Relistor Generic: When Will Generic Methylnaltrexone Be Available?
This page is aggregated from FDA records, court filings and company announcements. Coded and designed by Dr. Brian Staiger, PharmD, BCPS
Updated October 9, 2026 How we build our data
Relistor Generic at a Glance
Four quick answers from FDA records and our estimate.
- When is the first generic expected? July 2027 About 9 months away Why then?
- Has the FDA approved a generic? Not yet None in the FDA’s records yet Why not yet?
- When does the last patent end? March 2031 12 patents listed with the FDA Why is a generic expected sooner?
- Can you buy a generic today? Not yet No company lists one for sale
Generic methylnaltrexone bromide is expected to be available in July 2027, about 9 months away, first for Relistor 12 mg/0.6 mL vial. None is for sale yet. Each product has its own month below.
Why July 2027?
The brand company and a generic maker settled their patent fight and agreed on when a generic can launch. We rate it probable: more likely than not, but it can still move.
If Relistor’s last patent runs to March 2031, how can a generic come sooner?
The 12 patents that run past the expected month, to March 2031 (12,303,592, 8,420,663, 8,822,490, 9,180,125 and 8 more), cover the product’s formulation and a way of using it. A patent like that protects one way of making or using the medicine, not the medicine itself. A generic company can often make its version a different way or leave that use off its label, or a court can rule the patent invalid or not infringed. Here, a settlement between the companies sets the date. Generic companies have been challenging Relistor’s patents with the FDA since July 2015. That is why the expected month comes before the last protection ends. See the road to a generic
Why hasn’t the FDA approved a generic yet?
That is normal before a launch. The FDA usually can’t give a generic its final approval while a patent or exclusivity still blocks it, so final approval often comes close to the day the generic can be sold. No company holds a “tentative” approval yet either (the FDA’s word for a generic that is ready but still blocked).
Will the generic cost less?
Usually, and more so as more companies sell one. 5 companies have applied to the FDA to make it. In the FDA’s study of past launches, pharmacies paid about 73% less once four companies sold a generic, which would take the $25.34 pharmacies pay per tablet for Relistor today to about $6.84. See the price estimate
What should I do now?
Keep taking Relistor as prescribed. When a generic arrives, your pharmacy may switch you to it automatically, and it may look different. What a generic means for you
- 8 mg/0.4 mL pre-filled syringe2027 to 2028Probable · settlement between companies
- 12 mg/0.6 mL pre-filled syringe2027 to 2028Probable · settlement between companies
- 12 mg/0.6 mL vialJuly 2027Probable · settlement between companies
- tablet2030 to 2031Probable · settlement between companies
Our month is only an estimate based on available information, so we never name a day.
Relistor by the Numbers
- Reason
- Settlement between companiesThe brand company and a generic maker settled their patent fight and agreed on when a generic can launch.
- How sure
- Probable More likely than not, but it can still move.
- Price competition
- Strong 5 companies have filed, 2 first in line
- Brand sales
- $257M a yearBig seller, all 4 products
- FDA approved 2008 April 2008 FDA Orange Book
- Patents listed 12 last runs to March 2031 A generic is expected sooner, in July 2027. See why FDA Orange Book
- Pharmacies pay $25.34 per tablet NADAC, February 2024
- Medicare Part D spent $142.3M in 2025, for 14.9K people CMS Part D Spending by Drug
- Medicaid prescriptions 18.7K in the last four reported quarters, $41.9M CMS Medicaid drug utilization, to Q4 2025
Relistor’s Road to a Generic
Relistor has had the market to itself since the FDA approved it in April 2008 (Salix Pharmaceuticals Inc). Its 12 listed patents run to March 2031. Generic companies have challenged its patents with the FDA since July 2015.
The first generic of Relistor is expected in July 2027.
Why that month: the brand company and a generic maker settled their patent fight and agreed on when a generic can launch. That is about 3.5 years before the last listed patent runs out, in March 2031.
