Nplate (Romiplostim)
Thrombopoietin receptor agonist for immune thrombocytopenia (ITP)
Nplate (romiplostim) is a prescription biologic medicine used to treat chronic immune thrombocytopenia (ITP) in adults. It belongs to a class of drugs called thrombopoietin receptor agonists (TPO-RAs), which work by stimulating the bone marrow to produce more platelets. Nplate is administered as a weekly subcutaneous injection and is typically reserved for patients who have not responded adequately to corticosteroids, immunoglobulins, or splenectomy. This guide covers uses, dosage, side effects, drug interactions, and important safety information based on international clinical guidelines.
Quick Facts
Key Takeaways
- Nplate (romiplostim) is a biologic thrombopoietin receptor agonist that stimulates platelet production in the bone marrow to treat chronic immune thrombocytopenia (ITP).
- It is administered as a once-weekly subcutaneous injection, with doses individualised based on platelet count response, starting at 1 mcg/kg body weight.
- Common side effects include headache, upper respiratory infections, and injection site reactions; serious risks include blood clots and bone marrow changes (reticulin fibrosis).
- Stopping Nplate may cause platelet counts to drop below pre-treatment levels within 14 days, requiring careful medical monitoring during discontinuation.
- Nplate is intended for adults with ITP who have not responded to first-line therapies; regular blood monitoring is essential throughout treatment.
What Is Nplate and What Is It Used For?
Nplate contains the active substance romiplostim, a recombinant fusion protein (peptibody) produced using DNA technology in Escherichia coli bacteria. It belongs to a class of medicines known as thrombopoietin receptor agonists (TPO-RAs). By binding to and activating the thrombopoietin receptor (c-Mpl) on megakaryocyte precursor cells in the bone marrow, romiplostim stimulates the proliferation and differentiation of megakaryocytes, which are the cells responsible for producing platelets (thrombocytes).
Platelets are small blood cells that play an essential role in blood clotting and wound healing. In immune thrombocytopenia (ITP), the body's immune system mistakenly destroys its own platelets, leading to abnormally low platelet counts (thrombocytopenia). When platelet levels fall significantly below normal (typically below 30 x 109/L), patients become vulnerable to bruising, petechiae (small red spots under the skin), and potentially life-threatening bleeding episodes including gastrointestinal haemorrhage and intracranial bleeding.
Nplate is specifically indicated for the treatment of chronic immune thrombocytopenia in adult patients (aged 18 years and older) who have an insufficient response to other treatments. According to the American Society of Hematology (ASH) 2019 guidelines and the International Consensus Report, TPO-RAs such as romiplostim are recommended as second-line therapy for patients who fail initial treatment with corticosteroids, or as an alternative to splenectomy. Patients may or may not have had their spleen removed (splenectomy) and must have previously received treatment with corticosteroids or immunoglobulins without adequate response.
The mechanism of Nplate is fundamentally different from other ITP therapies. Rather than suppressing the immune destruction of platelets (as corticosteroids and rituximab do), romiplostim increases platelet production to compensate for the accelerated destruction. This approach has been shown in randomised controlled trials to be effective in raising and maintaining platelet counts above 50 x 109/L in approximately 80-90% of patients, significantly reducing the risk of bleeding and the need for rescue medications.
Romiplostim has been approved by the European Medicines Agency (EMA), the U.S. Food and Drug Administration (FDA), and regulatory authorities worldwide since 2008-2009. It was the first TPO-RA approved for ITP and has accumulated over 15 years of post-marketing safety data in clinical practice.
What Should You Know Before Taking Nplate?
Contraindications
Nplate must not be used if you have a known allergy (hypersensitivity) to romiplostim, to any of the other ingredients in this medicine (mannitol, sucrose, L-histidine, hydrochloric acid, polysorbat 20), or to any other medicines produced by DNA technology using Escherichia coli (E. coli). Allergic reactions to Nplate can include skin rash, swelling of the face, lips, tongue, or throat (angioedema), and in rare cases, anaphylaxis.
