Transfusion medicine handbook

5. Fractionated Products

5.4.9 RHOPHYLAC (Anti-D immunoglobulin)

Rhophylac does not have full New Zealand registration and so consultation with an NZBS Transfusion Medicine Specialist / Medical Officer is required prior to product release. It is supplied by NZBS under Section 29, a provision in the Medicines Act 1981, whereby a medical practitioner can prescribe a medicine that is not registered with Medsafe.

Rhophylac is a sterile, preservative-free solution in a pre-filled 2 mL syringe containing 1500 IU (300 µg) anti-D IgG immunoglobulin. Rhophylac is manufactured from plasma obtained from remunerated donors who have been immunised to the RhD antigen. It is important to note that this product is obtained from a screened and carefully monitored donor pool and has a similar safety profile to Rh(D) Immunoglobulin-VF. Rhophylac may safely be administered intramuscularly or intravenously [14].

Indications for Use

Rhophylac has similar indications and contraindications for use as other anti-D immunoglobulin products. While Rhophylac is an acceptable alternative to Rh(D) Immunoglobulin-VF, it is supplied by NZBS only when stock of this product is unavailable, large doses of anti-D are indicated (i.e., > 2 vials 625 IU Rh(D) Immunoglobulin-VF), or when a product suitable for intravenous administration is required.

Dosage and Administration

A maximum dose of 15,000 IU (3000 µg) is sufficient in the case of larger incompatible transfusions independent of whether the transfusion volume is greater than 300 mL of RhD positive red cells. Treatment can usually be given without preceding exchange transfusion when the transfused RhD positive blood represents less than 20% of the total circulating red blood cells. If the volume exceeds 20%, consideration should be given to red cell exchange transfusion to reduce the load of RhD positive cells prior to Rhophylac administration.

Precautions

• Following a large fetomaternal bleed or incompatible transfusion, patients receiving large doses of anti-D immunoglobulin should be monitored, as there is a risk of haemolytic reaction. To reduce this risk, the maximum recommended dose administration rate is 3000 IU (600 µg) every 8 hours.
• Rhophylac can contain antibodies to other Rh antigens and the passive transfer of these antibodies may be detectable by serological testing methods.
• There is some evidence to suggest that intramuscular administration of anti-D immunoglobulin may be associated with an increased risk of lack of effect in patients with a body mass index (BMI)≥30. An Expert Panel Consensus Position Statement (available online at Expert Panel Consensus Position Statement ) provides recommendations regarding the use of anti-D immunoglobulin in these patients.