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Coagulation Factor Replacement — Haemophilia B Pregnancy: §4.6: 'Animal reproduction studies have not been conducted with factor IX. Based on the rare occurrence of haemophilia B in women, experience regarding the use of factor IX during pregnancy and breastfeeding is not available. Therefore, factor IX should be used during pregnancy and breast-feeding only if clearly indicated. The effect of BeneFIX on fertility has not been established.' No pregnancy category letter is assigned in the UK SPC.

Factor IX Concentrate

Brand names: BeneFIX, Idelvion, Refixia (extended half-life)

Factor IX concentrate is a clotting factor replacement product used for the prevention and treatment of bleeding in haemophilia B (factor IX deficiency), and around surgery in affected patients.

Adult dose

Dose: BeneFIX only (recombinant factor IX, standard half-life) — treatment and prophylaxis of bleeding in haemophilia B (§4.1). §4.2: dose and duration 'depend on the severity of the factor IX deficiency, on the location and extent of bleeding, and on the patient's clinical condition.' ON-DEMAND TREATMENT is dosed to a target plasma factor IX level. §4.2: 'one unit of factor IX activity per kg body weight is expected to increase the circulating level of factor IX, an average of 0.8 IU/dL (range from 0.4 to 1.4 IU/dL) in patients ≥ 12 years'. Factor IX activity 'should not fall below' these levels (§4.2 table): early haemarthrosis, muscle bleeding or oral bleeding 20-40 IU/dL; more extensive haemarthrosis, muscle bleeding or haematoma 30-60; life-threatening haemorrhage 60-100; minor surgery (including tooth extraction) 30-60; major surgery 80-100 (pre- and postoperative). ⚠️ The SPC's formula for converting a target level into an IU dose is a graphic that did NOT come through the text fetch, so no IU/kg bleeding dose is stated here — read the formula from the SPC itself. LONG-TERM PROPHYLAXIS: the SPC gives only a clinical-study average, not a fixed recommended dose — §4.2: 'In a clinical study for routine secondary prophylaxis the average dose for previously treated patients (PTP) was 40 IU/kg (range 13 to 78 IU/kg) at intervals of 3 to 4 days. In some cases, especially in younger patients, shorter dosage intervals or higher doses may be necessary.' Children: use a children's formulary and the haemophilia centre — no paediatric dose is published here.
Route: Intravenous infusion after reconstitution of the lyophilised powder with sterile 0.234% sodium chloride solution. §4.2: 'BeneFIX should be administered at a slow infusion rate. In most of the cases, an infusion rate of up to 4 mL per minute has been used. The rate of administration should be determined by the patient's comfort level.' 'Administration by continuous infusion has not been approved and is not recommended.'
Frequency: On-demand, per the §4.2 table: early haemarthrosis, muscle or oral bleeding — 'Repeat every 24 hours. At least 1 day, until the bleeding episode as indicated by pain is resolved or healing is achieved'; more extensive haemarthrosis, muscle bleeding or haematoma — 'Repeat infusion every 24 hours for 3-4 days or more until pain and acute disability are resolved'; life-threatening haemorrhage — 'Repeat infusion every 8 to 24 hours until threat is resolved'; minor surgery — 'Every 24 hours, at least 1 day, until healing is achieved'; major surgery — 'Repeat infusion every 8-24 hours until adequate wound healing, then therapy for at least another 7 days to maintain a factor IX activity of 30% to 60% (IU/dL)'. Prophylaxis: intervals of 3 to 4 days in the clinical study. §4.2: 'The amount to be administered and the frequency of administration should always be oriented to the clinical effectiveness in the individual case.'
SCOPE: this record covers BeneFIX only. The page also names Idelvion and Refixia (extended half-life factor IX products) whose SPCs are NOT in the bundle; the 0.8 IU/dL recovery and the 3-to-4-day prophylaxis interval above are BeneFIX values and must not be applied to an extended half-life product. Plasma-derived factor IX concentrates are likewise not covered. PRESCRIBING SETTING, §4.2: 'Treatment should be under the supervision of a physician experienced in the treatment of haemophilia.' §4.2: 'Dose based on bodyweight may require adjustment in underweight or overweight patients.' §4.2: aPTT-based one-stage clotting assay results 'can be significantly affected by both the type of aPTT reagent and the reference standard used in the assay'. PAEDIATRIC / ELDERLY: §4.1 says BeneFIX 'can be used for all age groups'; no paediatric figure is drafted because the only paediatric dosing in §4.2 is an observed trial mean, not a recommended dose, and §4.2 says the amount and frequency 'should always be oriented to the clinical effectiveness in the individual case'. §4.2 elderly: 'dose selection for an elderly patient should be individualised.' ADMINISTRATION HAZARD, §4.2: if agglutination of red blood cells is seen in the tubing or syringe, 'discard all this material (tubing, syringe and BeneFIX solution) and resume administration with a new package.'

Dose adjustments

Renal

No renal dose adjustment is stated in the retrieved sections. §4.4: 'Nephrotic syndrome has been reported following attempted immune tolerance induction in haemophilia B patients with factor IX inhibitors and a history of allergic reaction.'

Hepatic

No hepatic dose adjustment is stated. §4.4: 'clinical surveillance for early signs of thrombotic and consumptive coagulopathy should be initiated with appropriate biological testing when administering this product to patients with liver disease'; the benefit of treatment 'should be weighed against the risk of these complications'.