Warnings and Precautions
Before starting Nplate, tell your doctor about all of your medical conditions. Several important warnings and precautions apply to the use of romiplostim:
Thrombotic and thromboembolic risk: Nplate can raise platelet counts above normal levels, which increases the risk of blood clots. The risk of thromboembolism is particularly elevated in patients who have additional risk factors, including:
- Age 65 years or older
- Liver disease or impaired hepatic function
- Prolonged bed rest or immobility
- Active cancer or history of malignancy
- Use of oral contraceptives or hormone replacement therapy
- Recent surgery, trauma, or injury
- Obesity (body mass index ≥ 30)
- Smoking
Your doctor will carefully adjust the Nplate dose to prevent platelet counts from becoming excessively high. Thrombotic events reported with romiplostim include deep vein thrombosis (DVT), pulmonary embolism, portal vein thrombosis, and transverse sinus thrombosis.
Bone marrow changes (reticulin and fibrosis): Long-term use of Nplate may cause changes in the bone marrow. These changes can lead to the formation of abnormal blood cells or reduced blood cell production. The milder form, known as increased reticulin deposition, has been observed in clinical trials and post-marketing surveillance. Whether this can progress to a more severe form called myelofibrosis remains under investigation. Signs of bone marrow changes may appear as abnormalities in blood test results. Your doctor may recommend a bone marrow biopsy if they suspect significant changes have occurred.
Worsening of blood cancers: In patients with myelodysplastic syndromes (MDS), the use of Nplate may increase the number of blast cells (immature blood cells), potentially accelerating progression to acute myeloid leukaemia (AML). It is important that your doctor confirms you have ITP and not another condition, such as MDS, before starting Nplate. A bone marrow biopsy may be performed for diagnostic confirmation.
Loss of response: If you lose response to romiplostim or fail to maintain an adequate platelet response, your doctor will investigate potential causes. This may include assessment for increased bone marrow reticulin (fibrosis) or the development of neutralising antibodies against romiplostim that may cross-react with endogenous thrombopoietin.
Pregnancy and Breastfeeding
If you are pregnant, think you may be pregnant, or are planning to have a baby, consult your doctor before using Nplate. There is very limited clinical data on the use of romiplostim during pregnancy. Animal reproduction studies have not revealed direct harmful effects on fertility or foetal development; however, as a precaution, Nplate is not recommended during pregnancy unless the potential benefit justifies the potential risk to the foetus.
It is not known whether romiplostim is excreted in human breast milk. A decision must be made whether to discontinue breastfeeding or to discontinue Nplate therapy, taking into account the benefit of breastfeeding for the child and the benefit of treatment for the mother. If you are breastfeeding, discuss the options carefully with your healthcare provider.
Driving and Operating Machinery
Some patients may experience dizziness or other side effects that could impair their ability to drive or operate machinery safely. If you experience dizziness or any other symptoms that affect your concentration, do not drive or use machines until these effects resolve. Discuss with your doctor whether it is safe for you to perform these activities during treatment.
How Does Nplate Interact with Other Drugs?
Drug interactions with Nplate are primarily related to its effect on platelet counts and the concurrent use of other medications that affect blood clotting or platelet function. Because romiplostim is a biologic protein rather than a small molecule, it is not metabolised by cytochrome P450 enzymes and has limited potential for traditional pharmacokinetic drug interactions. However, pharmacodynamic interactions are clinically important.
