Fitusiran Dosage

Medically reviewed by Drugs.com. Last updated on May 5, 2025.

Usual Adult Dose for Hemophilia A

Initial dose: 50 mg subcutaneously every 2 months
Maintenance dose: Adjust dose and/or interval to maintain antithrombin (AT) activity between 15 to 35%

Comments:

• Monitor AT activity prior to therapy and during treatment as recommended by the manufacturer; use an FDA-approved test.
• Do not initiate treatment if AT activity is less than 60%.

Use: For routine prophylaxis to prevent or reduce the frequency of bleeding episodes in patients with hemophilia A or B with or without factor VIII or IX inhibitors

Usual Adult Dose for Hemophilia B

Initial dose: 50 mg subcutaneously every 2 months
Maintenance dose: Adjust dose and/or interval to maintain antithrombin (AT) activity between 15 to 35%

Comments:

• Monitor AT activity prior to therapy and during treatment as recommended by the manufacturer; use an FDA-approved test.
• Do not initiate treatment if AT activity is less than 60%.

Use: For routine prophylaxis to prevent or reduce the frequency of bleeding episodes in patients with hemophilia A or B with or without factor VIII or IX inhibitors

Usual Adult Dose for Hemophilia A with Inhibitors

Initial dose: 50 mg subcutaneously every 2 months
Maintenance dose: Adjust dose and/or interval to maintain antithrombin (AT) activity between 15 to 35%

Comments:

• Monitor AT activity prior to therapy and during treatment as recommended by the manufacturer; use an FDA-approved test.
• Do not initiate treatment if AT activity is less than 60%.

Use: For routine prophylaxis to prevent or reduce the frequency of bleeding episodes in patients with hemophilia A or B with or without factor VIII or IX inhibitors

Usual Adult Dose for Hemophilia B with Inhibitors

Initial dose: 50 mg subcutaneously every 2 months
Maintenance dose: Adjust dose and/or interval to maintain antithrombin (AT) activity between 15 to 35%

Comments:

• Monitor AT activity prior to therapy and during treatment as recommended by the manufacturer; use an FDA-approved test.
• Do not initiate treatment if AT activity is less than 60%.

Use: For routine prophylaxis to prevent or reduce the frequency of bleeding episodes in patients with hemophilia A or B with or without factor VIII or IX inhibitors

Usual Pediatric Dose for Hemophilia A

12 YEARS AND OLDER:
Initial dose: 50 mg subcutaneously every 2 months
Maintenance dose: Adjust dose and/or interval to maintain antithrombin (AT) activity between 15 to 35%

Comments:

• Monitor AT activity prior to therapy and during treatment as recommended by the manufacturer; use an FDA-approved test.
• Do not initiate treatment if AT activity is less than 60%.

Use: For routine prophylaxis to prevent or reduce the frequency of bleeding episodes in patients with hemophilia A or B with or without factor VIII or IX inhibitors

Usual Pediatric Dose for Hemophilia B

12 YEARS AND OLDER:
Initial dose: 50 mg subcutaneously every 2 months
Maintenance dose: Adjust dose and/or interval to maintain antithrombin (AT) activity between 15 to 35%

Comments:

• Monitor AT activity prior to therapy and during treatment as recommended by the manufacturer; use an FDA-approved test.
• Do not initiate treatment if AT activity is less than 60%.

Use: For routine prophylaxis to prevent or reduce the frequency of bleeding episodes in patients with hemophilia A or B with or without factor VIII or IX inhibitors

Usual Pediatric Dose for Hemophilia A with Inhibitors

12 YEARS AND OLDER:
Initial dose: 50 mg subcutaneously every 2 months
Maintenance dose: Adjust dose and/or interval to maintain antithrombin (AT) activity between 15 to 35%

Comments:

• Monitor AT activity prior to therapy and during treatment as recommended by the manufacturer; use an FDA-approved test.
• Do not initiate treatment if AT activity is less than 60%.

