptor (HCA2) agonist in vitro

Starting dose: 95 mg orally twice daily for 7 days
Maintenance dose: 190 mg (two 95 mg capsules) orally twice daily thereafter
For persistent intolerability, temporary reduction to 95 mg twice daily may be considered
Swallow capsules whole and intact; do not crush, chew, or mix contents with food
May be taken with or without food

Known hypersensitivity to monomethyl fumarate, dimethyl fumarate, diroximel fumarate, or to any of the excipients
Concurrent use of dimethyl fumarate or diroximel fumarate, since both are metabolized to monomethyl fumarate

Contraindicated with dimethyl fumarate or diroximel fumarate, as both convert to monomethyl fumarate
No clinically significant interactions identified via CYP450 enzymes
No relevant pharmacokinetic interaction with oral contraceptives, interferon beta-1a, glatiramer acetate, or aspirin

Flushing (~40%), generally mild-to-moderate and improving over time
Abdominal pain (~18%), diarrhea (~14%), nausea (~12%)
Vomiting; GI symptoms typically most prominent early in treatment and decrease over time
Lymphopenia — mean lymphocyte counts decrease ~30% during the first year; 6% develop counts <0.5×10⁹/L
Progressive multifocal leukoencephalopathy (PML) — reported (fatal case) with prolonged lymphopenia (<0.5×10⁹/L for 3.5 years) in the fumarate drug class
Serious infections including disseminated herpes zoster
Serious gastrointestinal events postmarketing (perforation, ulceration, hemorrhage, obstruction), primarily within 6 months of initiation
Anaphylaxis and angioedema, can occur after the first dose or at any time during treatment
Liver injury — postmarketing cases with aminotransferases >5x ULN and total bilirubin >2x ULN

Obtain CBC with lymphocyte count before initiating treatment
Repeat CBC with lymphocyte count at 6 months, then every 6–12 months thereafter
Continue monitoring lymphocyte counts after discontinuation given potential for delayed recovery
Obtain baseline serum aminotransferases, alkaline phosphatase, and bilirubin; monitor as clinically indicated during therapy
Obtain MRI for any new neurologic signs/symptoms suggestive of PML; withhold drug at first sign/symptom
Consider withholding treatment in cases of serious infection until resolved

Pregnancy: based on animal data, may cause fetal harm; embryofetal toxicity and neurobehavioral impairment demonstrated in animal studies at clinically relevant doses
Registry data (shared fumarate-class pregnancy registry, 362 live births/stillbirths) showed a 3.6% major birth defect rate with no specific pattern identified
Pregnancy registry available for enrollment (1-866-663-9564)
Lactation: no data on the presence of dimethyl fumarate or monomethyl fumarate in human milk, or on effects on the breastfed infant or milk production — weigh clinical need against potential risk