Diroximel fumarate (Vumerity)

How Medicare covers it

Part D (forms used at home). Part A during a covered inpatient stay. No Part B clinician-administered form in the CMS Part B spending file.

What it treats

Treats relapsing forms of multiple sclerosis (MS) in adults, to include clinically isolated syndrome, relapsing-remitting disease, and active secondary progressive disease.

What it is for, in depth

Diroximel fumarate treats relapsing forms of multiple sclerosis, or MS, in adults. The label includes clinically isolated syndrome, relapsing-remitting disease, and active secondary progressive disease. The body converts diroximel fumarate into monomethyl fumarate, which is the same active form as dimethyl fumarate. The label says the fumarates calm immune activity involved in the attack on nerve coverings in MS, and it bases this drug's effectiveness on studies comparing it with dimethyl fumarate. It comes as delayed-release capsules of 231 mg taken by mouth twice a day. The starting dose is 231 mg twice a day for 7 days. After 7 days, the maintenance dose is 462 mg, which is two 231 mg capsules, twice a day. The capsules are swallowed whole and intact.

How it works

Diroximel fumarate is converted in the body to monomethyl fumarate — the same active metabolite as dimethyl fumarate. The fumarates calm immune activity involved in the attack on nerve coverings in MS; the label bases Vumerity's effectiveness on bioavailability studies against dimethyl fumarate.

How it is taken

Delayed-release capsules (231 mg) by mouth twice a day: the starting dose is 231 mg twice a day for 7 days, and the maintenance dose after 7 days is 462 mg (two 231 mg capsules) twice a day. Swallow the capsules whole and intact — do not crush, chew, or sprinkle the contents on food. Avoid taking it with a high-fat, high-calorie meal or snack, and avoid co-administration with alcohol. Blood tests (including a CBC with lymphocyte count and liver tests) are required before starting.

Common side effects

Flushing, abdominal pain, diarrhea, and nausea — the most common reactions for dimethyl fumarate, which has the same active metabolite as Vumerity (incidence at least 10% and at least 2% more than placebo).

Serious warnings

Anaphylaxis and angioedema can occur (discontinue and do not restart). Progressive multifocal leukoencephalopathy (PML) is a labeled risk — withhold the drug at the first sign or symptom suggestive of PML. Herpes zoster and other serious opportunistic infections can occur, and withholding treatment during a serious infection is considered until it resolves. Lymphopenia (low lymphocyte counts) can be prolonged — counts are checked before starting, after 6 months, and every 6 to 12 months, and interruption is considered if counts below 0.5 x 10^9/L persist for more than six months. Liver injury is a labeled risk, with liver tests before starting and during treatment, and discontinuation if significant drug-induced liver injury is suspected. Flushing and serious gastrointestinal reactions are also labeled.

Who should be careful

Contraindicated in patients with known hypersensitivity to diroximel fumarate, dimethyl fumarate, or any of the excipients (reactions may include anaphylaxis and angioedema) and in patients taking dimethyl fumarate. It is not recommended in patients with moderate or severe renal impairment. Based on animal data, it may cause fetal harm, and a pregnancy exposure registry exists. Safety and effectiveness in pediatric patients have not been established.

Major interactions

It is contraindicated in patients currently taking dimethyl fumarate, which is also metabolized to monomethyl fumarate — Vumerity may be started the day after dimethyl fumarate is stopped. Avoid co-administration with alcohol and avoid taking it with a high-fat, high-calorie meal.

Why it is in its tier

This drug is most often placed on Tier 5. In the CMS Part D formulary data for plan year 2027, it is listed by 843 plans, which is a listing share of 15.34%. Among those listing plans, 93.48% place it on Tier 5, making Tier 5 the modal, or most common, tier. The tier distribution in the data is 48 plans on Tier 1, 7 plans on Tier 4, and 788 plans on Tier 5. Tier 1 is the lowest tier, with $0-$15 copays, and Tier 5 is the specialty tier, the highest tier, so this drug's most common placement is on the highest tier. For cost context, the CMS dashboard average spending per beneficiary in 2024 was 68720.13366, labeled as a CMS program average, not a copay.

Sources

• VUMERITY (diroximel fumarate) capsule — DailyMed
• MedlinePlus — National Library of Medicine
• MedlinePlus — Diroximel Fumarate

What official patient guides say

Diroximel fumarate comes as a delayed-release capsule taken by mouth, usually twice a day at around the same times every day, following the prescription label exactly and never taking more, less, or more often than prescribed. It may be taken with or without food, but it should not be taken with a high-fat, high-calorie meal or snack, which must contain less than 700 calories and less than 30 grams of fat, and alcoholic beverages should not be drunk at the same time as a dose. The capsules should be swallowed whole and should not be split, chewed, crushed, or sprinkled. The doctor will probably start treatment at a low dose and increase it after 7 days, and treatment should be continued even when the person feels well and never stopped without talking to the doctor. If a dose is missed, it should be taken as soon as it is remembered, unless it is almost time for the next dose, in which case it should be skipped and the regular schedule continued, without doubling a dose. The medication should be kept in the container it came in, tightly closed and out of reach of children, stored at room temperature away from excess heat and moisture, and not kept in the bathroom.

Source: MedlinePlus — Diroximel Fumarate

Part D formulary coverage

Source: CMS Prescription Drug Plan Formulary, Pharmacy Network, and Pricing Information Files — Monthly file 2026-10-15 (plan year 2027), file 2027_20261008.zip (data.cms.gov dataset ed1496ea-23e7-41f1-9292-172fa842ccfb): basic drugs formulary file + plan information file, both dated 20261031 inside the zip; downloaded and aggregated 2026-10-30. Medication RxCUI sets resolved through the NLM RxNav (RxNorm) API.

What you pay

A tier is not a price; what you pay depends on your plan, pharmacy, and benefit stage; Extra Help or Medicaid can lower it further.

Sources: CMS Plan Benefit Package + formulary data; CMS NADAC · Checked 2026-11-07

Coverage by plan and tier

Of the 5,495 Medicare drug plans we track for 2027, 843 list Diroximel fumarate (Vumerity) — 15.3% of plans. Most of those plans put it on Tier 5: 788 plans, 93.5% of the plans that list it. Other plans place it on Tier 1 (48 plans) or Tier 4 (7 plans). For example: CareSource MyCare Ohio (HMO D-SNP) puts it on Tier 1; Essence Advantage Select (HMO) puts it on Tier 5; CalOptima Health OneCare Complete (HMO D-SNP) puts it on Tier 1. You can compare these plans side by side on our Medicare Advantage hub. A tier is not a price. What you pay also depends on whether you have met your plan';s deductible, whether the drug costs a flat copay or a share of the price, and whether you get Extra Help or Medicaid.

Read next

• Part D in 2027: The $700 Deductible, the $2,400 Cap, and the $35 Insulin Rule
• Extra Help in 2027: Lower Drug Copays and Who Qualifies
• Checking Medicare Savings Programs and Extra Help

Part D spending averages (2024)

Source: CMS Medicare Part D Spending by Drug (Drug Spending Dashboard), release RY26 P04 V10, data through 2024 (DSD_PTD_RY26_P04_V10_DY24_BGM.csv), downloaded 2026-10-30

Companies covering this drug

Part D and Medicare Advantage plan sponsors that list this drug on a formulary, 50 at a time.