Use: For routine prophylaxis to prevent or reduce the frequency of bleeding episodes in patients with hemophilia A or B with or without factor VIII or IX inhibitors

Usual Pediatric Dose for Hemophilia B with Inhibitors

12 YEARS AND OLDER:
Initial dose: 50 mg subcutaneously every 2 months
Maintenance dose: Adjust dose and/or interval to maintain antithrombin (AT) activity between 15 to 35%

Comments:

• Monitor AT activity prior to therapy and during treatment as recommended by the manufacturer; use an FDA-approved test.
• Do not initiate treatment if AT activity is less than 60%.

Use: For routine prophylaxis to prevent or reduce the frequency of bleeding episodes in patients with hemophilia A or B with or without factor VIII or IX inhibitors

Renal Dose Adjustments

Data not available

Liver Dose Adjustments

Liver dysfunction (Child-Pugh A, B, or C): Avoid use

For ALT/AST greater than 5 times the upper limit of normal: Interrupt therapy; consider benefit vs. risk of resuming treatment after resolution.

• For recurrence, or for jaundice (total bilirubin at least 2.5 mg/dL) secondary to hepatotoxicity: Permanently discontinue treatment.

Dose Adjustments

DOSE MODIFICATIONS BASED ON ANTITHROMBIN (AT) ACTIVITY:
General Recommendations:

• Measure AT activity using an FDA-cleared test at Weeks 4 (Month 1), 12 (Month 3), 20 (Month 5) and 24 (Month 6) following the starting dose and after any dose modification.
• For AT activity less than 15%, a dose reduction is required and should be initiated 3 months after prior dose.
• For AT activity greater than 35% after 6 months or if satisfactory bleed control is not achieved, consider dose escalation.
• Once the patient's target dose is identified based on AT activity 15-35%, measure AT activity annually. Additional measurements can be considered if bleeding control is not adequate.
• Review the recommended AT monitoring schedule and dosing table in the manufacturer product information.

Current dose 50 mg every 2 months:

• AT activity level less than 15%: Reduce to 20 mg subcutaneously every 2 months
• AT activity level 15 to 35%: Continue current dosage
• AT activity level greater than 35% after 6 months: Increase to 50 mg subcutaneously once a month

Current dose 20 mg every 2 months:

• AT activity level less than 15%: Reduce to 10 mg subcutaneously every 2 months
• AT activity level 15 to 35%: Continue current dosage
• AT activity level greater than 35% after 6 months: Increase to 20 mg subcutaneously once a month

Current dose 10 mg every 2 months:

• AT activity level less than 15%: Discontinue therapy
• AT activity level 15 to 35%: Continue current dosage
• AT activity level greater than 35% after 6 months: Increase to 10 mg subcutaneously once a month

MANAGEMENT OF BREAKTHROUGH BLEEDING:
Use of Clotting Factor Concentrates (CFC) or Bypassing Agents (BPA) During Therapy:

• Within 7 days of therapy initiation: Manage using the patient's prior dosing regimen of CFC or BPA.
• After 7 days of therapy: Consult the CFC/BPA dose modification table in the manufacturer product information.
• Initially, reduce the weight-based dose and double the dosing interval as compared to standard dosing.
• If hemostatic control is not achieved, higher dose/frequency may be used based on clinical judgement.
• Six months after therapy cessation: Standard doses of CFC or BPA may be used; however, if bleeding occurs prior, monitor AT activity level before dosing.

PERIOPERATIVE RECOMMENDATIONS:
For Major and Minor Surgical Procedures:

• Utilize bleed management guidelines during the perioperative period for hemostatic management.
• In clinical studies, patients with hemophilia A or B (with or without inhibitors) underwent major/minor surgical procedures without discontinuing therapy with this drug.

RECOMMENDED MODIFICATIONS FOR ADVERSE EVENTS:

• Gallbladder Disease: Consider interruption or discontinuation of therapy.
• Thrombotic Events: Interrupt therapy and manage as clinically indicated.

