Anagrelide Viatris: Uses, Dosage & Side Effects
A platelet-reducing agent used to treat essential thrombocythemia, a myeloproliferative neoplasm characterized by abnormally high platelet counts in the blood
Anagrelide Viatris contains the active substance anagrelide, a platelet-reducing medication used to treat essential thrombocythemia (ET). Essential thrombocythemia is a chronic myeloproliferative neoplasm in which the bone marrow overproduces platelets, the small blood cells responsible for blood clotting. Excessively high platelet counts can lead to dangerous thrombotic events such as stroke, heart attack, and deep vein thrombosis, as well as paradoxical bleeding complications. Anagrelide works by specifically inhibiting the maturation of megakaryocytes in the bone marrow, thereby reducing the number of platelets released into the bloodstream. It is taken as a 0.5 mg capsule, typically starting at one capsule twice daily, with the dose adjusted by your doctor to achieve optimal platelet control.
Quick Facts: Anagrelide Viatris
Key Takeaways
- Anagrelide Viatris is a prescription medication specifically designed to reduce abnormally elevated platelet counts in patients with essential thrombocythemia, helping to prevent dangerous blood clots and bleeding events.
- The medication works as a phosphodiesterase III inhibitor that selectively targets megakaryocyte maturation in the bone marrow, reducing platelet production without significantly affecting white or red blood cell counts.
- Treatment must never be stopped abruptly – sudden discontinuation can cause a rapid rebound increase in platelets, potentially leading to life-threatening thrombotic complications including stroke.
- Cardiovascular assessment (including ECG and echocardiography) is recommended before starting treatment, as anagrelide can affect heart rate and rhythm, and regular cardiac monitoring is essential throughout therapy.
- Anagrelide Viatris is a generic equivalent of Xagrid; other available brands include Anagrelide Sandoz, Anagrelide STADA, Anagrelide Glenmark, and Anagrelide Bluefish – all containing the same active substance at the same strength.
What Is Anagrelide Viatris and What Is It Used For?
Anagrelide Viatris contains the active ingredient anagrelide (as anagrelide hydrochloride monohydrate), a medication that belongs to the class of platelet-reducing agents. Specifically, anagrelide is a phosphodiesterase III (PDE III) inhibitor that exerts its therapeutic effect by interfering with the development and maturation of megakaryocytes, the large bone marrow cells responsible for producing platelets. By inhibiting the later stages of megakaryocyte development, anagrelide selectively reduces the number of platelets released into the bloodstream without significantly altering white blood cell or red blood cell counts at therapeutic doses.
Essential thrombocythemia (ET) is classified by the World Health Organization (WHO) as a chronic myeloproliferative neoplasm (MPN). It is characterized by a sustained elevation in platelet count (typically above 450 × 109/L) and by the proliferation of large, mature megakaryocytes in the bone marrow. ET affects approximately 1 to 2.5 people per 100,000 per year, with a median age at diagnosis of around 60 years, although it can occur at any age. The condition has a slight female predominance. Many patients carry a driver mutation in JAK2, CALR, or MPL genes, which helps drive the abnormal proliferation of megakaryocytes.
When platelet counts are significantly elevated, patients with ET face an increased risk of both thrombotic (blood clotting) and hemorrhagic (bleeding) events. Thrombotic complications may include stroke, transient ischemic attack (TIA), heart attack (myocardial infarction), deep vein thrombosis (DVT), pulmonary embolism, and microvascular disturbances such as erythromelalgia (burning pain and redness in the extremities). Paradoxically, very high platelet counts (typically above 1,000–1,500 × 109/L) may be associated with an acquired von Willebrand syndrome, leading to an increased risk of bleeding rather than clotting.
The primary goal of treatment with anagrelide is to reduce the platelet count to a safer range, thereby lowering the risk of these potentially life-threatening complications. Anagrelide is particularly used in patients who are intolerant of or refractory to first-line cytoreductive therapy (typically hydroxycarbamide/hydroxyurea), or in whom hydroxycarbamide is contraindicated. In some clinical settings and international guidelines, anagrelide may also be considered as an alternative first-line cytoreductive agent, particularly in younger patients where long-term leukemogenic risk is a concern.
