Pentosan polysulfate

Also called pentosan polysulfate sodium, PPS, Elmiron (capsules), iPPS or Zilosul (Paradigm's injection), Zycosan and Cartrophen Vet (animal injections)^{1, 8, 11, 19}

Pentosan polysulfate is not a peptide. It is a semi-synthetic chain of sulfated sugars made from beech-wood xylan, chemically similar to heparin.^{1, 7} In the US it is approved only as Elmiron capsules, for bladder pain or discomfort from interstitial cystitis.¹ Since June 2020 its label has warned of retinal damage, called pigmentary maculopathy, with long-term use.² Vets inject it for arthritis in horses and dogs. Animal products are sometimes injected by people for their own joints, a use no regulator has approved.^{8, 11} The human joint evidence is small. Paradigm Biopharmaceuticals' phase 3 knee trial failed its interim test in September 2026, and the company is in administration.^{19, 21}

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At a glance

Where to get it

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Molecular structure

Not a chain of amino acids. A chain of xylose sugar rings, most carrying two sulfate groups. This shows one repeating unit; the wavy ends mark where the chain continues.

The two sulfate groups that make it a "polysulfate"

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Type

Semi-synthetic sulfated polysaccharide, not a peptide

Source

Xylan from beech wood

Unit

C5H6Na2O10S2, 336.2 g/mol

Chain weight

4,000 to 6,000 daltons, about 12 to 18 units

Salt

Sodium

Absorbed by mouth

About 6%

A simplified drawing: real batches are a mix of chain lengths. Source and weight from the label and a 2023 review; the unit formula is our calculation for a disulfated xylose unit.^{1, 7}

What it is

Pentosan polysulfate is made by chemically adding sulfate groups to xylan, a sugar polymer taken from beech trees.⁷ The Elmiron label calls it a "heparin-like" carbohydrate that resembles the body's glycosaminoglycans, the sugar chains found in cartilage and the bladder lining.¹ It is not a peptide. We cover it because it is often sold and discussed with injectable peptides for joints.

It comes in three main forms:

• Elmiron capsules. FDA-approved for "the relief of bladder pain or discomfort associated with interstitial cystitis."¹ The EU authorised it in 2017 for bladder pain syndrome with specific bladder findings.⁶
• Animal injections. Zycosan was approved by FDA in December 2022 for arthritis signs in horses.⁸ Cartrophen Vet is authorised in some countries for arthritis in dogs.^{11, 12} FDA "strongly encourages" vets to use the approved horse product rather than unapproved or compounded pentosan.⁸
• Paradigm's injection (iPPS, Zilosul). An investigational injection under the skin for knee osteoarthritis, with FDA Fast Track status.¹⁹

How it works

For joints, the case rests on lab and animal work.⁷

• Cartilage cells. In lab studies it raised production of proteoglycans, key building blocks of cartilage.⁷
• Inflammation and pain signals. It changed inflammatory signals and lowered nerve growth factor, a pain-related molecule, in cell studies.⁷
• Blood flow. It is a weak anticoagulant that also helps break down clots.^{1, 7} A review says it may clear fat deposits from small vessels in the bone under cartilage.⁷

Only about 6% of an oral dose is absorbed.¹ The joint products studied in people and animals are injected.^{8, 13}

Evidence map

Each use is graded separately, because the evidence differs by use.

Scale: 5 FDA-approved, 4 strong human, 3 limited human, 2 animal or lab only, 1 anecdotal

Key studies

Paradigm says operational problems at US sites left many missing pain scores, which counted against the drug in the interim analysis.^{19, 21} A company's own post hoc subgroup can't rescue a failed trial, but it may shape any future study. Paradigm also registered an earlier phase 2/3 knee trial, PARA_OA_002; we found no published results.¹⁶

By goal

Pick your goal to see what the evidence supports.

Sources: Elmiron label,¹ FDA,⁸ Paradigm.²¹

How it's used

We don't give a dose for joints. None has been approved.