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via the eMC — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • §4.3: 'Hypersensitivity to the active substance or to any of the excipients listed in section 6.1.'
  • §4.3: 'Known allergic reaction to hamster proteins.'

Side effects

  • §4.8: hypersensitivity or allergic reactions, 'which may include angioedema, burning and stinging at the infusion site, chills, flushing, generalised urticaria, headache, hives, hypotension, lethargy, nausea, restlessness, tachycardia, tightness of the chest, tingling, vomiting, wheezing', which 'may in some cases progress to severe anaphylaxis (including shock)'; in some cases these have occurred in close temporal association with development of factor IX inhibitors.
  • §4.8 table (the flattened text does not preserve the frequency columns reliably, so no frequency is assigned here): infusion-site cellulitis; factor IX inhibition; hypersensitivity; anaphylactic reaction; headache; dizziness; dysgeusia; somnolence; tremor; visual impairment; tachycardia; phlebitis; flushing; hypotension; superior vena cava syndrome; deep vein thrombosis; thrombosis; thrombophlebitis; cough; vomiting; nausea; rash; urticaria; renal infarct; pyrexia; chest discomfort; infusion-site reaction; infusion-site pain.
  • §4.8: development of neutralising antibodies (inhibitors) to factor IX — 'If such inhibitors occur, the condition will manifest itself as an insufficient clinical response. In such cases, it is recommended that a specialised haemophilia centre be contacted.'
  • §4.8: 'Nephrotic syndrome has been reported following attempted immune tolerance induction in haemophilia B patients with factor IX inhibitors and a history of allergic reaction.'
  • §4.8: 'Very rarely development of antibodies to hamster protein with related hypersensitivity reactions has been observed.'
  • §4.8: 'There is a potential risk of thromboembolic episodes following the administration of factor IX products, see section 4.4.'
  • §4.4: post-marketing reports of thrombotic events, including life-threatening superior vena cava (SVC) syndrome in critically ill neonates, while receiving continuous-infusion BeneFIX through a central venous catheter.
  • ⚠️ This list is INCOMPLETE — the fetched §4.8 table is cut off at the source-fetch limit partway through 'Inadequate therapeutic…'.

Interactions

  • §4.5: 'No interactions of human coagulation factor IX (rDNA) products with other medicinal products have been reported.'

Monitoring

  • §4.2: 'During the course of treatment, appropriate determination of factor IX levels is advised to guide the dose to be administered and the frequency of repeated infusions. Individual patients may vary in their response to factor IX, demonstrating different half-lives and recoveries.'
  • §4.2: 'In the case of major surgical interventions in particular, precise monitoring of the substitution therapy by means of coagulation analysis (plasma factor IX activity) is indispensable.'
  • §4.4: monitor for factor IX inhibitors — 'patients treated with BeneFIX should be carefully monitored for the development of factor IX inhibitors that should be titrated in Bethesda Units using appropriate biological testing.' Patients experiencing allergic reactions 'should be evaluated for the presence of an inhibitor'.
  • §4.4: 'the initial administrations of factor IX should, according to the treating physician's judgement, be performed under medical observation where proper medical care for allergic reactions could be provided.'
  • §4.4: patients with known major deletion mutations of the factor IX gene 'should be observed closely for signs and symptoms of acute hypersensitivity reactions, particularly during the early phases of initial exposure to product.'
  • §4.4: 'clinical surveillance for early signs of thrombotic and consumptive coagulopathy should be initiated with appropriate biological testing when administering this product to patients with liver disease, to patients post-operatively, to new-born infants, or to patients at risk of thrombotic phenomena or DIC.'
  • §4.4 traceability: 'the name and the batch number of the administered product should be clearly recorded.'
  • §4.2: aPTT-based one-stage clotting assay results are affected by the reagent and reference standard used — 'This is of importance particularly when changing the laboratory and/or reagents used in the assay.'

Clinical monograph

How it works

It replaces the deficient coagulation factor IX, restoring the intrinsic pathway of the clotting cascade so that adequate thrombin and a stable fibrin clot can form.

Prescribing in practice

  • Development of inhibitory antibodies to factor IX can occur and may be accompanied by allergic or anaphylactic reactions, so initial exposures should be monitored and inhibitor testing performed if response is inadequate.
  • Thrombotic and disseminated intravascular coagulation risk is greater with older prothrombin-complex-type products, so a high-purity or recombinant factor IX product is preferred where available.
  • As a product that may be plasma-derived, appropriate viral-safety counselling and immunisation against hepatitis A and B are advised.

Monitoring

Monitor factor IX levels to guide dosing, watch for inhibitor development if response wanes, and observe for signs of thrombosis with high-dose or prothrombin-complex-type products.

Counselling the patient

  • Report any allergic-type reaction such as wheeze, swelling or rash during or after an infusion immediately.
  • Tell the haemophilia centre if injections seem less effective, as this may indicate an inhibitor.
  • Keep accurate treatment records and ensure recommended hepatitis vaccinations are up to date.

Evidence & guidelines

Factor IX replacement is the cornerstone of haemophilia B management in UK haemophilia centres, with product selection and inhibitor surveillance reflected in national haemophilia guidance.

Reference: UKHCDO Guidelines; BSH Haemophilia Guidelines 2018; World Federation of Haemophilia; Confirm identity and dosing against the manufacturer SPC (eMC) and NICE. Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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