Istradefylline
Istradefylline is an adenosine receptor antagonist used as an add-on treatment to levodopa/carbidopa in adults with Parkinson's disease who experience 'off' episodes.
🧬 Where this information comes from Click to expand
The clinical label records used on this page are FDA-filed Structured Product Labeling (SPL) retrieved through openFDA. We identified 1 clinical label set within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. Forms, routes, brands, labelers, strengths, and NDC product-record counts are built separately from matching FDA National Drug Code Directory records. The linked DailyMed document is a representative official source for verification, not the page’s only clinical source. View the linked label on DailyMed →
📖 Istradefylline: Patient Information Guide
A plain-language walkthrough of Istradefylline — what it treats, how it works, how it’s taken, side effects, warnings and interactions. Tap any section to expand it.
🎯What it's used for▾
Istradefylline is approved for use in adults with Parkinson's disease to reduce 'off' episodes — times when levodopa stops working well and symptoms return.
- Nourianz (istradefylline) tablets are indicated as adjunctive (add-on) treatment to levodopa/carbidopa in adult patients with Parkinson's disease experiencing 'off' episodes
- Nourianz is not used alone — it must be taken alongside levodopa/carbidopa
⚙️How it works▾
Istradefylline is an adenosine A2A receptor antagonist — meaning it blocks a specific receptor in the brain called the adenosine A2A receptor. By blocking this receptor, it is believed to modulate the brain pathways involved in movement control, helping levodopa work more consistently and reducing the motor fluctuations known as 'off' episodes. The precise mechanism by which it produces this benefit in Parkinson's disease is not fully established.
💊How it's taken▾
Nourianz tablets are taken once daily by mouth, with or without food. No gradual dose ramp-up is needed at the start. Your doctor may increase the dose over time based on your response and how well you tolerate it. Heavy tobacco smokers (20 or more cigarettes per day) may be prescribed a higher dose because smoking significantly lowers istradefylline levels in the blood. People with moderate liver disease, or those taking certain interacting medications, may need a lower dose — always follow your prescriber's specific instructions.
🤒Side effects — in detail▾
The most common side effects of Nourianz include:
- Dyskinesia (uncontrolled, involuntary movements) — the most frequently reported
- Dizziness
- Constipation
- Nausea
- Hallucinations
- Insomnia (trouble sleeping)
- Decreased appetite
- Rash
More serious reactions — including hallucinations, psychotic behavior, and impulse control problems — require prompt medical attention. Contact your doctor right away if you or a caregiver notice any of these.
⚠️Warnings & precautions▾
- Dyskinesia: Nourianz combined with levodopa can cause or worsen uncontrolled movements. Tell your doctor if this happens — the dose may need to be adjusted.
- Hallucinations and psychotic behavior: Nourianz can cause hallucinations, paranoia, confusion, or agitation, especially at higher doses. People with a major psychotic disorder should not take this medication. If psychotic symptoms appear, your doctor may reduce the dose or stop the drug.
- Impulse control problems: Some patients develop strong, hard-to-control urges — such as gambling, increased sexual urges, compulsive spending, or binge eating. These may not feel abnormal to the patient, so caregivers should watch carefully. Dose reduction or stopping the medication has resolved these urges in some cases.
🔀What it interacts with▾
Several medications and substances can significantly affect how Nourianz works — or how other drugs work when taken with it:
- Strong CYP3A4 inhibitors (e.g., itraconazole, ketoconazole, clarithromycin): Raise istradefylline blood levels substantially — a lower maximum daily dose of Nourianz applies when these are used together
- Strong CYP3A4 inducers (e.g., rifampin, carbamazepine, phenytoin, St. John's wort): Dramatically reduce istradefylline levels, making it much less effective — avoid combining with Nourianz
- CYP3A4 substrate drugs (e.g., atorvastatin): Nourianz at 40 mg can raise the blood levels of some of these drugs — monitor for increased side effects
- P-glycoprotein substrate drugs (e.g., digoxin): Nourianz can increase their levels — watch for increased side effects from those medications
- Heavy tobacco smoking (20+ cigarettes/day): Lowers istradefylline exposure by 38–54% — dose adjustments may be necessary
This is not a complete list of interactions. Always talk with your doctor or pharmacist before starting, stopping, or changing any medication.
