Can I give Zykast (antihistamine) to patients with Glucose-6-phosphate dehydrogenase (G6PD) deficiency?

Zykast Can Be Safely Administered to Patients with G6PD Deficiency

Zykast (antihistamine) can be safely administered to patients with G6PD deficiency as it is not among the medications known to cause hemolytic reactions in these patients. 1, 2

Safety of Zykast in G6PD Deficiency

• Antihistamines like Zykast are not included in the list of medications that should be avoided in G6PD-deficient patients according to current guidelines 1
• A comprehensive review of medications contraindicated in G6PD deficiency identified only seven medications that should be strictly avoided: dapsone, methylthioninium chloride (methylene blue), nitrofurantoin, phenazopyridine, primaquine, rasburicase, and tolonium chloride 2
• Zykast is not mentioned among medications that pose a risk to G6PD-deficient patients in any of the current clinical guidelines 1, 3, 4

Medications to Avoid in G6PD Deficiency

• High-risk medications that should be strictly avoided in G6PD-deficient patients include:
  • Dapsone - associated with significant hemolytic reactions 1, 2
  • Methylene blue - can cause significant hemolytic anemia and may worsen G6PD deficiency-related hemolysis 1
  • Primaquine - causes hemolytic anemia in G6PD deficiency 1
  • Nitrofurantoin - identified as causing hemolysis in G6PD-deficient patients 2
  • Rasburicase - contraindicated in G6PD deficiency 2, 4

Clinical Considerations When Prescribing for G6PD-Deficient Patients

• The severity of G6PD deficiency varies by genetic variant, with the Mediterranean variant (B-) carrying higher risk of severe hemolysis than the African variant (A-) 1
• Recent real-world evidence suggests that many medications previously thought to be risky have been prescribed safely to G6PD-deficient patients 5
• In a large cohort study of 31,962 G6PD-deficient patients, only 0.2% experienced major hemolysis requiring hospitalization, with just 4.2% of those cases potentially associated with medications 5

Monitoring Recommendations

• If initiating any new medication in a G6PD-deficient patient, it is prudent to:
  • Obtain a baseline complete blood count with hemoglobin determination 3
  • Educate patients about signs of hemolysis, particularly darkening of urine 3, 6
  • Instruct patients to discontinue the medication and seek medical attention if signs of hemolysis develop 3

Common Pitfalls to Avoid

• Avoid confusing medication-induced hemolysis with infection-related hemolytic episodes, which are more common in G6PD-deficient patients 2
• Do not unnecessarily restrict medications that have no evidence of causing hemolysis in G6PD deficiency 2, 5
• Remember that fava bean ingestion (71.8%) and infections (8.5%) are more common causes of hemolysis in G6PD-deficient patients than medications 5