Medications to Avoid in G6PD Deficiency
Only seven medications have solid evidence requiring absolute avoidance in G6PD-deficient patients: dapsone, methylthioninium chloride (methylene blue), nitrofurantoin, phenazopyridine, primaquine, rasburicase, and tolonium chloride (toluidine blue). 1
High-Risk Medications (Absolute Contraindications)
The following drugs carry definitive evidence of causing life-threatening hemolysis and must be avoided:
Antimalarials
- Primaquine: Causes severe hemolysis, particularly dangerous when used beyond 5 days in populations with severe G6PD deficiency (notably Asians and those with Mediterranean variants). If primaquine is absolutely necessary for P. vivax radical cure, limit to ≤5 days and test for G6PD deficiency beforehand 2, 3, 4
Oncology/Uric Acid Management
- Rasburicase: Absolutely contraindicated due to risk of acute hemolytic anemia and methemoglobinemia. Screen all patients for G6PD deficiency before administration, including thorough history of drug-induced hemolytic anemia and ethnic background (African American, Mediterranean, Southeast Asian descent at highest risk) 5, 6
Antibiotics
- Dapsone: Solid evidence for hemolysis 1
- Nitrofurantoin: Despite being prescribed safely to 1,366 G6PD-deficient patients in one real-world study 7, it remains on the high-risk list with solid evidence 1
Other Medications
- Methylthioninium chloride (methylene blue): Cannot be used in G6PD deficiency as it is ineffective and worsens hemolysis. This is critical for methemoglobinemia treatment, where methylene blue is first-line therapy in normal patients but absolutely contraindicated in G6PD deficiency 8, 1
- Phenazopyridine: Solid evidence for avoidance 1
- Tolonium chloride (toluidine blue): Solid evidence for avoidance 1
Important Clinical Caveats
Testing Requirements
Before administering high-risk medications, G6PD testing is mandatory:
- Quantitative enzyme assay remains the mainstay of screening 9
- For genotyping: look for history of prior drug-induced hemolytic anemia, ethnic background, and semiquantitative laboratory tests
- Definitive testing includes measurement of RBC NADPH formation 5
Variant-Specific Considerations
The Mediterranean variant (B-) carries very high risk of severe hemolysis, while the African variant (A-) has mild deficiency and is relatively resistant to severe primaquine-induced hemolysis 4. This distinction matters for dose-limiting decisions.
Primaquine Special Circumstances
If primaquine is unavoidable for P. vivax/P. ovale radical cure in patients with intermediate G6PD deficiency (>30% to <70%) and non-Mediterranean variant (A-), use weekly dosing at 0.75 mg base/kg (maximum 45 mg) for 8 weeks with close monitoring for hemolysis 4
Medications That Are Actually Safe
Real-world evidence contradicts many traditional warnings. The following have been prescribed safely to thousands of G6PD-deficient patients without causing major hemolysis requiring hospitalization 7:
- Ciprofloxacin and ofloxacin (fluoroquinolones)
- Sulfamethoxazole/cotrimoxazole
- Sulfasalazine and sulfacetamide
- Hydroxychloroquine and chloroquine (safe even in pregnancy) 2
- Glibenclamide and glimepiride
- Mesalazine
- Ibuprofen: Despite being listed as medium-risk on many websites, systematic review shows extremely rare association (approximately 1/100,000 affected children per year), making it appropriate for perioperative pain management 10
Critical Clinical Pitfall
Many compounds have been wrongly cited as causing hemolysis because they were administered during infection-related hemolytic episodes 1. In a real-world study of 31,962 G6PD-deficient patients, 71.8% of major hemolysis cases were caused by fava beans and 8.5% by infections—only 4.2% were potentially medication-related 7.
Algorithm for Medication Decision-Making
- Check if medication is one of the seven high-risk drugs listed above → If yes, absolutely avoid
- If rasburicase or methylene blue needed → Screen for G6PD deficiency first; if positive, use alternative (exchange transfusion for methemoglobinemia, allopurinol for tumor lysis syndrome)
- If primaquine needed → Test G6PD, assess variant type, limit duration to ≤5 days in severe deficiency
- For all other medications → Can be used with standard precautions per most recent evidence 1, 6, 7