Why a Generic Can Come Before March 2031
The last listed patent runs to March 2031, but it covers the product’s formulation and a way of using it, not the medicine itself, which a generic can often work around or challenge. Dr. Brian explains
Each bar runs from the brand’s approval to the day that protection ends. The green band is our projection for the first generic: a month, never a day, because legal dates move and a generic reaches shelves days to weeks after it is allowed. Sources: FDA Orange Book; the expected month from court records and company announcements.
Relistor Patents and FDA Protections
Every patent and exclusivity the FDA Orange Book lists for Relistor’s own applications. A protection running past the expected month does not mean the date is wrong: a settlement or a court ruling can let a generic in before a patent ends, and a patent on one formulation or use does not block every generic.
| Patent | What it covers | Protects until | Status |
|---|---|---|---|
| 12,303,592 | The product’s formulation; a way of using it (U-4197, U-4198) | August 2027 | Active |
| 8,420,663 | A way of using it (U-1185) | September 2029 | Active |
| 8,822,490 | The product’s formulation; a way of using it (U-1185) | September 2029 | Active |
| 9,180,125 | The product’s formulation; a way of using it (U-1185) | September 2029 | Active |
| 9,492,445 | The product’s formulation; a way of using it (U-1185) | September 2029 | Active |
| 9,724,343 | The product’s formulation; a way of using it (U-1185) | September 2029 | Active |
| 8,247,425 | A way of using it (U-1185) | December 2030 | Active |
| 8,524,276 | The product’s formulation | March 2031 | Active |
| 8,956,651 | The product’s formulation | March 2031 | Active |
| 9,314,461 | The product’s formulation | March 2031 | Active |
| 10,307,417 | The product’s formulation | March 2031 | Active |
| 10,376,505 | The product’s formulation | March 2031 | Active |
Source: FDA Orange Book, application 021964, 208271. Patent numbers open the patent on Google Patents.
Patent Challenges to Relistor
The first patent challenge to Relistor reached the FDA in July 2015, from one company on that first day. The FDA’s list has 4 entries for Relistor, by form and strength. The FDA approved a first challenger’s generic in August 2024, and the list records no sale by a first challenger yet.
What Is a Patent Challenge?
A generic company that wants to sell its version before Relistor’s patents run out can tell the FDA that a patent is invalid, or that its version does not infringe it. The FDA calls this a “Paragraph IV certification.” The brand company usually sues, and the FDA then generally cannot approve that generic for up to 30 months while the case runs. To reward going first, the companies that challenge first can get a 180-day head start: the FDA cannot approve the generics that came after them until it ends.
| Product | First challenged | Companies that day | 180-day head start | First challenger’s generic | Challenged patents run to | |
|---|---|---|---|---|---|---|
| Approved | On sale | |||||
| Injection, 12 mg/0.6 mL, Single Dose Vial | July 2015 | 1 company | First challenger eligible decided June 2025 | May 2025 | Not yet | December 2030 |
| Injection, 12 mg/0.6 mL, Single Dose Prefilled Syringe | September 2015 | 1 company | Head start still held decided February 2025 Earlier: decision deferred, August 2024 | August 2024 | Not yet | December 2030 |
| Injection, 8 mg/0.4 mL, Single Dose Prefilled Syringe | September 2015 | 1 company | Head start still held decided May 2025 Earlier: decision deferred, August 2024 | August 2024 | Not yet | December 2030 |
| Tablets, 150 mg | September 2016 | 1 company | Not posted | Not posted | Not posted | March 2031 |
Source: the FDA’s Paragraph IV Patent Certifications list, as of September 2026. The FDA began posting the 180-day decisions and the first challenger’s approval and first sale in June 2019: an older entry it has not updated since reads “Not posted”, and “Not yet” means the list records no such event. “Companies that day” is the FDA’s count of challenges that arrived on the first day.
Who Is Lined Up to Make Generic Methylnaltrexone Bromide
Three steps stand between a brand and a generic you can buy: a company applies to the FDA, the FDA approves it, and the company starts selling it.
