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Last reviewed on RxList: 10/25/2019
Nplate Side Effects Center

Last reviewed on RxList 10/25/2019

What Is Nplate?

Nplate (romiplostim) is an Fc-peptide fusion protein (peptibody), a man-made form of a protein that increases production of platelets (blood-clotting cells) in the body, used to prevent bleeding episodes in people with chronic immune thrombocytopenic purpura (ITP), a bleeding condition caused by a lack of platelets in the blood. Nplate is usually given after other medications have been tried without successful treatment of symptoms.

What Are Side Effects of Nplate?

Common side effects of Nplate include:

  • headache,
  • joint or muscle pain,
  • dizziness,
  • heartburn,
  • abdominal pain,
  • stomach upset,
  • tingling or numbness in hands or feet,
  • trouble sleeping (insomnia), or
  • pain in your arms/legs/shoulder

Dosage for Nplate

The initial dose for Nplate is 1 mcg/kg based on actual body weight.

What Drugs, Substances, or Supplements Interact with Nplate?

Other drugs may interact with Nplate. Tell your doctor all medications and supplements you use.

Nplate and Pregnancy

During pregnancy, Nplate should be used only when prescribed. It is unknown if this drug passes into breast milk. Consult your doctor before breastfeeding.

Additional Information

Our Nplate (romiplostim) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


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Nplate Consumer Information

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

  • severe or ongoing diarrhea;
  • purple or red spots under your skin;
  • signs of an ear infection (more common in children)--fever, ear pain or full feeling, trouble hearing, drainage from the ear, fussiness in a child;
  • signs of a stroke--sudden numbness or weakness (especially on one side of the body), severe headache, slurred speech, balance problems;
  • signs of a blood clot in the lung--chest pain, sudden cough, wheezing, rapid breathing, coughing up blood; or
  • signs of a blood clot in your leg--swelling, warmth, or redness in an arm or leg.

Common side effects may include:

  • bruising;
  • headache;
  • dizziness;
  • muscle or joint pain;
  • pain in your arms, legs, or shoulder;
  • numbness, tingling, or swelling in your hands or feet;
  • trouble sleeping;
  • stomach pain, indigestion, diarrhea;
  • eye redness;
  • rash;
  • fever; or
  • cold symptoms such as stuffy nose, sneezing, sinus pain, cough, sore throat.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Read the entire detailed patient monograph for Nplate (Romiplostim)


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Nplate Professional Information


The following serious adverse reactions are discussed in greater detail in other sections:

  • Progression of Myelodysplastic Syndromes [see WARNINGS AND PRECAUTIONS]
  • Thrombotic/Thromboembolic Complications [see WARNINGS AND PRECAUTIONS]
  • Loss of Response to Nplate [see WARNINGS AND PRECAUTIONS]
  • Laboratory Monitoring [see WARNINGS AND PRECAUTIONS]

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

The data described below reflect Nplate exposure to 271 patients with chronic ITP, aged 18 to 88, of whom 62% were female. Nplate was studied in two randomized, placebo-controlled, double-blind studies that were identical in design, with the exception that Study 1 evaluated nonsplenectomized patients with ITP and Study 2 evaluated splenectomized patients with ITP. Data are also reported from an open-label, single-arm study in which patients received Nplate over an extended period of time. Overall, Nplate was administered to 114 patients for at least 52 weeks and 53 patients for at least 96 weeks.

In the placebo-controlled studies, headache was the most commonly reported adverse drug reaction, occurring in 35% of patients receiving Nplate and 32% of patients receiving placebo. Headaches were usually of mild or moderate severity. Table 2 presents adverse drug reactions from Studies 1 and 2 with a ≥ 5% higher patient incidence in Nplate versus placebo. The majority of these adverse drug reactions were mild to moderate in severity.