Clinically Significant Interactions
| Interacting Drug | Type | Clinical Effect | Recommendation |
|---|---|---|---|
| Anticoagulants (warfarin, heparin, LMWH) | Pharmacodynamic | Increased bleeding risk; Nplate raises platelets while anticoagulants impair clotting | Monitor closely; INR checks more frequently |
| Antiplatelet agents (aspirin, clopidogrel) | Pharmacodynamic | Increased bleeding risk due to impaired platelet aggregation despite higher platelet counts | Use with caution; assess bleeding risk |
| Corticosteroids (prednisolone, dexamethasone) | Therapeutic | Combined effect on platelet counts; corticosteroid dose may be reduced or discontinued | Taper corticosteroids gradually as Nplate takes effect |
| Danazol | Therapeutic | Additive platelet-raising effect; dose reduction of danazol may be needed | Monitor platelet counts; consider dose reduction |
| Azathioprine | Therapeutic | Combined immunosuppressive and platelet-stimulating effect | May need dose reduction; regular blood monitoring |
| IVIg / Anti-D immunoglobulin | Therapeutic | Both raise platelet counts through different mechanisms; may be used as rescue therapy | Can be used concurrently for acute bleeding episodes |
Concomitant ITP Therapies
When Nplate is initiated, patients are often already receiving other ITP treatments such as corticosteroids, danazol, azathioprine, or intravenous immunoglobulin (IVIg). As romiplostim begins to increase platelet counts, your doctor may gradually reduce or discontinue these concurrent medications. This process should be done carefully and under close medical supervision, as abrupt withdrawal of corticosteroids in particular can cause adrenal insufficiency.
In clinical trials, approximately 50% of patients receiving romiplostim were able to reduce or discontinue their concurrent ITP medications within the first few months of treatment. The combination of romiplostim with other TPO-RAs (such as eltrombopag) has not been studied and is not recommended due to the unknown safety profile and risk of excessive platelet elevation.
Always inform your doctor, pharmacist, or nurse about all medications you are taking, have recently taken, or might take, including over-the-counter medicines, herbal supplements, and vitamins. This is particularly important for any medicines that affect blood clotting or the immune system.
What Is the Correct Dosage of Nplate?
Nplate dosing is highly individualised and based on your platelet count response. The medicine must be initiated and supervised by a physician experienced in the treatment of haematological diseases, particularly immune thrombocytopenia. Your doctor will regularly monitor your blood counts and adjust the dose accordingly.
Adults (18 Years and Older)
Starting Dose
The recommended starting dose is 1 microgram per kilogram of body weight, administered as a subcutaneous injection once per week. For example, a patient weighing 70 kg would receive a starting dose of 70 micrograms.
Dose Adjustments
Your doctor will adjust the weekly dose by increments of 1 mcg/kg until your platelet count reaches a level sufficient to reduce the risk of bleeding (target: ≥50 x 109/L). The dose should not be increased more frequently than once per week. The maximum recommended dose is 10 mcg/kg per week.
Dose Reduction
If your platelet count exceeds 200 x 109/L, the dose should be reduced. If platelet counts exceed 400 x 109/L, Nplate should be temporarily withheld. Once the platelet count falls below 200 x 109/L, treatment can be restarted at a dose reduced by 1 mcg/kg.
| Platelet Count | Action | Dose Adjustment |
|---|---|---|
| <50 x 109/L | Increase dose | Increase by 1 mcg/kg (max 10 mcg/kg) |
| 50–200 x 109/L | Maintain current dose | No change; continue weekly monitoring |
| >200 x 109/L for 2 consecutive weeks | Reduce dose | Decrease by 1 mcg/kg |
| >400 x 109/L | Withhold treatment | Restart at reduced dose when <200 x 109/L |
Children and Adolescents
Nplate is not recommended for use in children and adolescents under 18 years of age. The safety and efficacy of romiplostim have not been established in this age group. Paediatric ITP is managed differently from adult ITP, often with observation alone for newly diagnosed cases. If treatment is required, options include corticosteroids, IVIg, or anti-D immunoglobulin. Eltrombopag, another TPO-RA, has been approved for paediatric ITP in some jurisdictions.
Elderly Patients
No specific dose adjustment is required for elderly patients (aged 65 years and older). However, elderly patients may be at greater risk for thromboembolic events. Platelet counts and signs of thrombosis should be monitored more closely in this population. Clinical trial data included patients over 65 years of age, and the efficacy and safety profile was generally comparable to that of younger adults.