Essential thrombocythemia is a chronic condition that typically requires lifelong monitoring and, in many cases, long-term treatment. While ET generally has a favorable prognosis with a near-normal life expectancy when properly managed, uncontrolled platelet counts carry significant risks. Risk stratification (based on age, history of thrombosis, and mutation status) guides treatment decisions, with higher-risk patients typically requiring cytoreductive therapy such as anagrelide to bring platelet counts under control.
What Should You Know Before Taking Anagrelide Viatris?
Contraindications
There are specific circumstances in which Anagrelide Viatris must not be used. Understanding these absolute contraindications is essential for safe treatment.
- Hypersensitivity: Do not take Anagrelide Viatris if you are allergic to anagrelide or any of the other ingredients in the capsules (lactose, croscarmellose sodium, povidone, microcrystalline cellulose, magnesium stearate, gelatin, or titanium dioxide E171). Allergic reactions may include rash, itching, swelling of the face or lips, or difficulty breathing.
- Moderate or severe liver impairment: Anagrelide is extensively metabolized by the liver. Patients with moderate or severe hepatic impairment must not take this medication, as drug accumulation could lead to increased toxicity and potentially dangerous cardiovascular effects.
- Moderate or severe kidney impairment: Patients with moderate or severe renal impairment should not take Anagrelide Viatris, as reduced kidney function may affect the elimination of the drug and its metabolites.
Warnings and Precautions
Never stop taking anagrelide abruptly without consulting your doctor. Sudden discontinuation can cause a rapid rebound increase in platelet count within 4 days, which may lead to potentially fatal thrombotic complications including stroke. Signs of stroke include sudden numbness or weakness in the face, arm or leg (especially on one side), sudden confusion, difficulty speaking or understanding speech, sudden vision problems, sudden difficulty walking, dizziness, loss of balance, or sudden severe headache. Seek emergency medical attention immediately if you experience any of these symptoms.
Before starting and during treatment with Anagrelide Viatris, talk to your doctor about the following:
- Heart problems: Anagrelide is a phosphodiesterase III inhibitor with positive inotropic and chronotropic effects, meaning it can increase the force and rate of heart contractions. If you have or suspect any heart problems, tell your doctor. A cardiovascular assessment including an electrocardiogram (ECG) and echocardiogram is recommended before starting treatment. Common cardiac side effects include palpitations and tachycardia. Uncommon but serious cardiac effects include heart failure, atrial fibrillation, and QT prolongation.
- QT prolongation: If you were born with or have a family history of prolonged QT interval (visible on ECG), or if you take other medications that can cause abnormal ECG changes, or if you have low levels of electrolytes such as potassium, magnesium, or calcium, inform your doctor. These conditions may increase the risk of serious heart rhythm disturbances when combined with anagrelide.
- Liver function: Even if you have only mild liver problems, inform your doctor. Your liver function will be monitored with regular blood tests before and during treatment, as anagrelide is primarily metabolized by the liver (via CYP1A2).
- Kidney function: If you have any kidney problems, inform your doctor. Your kidney function will be monitored regularly throughout treatment.
- Concomitant aspirin use: Taking acetylsalicylic acid (aspirin) together with anagrelide increases the risk of major bleeding. Many patients with ET also take low-dose aspirin for cardiovascular protection, but this combination requires careful medical supervision and risk-benefit assessment for each individual patient.
Pregnancy and Breastfeeding
Anagrelide Viatris should not be taken during pregnancy. If you are pregnant, think you may be pregnant, or are planning to become pregnant, tell your doctor immediately. Women of childbearing potential must use effective contraception while taking anagrelide. Animal studies have not fully evaluated the reproductive toxicity of anagrelide, and the potential risk to a developing fetus is not fully known. Your doctor will discuss alternative treatment options if you are planning to conceive.
You must not breastfeed while taking Anagrelide Viatris. It is not known whether anagrelide or its metabolites are excreted in human breast milk, and a risk to the nursing infant cannot be excluded. If you need to take anagrelide, you must stop breastfeeding. Discuss alternative feeding options with your doctor or midwife.