📋Before taking it▾
- People with a major psychotic disorder should not take Nourianz — it can worsen psychosis
- People with moderate liver disease need a lower maximum dose; those with severe liver disease should avoid Nourianz entirely
- Pregnancy: Animal studies showed potential fetal harm, including structural abnormalities and fetal death. Women who can become pregnant should use contraception while taking Nourianz. The combination of istradefylline and levodopa/carbidopa showed even greater fetal risk in animals.
- Breastfeeding: It is unknown whether istradefylline passes into human breast milk — discuss risks and benefits with your doctor
- Children: Safety and effectiveness in pediatric patients have not been established
- Older adults: No dose adjustment is needed based on age alone; Nourianz has been studied in patients up to 84 years old
- Nourianz has not been studied in patients with end-stage renal disease or on dialysis — use with caution if kidney function is severely reduced
🚑If you take too much▾
Taking too much Nourianz can cause hallucinations, agitation, and worsened uncontrolled movements. There is no specific antidote for an istradefylline overdose. If an overdose is suspected, stop the medication and seek medical support right away — and contact a Certified Poison Control Center for guidance. Keep in mind that istradefylline stays in the body for a long time (half-life of about 83 hours), so effects may be prolonged.
📡Pharmacodynamics — effects in the body▾
Nourianz has been studied for its effect on heart rhythm (QTc interval), and at doses up to four times the maximum recommended dose, it did not cause clinically significant changes. This means it is not expected to cause dangerous heart rhythm problems at therapeutic doses.
🔬Pharmacokinetics — how your body processes it▾
After you take a Nourianz tablet, it reaches peak levels in the blood in about 4 hours. The drug has a long half-life of approximately 83 hours, meaning it stays in the body for several days — and it takes about 2 weeks of once-daily dosing to reach steady, stable levels. Istradefylline is almost entirely broken down by the liver (primarily through enzymes CYP1A1 and CYP3A4), and eliminated through feces and urine. It is very tightly bound to proteins in the blood (about 98%), and heavy smoking significantly reduces how much of it reaches your system.
📦How to store it▾
Store at 20°C to 25°C (68°F to 77°F); excursions permitted between 15°C and 30°C (59°F to 86°F) .
📄 Written from Istradefylline’s FDA-approved label information, summarized in plain language with AI, and reviewed by our pharmacy team before publication. Every point is grounded in that labeling — nothing is invented. How we use AI →
Supplements & herbs that interact with Istradefylline
138 supplements and herbal products have documented interactions with Istradefylline in the licensed clinical database we use. Most are manageable — but your pharmacist should know about everything you take, including vitamins and herbals.
- Major · 3
- Moderate · 94
- Minor · 41
Educational information from a licensed clinical database (Natural Medicines) — see our data sources & update cadence. Not medical advice: an interaction being documented does not mean it will happen to you; do not start or stop medications or supplements without professional guidance.
🩺 Pharmacist Counseling Corner
Quick, plain-English answers to the questions patients ask most about Istradefylline — the kind of thing our pharmacy team would talk through with you at the counter.
What exactly is Nourianz supposed to do for my Parkinson's disease? ▾
Can I take Nourianz with or without food? ▾
What side effects should I actually watch out for? ▾
I take a few other medications. Is that a problem? ▾
I smoke. Does that affect how Nourianz works? ▾
Is Nourianz safe to take if I'm pregnant or thinking about becoming pregnant? ▾
Is Istradefylline available over the counter? ▾
When was Istradefylline first available? ▾
Who makes Istradefylline? ▾
💬 Answers drafted from Istradefylline’s FDA-approved label information, summarized in plain language with AI, and reviewed by our pharmacy team before publication. Grounded in that labeling — nothing is made up. How we use AI →
🧰 Keep exploring
💊 How Istradefylline comes
Istradefylline is available in 1 form. Different forms and brands can have different approved uses, doses, schedules, and directions. Follow the instructions for your exact product, and do not switch forms without guidance from your prescriber or pharmacist.