Applied to the FDA
5 companies have applied to the FDA to make generic methylnaltrexone bromide.
The FDA names a company only once it approves its application, even tentatively, and it has not done that for these yet, so the companies are not named here. Names often come out in the brand company’s patent lawsuits or in the companies’ own announcements.
First in line. 2 of them were first in line, both filing on the first day any company did: they can share 180 days on the market before the other generics, which is why being first matters.
Generic companies have challenged Relistor’s patents with the FDA since July 2015: see the patent challenges.
Approved by the FDA
Not yet. The FDA has not approved a generic methylnaltrexone bromide. Final approval often comes close to the day a generic can be sold.
For Sale in Pharmacies
Not yet. No company lists a generic methylnaltrexone bromide for sale with the FDA.
Sources: how many companies have applied, from court records and company announcements; approved generics from the FDA Orange Book; tentative approvals from Drugs@FDA; what is for sale from the FDA NDC Directory. The FDA does not disclose an application before it approves it (21 CFR 314.430).
Relistor Price: What Pharmacies Pay and What Generics Usually Do
What a Generic Could Cost
How we estimate it. We start from what pharmacies pay for Relistor today: $25.34 per tablet for Relistor 150 mg tablet in February 2024, from the national NADAC survey. Then we apply the FDA’s finding of how far that price usually falls as generic companies join: about 31% with one company, 44% with two, 73% with four and over 95% with six or more (the typical drop for every drug whose first generic came out from 2015 to 2017). Relistor has 5 companies lined up, so our estimate uses the figure for four companies. More companies would bring the price lower; fewer, less of a drop.
Dollar figures apply FDA’s median drops to the $25.34 pharmacies pay per tablet today. An estimate from the pattern, not a price quote: what you pay depends on your insurance or discount card.
Median prices pharmacies paid for the generic (invoice prices), compared with the brand’s price before generic entry, from FDA’s 2019 analysis “Generic Competition and Drug Prices”. At the manufacturer’s price FDA found steeper drops (about 39%, 54%, 79% and over 95%), the figures quoted elsewhere on this tracker. A typical pattern, not a price quote for this medicine.
What Medicare and Medicaid Spend on Relistor
Big public spending is part of why generic makers line up for a medicine, and why its first generic matters beyond the pharmacy counter. Figures are before manufacturer rebates, which are confidential.
Medicare Part D Spending
What Medicare drug plans spent on Relistor, before manufacturer rebates.
- $29.5M
- January to March 2026, the latest CMS has posted
For 6,351 people, about $2,676 per prescription fill - $142.3M
- 2025, the whole year
For 14,919 people, about $2,535 per prescription fill
See the numbers
| Period | Spending | People | Per fill |
|---|---|---|---|
| January to March 2026 | $29,531,463 | 6,351 | $2,675.68 |
| 2025 | $142,300,906 | 14,919 | $2,534.52 |
Source: CMS Medicare Part D Spending by Drug, matched by the brand name Relistor only, so no generic is counted in it. What CMS says it is used for: This medication is used to treat constipation caused by opioid medication. It blocks the effect of opioids on the gut without blocking the effect on pain.
Medicaid Prescriptions by Quarter
18,650 prescriptions in the four quarters to Q4 2025, $41.9M paid.
See the numbers
| Quarter | Prescriptions | Medicaid paid |
|---|---|---|
| Q4 2025 | 57 | $130,334 |
| Q3 2025 | 6,344 | $14,461,906 |
| Q2 2025 | 6,120 | $13,679,523 |
| Q1 2025 | 6,129 | $13,592,598 |
Source: CMS Medicaid State Drug Utilization Data, over Relistor’s own package codes.
Relistor Strengths and Forms
| Strength | Form | How it is taken | Approved | Status |
|---|---|---|---|---|
| 12MG/0.6ML (12MG/0.6ML) | Solution | Subcutaneous | April 2008 | Prescription reference product |
| 8MG/0.4ML (8MG/0.4ML) | Solution | Subcutaneous | September 2010 | Prescription reference product |
| 150MG | Tablet | Oral | July 2016 | Prescription reference product |
Source: FDA Orange Book, Salix Pharmaceuticals Inc. Listed for sale today by Salix Pharmaceuticals, Inc. (FDA NDC Directory).