Driving and Operating Machinery
Dizziness has been reported by some patients taking anagrelide. If you experience dizziness while taking Anagrelide Viatris, do not drive or operate machinery until the dizziness resolves. Be particularly cautious when starting treatment or during dose adjustments, as dizziness may be more likely during these periods.
Important Information About Ingredients
Anagrelide Viatris contains lactose. If you have been told by your doctor that you have an intolerance to some sugars, contact your doctor before taking this medicine. This medication also contains less than 1 mmol (23 mg) sodium per capsule, meaning it is essentially sodium-free.
Children and Adolescents
Data on the use of anagrelide in children and adolescents are limited. This medication should therefore be used with particular caution in pediatric populations. Essential thrombocythemia is rare in children, and treatment decisions should be made by a specialist hematologist experienced in managing myeloproliferative neoplasms in young patients.
How Does Anagrelide Viatris Interact with Other Drugs?
Anagrelide is primarily metabolized by the enzyme CYP1A2 in the liver. Medications that inhibit CYP1A2 can increase the blood levels of anagrelide and its active metabolite, potentially amplifying both therapeutic and toxic effects. Conversely, anagrelide may affect the action of other medications through its phosphodiesterase III inhibitory properties and its effects on the cardiovascular system. It is essential to inform your doctor or pharmacist about all medications, supplements, and herbal products you are currently taking or have recently taken.
Major Interactions
| Interacting Drug | Effect | Clinical Significance |
|---|---|---|
| Fluvoxamine (CYP1A2 inhibitor) | Significantly increases anagrelide blood levels; increased risk of cardiovascular side effects | Avoid combination or use with extreme caution under close monitoring |
| Enoxacin and other quinolone antibiotics | CYP1A2 inhibition increases anagrelide exposure; risk of toxicity | Avoid combination; consider alternative antibiotic |
| Sotalol, Amiodarone (antiarrhythmics) | Additive QT prolongation risk; may cause serious heart rhythm disturbances | Avoid if possible; if unavoidable, ECG monitoring is essential |
| Acetylsalicylic acid (Aspirin) | Increased risk of major bleeding due to combined antiplatelet effects | Use only under careful medical supervision with regular bleeding assessment |
| Milrinone, Cilostazol, Enoximone (PDE III inhibitors) | Additive inotropic and vasodilatory effects; risk of hypotension and cardiac complications | Concurrent use not recommended |
Other Interactions
| Interacting Drug | Effect | Clinical Significance |
|---|---|---|
| Theophylline | CYP1A2 substrate; anagrelide may alter theophylline levels | Monitor theophylline levels; dose adjustment may be needed |
| Omeprazole | Potential pharmacokinetic interaction affecting acid secretion and anagrelide absorption | Use with caution; monitor for altered response |
| Clopidogrel and other antiplatelet agents | Additive antiplatelet activity; increased bleeding risk | Combination requires careful risk-benefit assessment and monitoring |
| Oral contraceptives | Severe diarrhea (a side effect of anagrelide) may reduce absorption of oral contraceptives | Use additional contraceptive method (e.g., condom) if diarrhea occurs |
This list is not exhaustive. Always inform your doctor or pharmacist about all medications you are taking, including over-the-counter products, herbal remedies, and dietary supplements. If you are unsure whether a medication may interact with anagrelide, consult your doctor or pharmacist before taking it.
What Is the Correct Dosage of Anagrelide Viatris?
Always take Anagrelide Viatris exactly as your doctor has prescribed. The dosage is individualized based on your platelet count response, overall health status, and tolerability. Do not change your dose or stop taking the medication without first consulting your doctor. Regular blood tests will be performed to monitor your platelet count and adjust the dose as needed.
Adults
Standard Starting Dose
The recommended starting dose is 1 mg per day, taken as one 0.5 mg capsule twice daily. This starting dose should be maintained for at least one week before any dose adjustment.
Dose Titration
After the initial week, your doctor may increase or decrease your dose. Dose adjustments are typically made in increments of 0.5 mg per day, at intervals of no less than one week, until the lowest effective dose is reached that maintains your platelet count below 600 × 109/L (ideally between 150 and 400 × 109/L).