Tablet
How this form is used
- Nourianz tablets are used as add-on treatment to levodopa/carbidopa in adults with Parkinson's disease experiencing 'off' episodes
- Nourianz tablets are taken by mouth once daily, with or without food
- Nourianz tablets do not require an initial dose titration period
- If you take a strong CYP3A4 inhibitor (such as ketoconazole or clarithromycin), the maximum dose of Nourianz is lower — follow your prescriber's guidance
- Avoid taking Nourianz with strong CYP3A4 inducers such as rifampin, carbamazepine, phenytoin, or St. John's wort
📊 Istradefylline across the U.S. market
How Istradefylline appears in the FDA’s National Drug Code Directory — including its dosage forms, strengths, brand names, manufacturers, and FDA-listed product records. These are directory records, not sales or prescription volume.
Also listed with the FDA, not a patient dose form: Powder (7) — bulk drug substance sold to compounders/manufacturers and multi-item kits. These aren’t counted in the dose-form total above.
Share of FDA-listed product records by manufacturer — FDA National Drug Code Directory. Record counts are not sales or prescription volume.
📈 How widely Istradefylline is used
A general measure of how commonly Istradefylline is prescribed, based on Medicaid — one of the largest public drug programs. The figure below is prescriptions filled in Q1–Q4 2025, summed across every form and brand of the drug.
Think of this as a proxy for how widely Istradefylline is used, drawn from freely available public data. Medicaid is just one program — these numbers don’t include Medicare, other government coverage, or commercial and cash-pay prescriptions, so real-world use is higher than what’s shown here.
How commonly is Istradefylline prescribed? Of the 1,596 medications we measure, Istradefylline ranks #1,383 by Medicaid prescriptions — more than 13% of them.
Utilization by Istradefylline product
Pick a product to see its own Medicaid numbers. Each chip is one clinical product — a specific strength & dosage form as defined by RxNorm — with brand-name and generic versions combined.
istradefylline 40 MG Oral Tablet Most dispensed
Summed across the 1 of 2 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 2199028
istradefylline 20 MG Oral Tablet
Summed across the 1 of 2 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 2199020
Shares are of the Medicaid prescriptions shown here. Product grouping follows RxNorm (the National Library of Medicine’s drug terminology), so “one product” means one strength & dosage form regardless of manufacturer. Dollar figures are gross Medicaid reimbursement before mandatory rebates — rebates (often large, especially for brand-name drugs) are confidential, so actual net cost to Medicaid is lower than shown.
Source: Medicaid State Drug Utilization Data (CMS), aggregated by generic ingredient — summed across every NDC (all brands, strengths, salt forms and dosage forms) of Istradefylline, and across all states and both fee-for-service and managed-care claims. A general popularity signal; it excludes Medicare, commercial insurance and cash prescriptions, so it is not total U.S. use. Based on the 2 of 4 listed Istradefylline NDCs with Medicaid activity.
🔍 Compare Istradefylline products
A representative set of FDA-listed product records for Istradefylline — across manufacturers, strengths, and dosage forms, grouped by form with each product’s manufacturer and how the FDA approved it. The same medicine may be made and packaged by different companies, so a single drug can have many directory entries. (It’s also why a refill can look different — a new shape, color, or box — even though it contains the same medication.)
| Strength | Route | Manufacturer / Labeler | Category ⓘ | Details |
|---|---|---|---|---|
| 💊Tablet | ||||
| 20 mg | Oral | Kyowa Kirin, Inc. × 3 listings | NDA | View NDC → |
| 40 mg | Oral | Kyowa Kirin, Inc. × 3 listings | NDA | View NDC → |
| 💊Bulk drug substance | ||||
| 1 kg/kg | — | Honour Lab Limited | BULK INGREDIENT | View NDC → |
| 1 kg/kg | — | Kyowa Pharma Chemical Co., Ltd. | BULK INGREDIENT | View NDC → |
| 1 kg/kg | — | MSN Life Sciences Private Limited | BULK INGREDIENT | View NDC → |
| 1 kg/kg | — | PROCOS SpA × 2 listings | BULK INGREDIENT | View NDC → |
| 25 kg/25 kg | — | Sun Pharmaceutical Industries, Inc. | BULK INGREDIENT | View NDC → |
| 1 kg/kg | — | Tateyama Kasei Co.,ltd. | BULK INGREDIENT | View NDC → |
Showing 13 of 13 products — FDA National Drug Code Directory. See every product, package size and price: browse all 13 Istradefylline NDCs →
📈 What people report — real-world data (FDA FAERS)
After a medicine reaches the market, patients, doctors and drugmakers can send the FDA reports of problems they think may be linked to it. Here’s what’s been reported for Istradefylline — a signal of what to watch for, not proof the drug caused it.