Precautions

US BOXED WARNINGS:

• THROMBOTIC EVENTS: Serious thrombotic events have occurred in patients with risk factors for thromboembolism including persistent AT activity less than 15%, use of 80 mg once monthly doses, presence of indwelling venous catheters, and in the post-operative setting when bleed management guidelines were not followed. Monitor AT activity using an FDA-cleared test and target AT activity at 15 to 35% to reduce the risk of thrombosis. Monitor patients for signs and symptoms of thrombotic events. Interrupt therapy in patients with a thrombotic event and manage as clinically indicated.
• ACUTE AND RECURRENT GALLBLADDER DISEASE: Acute and recurrent gallbladder disease, including cholelithiasis and cholecystitis have occurred during therapy; some cases required cholecystectomy or had complications (e.g., pancreatitis) related to gallbladder disease. Monitor patients for signs/symptoms of acute and recurrent gallbladder disease. Consider interruption or discontinuation of treatment if gallbladder disease occurs. Consider alternative therapy for hemophilia in patients with a history of symptomatic gallbladder disease.

CONTRAINDICATIONS: None

Safety and efficacy have not been established in patients younger than 12 years.

Consult WARNINGS section for additional precautions.

Dialysis

Data not available

Other Comments

Administration advice:

• Consult the manufacturer product information for detailed recommendations on drug administration and monitoring.
• Prior to starting therapy, measure AT activity; do not initiate treatment if AT activity is less than 60%.
• Prophylaxis with CFC or BPA may be continued during the first 7 days of treatment, but should be discontinued 7 days after the initial dose of this drug.
• Administer subcutaneously into the thigh or abdomen, or upper arm (if given by a caregiver); avoid injection into a vein or tender, damaged, bruised, or scarred skin, or within 2 inches (5 cm) of the navel.
• If administered by a patient/caregiver, ensure proper training prior to first use; pediatric patients should be supervised during self-injection or have an adult administer injection.
• If a dose is missed, administer as soon as possible and resume the usual dosing schedule from the last dose (e.g., once a month, or every 2 months).

Storage requirements:

• Prefilled Pen: Store refrigerated at 2C to 8C (36F to 46F) in the original carton to protect from light.
• May store at room temperature between 15C to 30C (59F to 86F) for a single period of up to 3 months.
• Discard after labeled expiration date or after 3 months at room temperature, whichever comes first.
• Vial: Store refrigerated or at room temperature in the original carton to protect from light.
• After storing pens or vials at room temperature, do not return to the refrigerator.
• Do not heat, freeze, or place in direct sunlight.

Reconstitution/preparation techniques:

• Refer to the manufacturer product information for illustrated instructions on preparation/administration.
• Bring refrigerated product to room temperature for at least 30 minutes before use; do not shake.
• Inspect product for discoloration or flakes/particles; do not use if discolored/cloudy, dropped, or damaged.

General:

• Treatment should be supervised by a health care provider experienced in the treatment of hemophilia or bleeding disorders.
• Information on FDA-cleared tests for AT activity is available at: http://www.fda.gov/CompanionDiagnostics.
• The combined use of antifibrinolytics with CFC or BPA has not been studied.

Monitoring:

• Cardiovascular: For signs/symptoms of thrombotic events (during therapy)
• Hematologic: Assess AT activity level:
• After the first dose or after any dose modification at week 4, week 12, week 20, and week 24
• Annually once target dose is determined
• As indicated if bleeding control is not adequate
• As indicated within 6 months of treatment cessation if CFC/BPA is required for bleeding management
• Hepatic: ALT, AST and total bilirubin (prior to therapy, monthly for at least the first 6 months, monthly for at least 6 months after dose increases, and then periodically as indicated)

Patient advice:

• Read the US FDA-approved patient labeling (Medication Guide and Instructions for Use).
• Discuss use of CFC or BPA during therapy with your health care provider prior to administration.
• Recognize the signs/symptoms of thrombotic events, gallbladder disease, and hepatotoxicity; seek medical attention if they occur.
• Understand proper preparation and administration of this drug before first use.
• Speak to a healthcare provider if you are pregnant, intend to become pregnant, or are breastfeeding.

See also:

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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