Maximum Dose
The maximum single dose is 2.5 mg. The maximum recommended total daily dose is 10 mg. Most patients respond to doses between 1 mg and 3 mg per day.
Children and Adolescents
Data regarding the use of anagrelide in children and adolescents are limited. If anagrelide is prescribed for a young patient, the treating hematologist will determine the appropriate starting dose and titration schedule on an individual basis, typically starting at a lower dose. Close monitoring of platelet counts and cardiovascular function is particularly important in pediatric patients.
Elderly Patients
No specific dose adjustment is required for elderly patients based on age alone. However, elderly patients may be more susceptible to cardiovascular side effects and may have reduced liver or kidney function. Your doctor will take these factors into account when determining your dose and monitoring schedule. The dose should be titrated carefully to the lowest effective level.
How to Take the Capsules
Capsules should be swallowed whole with water. Do not crush, chew, or open the capsules, and do not dissolve the contents in liquid. Anagrelide can be taken with food, after a meal, or on an empty stomach. Try to take your capsules at the same time each day to maintain consistent blood levels.
Missed Dose
If you forget to take a dose, take it as soon as you remember. However, if it is almost time for your next scheduled dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are unsure about what to do, contact your doctor or pharmacist.
Overdose
If you take more Anagrelide Viatris than prescribed, or if someone else takes your medication, contact your doctor or pharmacist immediately. Show them the Anagrelide Viatris packaging. Overdose may cause a drop in blood pressure and potentially cardiovascular effects due to the drug’s PDE III inhibitory action. There is no specific antidote; treatment is supportive and symptomatic.
What Are the Side Effects of Anagrelide Viatris?
Like all medicines, Anagrelide Viatris can cause side effects, although not everyone gets them. The side effects listed below are based on clinical trial data and post-marketing surveillance reports. If you experience any side effects that concern you, talk to your doctor, pharmacist, or nurse. Side effects are classified by how often they occur:
Very Common
- Headache
Common
- Dizziness
- Fatigue
- Rapid heartbeat (tachycardia)
- Irregular or forceful heartbeat (palpitations)
- Nausea
- Diarrhea
- Abdominal pain
- Flatulence (gas)
- Vomiting
- Anemia (decreased red blood cells)
- Fluid retention (edema)
- Skin rash
Uncommon
- Heart failure (shortness of breath, chest pain, leg swelling)
- Severe heart rhythm problems (ventricular tachycardia, supraventricular tachycardia, atrial fibrillation)
- Pancreatitis (severe pain in abdomen and back)
- Blood in vomit or black/bloody stools
- Pancytopenia (severe decrease in all blood cells causing weakness, bruising, bleeding, or infections)
- Pulmonary hypertension (increased blood pressure in lung arteries, causing shortness of breath, swollen legs, bluish skin)
- High blood pressure
- Irregular heartbeat or fainting
- Chills or fever
- Indigestion or loss of appetite
- Constipation
- Bruising or bleeding
- Swelling (edema)
- Weight loss
- Muscle, joint, or back pain
- Numbness, tingling, or reduced sensation
- Insomnia, depression, confusion, or nervousness
- Dry mouth or memory loss
- Shortness of breath or nosebleeds
- Serious lung infection
- Hair loss, itching, or skin discoloration
- Impotence
- Chest pain
- Thrombocytopenia (low platelets, increasing bleeding risk)
- Pleural effusion (fluid around the lungs)
- Elevated liver enzymes
Rare
- Bleeding gums or weight gain
- Severe chest pain (angina pectoris)
- Cardiomyopathy (heart muscle disease causing fatigue, chest pain, palpitations)
- Heart enlargement
- Pericardial effusion (fluid around the heart)
- Prinzmetal’s angina (painful spasms of heart blood vessels, usually at night)
- Loss of coordination or speech difficulties
- Dry skin or migraine
- Visual disturbances or double vision
- Tinnitus (ringing in ears) or postural dizziness
- Increased nighttime urination
- Drowsiness or widened blood vessels
- Colitis (inflammation of large intestine – diarrhea with blood or mucus, abdominal pain, fever)
- Gastritis (stomach inflammation)
- Kidney failure (little or no urine output)
- Myocardial infarction (heart attack)
Not Known
- Torsade de pointes (potentially life-threatening irregular heart rhythm)
- Hepatitis (liver inflammation – nausea, vomiting, itching, yellowing of skin/eyes, dark urine)
- Allergic alveolitis including interstitial lung disease and pneumonitis (lung inflammation causing fever, cough, breathing difficulties, wheezing with potential scarring)
- Tubulointerstitial nephritis (kidney inflammation)
- Stroke
Contact your doctor immediately if you experience any of the following: shortness of breath or difficulty breathing, chest pain, severe abdominal pain, blood in vomit or stools, sudden weakness or numbness on one side of the body, sudden severe headache, difficulty speaking, or signs of severe allergic reaction (facial swelling, difficulty breathing).
