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Recombinant factor XIII A-subunit Pregnancy: §4.6: 'There are no studies in pregnant women investigating drug associated risks. There are limited amount of data from the clinical use of NovoThirteen in pregnant women and available data do not show any negative effects on the health of the foetus/new-born child or for the pregnant woman. The use of NovoThirteen may be considered during pregnancy only if clearly indicated.' Breast-feeding: 'It is unknown whether rFXIII is excreted in human breast milk... A decision on whether to continue/discontinue breast-feeding or to continue/discontinue therapy with NovoThirteen should be made taking into account the benefit of breast-feeding to the child and the benefit of NovoThirteen therapy to the mother.' Fertility: 'No effects on reproductive organs have been seen in non-clinical studies. There are no human data on potential effects on fertility.'

Factor XIII A-subunit (Specialist drug)

Brand names: NovoThirteen

Factor XIII A-subunit concentrate is a specialist clotting factor replacement used for prophylaxis and treatment of bleeding in congenital factor XIII A-subunit deficiency.

Adult dose

Dose: Congenital factor XIII A-subunit deficiency — routine prophylaxis: 35 IU/kg body weight once monthly (every 28 days ± 2 days), administered as an intravenous bolus injection. Treatment of bleeds: 'If a breakthrough bleed occurs during regular prophylaxis, it is recommended to treat with a single dose of 35 IU/kg body weight administered as an intravenous bolus injection. If bleeds occur in a patient who is not on regular prophylaxis, a single dose of 35 IU/kg body weight as an intravenous bolus injection may be administered at the discretion of the treating physician in order to control the bleed.'
Route: Intravenous — §4.2: 'The preparation should be administered immediately after reconstitution as a slow bolus intravenous injection at a rate not higher than 2 ml/minute.'
Frequency: Prophylaxis: once monthly (every 28 days ± 2 days). Bleeds: a single dose.
⚠️ POTENCY IS PRODUCT-SPECIFIC — §4.2, verbatim: 'The potency of this medicinal product is expressed in international units (IU). Although expressed in the same unit (IU), the posology of NovoThirteen is different from the dosing schedule of the other FXIII containing products (see section 4.4).' §4.4 repeats: 'careful attention should be paid to the calculation of the appropriate dose for the individual patient'. Do not apply these IU/kg figures to plasma-derived FXIII concentrates. DOSE VOLUME, verbatim: 'Based on the actual concentration of NovoThirteen, the volume (in millilitres) to be administered to patients weighing at least 24 kg can be calculated from the formula below: Dose volume in ml = 0.042 x subject body weight (kg).' No single reconstituted concentration figure is stated in the fetched sections, so none is published. DOSE ADJUSTMENT, verbatim: 'Dose adjustment can be considered necessary by the physician in certain situations where the prevention of bleeding is not appropriately covered by the recommended 35 IU/kg/month dose. This dose adjustment should be based on FXIII activity levels.' No maximum dose is stated in this SPC, so no ceiling is published. INITIATION: 'Treatment should be initiated under the supervision of a doctor experienced in the treatment of rare bleeding disorders. The congenital factor XIII A-subunit deficiency should be confirmed by appropriate diagnostic procedures including factor XIII activity and immunoassay and if applicable genotyping.' MINOR SURGERY: 'It is recommended that minor surgery, including tooth extraction is done in connection with prophylactic dosing. Otherwise, an additional dose can be given if needed. The dose should be based on the FXIII activity levels.' NOT EFFECTIVE IN B-SUBUNIT DEFICIENCY (§4.4): 'NovoThirteen is not effective if used for monthly prophylactic treatment of bleeding in patients with congenital FXIII B-subunit deficiency... The subunit deficiency of patients should be determined prior to treatment.' Some sections of the product information we used were incomplete — check the full SPC.

Paediatric dose

Dose: 35 IU/kg
Route: Intravenous bolus injection at a rate not higher than 2 ml/minute
Frequency: Prophylaxis: once monthly (every 28 days ± 2 days). Treatment of a bleed: a single dose.
This is the SPC's own paediatric figure, not a scaled adult dose — §4.2 Paediatric population, verbatim: 'No dose adjustment is required when NovoThirteen is used in paediatric patients and the dose of 35 IU/kg body weight should be used for both prophylaxis and treatment of bleeds.' ⚠️ CHILDREN UNDER 24 kg NEED A DIFFERENT PREPARATION STEP AND A DIFFERENT VOLUME FORMULA, verbatim: 'However, if the paediatric patient weighs less than 24 kg, the reconstituted NovoThirteen should be further diluted with 6 ml of sodium chloride 0.9%, solution for injection to handle the dosing of small children... The dose volume for small children can then be calculated by using the below formula: Dose volume in ml = 0.117 x body weight in kilograms. The calculation of the correction factor 0.117 is related to the exact quantity of the product and not the nominal value of the product.' For patients weighing at least 24 kg the formula is 'Dose volume in ml = 0.042 x subject body weight (kg)'. The calculator above returns the dose in IU only — it does NOT compute a volume, because the reconstituted concentration depends on which of the two preparation routes above is used; take the volume from the formula that matches the child's weight. No maximum dose is stated in the SPC. Non-neutralising antibodies were reported in four exposed patients under 18 (ages 8, 8, 14 and 16) in clinical trials (§4.8). Verify any under-18 dose against a children's formulary and specialist haemophilia-centre guidance before administration.

