Nplate Dosage

Generic name: romiplostim
Dosage form: injection, powder, lyophilized, for solution

The information at Drugs.com is not a substitute for medical advice. ALWAYS consult your doctor or pharmacist.

Recommended Dosage Regimen

Use the lowest dose of Nplate to achieve and maintain a platelet count ≥ 50 x 109/L as necessary to reduce the risk for bleeding. Administer Nplate as a weekly subcutaneous injection with dose adjustments based upon the platelet count response.

The prescribed Nplate dose may consist of a very small volume (eg, 0.15 mL). Administer Nplate only with a syringe that contains 0.01 mL graduations.

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

Dose Adjustments
Use the actual body weight at initiation of therapy, then adjust the weekly dose of Nplate by increments of 1 mcg/kg until the patient achieves a platelet count ≥ 50 x 109/L as necessary to reduce the risk for bleeding; do not exceed a maximum weekly dose of 10 mcg/kg. In clinical studies, most patients who responded to Nplate achieved and maintained platelet counts ≥ 50 x 109/L with a median dose of 2 mcg/kg.

During Nplate therapy, assess CBCs, including platelet counts, weekly until a stable platelet count (≥ 50 x 109/L for at least 4 weeks without dose adjustment) has been achieved. Obtain CBCs, including platelet counts, monthly thereafter.

Adjust the dose as follows:

  • If the platelet count is < 50 x 109/L, increase the dose by 1 mcg/kg.
  • If platelet count is > 200 x 109/L for 2 consecutive weeks, reduce the dose by 1 mcg/kg.
  • If platelet count is > 400 x 109/L, do not dose. Continue to assess the platelet count weekly. After the platelet count has fallen to < 200 x 109/L, resume Nplate at a dose reduced by 1 mcg/kg.

Discontinuation
Discontinue Nplate if the platelet count does not increase to a level sufficient to avoid clinically important bleeding after 4 weeks of Nplate therapy at the maximum weekly dose of 10 mcg/kg [see Warnings and Precautions (5.5)]. Obtain CBCs, including platelet counts, weekly for at least 2 weeks following discontinuation of Nplate [see Warnings and Precautions (5.6)].

Preparation and Administration

To mitigate against medication errors (both overdose and underdose), ensure that these preparation and administration instructions are followed.

Calculate the dose and reconstitute with the correct volume of sterile water for injection.  Withdraw the appropriate volume of the calculated dose from the vial.  Only administer subcutaneously [see Overdosage (10)].

Nplate is supplied in single-use vials as a sterile, preservative-free, white lyophilized powder that must be reconstituted as outlined in Table 1 and administered using a syringe with 0.01 mL graduations.  Using aseptic technique, reconstitute Nplate with preservative-free Sterile Water for Injection, USP as described in Table 1.  Do not use bacteriostatic water for injection.

Table 1. Reconstitution of Nplate Single-Use Vials
*
Use preservative-free Sterile Water for Injection.
Nplate
Single-Use Vial
 Total Vial Content
of Nplate
  Sterile Water
for Injection*
   Deliverable
Product and Volume
Final 
Concentration
 250 mcg 375 mcg  add  0.72 mL   =  250 mcg in 0.5 mL    500 mcg/mL 
 500 mcg 625 mcg  add  1.2 mL  =  500 mcg in 1 mL  500 mcg/mL

Gently swirl and invert the vial to reconstitute.  Avoid excess or vigorous agitation: DO NOT SHAKE. Generally, dissolution of Nplate takes less than 2 minutes.  The reconstituted Nplate solution should be clear and colorless.  Visually inspect the reconstituted solution for particulate matter and/or discoloration.  Do not administer Nplate if particulate matter and/or discoloration is observed.

Reconstituted Nplate can be kept at room temperature (25°C/77°F) or refrigerated at 2° to 8°C (36° to 46°F) for up to 24 hours prior to administration. Protect the reconstituted product from light.

To determine the injection volume to be administered, first identify the patient’s total dose in micrograms (mcg) using the dosing information in Section 2.1.  For example, a 75 kg patient initiating therapy at 1 mcg/kg will begin with a dose of 75 mcg.  Next, calculate the volume of Nplate solution that is given to the patient by dividing the microgram dose by the concentration of the reconstituted Nplate solution (500 mcg/mL).  For this patient example, the 75 mcg dose is divided by 500 mcg/mL, resulting in an injection volume of 0.15 mL.

As the injection volume may be very small, use a syringe with graduations to 0.01 mL. Verify that the syringe contains the correct dosage.

Discard any unused portion.  Do not pool unused portions from the vials.  Do not administer more than one dose from a vial.

Use of Nplate With Concomitant Medical ITP Therapies

Nplate may be used with other medical ITP therapies, such as corticosteroids, danazol, azathioprine, intravenous immunoglobulin (IVIG), and anti-D immunoglobulin. If the patient’s platelet count is ≥ 50 x 109/L, medical ITP therapies may be reduced or discontinued [see Clinical Studies (14.1)].

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