If you experience any side effects, including those not listed above, talk to your doctor or pharmacist. Reporting suspected side effects helps monitor the ongoing safety profile of this medicine. You can report side effects to your national health authority or through the European Medicines Agency (EMA) reporting system.
How Should You Store Anagrelide Viatris?
Proper storage of medications is essential to maintain their safety and effectiveness. Follow these storage guidelines for Anagrelide Viatris:
- Keep out of sight and reach of children: Store the medication in a safe location where children cannot access it.
- Check expiry date: Do not use this medicine after the expiry date (EXP) stated on the carton and bottle label. The expiry date refers to the last day of the stated month.
- Store in original packaging: Keep the capsules in the original plastic bottle with the desiccant to protect them from moisture and light.
- No special temperature requirements: This medicine does not require specific temperature conditions for storage.
- Disposal: If your doctor stops your treatment, do not keep leftover capsules unless specifically told to do so. Do not throw medicines away via wastewater or household waste. Ask your pharmacist how to dispose of medicines no longer needed. These measures help protect the environment.
What Does Anagrelide Viatris Contain?
Understanding what your medicine contains is important, especially if you have known allergies or intolerances to specific ingredients.
Active Substance
The active substance is anagrelide. Each hard capsule contains anagrelide hydrochloride monohydrate equivalent to 0.5 mg anagrelide.
Other Ingredients
- Capsule contents: Lactose, croscarmellose sodium, povidone, microcrystalline cellulose, magnesium stearate
- Capsule shell: Gelatin and titanium dioxide (E171)
Appearance and Packaging
Anagrelide Viatris 0.5 mg hard capsules have a white body and white cap. Each capsule contains white or almost white powder. The capsules measure approximately 14.3 × 5.3 mm. They are supplied in 30 mL or 75 mL plastic bottles with a desiccant, a tamper-evident seal, and a child-resistant closure. Each bottle contains 100 hard capsules.
Other Available Brands
The same active ingredient (anagrelide 0.5 mg) is available under several brand names, including Xagrid (the original branded product), Anagrelid Accordpharma, Anagrelide Sandoz, Anagrelide STADA, Anagrelide Glenmark, Anagrelide Bluefish, and Anagrelid Avansor. All approved formulations undergo bioequivalence testing to confirm they provide the same therapeutic effect.
Viatris Limited, Damastown Industrial Park, Mulhuddart, Dublin 15, Ireland. Manufactured by Synthon Hispania SL, Barcelona, Spain, and Synthon BV, Nijmegen, Netherlands. For further information, contact Viatris AB, Tel: +46 (0)8 630 19 00.
Frequently Asked Questions
Anagrelide Viatris is used to treat essential thrombocythemia (ET), a chronic myeloproliferative neoplasm in which the bone marrow produces too many platelets. By reducing the platelet count, anagrelide helps lower the risk of serious blood clotting complications such as stroke, heart attack, deep vein thrombosis, and pulmonary embolism, as well as bleeding complications that can occur with very high platelet counts. It is typically used when first-line therapy (usually hydroxycarbamide) is not tolerated or is inadequate.
No, you should never stop taking anagrelide suddenly without consulting your doctor. Abruptly discontinuing anagrelide can cause a rapid rebound increase in platelet count within approximately 4 days, which may lead to potentially life-threatening thrombotic events including stroke, heart attack, or pulmonary embolism. If your doctor decides to stop treatment, the dose will be tapered gradually under close medical supervision with regular blood tests to monitor your platelet count during the withdrawal period.