For interstitial cystitis, the Elmiron label dose is 300 mg a day, taken as one 100 mg capsule three times a day, with a review at 3 months.¹ That is the label's dose for bladder pain only. The knee studies used injections under the skin, once or twice a week for about six weeks.^{13, 16} We report this as information, not instruction.

Side effects and who should avoid it

• Retinal damage. Since June 2020 the label has warned of "pigmentary changes in the retina" with long-term use. Cumulative dose appears to be a risk factor, the changes may be permanent, and the label suggests a retinal exam within six months of starting and regular exams after that.^{1, 2} The first report described six patients who had taken it for a median of 15.5 years.³ A urogynecology society advises keeping total long-term exposure low.⁴
• Bleeding. It is a weak blood thinner. In trials, 6.3% had rectal bleeding at the label dose. Bruising, nosebleeds and gum bleeding were also reported.¹
• Common side effects. Hair loss, diarrhea and nausea, each in about 4%, then headache and rash.¹
• Liver tests. Mild rises in liver enzymes in about 1.2%.¹
• Animal products in people. Zycosan is labeled "for intramuscular use in horses only."⁸ Animal products are not made or tested for human use.
• Who should take extra care. People on blood thinners or with a bleeding risk, and people with a history of heparin-induced low platelets. Talk to a doctor first.¹

Compared with

Sources: Elmiron label,¹ Paradigm.¹⁹ See our TB-500 and BPC-157 guides.

Stacks

We found no study of pentosan combined with BPC-157, TB-500 or other peptides. Because it thins the blood, combining it with other blood thinners, including aspirin and other anti-inflammatory painkillers, raises bleeding risk.¹

Myths vs evidence

All options

MoveWell sells nothing. Checked November 1, 2026

Prescription

Elmiron capsules need a prescription and are approved for bladder pain from interstitial cystitis.¹ A doctor may prescribe an approved drug off-label, but there is no approved human pentosan product for joints. Because pentosan is the active ingredient of an approved drug, a licensed 503A pharmacy may, in principle, compound it for a named patient with a prescription.²² We found no US pharmacy or telehealth service we could verify offering it for joints, so we list none.

Clinical trials

Paradigm's phase 3 knee trial is ending.²¹ We found no other open trial of pentosan for joints.

Veterinary products

Zycosan, Cartrophen Vet and similar products are for animals and need a vet's prescription.^{8, 11} We don't link them for human use.

Legal status history

Newest first.

1. Current statusNov 1, 2026FDA-approved as Elmiron capsules for interstitial cystitis, and as Zycosan for horses. No approved human product for joints.^{1, 8}
2. Next · no dateAny rescue proposal is uncertain. On Oct 15 the administrators said none had yet been received.²¹
3. Oct 30, 2026Quarterly report: cash about A$4.3 million. The board says it intends to propose a deed of company arrangement with the administrators.²⁴
4. Oct 15, 2026Paradigm says the phase 3 knee trial "will not proceed" and reports a post hoc result in non-US sites.²¹
5. Sep 29, 2026Voluntary administrators appointed to Paradigm. Shares stay suspended.²¹
6. Sep 23, 2026PARA_OA_012 interim analysis meets its futility criterion.^{19, 20}
7. Aug 13, 2026Safety board recommends the trial continue unchanged, after its third safety review.¹⁸
8. Jan 2026Phase 2 biomarker results published in Arthritis Research & Therapy.¹⁴
9. Dec 20, 2022FDA approves Zycosan, the first injectable pentosan for horses.^{8, 9}
10. Aug 2020Urogynecology society issues eye-screening advice for long-term users.⁴
11. Jun 2020Elmiron label adds the retinal pigmentary changes warning.²
12. 2018Eye specialists describe a new maculopathy linked to long-term use.³
13. Jun 2, 2017EU authorises Elmiron for bladder pain syndrome.⁶

See every peptide's status in the regulatory tracker.

FAQ

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References