WHY is this medicine prescribed?
Marstacimab-hncq injection is used to prevent or reduce the frequency of bleeding with certain types of hemophilia A (condition in which the blood does not clot normally because of a missing or faulty blood clotting factor VII) or hemophilia B (condition in which the blood does not clot normally because of a missing or faulty blood clotting factor IX). Marstacimab-hncq is in a class of medications called hemostatic antibodies. It works by decreasing the activity of a naturally occurring substance in the body that prevents blood clotting.
HOW should this medicine be used?
Marstacimab-hncq injection comes as a solution (liquid) in prefilled syringes and prefilled pens to be injected subcutaneously (under the skin). It is given as two injections for the first dose, followed by one injection once a week.
Use marstacimab-hncq injection exactly as directed. Do not inject more or less of it or inject it more often than prescribed by your doctor.
You or a caregiver will be shown how to inject the medicine before your first dose. You will also be given the instructions for use. Read these carefully. Talk to your doctor or pharmacist if you have any questions on how to use the medicine.
Use each syringe or pen only once and inject all the solution in the syringe or pen. Do not reuse marstacimab-hncq prefilled syringes and do not recap the syringes after use. Dispose of used syringes and pens in a puncture-resistant container. Talk to your doctor or pharmacist about how to dispose of the puncture-resistant container.
If you are using a prefilled syringe or prefilled pen that has been refrigerated, place the syringe or pen on a flat surface without removing the needle cap and allow it warm to room temperature for 15 to 30 minutes before you are ready to inject the medication. Do not try to warm the medication by heating it in a microwave, placing it in hot water, or through any other method.
Do not shake a syringe or pen that contains marstacimab-lbkz injection.
Always look at marstacimab-lbkz solution before injecting it. Check that the expiration date has not passed and that the liquid is clear and colorless or pale yellow. The liquid should not contain visible particles. Do not use a syringe or dosing pen if it is cracked or broken, if it is expired, or if the liquid is cloudy or contains large or colored particles.
You can inject marstacimab-lbkz in your thigh or stomach area, except for a 2 inch the area around your belly button If someone else is giving you the injection, the back of the upper arm or buttocks may also be used. To reduce the chances of soreness or redness, use a different injection site for each injection. Do not inject the medication into an area where the skin is tender, bruised, red, or hard or where you have scars or stretch marks.
Marstacimab-lbkz controls bleeding in people with hemophilia but does not cure it. Continue to use marstacimab-lbkz injection even if you feel well. Do not stop using marstacimab-lbkz injection without talking to your doctor.
Are there OTHER USES for this medication?
This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.
What SPECIAL PRECAUTIONS should I follow?
Before using marstacimab-hncq injection,
What SPECIAL DIETARY instructions should I follow?
Unless your doctor tells you otherwise, continue your normal diet.
What should I do IF I FORGET to take a dose?
Inject the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not inject a double dose to make up for a missed one. If you are not sure when to inject marstacimab-hncq injection, call your doctor.
What SIDE EFFECTS can this medicine cause?
Marstacimab-hncq injection may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:
Some side effects can be serious. If you experience any of these symptoms, call your doctor immediately or get emergency medical treatment:
Marstacimab-hncq injection may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.
If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).
What should I do in case of OVERDOSE?
In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at http://www.poisonhelp.org/help. If the victim has collapsed, had a seizure, has trouble breathing, or can't be awakened, immediately call emergency services at 911.
What should I know about STORAGE and DISPOSAL of this medication?
Keep this medication in the container it came in, tightly closed, and out of reach of children. Store marstacimab-hncq injection in the refrigerator but do not freeze. Keep the prefilled syringes or dosing pens in their original cartons to protect them from light. If needed, marstacimab-hncq injection may be stored at room temperature for up to 7 days, but should not be returned to the refrigerator. Dispose of any unused medication that has been stored at room temperature for more than 7 days.
Keep all medication out of sight and reach of children as many containers are not child-resistant. Always lock safety caps. Place the medication in a safe location, one that is up and away and out of their sight and reach. http://www.upandaway.org
Dispose of unneeded medications in a way so that pets, children, and other people cannot take them. Do not flush this medication down the toilet. Use a medicine take-back program. Talk to your pharmacist about take-back programs in your community. Visit the FDA's Safe Disposal of Medicines website http://goo.gl/c4Rm4p for more information.
What OTHER INFORMATION should I know?
Keep all appointments with your doctor.
Before having any laboratory test, tell your doctor and the laboratory personnel that you are using marstacimab-hncq injection.
Do not let anyone else use your medication. Ask your pharmacist any questions you have about refilling your prescription.
Keep a written list of all of the prescription and nonprescription (over-the-counter) medicines, vitamins, minerals, and dietary supplements you are taking. Bring this list with you each time you visit a doctor or if you are admitted to the hospital. You should carry the list with you in case of emergencies.
This report on medications is for your information only, and is not considered individual patient advice. Because of the changing nature of drug information, please consult your physician or pharmacist about specific clinical use.
The American Society of Health-System Pharmacists, Inc. represents that the information provided hereunder was formulated with a reasonable standard of care, and in conformity with professional standards in the field. The American Society of Health-System Pharmacists, Inc. makes no representations or warranties, express or implied, including, but not limited to, any implied warranty of merchantability and/or fitness for a particular purpose, with respect to such information and specifically disclaims all such warranties. Users are advised that decisions regarding drug therapy are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and the information is provided for informational purposes only. The entire monograph for a drug should be reviewed for a thorough understanding of the drug's actions, uses and side effects. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information is not a substitute for medical care.
AHFS® Patient Medication Information™ Copyright, 2026. The American Society of Health-System Pharmacists®, 4500 East-West Highway, Suite 900, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.
Selected Revisions: August 15, 2026.