Taking aspirin (acetylsalicylic acid) together with anagrelide increases the risk of major bleeding. While some patients with essential thrombocythemia do take low-dose aspirin for cardiovascular protection, this combination requires careful medical supervision. Always inform your doctor if you are taking aspirin or any other blood-thinning or antiplatelet medications before starting or during treatment with anagrelide. Your doctor will individually assess the bleeding risk against the thrombotic risk.
Yes, anagrelide can affect the heart. As a phosphodiesterase III inhibitor, it has positive inotropic (increases contractility) and chronotropic (increases heart rate) effects. Common cardiovascular side effects include palpitations and rapid heartbeat. In uncommon cases, more serious effects such as heart failure, atrial fibrillation, supraventricular tachycardia, or QT prolongation may occur. A cardiovascular assessment including an ECG and echocardiogram is recommended before starting treatment, and your heart function should be monitored regularly during therapy.
Anagrelide Viatris and Xagrid both contain the same active ingredient, anagrelide, at the same strength (0.5 mg capsules). Xagrid is the original branded product, while Anagrelide Viatris is a generic equivalent that has undergone rigorous bioequivalence testing to ensure it works in the same way. Other generic versions include Anagrelide Sandoz, Anagrelide STADA, Anagrelide Glenmark, and Anagrelide Bluefish. All approved formulations must meet the same quality, safety, and efficacy standards set by regulatory authorities.
Anagrelide typically begins to reduce the platelet count within the first week of treatment. However, the full therapeutic response – achieving a stable, target platelet count – usually takes 2 to 4 weeks, and sometimes longer depending on the starting platelet level and the dose required. Your doctor will perform regular blood tests (typically weekly at first) to monitor your platelet count and adjust the dose accordingly until the optimal response is achieved. Once a stable maintenance dose is established, blood tests are usually performed less frequently.
References
- European Medicines Agency (EMA). Anagrelide – Summary of Product Characteristics. Last updated 2025. Available at: www.ema.europa.eu
- Harrison CN, Campbell PJ, Buck G, et al. Hydroxyurea compared with anagrelide in high-risk essential thrombocythemia. New England Journal of Medicine. 2005;353(1):33–45. doi:10.1056/NEJMoa043800
- Gisslinger H, Gotic M, Holowiecki J, et al. Anagrelide compared with hydroxyurea in WHO-classified essential thrombocythemia: the ANAHYDRET Study, a randomized controlled trial. Blood. 2013;121(10):1720–1728. doi:10.1182/blood-2012-07-443770
- Barbui T, Tefferi A, Vannucchi AM, et al. Philadelphia chromosome–negative classical myeloproliferative neoplasms: revised management recommendations from European LeukemiaNet. Leukemia. 2018;32(5):1057–1069. doi:10.1038/s41375-018-0077-1
- British Society for Haematology (BSH). Guidelines for the Diagnosis, Investigation and Management of Polycythaemia/Erythrocytosis and Essential Thrombocythaemia. 2024.
- World Health Organization (WHO). Classification of Tumours of Haematopoietic and Lymphoid Tissues. 5th ed. 2022.
- National Comprehensive Cancer Network (NCCN). NCCN Clinical Practice Guidelines in Oncology: Myeloproliferative Neoplasms. Version 1.2025.
- Birgegard G. Anagrelide treatment in myeloproliferative disorders. Seminars in Thrombosis and Hemostasis. 2006;32(3):260–266. doi:10.1055/s-2006-942758
- Tefferi A, Barbui T. Polycythemia vera and essential thrombocythemia: 2021 update on diagnosis, risk-stratification and management. American Journal of Hematology. 2020;95(12):1599–1613. doi:10.1002/ajh.26008
- British National Formulary (BNF). Anagrelide. National Institute for Health and Care Excellence (NICE). Updated 2025.
Editorial Team
This article was written and reviewed by the iMedic Medical Editorial Team, comprising licensed specialist physicians with expertise in hematology, oncology, and clinical pharmacology.
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