Table 2. Adverse Drug Reactions Identified in Two Placebo-Controlled Studies

Preferred Term Nplate
(n = 84)
(n = 41)
Arthralgia 26% 20%
Dizziness 17% 0%
Insomnia 16% 7%
Myalgia 14% 2%
Pain in Extremity 13% 5%
Abdominal Pain 11% 0%
Shoulder Pain 8% 0%
Dyspepsia 7% 0%
Paresthesia 6% 0%

Among 142 patients with chronic ITP who received Nplate in the single-arm extension study, the incidence rates of the adverse reactions occurred in a pattern similar to those reported in the placebo-controlled clinical studies.

Bone Marrow Reticulin Formation And Collagen Fibrosis

Nplate administration may increase the risk for development or progression of reticulin fiber formation within the bone marrow. This formation may improve upon discontinuation of Nplate. In a clinical trial, one patient with ITP and hemolytic anemia developed marrow fibrosis with collagen during Nplate therapy.

An open-label clinical trial prospectively evaluated changes in bone marrow reticulin formation and collagen fibrosis in adult patients with ITP treated with Nplate or a non-US approved romiplostim product. Patients were administered romiplostim by SC injection once weekly for up to 3 years. Based on cohort assignment at time of study enrollment, patients were evaluated for bone marrow reticulin and collagen at year 1 (cohort 1), year 2 (cohort 2), or year 3 (cohort 3) in comparison to the baseline bone marrow at start of the trial. Patients were evaluated for bone marrow reticulin formation and collagen fibrosis using the modified Bauermeister grading scale. From the total of 169 patients enrolled in the 3 cohorts, 132 (78%) patients were evaluable for bone marrow collagen fibrosis and 131 (78%) patients were evaluable for bone marrow reticulin formation. Two percent (2/132) of patients (both from cohort 3) developed Grade 4 findings (presence of collagen). There was no detectable bone marrow collagen in one patient on repeat testing 12 weeks after discontinuation of romiplostim. Progression of bone marrow reticulin formation (increase greater than or equal to 2 grades or more) or an increase to Grade 4 (presence of collagen) was reported in 7% (9/131) of patients.

Postmarketing Experience

The following adverse reactions have been identified during post approval use of Nplate. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.


As with all therapeutic proteins, patients may develop antibodies to the therapeutic protein. Patients were screened for immunogenicity to romiplostim using a BIAcore-based biosensor immunoassay. This assay is capable of detecting both high-and low-affinity binding antibodies that bind to romiplostim and cross-react with TPO. The samples from patients that tested positive for binding antibodies were further evaluated for neutralizing capacity using a cell-based bioassay.

In clinical studies in patients with ITP, the incidence of preexisting antibodies to romiplostim was 5% (53/1112) and the incidence of binding antibody development during treatment with Nplate or a non-US approved romiplostim product was 4% (50/1112). The incidence of preexisting antibodies to endogenous TPO was 4% (40/1112) and the incidence of binding antibody development to endogenous TPO during treatment was 3% (38/1112). Of the patients with positive binding antibodies that developed to romiplostim or to TPO, five patients had neutralizing activity to romiplostim and none had neutralizing activity to TPO. No apparent correlation was observed between antibody activity and clinical effectiveness or safety.

A postmarketing registry study involving patients with thrombocytopenia on Nplate or a non-US approved romiplostim product was conducted to assess the long-term consequences of the anti-romiplostim antibodies. Patients who lacked response or lost response to Nplate or a non-US approved romiplostim product were enrolled. The incidence of new binding antibody development was 3% (5/186) to romiplostim and 1% (2/186) to TPO. One patient was positive for binding antibodies to both romiplostim and TPO. Of the five patients with positive binding antibodies to romiplostim, two (1%) were positive for neutralizing antibodies to romiplostim only.

Immunogenicity assay results are highly dependent on the sensitivity and specificity of the assay used in detection and may be influenced by several factors, including sample handling, concomitant medications, and underlying disease. For these reasons, comparison of incidence of antibodies to romiplostim with the incidence of antibodies to other products may be misleading.

Read the entire FDA prescribing information for Nplate (Romiplostim)

Related Resources for Nplate

Read the Nplate User Reviews »

© Nplate Patient Information is supplied by Cerner Multum, Inc. and Nplate Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.


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