Multiple Sclerosis (MS) is a chronic, unpredictable disease of the central nervous system that disrupts the flow of information within the brain and body. Managing MS often relies on disease-modifying therapies (DMTs) to slow progression and reduce relapse frequency. Since the annual cost for many DMTs averages tens of thousands of dollars, securing Medicare coverage is a primary concern for beneficiaries. Medicare covers these specialized MS drugs, but coverage depends entirely on the specific medication, how it is administered, and where the patient receives it. Understanding the program’s structure is key to determining the patient’s financial responsibility for these high-cost treatments.
Distinguishing Coverage for MS Medications
The specific Medicare part covering an MS drug is determined by its method of administration: whether it is self-administered or given by a healthcare professional. This distinction dictates different rules, prior authorization processes, and patient costs.
Medicare Part B covers drugs requiring administration by a healthcare provider in an outpatient setting, such as a doctor’s office or an infusion center. This includes most intravenous (IV) infusion therapies, a common treatment modality for MS. Examples of Part B-covered infused DMTs are ocrelizumab (Ocrevus) and natalizumab (Tysabri). Part B also covers certain injectable drugs that must be administered by a medical professional, not self-injected at home.
In contrast, Medicare Part D, the prescription drug benefit, covers medications that patients administer themselves. This category includes most oral MS medications, such as fingolimod (Gilenya) and dimethyl fumarate (Tecfidera). It also covers self-injectable DMTs, like glatiramer acetate (Copaxone), which are filled at a pharmacy and taken home. The classification is strictly based on the route of administration.
The setting can sometimes change the coverage part for a drug, creating confusion for beneficiaries. For instance, if an MS patient receives a high-dose steroid treatment while admitted to a hospital, that drug is covered under Medicare Part A. If the same steroid is administered in an outpatient clinic, it is covered under Part B. Patients must confirm the coverage part for their specific drug and setting before treatment begins.
Patient Costs and the Coverage Gap
Once the appropriate coverage part for an MS drug is identified, the next consideration is the patient’s financial obligation. The cost structure for drugs covered under Part B differs substantially from Part D. These structures determine the patient’s out-of-pocket spending, which is significant given the high list prices of DMTs.
For Part B-covered drugs, such as infusions, the patient is responsible for a standard 20% coinsurance of the Medicare-approved amount after meeting the annual Part B deductible. Since the list price of an infused MS drug is high, that 20% coinsurance often translates into thousands of dollars in patient costs. For example, the 20% coinsurance for a common twice-yearly infusion may result in an annual out-of-pocket cost exceeding $10,000 for the drug alone. Original Medicare Part B has no annual out-of-pocket maximum, meaning the 20% coinsurance continues indefinitely.
Part D-covered drugs, including most oral and self-injectable DMTs, involve a four-phase cost structure that patients move through each calendar year. The first phase is the Deductible, where the patient pays the full negotiated cost until the deductible amount is met. Following this is the Initial Coverage Phase, where the patient pays a copayment or coinsurance until the total cost of the drugs reaches a specific limit.
The third phase is the Coverage Gap, where patients previously saw their costs increase significantly. However, the high cost of MS drugs quickly pushes patients through the Deductible and Initial Coverage phases. The fourth phase is Catastrophic Coverage, entered after out-of-pocket spending reaches a set threshold. Recent legislation significantly altered these phases: starting in 2025, there is a $2,000 cap on a beneficiary’s annual out-of-pocket spending for Part D-covered drugs. Once this cap is reached, the patient pays nothing for covered drugs for the remainder of the year.
Options for Reducing Out-of-Pocket Expenses
Given the substantial out-of-pocket costs associated with MS drugs under both Part B and Part D, beneficiaries have several options to mitigate their financial responsibility. These secondary programs and alternative enrollment methods offer considerable relief.
One option is enrolling in a Medicare Advantage (Part C) plan, offered by private insurance companies approved by Medicare. These plans must cover everything Original Medicare (Parts A and B) covers, and most include Part D prescription drug coverage. Part C plans are advantageous for MS patients because they often impose an annual out-of-pocket maximum for covered medical services, including Part B drug costs. This maximum offers financial predictability that Original Medicare Part B does not provide.
The federal Extra Help program, also known as the Low-Income Subsidy (LIS), provides substantial assistance for Part D costs. This program is designed for beneficiaries with limited income and resources, helping them pay for Part D premiums, deductibles, and copayments. For those who qualify, out-of-pocket costs for Part D-covered MS drugs are reduced to a low, fixed copayment, such as no more than $12.15 for a brand-name drug in 2025.
Beyond Medicare programs, drug manufacturers and non-profit organizations offer various financial assistance programs. Many pharmaceutical companies that produce high-cost MS drugs have co-pay assistance programs to help cover the patient’s portion of the bill. Disease-specific non-profits, such as the HealthWell Foundation or the Patient Access Network (PAN) Foundation, also provide grants to cover out-of-pocket costs. These options are particularly relevant for Part B drugs, where the 20% coinsurance remains uncapped in Original Medicare.