Source: openFDA, from the FDA Adverse Event Reporting System (FAERS). These are voluntary reports — they don’t prove the drug caused the effect, and counts reflect how often something was reported, not how often it actually happens. Reports also often name the very problem the medicine is taken for — a common reason to file one is that the drug didn’t help — so for a pain reliever you may see “pain” high on the list; that points to why the report was filed, not to the drug causing the symptom. This counts every report that lists Istradefylline in any role, so the total runs higher than the FDA’s official dashboard, which counts only cases where the drug is the suspect. For the authoritative figures, see the FDA FAERS Public Dashboard. Always talk to your pharmacist or doctor.
🏛️ The road to your pharmacy
How Istradefylline went from FDA review to the pharmacy shelf — the key milestones in its regulatory journey.
Source: Drugs@FDA.
🚨 Recall history
A recall is when a specific batch of a medicine is pulled from the market — usually a manufacturing issue, not a problem with the drug itself. Class I is most serious, Class III least.
Source: openFDA drug enforcement (recall) reports.
RxNorm Concept Web — From Ingredient to Every Form and Strength
This page starts with one ingredient concept (IN). The branches below show its dose-form concepts (SCDF), then the available clinical drug and strength concepts (SCD). Combination products remain separate concepts with their own pages.
RxCUI 2199015 1 dose form · 2 strengths
-
Dose form (SCDF) Oral Tablet RxCUI 2199019In current FDA listings
Look up RxCUI 2199015 in the RxCUI Atlas →
RxNorm is the U.S. National Library of Medicine’s normalized drug vocabulary. Its concept hierarchy can include forms that are not currently marketed; the status on each branch compares that concept with current FDA listings. RxCUIs identify vocabulary concepts, not individual packages or manufacturers.
📦 Supply & shortage status
Whether Istradefylline is in short supply in the U.S. right now, plus any shortage history the FDA has on record. A shortage usually reflects a manufacturing or demand issue — not a safety problem with the drug.
Source: openFDA, from the FDA Drug Shortages database.
🏷️ Sold under these brand names
🏭 Manufacturers & labelers
RxNorm drug class
Istradefylline belongs to the Other antiparkinson drugs class.
Classified by RxNorm RxClass — the U.S. National Library of Medicine's standardized drug-classification service (Established Pharmacologic Class from the FDA, the ATC drug family from the WHO, and mechanism of action). Reference only, not medical advice.
🔬 Where this comes from
Core label, product, RxNorm, safety, and utilization data on this page come from the sources identified below. AI-written, editorial, and licensed sections are labeled separately.
How we combine label and product data
HelloPharmacist combines public FDA and NLM records; we don’t author the underlying clinical facts. We identified 1 FDA-filed SPL label set within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. The representative label is the starting point for the displayed reference monograph; the 12 largest stored in-scope SPL records, which may include that representative, are compared section by section, and the longest available version of each section is retained. Forms, routes, brands, labelers, product-listed strengths, and product-record counts are aggregated separately from ingredient-matched FDA NDC Directory records; package records listed above are associated with the linked SPL; and the normalized concept hierarchy comes from NLM RxNorm.
For canonical ingredient pages, bounded product-attributed indication and administration excerpts may be added to the AI evidence, and the generator is instructed to preserve available product, brand, route, and form qualifiers instead of treating one label as universal. Where a section is identified as AI-written, its plain-language text is generated from bounded label evidence. New draft drug pages remain in the admin review queue before first publication. Kyowa Kirin, Inc. is the representative DailyMed label linked for verification and dates; it is not the sole source used for the page.
This is general education, not medical advice — always consult your doctor or pharmacist about your medications and any medical condition. For the exact wording of the linked representative label, view that label on DailyMed; some displayed composite sections may come from other in-scope SPL labels. Learn how we use AI and our data sources & update cadence.