Dose adjustments

Hepatic

§4.4: 'Patients with hepatic impairment have not been studied. NovoThirteen may not be effective in patients with hepatic impairment if the hepatic impairment is severe enough to result in decreased levels of FXIII B-subunits.' No hepatic dose adjustment is given.

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.

Paediatric weight-based calculator

This is the SPC's own paediatric figure, not a scaled adult dose — §4.2 Paediatric population, verbatim: 'No dose adjustment is required when NovoThirteen is used in paediatric patients and the dose of 35 IU/kg body weight should be used for both prophylaxis and treatment of bleeds.' ⚠️ CHILDREN UNDER 24 kg NEED A DIFFERENT PREPARATION STEP AND A DIFFERENT VOLUME FORMULA, verbatim: 'However, if the paediatric patient weighs less than 24 kg, the reconstituted NovoThirteen should be further diluted with 6 ml of sodium chloride 0.9%, solution for injection to handle the dosing of small children... The dose volume for small children can then be calculated by using the below formula: Dose volume in ml = 0.117 x body weight in kilograms. The calculation of the correction factor 0.117 is related to the exact quantity of the product and not the nominal value of the product.' For patients weighing at least 24 kg the formula is 'Dose volume in ml = 0.042 x subject body weight (kg)'. The calculator above returns the dose in IU only — it does NOT compute a volume, because the reconstituted concentration depends on which of the two preparation routes above is used; take the volume from the formula that matches the child's weight. No maximum dose is stated in the SPC. Non-neutralising antibodies were reported in four exposed patients under 18 (ages 8, 8, 14 and 16) in clinical trials (§4.8). Verify any under-18 dose against a children's formulary and specialist haemophilia-centre guidance before administration.

Verify in a children's formulary

Contraindications

  • §4.3: 'Hypersensitivity to the active substance or to any of the excipients listed in section 6.1.' — this is the only contraindication stated
  • Not effective for monthly prophylaxis in congenital FXIII B-subunit deficiency (§4.4) — determine the subunit deficiency before treating
  • Patients known to have neutralising antibodies to FXIII 'should not be treated with NovoThirteen without close monitoring' (§4.4)
  • Stop permanently after an allergic or anaphylactic-type reaction — §4.4: 'If allergic or anaphylactic-type reactions occur, the administration should be immediately discontinued and further treatment with NovoThirteen should not be given.'

Side effects

  • Most frequent: headache — 'reported in 37% of patients' (§4.8)
  • Blood and lymphatic (common): leucopenia and aggravated neutropenia (§4.8)
  • Musculoskeletal (common): pain in extremity (§4.8)
  • General and administration site (common): injection site pain (§4.8)
  • Investigations (common): non-neutralising antibodies; fibrin D-dimer increased (§4.8)
  • Allergic reactions including anaphylactic reactions — §4.4: 'As NovoThirteen contains a recombinant protein it may cause allergic reactions including anaphylactic reactions. Patients should be informed of the early signs of hypersensitivity reactions (including hives, generalised urticaria, tightness of the chest, wheezing, hypotension) and anaphylaxis.'
  • Thromboembolic risk (§4.4): incorrect storage after reconstitution 'may result in loss of sterility and in increased levels of non-proteolytically activated NovoThirteen. Increased levels of activated NovoThirteen may increase the risk of thrombosis'; caution where there is a predisposition to thrombosis
  • This side-effect list may be incomplete — check the full SPC.

Monitoring

  • FXIII activity — §4.2: 'Monitoring NovoThirteen activity levels using a standard FXIII activity assay is recommended.' Dose adjustment, and the dose for minor surgery, are both based on FXIII activity levels
  • Confirm the diagnosis before treatment: 'factor XIII activity and immunoassay and if applicable genotyping', and determine the A- versus B-subunit deficiency (§4.2, §4.4)
  • Suspect inhibitors on loss of response — §4.4: 'Inhibitors may be suspected in the event of lack of therapeutic response which is observed as bleeding or demonstrated by laboratory findings including FXIII activity that fails to reach expected levels. In the event that inhibitors are suspected analysis for antibodies should be performed.'
  • Traceability — §4.4: 'the name and the batch number of the administered product should be clearly recorded'

Clinical monograph

How it works

It replaces the deficient factor XIII A-subunit, restoring the transglutaminase that cross-links fibrin to stabilise the clot and protect it from premature breakdown.

Prescribing in practice

  • Inhibitory antibodies to factor XIII can develop and reduce efficacy, so loss of response should prompt inhibitor testing under specialist supervision.
  • It replaces only the A-subunit and is therefore not suitable for the rare B-subunit deficiency, so the deficiency type must be confirmed before use.
  • Hypersensitivity and, rarely, thromboembolic events can occur, and viral-safety considerations apply to factor products.

Monitoring

Monitor factor XIII activity levels to guide prophylactic dosing and screen for inhibitors if breakthrough bleeding occurs.

Counselling the patient

  • Report new or breakthrough bleeding despite regular treatment, as this may indicate an inhibitor.
  • Report any allergic-type reaction during or after administration.
  • Attend scheduled reviews so factor levels can be checked and prophylaxis adjusted.

Evidence & guidelines

Replacement therapy is the established approach for congenital factor XIII deficiency, managed within specialist haemophilia and bleeding-disorder centres.

Reference: UKHCDO; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). 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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