Nplate (Romiplostim): A Comprehensive Guide

Nplate is a medication that is in the form of a subcutaneous injection typically prescribed to treat immune thrombocytopenia (a condition characterized by low platelet count) in adults and pediatric patients when previous treatments like corticosteroids, splenectomy, or immunoglobulins do not give promising results. 

This branded medication was first approved by the FDA in 2008 and is also known by its generic name, “romiplostim.” It belongs to the class of thrombopoietin receptor agonists (drug agents that stimulate platelet production).

Nplate is only available in a branded form and comes in single-dose vials of different strengths. 

What Is Nplate Used To Treat?

Nplate is indicated to treat immune thrombocytopenia (ITP), an autoimmune condition in which a patient’s immune system produces autoantibodies that mistakenly attack and destroy the platelets, resulting in a low platelet level in the blood. 

Platelets are a type of blood cell produced by the bone marrow and circulate in the blood. Normally, these cells aggregate (stick together) during injury or cuts to seal the damaged blood vessels and limit excess blood loss. 

However, in ITP, the patient’s body experiences trouble stopping bleeding due to low platelet counts, which eventually increases the risk of severe internal or external bleeds or bruising. 

Nplate is used to keep the platelet count at least at or above 50,000/µL to prevent bleeding episodes or bruises associated with ITP. The FDA has only approved the drug to treat low platelet counts caused by ITP, not by other medical conditions such as myelodysplastic syndrome (MDS). 

In some cases, Nplate is also used to increase the survival rate in patients whose bone marrow has been affected due to exposure to myelosuppressive (suppressing the bone marrow) doses of radiation. 

How Does Nplate Work?

Nplate contains an active component called “romiplostim” that mimics the action of thrombopoietin (TPO). TPO is a hormone naturally produced mainly by the liver to regulate blood platelet production. This hormone stimulates the production of platelets in the bone marrow in order to maintain the level of platelet cells in the blood. 

Romiplostim has been designed in such a way that it attaches to the same target (bone marrow), just like natural thrombopoietin (TPO), and stimulates the bone marrow to produce more platelets in patients with ITP. In other words, Nplate works to increase the platelet level and reduce the risk of bleeding in ITP patients. 

How Long Does It Take for Nplate To Work?

The effectiveness of Nplate may vary from person to person. In some patients, the drug typically starts to increase platelet levels at 4 to 9 days after the dose injection, and peak platelet counts are usually achieved at 12 to 16 days after the dose injection. 

Nplate Dosage Form and Strength

Nplate comes in single-dose vials that contain a sterile lyophilized, solid white powder of the following strengths:

• 125 mcg (micrograms)
• 250 mcg
• 500 mcg

The powder is first reconstituted with sterile water to form a solution and then given to patients as a subcutaneous injection (under the skin). 

Nplate Dosing Information

The dose of Nplate is calculated according to the patient’s weight. The dose can then be adjusted according to the response to the treatment and platelet count (targeting to maintain platelet count at or above 50,000/mm3) as necessary to reduce the risk of bleeding.

Nplate should not be used to normalize platelet counts.

For Adults and Pediatrics With ITP

The initial dose is calculated according to the actual body weight of an adult or pediatric patient. The initial dose is 1 mcg/kg given once a week. 

After the initial dose, future doses are adjusted according to the platelet count. The weekly dose is adjusted with increments of 1 mcg/kg until the patient (adult/pediatric) achieves a platelet count of 50,000/mm3 or greater. 

The maximum weekly doses should not exceed 10 mcg/kg.

For Adult and Pediatric Patients with Hematopoietic Syndrome of Acute Radiation Syndrome (HSARS)

Adult and pediatric patients, including neonates with HSARS, receive one dose of 10 mcg/kg as a subcutaneous injection immediately after exposure to radiation. 

Overdose/Missed Dose of Nplate

If you have missed your dose, call your healthcare provider to arrange for your next dose as soon as possible. In case of overdose, consult your healthcare provider, as a high level of platelets in the body may increase the risk of blood clotting. 

How Is Nplate Given?

Nplate injection is only given subcutaneously (under the skin) using a syringe. It can only be obtained via a doctor’s prescription.

You may NOT give injections to yourself.

Is Nplate a Form of Chemotherapy?

No, Nplate is not chemotherapy but a prescription medicine used to treat low blood platelets in ITP patients.  

Possible Side Effects

Like all medications, Nplate may cause some side effects. 

The most common side effects (affecting more than 1 in 10 patients) in adults with ITP include:

• Headache and dizziness
• Allergic reaction (swelling, itching, rashes)
• Upper respiratory tract infections
• Insomnia

The most common side effects reported in children and adolescents with ITP include:

• Nose and throat infection (upper respiratory tract infections)
• Diarrhea and abdominal pain
• Runny nose, cough, and fever
• Rash and bruising
• Mouth and throat pain
• Pyrexia
• Oropharyngeal pain
• Contusion

The less common or adverse side effects (affecting up to 1 in 100 patients) you may experience include:

• Thrombotic/thromboembolic complications due to high platelet levels 
• Progression of MDS (myelodysplastic syndrome)
• Bone marrow failure due to reticulin fiber formation within the bone marrow
• Muscle tightness, muscle weakness
• Loss of response to Nplate
• A condition called erythromelalgia (a rare condition that causes episodes of burning pain and redness in the feet and sometimes the hands, arms, legs, ears, and face)

These are not all the possible side effects that might be caused by Nplate. Speak to your doctor or pharmacist for more information.

Precautions

Nplate is not for every patient who has a low platelet count. You should consult your healthcare provider before taking an Nplate injection if you:

• Are pregnant, as this drug may harm your unborn baby. 
• Are planning to become pregnant. If you’re receiving an Nplate injection, then you must use birth control. 
• Are breastfeeding or planning to breastfeed. Since the data on Nplate secretion in breast milk is limited, avoid taking Nplate in such cases as it is NOT recommended.
• Have MDS (a type of bone marrow cancer). Taking Nplate may worsen the condition and increase the risk of progression of MDS to AML (acute myeloid leukemia). 

Cost 

The cost of Nplate varies depending on several factors, such as location and pharmacy. Ask your pharmacist to get an exact cost.