Self-Injection
After receiving appropriate training from your healthcare provider, you may be able to self-inject Nplate at home. Before self-injection is permitted, you must demonstrate that you can correctly reconstitute the powder and accurately measure and administer the prescribed dose. During the first month of self-injection, you must return to your doctor to verify your technique. Nplate must be reconstituted with the provided sterile water for injection and used immediately after preparation. Recommended injection sites include the middle of the front of the thigh, the abdomen (avoiding 5 cm around the navel), and the outer upper arm (if injected by another person). Rotate injection sites with each dose.
Missed Dose
If you miss a dose of Nplate, contact your doctor immediately to arrange for the next injection. Do not inject a double dose to make up for a missed one. Missing doses may cause your platelet count to decrease, increasing the risk of bleeding.
Overdose
In the event of an overdose, platelet counts may rise to excessively high levels, increasing the risk of thromboembolic complications. There is no specific antidote for romiplostim overdose. If overdose is suspected, your doctor will monitor you closely for signs and symptoms of adverse effects, including excessive platelet elevation and thromboembolic events. Supportive care and dose withholding are the primary management strategies. If you self-inject and accidentally use too much Nplate, contact your doctor immediately.
What Are the Side Effects of Nplate?
Like all medicines, Nplate can cause side effects, although not everybody gets them. The side effects listed below are based on data from clinical trials and post-marketing surveillance involving thousands of patients treated with romiplostim worldwide.
Very Common
May affect more than 1 in 10 patients
- Headache
- Allergic reaction
- Upper respiratory tract infection (cold, sinusitis)
Common
May affect up to 1 in 10 patients
- Bone marrow changes (increased reticulin)
- Insomnia (difficulty sleeping)
- Dizziness
- Tingling or numbness in hands or feet (paraesthesia)
- Migraine
- Flushing (skin redness)
- Pulmonary embolism (blood clot in the lungs)
- Deep vein thrombosis (blood clot in leg veins)
- Nausea, diarrhoea, abdominal pain, constipation
- Indigestion (dyspepsia)
- Itching (pruritus), bruising (contusion, ecchymosis)
- Skin rash
- Joint pain (arthralgia), muscle pain (myalgia)
- Pain in extremities, back pain, bone pain
- Muscle cramps
- Fatigue, weakness (asthenia), fever
- Chills
- Injection site reactions
- Peripheral oedema (swelling of hands and feet)
- Influenza-like symptoms
- Palpitations
- Sinusitis, bronchitis
- Angioedema (swelling of face, lips, tongue, or throat)
- Low platelet count after stopping treatment
- Higher than normal platelet count (thrombocytosis)
- Anaemia
Uncommon
May affect up to 1 in 100 patients
- Bone marrow failure, myelofibrosis
- Enlarged spleen (splenomegaly)
- Heart attack (myocardial infarction), increased heart rate
- Vertigo (dizziness with spinning sensation)
- Eye problems including blurred vision, eye bleeding, eye itching
- Vomiting, difficulty swallowing (dysphagia), acid reflux (GERD)
- Mouth ulcers (stomatitis), blood in stools
- Weight changes, decreased appetite, dehydration
- Gout
- Hair loss (alopecia), acne, dry skin, eczema
- Light sensitivity (photosensitivity)
- Depression, abnormal dreams
- Peripheral neuropathy, altered taste (dysgeusia)
- Portal vein thrombosis, transverse sinus thrombosis
- Low blood pressure (hypotension), high blood pressure
- Erythromelalgia (burning pain, redness, warmth in hands and feet)
- Aplastic anaemia, increased white blood cell count
- Elevated liver enzymes, protein in urine
Rare & Post-Marketing Reports
May affect fewer than 1 in 1,000 patients
- Multiple myeloma (reported in clinical trials)
- Severe allergic reactions (anaphylaxis)
- Neutralising antibodies against romiplostim
If any of the side effects get serious, or if you notice any side effects not listed above, please tell your doctor, pharmacist, or nurse. You can also report suspected adverse reactions to your national pharmacovigilance authority, which helps to continuously monitor the benefit-risk balance of medicines.