Relistor NDC Codes and Packages
Each Relistor package sold today has its own NDC, the product number printed on the box and on the pharmacy label. Open one to see that package’s details, what pharmacies pay for it and its patent timeline.
| NDC | Product | Package | Company |
|---|---|---|---|
| 65649-0551-02 | METHYLNALTREXONE BROMIDE 12 mg/.6mL injection, solution | vial of .6 mL | Salix Pharmaceuticals, Inc. |
| 65649-0551-02 | METHYLNALTREXONE BROMIDE 12 mg/.6mL injection, solution | vial of .6 mL | Salix Pharmaceuticals, Inc. |
| 65649-0551-03 | METHYLNALTREXONE BROMIDE 12 mg/.6mL injection, solution | carton of 7 blister packs of 1 syringe of .6 mL | Salix Pharmaceuticals, Inc. |
| 65649-0551-03 | METHYLNALTREXONE BROMIDE 12 mg/.6mL injection, solution | carton of 7 blister packs of 1 syringe of .6 mL | Salix Pharmaceuticals, Inc. |
| 65649-0551-07 | METHYLNALTREXONE BROMIDE 12 mg/.6mL injection, solution | syringe of .6 mL | Salix Pharmaceuticals, Inc. |
| 65649-0551-07 | METHYLNALTREXONE BROMIDE 12 mg/.6mL injection, solution | syringe of .6 mL | Salix Pharmaceuticals, Inc. |
| 65649-0150-06 | METHYLNALTREXONE BROMIDE 150 mg/1 tablet | bottle of 6 tablets | Salix Pharmaceuticals, Inc. |
| 65649-0150-06 | METHYLNALTREXONE BROMIDE 150 mg/1 tablet | bottle of 6 tablets | Salix Pharmaceuticals, Inc. |
Show the other 4 Relistor packages
| NDC | Product | Package | Company |
|---|---|---|---|
| 65649-0150-90 | METHYLNALTREXONE BROMIDE 150 mg/1 tablet | bottle of 90 tablets | Salix Pharmaceuticals, Inc. |
| 65649-0150-90 | METHYLNALTREXONE BROMIDE 150 mg/1 tablet | bottle of 90 tablets | Salix Pharmaceuticals, Inc. |
| 65649-0552-04 | METHYLNALTREXONE BROMIDE 8 mg/.4mL injection, solution | carton of 7 blister packs of 1 syringe of .4 mL | Salix Pharmaceuticals, Inc. |
| 65649-0552-04 | METHYLNALTREXONE BROMIDE 8 mg/.4mL injection, solution | carton of 7 blister packs of 1 syringe of .4 mL | Salix Pharmaceuticals, Inc. |
Source: the FDA NDC Directory, current listings only. Only packages sold under Relistor’s own FDA approval (NDA 21964, NDA 208271) are listed, never a generic. Some codes belong to companies that repackage Relistor: it is the same medicine in a different package.
What a Generic Relistor Means for You
Nothing Changes Until It Is in Pharmacies
Until a generic is actually for sale, keep filling Relistor as usual. When one arrives, there is nothing you need to sign up for.
Your Pharmacy May Switch You Automatically
Every state lets pharmacists fill a brand-name prescription with an FDA-approved generic rated as equivalent to it, and about 19 states require them to, unless your prescriber writes “dispense as written” or “brand medically necessary” on the prescription. Some states ask the pharmacist to tell you, or to get your OK first. A study of every state’s law has the details.
It Will Probably Look Different
US trademark law does not let a generic look exactly like the brand, so the color, shape or markings usually change. The active ingredient, strength and form are the same. An “authorized generic,” made by or for the brand’s own company, can look identical. The FDA explains.
