Usage
- Anti Rh D immunoglobulin is prescribed to prevent Rh isoimmunization in Rh-negative women who are pregnant or have been exposed to Rh-positive blood. This includes routine antenatal prophylaxis during pregnancy, as well as administration after potential sensitizing events such as miscarriage, abortion, ectopic pregnancy, amniocentesis, abdominal trauma, or delivery of an Rh-positive infant. It’s also used after incompatible transfusions of Rh-positive blood to Rh-negative individuals. In some cases it is used in the treatment of Idiopathic Thrombocytopenic Purpura (ITP) in Rh-positive patients.
- Pharmacological classification: Immunoglobulin, immunizing agent.
Alternate Names
- Rh D immunoglobulin
- Rho(D) immune globulin
- Anti-D
- RhIG
- WinRho (Canada)
How It Works
- Pharmacodynamics: Anti-Rh D immunoglobulin binds to Rh-positive fetal red blood cells that have entered the maternal circulation. This prevents the mother’s immune system from recognizing the Rh D antigen as foreign and producing anti-D antibodies. This, in turn, prevents Rh hemolytic disease of the newborn in subsequent pregnancies.
- Pharmacokinetics: Administered intramuscularly (IM) or intravenously (IV). IM administration results in peak plasma concentrations in 2-5 days, whereas IV administration reaches peak concentration in a few hours. The half-life is approximately 21–24 days (IM) and is metabolized by the reticuloendothelial system.
- Mode of action: The exact mechanism of action of RhIG is not fully understood, but it’s believed to involve the suppression of the primary immune response by blocking antigen presentation or interfering with B-cell activation. It’s also thought to promote the clearance of Rh-positive red blood cells from the maternal circulation.
Dosage
Standard Dosage
Adults:
- Antenatal Prophylaxis: A single dose of 300 mcg (1500 IU) at 28 weeks gestation OR two doses of 150 IU (50 mcg) at 28 and 34 weeks gestation.
- Postpartum: 300 mcg (1500 IU) IM or IV within 72 hours of delivery of an Rh-positive infant.
- Following Sensitizing Events: The dose depends on the gestation period: 50 mcg (250 IU) up to 12 weeks, and 300 mcg (1500 IU) at or beyond 13 weeks gestation. Administer as soon as possible, ideally within 72 hours of the event.
- Incompatible Transfusion: 20 mcg (100 IU) per 2 mL of Rh-positive whole blood transfused or 20 mcg (100 IU) per 1 mL of Rh-positive red blood cell concentrate.
Children: Dosages are weight-based and will vary depending on the reason for the administration.
Special Cases:
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Elderly Patients: No specific dose adjustments are generally recommended unless there is renal impairment.
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Patients with Renal Impairment: Caution should be exercised, but generally, dosage adjustments are not recommended unless there is significant renal dysfunction.
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Patients with Hepatic Dysfunction: No specific dose adjustments are recommended.
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Patients with Comorbid Conditions: Patients with pre-existing hemolysis, autoimmune hemolytic anemia, or those at high risk for hemolysis should be monitored closely. Patients with IgA deficiency and anti-IgA antibodies should avoid RhIG.
Clinical Use Cases
Anti-Rh D immunoglobulin is not typically used in scenarios like intubation, surgical procedures, mechanical ventilation, or ICU use. Its primary indications are for the prevention of Rh alloimmunization and rarely, the treatment of ITP.
Side Effects
Common Side Effects
- Pain, swelling, and redness at the injection site
- Mild fever
- Headache, dizziness, or malaise
Rare but Serious Side Effects
- Allergic reactions, including anaphylaxis (rare)
- Hemolytic reactions (rare)
- Thromboembolic events (very rare)
Contraindications
- Rh-positive individuals (except for ITP treatment)
- Individuals previously sensitized to Rh D antigen
- History of anaphylactic or severe systemic reaction to human immunoglobulins
- IgA deficiency with anti-IgA antibodies
Drug Interactions
- Live attenuated vaccines (MMR, varicella): May reduce vaccine effectiveness. Administer vaccines either 3 months before or 2 weeks after RhIG.
- No known significant interactions with other drugs.
Pregnancy and Breastfeeding
- Pregnancy Category C. Generally considered safe during pregnancy and is routinely used for antenatal prophylaxis.
- Anti-D immunoglobulin is not known to be harmful during breastfeeding. IgG is a normal component of breastmilk.
Drug Profile Summary
- Mechanism of Action: Suppresses the maternal immune response to Rh-positive fetal red blood cells.
- Side Effects: Pain at the injection site, mild fever, headache, allergic reactions (rare).
- Contraindications: Rh-positive individuals (except for ITP), prior Rh sensitization, hypersensitivity to immunoglobulins.
- Drug Interactions: Live attenuated vaccines.
- Pregnancy & Breastfeeding: Generally safe during pregnancy and breastfeeding.
- Dosage: Varies depending on indication and gestational age. See detailed dosage section.
- Monitoring Parameters: Monitor for signs of allergic reaction, hemolysis.
Popular Combinations
- Anti-Rh D immunoglobulin is typically used as a single agent.
Precautions
- Monitor for allergic reactions, especially in patients with a history of allergies.
- Ensure correct Rh status before administration.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Anti Rh D Immunoglobulin?
A: The dosage varies depending on the indication. See the detailed dosage section above.
Q2: How soon after exposure to Rh-positive blood should RhIG be administered?
A: Ideally within 72 hours, but it may still provide some benefit if given within 10 days, depending on the specific scenario.
Q3: Can RhIG be given to Rh-positive individuals?
A: No, except in certain cases of ITP. Giving RhIG to Rh-positive individuals may cause a hemolytic reaction.
Q4: Can RhIG be given during pregnancy?
A: Yes, it is routinely administered during pregnancy for antenatal prophylaxis in Rh-negative women.
Q5: What are the side effects of RhIG?
A: Common side effects include pain at the injection site, mild fever, and headache. Serious side effects like allergic reactions are rare.
Q6: Is it safe to breastfeed after receiving RhIG?
A: Yes, it is considered safe to breastfeed after receiving RhIG.
Q7: What happens if a large fetomaternal hemorrhage is suspected?
A: The Kleihauer-Betke test or flow cytometry should be performed to quantify the FMH. Additional doses of RhIG may be required based on the test result.
Q8: Can RhIG prevent sensitization if given after the development of anti-D antibodies?
A: No, RhIG is only effective in preventing sensitization. It cannot reverse the effects of pre-existing anti-D antibodies.
Q9: How is Rh incompatibility determined?
A: Blood typing tests are performed to determine the Rh status of the mother and, after birth, the baby.
Q10: Are there different brands of RhIG available?
A: Yes, different brands are available, but they all contain the same active ingredient: anti-Rh D immunoglobulin. Always refer to the specific product information for detailed instructions.