How Should You Store Nplate?
Proper storage of Nplate is essential to maintain the stability and effectiveness of the medicine. Store the unopened vials in a refrigerator at 2°C to 8°C (36°F to 46°F). Do not freeze Nplate. If the product has been frozen, it must not be used. Keep the medicine in its original packaging to protect it from light, as romiplostim is a light-sensitive protein.
Nplate may be removed from the refrigerator and stored at room temperature (not exceeding 25°C / 77°F) for a single period of up to 30 days, provided it remains in its original packaging. Do not return the medicine to the refrigerator after room temperature storage. Record the date when the product is first removed from the refrigerator to ensure it is used within the 30-day window.
Do not use Nplate after the expiry date printed on the vial label (EXP). The expiry date refers to the last day of the stated month. After reconstitution with the provided sterile water for injection, the solution should be used immediately. Do not store the reconstituted solution. Any remaining solution in the vial after injection must be discarded and must never be reused for another injection.
Keep Nplate out of the sight and reach of children. Do not dispose of medicines via wastewater or household waste. Ask your pharmacist how to dispose of medicines you no longer use, in accordance with local regulations for the safe disposal of medicinal waste.
What Does Nplate Contain?
Active Ingredient
The active substance is romiplostim. Each vial of Nplate 250 mcg powder for solution for injection contains a total of 375 micrograms of romiplostim. Each vial contains an overfill to ensure that 250 micrograms of romiplostim can be delivered. After reconstitution, an administrable volume of 0.5 mL contains 250 micrograms of romiplostim (500 mcg/mL).
Each vial of Nplate 500 mcg powder for solution for injection contains a total of 625 micrograms of romiplostim. After reconstitution, an administrable volume of 1 mL contains 500 micrograms of romiplostim (500 mcg/mL).
Inactive Ingredients (Excipients)
- Powder: Mannitol (E421), sucrose, L-histidine, hydrochloric acid (for pH adjustment), polysorbat 20
- Solvent: Water for injections
Appearance and Pack Sizes
Nplate is a white powder for solution for injection, supplied in a 5 mL single-use glass vial. Each self-injection preparation kit contains:
- 1 vial of 250 mcg or 500 mcg romiplostim powder
- 1 pre-filled syringe with 0.72 mL or 1.2 mL water for injections
- 1 plunger rod for the pre-filled syringe
- 1 sterile vial adapter
- 1 sterile 1 mL Luer-lock syringe
- 1 sterile safety needle
- 4 alcohol swabs
Nplate is available as individual kits or multipacks of 4 kits. Not all pack sizes may be marketed in all countries.
Marketing Authorisation Holder
Amgen Europe B.V., Minervum 7061, 4817 ZK Breda, Netherlands. For further information about Nplate, contact your local Amgen representative or visit the European Medicines Agency website for the full product information.
Frequently Asked Questions About Nplate
Nplate (romiplostim) is used to treat low platelet counts (thrombocytopenia) in adults with primary immune thrombocytopenia (ITP) who have not responded adequately to other treatments such as corticosteroids or immunoglobulins. It works by stimulating the bone marrow to produce more platelets, helping to prevent bruising and serious bleeding. Nplate is a second-line therapy and may be used regardless of whether the patient has had their spleen removed.
Nplate is given as a subcutaneous (under the skin) injection once weekly. The starting dose is 1 microgram per kilogram of body weight, adjusted by your doctor based on your platelet count response. After appropriate training, some patients may be able to self-inject at home. The recommended injection sites are the thigh, abdomen, or outer upper arm, and you should rotate sites with each injection.