Your Insurance May Change Too
Once a lower-cost version is available, many insurance plans charge more for the brand, or stop covering it. Your plan’s drug list (formulary) says how.
Until a generic is on US pharmacy shelves, be careful with websites that offer “generic Relistor”. The FDA warns that unlicensed online pharmacies sell counterfeit and unapproved medicines; its BeSafeRx page shows how to check a pharmacy.
Questions people ask about Relistor
Is there a generic for Relistor right now?
No. As of October 9, 2026 no generic methylnaltrexone bromide is listed for sale in the FDA NDC Directory.
When will Relistor go generic?
July 2027 is the expected month, and that is probable but not certain. The brand company and a generic maker settled their patent fight and agreed on when a generic can launch. The last listed patent runs to March 2031, but it covers the product’s formulation and a way of using it, not the medicine itself, which a generic can often work around or challenge.
Will generic methylnaltrexone bromide be the same as Relistor?
Yes in the ways that matter: the same active ingredient, strength and form, with proof that it reaches your blood the same way. Inactive ingredients can differ, which is why some people notice a different look or taste.
How much will the generic cost?
Nobody can say for sure before launch. 5 companies have applied to the FDA to make it. In the FDA’s study of past launches, pharmacies paid about 73% less once four companies sold a generic, which would take the $25.34 pharmacies pay per tablet for Relistor today to about $6.84. That is a pattern from past launches, not a prediction for this one.
Has the FDA approved a generic Relistor?
Not yet. The FDA Orange Book lists no approved generic version of Relistor.
When does the Relistor patent expire?
The FDA Orange Book lists 12 patents for Relistor; the last runs to March 2031. A patent date is not the launch date: settlements and court rulings often bring a generic earlier, and FDA approval or a company’s own plans can make it later. The expected month on this page (July 2027) weighs all of that.
Has anyone challenged the Relistor patents?
Yes. The first patent challenge to Relistor reached the FDA in July 2015, from one company on that first day. The FDA approved a first challenger’s generic in August 2024, and the list records no sale by a first challenger yet. A patent challenge (a “Paragraph IV certification”) is a generic company telling the FDA that a patent listed for the brand is invalid or will not be infringed by its version. The first companies to file one can earn a 180-day head start, during which the FDA cannot approve the generics that filed after them.
How much does Relistor cost now?
Pharmacies paid about $25.34 per tablet for Relistor 150 mg tablet in February 2024, by the national survey of what pharmacies pay (NADAC). That is the pharmacy’s cost, not your price: what you pay depends on your insurance or discount card.
Changes to This Projection
- First generic expected July 2027 on this month’s schedule. A line is added here whenever a monthly update moves the month, the reason or how sure it is.
Every change to the expected month is logged here with the month we saw it.
Also Going Generic
- Xartemis XRAcetaminophen and Oxycodone Hydrochloride2027 to 2028
- Kisqali Femara Co-PackLetrozole and RibociclibJuly to September 2031
- SutabMagnesium Sulfate, Potassium Chloride, and Sodium Sulfate2033 to 2034
- ErleadaApalutamide2035 to 2036
- BafiertamMonomethyl FumarateFebruary 2035
- OrtikosBudesonideSeptember 2036
About Relistor
- Generic name methylnaltrexone bromide
- How it is taken Injection under the skin
- Company Salix Pharmaceuticals Inc
- Patent challenges Since July 2015 (FDA)
- More drugs Brand-name drugs starting with R
- Have a question? A pharmacist answers, free. Ask about Relistor
Sources. The expected month: FDA Paragraph IV Patent Certifications list, federal court records, company announcements and securities filings (settlement dates, launch plans, sales). The record on this page: FDA Orange Book, Drugs@FDA (tentative approvals), FDA NDC Directory, FDA Paragraph IV Patent Certifications list, NADAC (CMS), CMS Medicare Part D Spending by Drug, Medicaid State Drug Utilization Data, FDA, Generic Competition and Drug Prices (2019). Updated October 9, 2026. Information, not medical advice.