Cysteamine (Procysbi / Cystagon / Cystaran / Cystadrops)

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

Nephropathic cystinosis in adults and in children 1 year of age and older. This label is for Procysbi, the delayed-release oral form.

What it is for, in depth

Procysbi is a delayed-release form of cysteamine for nephropathic cystinosis, a rare inherited condition in which cystine builds up inside cells and damages the kidneys and other organs. It comes as 25 mg and 75 mg capsules, swallowed whole with water or fruit juice (not grapefruit), and as granule packets sprinkled on applesauce, berry jelly, or fruit juice. Dosing is personal: it starts as a fraction of the full dose, is raised slowly, and is tuned to a target cystine level measured in white blood cells, up to 1.95 grams/m2 a day. Food rules are strict — no food for 2 hours before and 30 minutes after a dose — and alcohol is avoided.

How it works

Cysteamine is a cystine-depleting agent. Inside the cell's lysosomes it changes cystine into cysteine and a cysteine-cysteamine mix, both of which can leave the lysosome. That lowers the cystine built up inside cells in cystinosis, a defect of lysosomal transport.

How it is taken

Procysbi comes as delayed-release capsules (25 mg and 75 mg of cysteamine) and delayed-release oral granule packets (75 mg and 300 mg). Swallow capsules whole — do not crush or chew. Granules are sprinkled and mixed in applesauce, berry jelly, or fruit juice (not grapefruit juice). The dose is weight-based, started low and raised in steps to a target white blood cell cystine level; the maximum is 1.95 grams/m2 per day. Do not eat for at least 2 hours before and 30 minutes after a dose (a small amount of food is allowed if needed), avoid high-fat food and alcohol around dosing, and take it at least 1 hour before or after medicines containing bicarbonate or carbonate.

Common side effects

["The label extract's adverse section does not give a percentage table; it lists the reactions discussed in the warnings: skin and bone lesions like Ehlers-Danlos syndrome, skin rash, stomach/intestine ulcers and bleeding, and central nervous system symptoms", 'Low white blood cell counts and raised alkaline phosphatase levels are monitored during treatment']

Serious warnings

['Ehlers-Danlos-like syndrome — skin and bone lesions can occur; the dose is reduced if they do', 'Severe skin rash, including erythema multiforme bullosa or toxic epidermal necrolysis — stop Procysbi if this occurs', 'Stomach and intestine (GI) ulcers and bleeding — watch for GI symptoms', 'Fibrosing colonopathy — severe, ongoing, or worsening belly symptoms should be checked; if confirmed, stop Procysbi for good and switch to immediate-release cysteamine', 'Central nervous system symptoms — the dose may be interrupted or reduced for severe or ongoing symptoms', 'Benign intracranial hypertension (raised pressure in the head) — watch for signs and symptoms']

Who should be careful

['People with a serious allergic reaction, including anaphylaxis, to penicillamine or cysteamine (contraindication)', 'People who develop skin or bone lesions, severe rash, or severe belly symptoms', 'People who are breastfeeding — breastfeeding is not recommended', 'Children under 1 year — this label covers patients 1 year and older']

Major interactions

['Drugs that raise stomach pH, such as medicines containing bicarbonate or carbonate — they can release cysteamine too early and raise white blood cell cystine levels; monitor the WBC cystine level (the label notes 20 mg omeprazole did not change cysteamine levels when Procysbi was taken with orange juice or water)', 'Grapefruit juice — capsules and granules are not taken with it', 'Alcohol — avoid drinking alcohol while taking Procysbi']

Cost and saving notes

Procysbi is a brand-only delayed-release product, and it sits on Tier 4 in most of the plans that list it — higher copays or coinsurance than preferred tiers. Ask about prior authorization and a tier exception, and check Extra Help if your income is limited. The 2027 Part D out-of-pocket cap is $2,400 for the year, and the Medicare Prescription Payment Plan can spread drug costs across the year.

Why it is in its tier

Cysteamine (Procysbi / Cystagon / Cystaran / Cystadrops) sits on Tier 4 in 81.48% of the plans that list it (4337 of 5323 listing plans). Tier 4 is the non-preferred tier — higher copays or coinsurance. The data-visible drivers: It is a brand-only product with no generic version in the formulary data, and the CMS dashboard puts its average Part D spending at about $644,082 per beneficiary for 2024 — among the highest-cost drugs in the program, which matches where plans place it. It is listed by 96.87% of Part D plans. The tier shown is the most common one; individual plans vary.

Sources

• PROCYSBI (CYSTEAMINE BITARTRATE) CAPSULE, DELAYED RELEASE PELLETS PROCYSBI (CYSTEAMINE BITARTRATE) GRANULE, DELAYED RELEASE [HORIZON THERAPEUTICS USA, INC.] — DailyMed
• PROCYSBI official patient site (Amgen) — Taking PROCYSBI

What official patient guides say

Cysteamine (Procysbi) comes as delayed-release capsules and delayed-release oral granule packets. The manufacturer's patient page walks through giving a dose through a gastrostomy tube (G-tube): wash your hands first, use strained applesauce (not chunky), water, or any fruit juice except grapefruit juice, make sure your hands are dry before opening a capsule, open it by holding each end and twisting slowly — do not pinch the capsule in the center or crush it — and sprinkle the microbeads on top of the applesauce; to open a packet, tear it along the perforated line and sprinkle the microbeads on the applesauce the same way. Give all of the mixture within 30 minutes of mixing and do not save any of it; rinse the bowl with water or juice (not grapefruit juice) and flush the tube so none of the mixture is left behind, and clean all of your equipment for the next use. Do not drink alcohol while taking Procysbi. Check your skin while taking Procysbi, and your doctor should check you for a low white blood cell count and abnormal liver function blood tests and should do eye examinations during treatment.

Source: PROCYSBI official patient site (Amgen) — Taking PROCYSBI

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, 5,323 list Cysteamine (Procysbi / Cystagon / Cystaran / Cystadrops) — 96.9% of plans. Most of those plans put it on Tier 4: 4,337 plans, 81.5% of the plans that list it. Other plans place it on Tier 3 (829 plans), Tier 1 (103 plans) or Tier 5 (53 plans). For example: Aetna Medicare Dual Extra (HMO D-SNP) puts it on Tier 4; Aetna Medicare Dual Extra Care (PPO D-SNP) puts it on Tier 4; Aetna Medicare Value Plus (PPO) puts it on Tier 4. 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.