The most common side effects (affecting more than 1 in 10 patients) include headache, allergic reactions, and upper respiratory tract infections. Common side effects (up to 1 in 10) include bone marrow changes, insomnia, dizziness, nausea, diarrhoea, joint and muscle pain, fatigue, injection site reactions, and peripheral oedema. Serious but less frequent risks include blood clots and bone marrow fibrosis.
Yes, Nplate can increase the risk of blood clots (thromboembolism), particularly when platelet counts become excessively high. Risk factors include older age (over 65), liver disease, immobility, cancer, use of hormonal contraceptives, recent surgery, obesity, and smoking. Your doctor will carefully monitor your platelet counts and adjust the dose to keep them within a safe range, typically between 50 and 200 x 109/L.
If you stop taking Nplate, your platelet count is likely to drop back to low levels within about 14 days. In some cases, platelet counts may fall below your pre-treatment baseline (rebound thrombocytopenia), which can increase the risk of bleeding. Never stop Nplate without consulting your doctor. After discontinuation, your platelet count should be monitored at least weekly for several weeks.
Nplate is not recommended during pregnancy unless clearly necessary and prescribed by your doctor. There is limited clinical data on the use of romiplostim in pregnant women. It is also not known whether romiplostim passes into breast milk. A decision to continue or stop breastfeeding, or to continue or stop Nplate, should be made jointly with your doctor, weighing the benefits and risks for both mother and child.
References
- European Medicines Agency (EMA). Nplate (romiplostim) - Summary of Product Characteristics. Last updated 2025. Available at: EMA - Nplate EPAR.
- Neunert C, Terrell DR, Arnold DM, et al. American Society of Hematology 2019 guidelines for immune thrombocytopenia. Blood Advances. 2019;3(23):3829-3866. doi:10.1182/bloodadvances.2019000966.
- Kuter DJ, Bussel JB, Lyons RM, et al. Efficacy of romiplostim in patients with chronic immune thrombocytopenic purpura: a double-blind randomised controlled trial. The Lancet. 2008;371(9610):395-403. doi:10.1016/S0140-6736(08)60203-2.
- Provan D, Arnold DM, Bussel JB, et al. Updated international consensus report on the investigation and management of primary immune thrombocytopenia. Blood Advances. 2019;3(22):3780-3817. doi:10.1182/bloodadvances.2019000812.
- National Institute for Health and Care Excellence (NICE). Romiplostim for treating chronic immune (idiopathic) thrombocytopenic purpura. Technology appraisal guidance [TA221]. 2011, reviewed 2023.
- Kuter DJ, Rummel M, Boccia R, et al. Romiplostim or standard of care in patients with immune thrombocytopenia. New England Journal of Medicine. 2010;363(20):1889-1899. doi:10.1056/NEJMoa1002625.
- U.S. Food and Drug Administration (FDA). Nplate (romiplostim) prescribing information. Reference ID: 5184780. Last revised 2024.
- World Health Organization (WHO). Model List of Essential Medicines - 23rd List, 2023. Geneva: WHO; 2023.
- Bussel JB, Kuter DJ, Pullarkat V, et al. Safety and efficacy of long-term treatment with romiplostim in thrombocytopenic patients with chronic ITP. Blood. 2009;113(10):2161-2171. doi:10.1182/blood-2008-04-150078.
- Rodeghiero F, Stasi R, Gernsheimer T, et al. Standardization of terminology, definitions and outcome criteria in immune thrombocytopenic purpura of adults and children. Blood. 2009;113(11):2386-2393. doi:10.1182/blood-2008-07-162503.
Editorial Team
This article has been written and medically reviewed by the iMedic Medical Editorial Team, which includes board-certified specialists in haematology, clinical pharmacology, and internal medicine. Our team follows strict evidence-based editorial guidelines aligned with international standards from the WHO, EMA, ASH, and NICE.
All content is reviewed by licensed physicians with expertise in haematology and pharmacology, ensuring clinical accuracy and adherence to current evidence-based guidelines.
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