Primaquine is contraindicated in patients with which enzyme deficiency, as it can cause severe hemolytic anemia?

Explanation

## Primaquine and G6PD Deficiency **Key Point:** Primaquine is an 8-aminoquinoline antimalarial that causes oxidative stress in red blood cells. In patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency, this oxidative stress overwhelms the antioxidant defense system, leading to hemolysis. ### Mechanism of Hemolysis in G6PD Deficiency **High-Yield:** G6PD is the first enzyme in the pentose phosphate pathway and generates NADPH, which is essential for maintaining reduced glutathione (GSH). Primaquine generates reactive oxygen species (ROS) that deplete GSH. Without sufficient NADPH production (due to G6PD deficiency), cells cannot regenerate GSH, leading to oxidative damage and hemolysis. ### G6PD Deficiency Characteristics | Feature | Detail | |---------|--------| | Inheritance | X-linked recessive | | Prevalence | Common in African, Mediterranean, and Asian populations | | Triggers for hemolysis | Primaquine, sulfonamides, aspirin, fava beans, infections | | Hemolysis pattern | Acute intravascular hemolysis with hemoglobinuria | | Screening | Fluorescent spot test, G6PD enzyme assay | **Mnemonic:** **SAPS** — Sulfonamides, Aspirin, Primaquine, Sulphones cause hemolysis in G6PD deficiency. **Clinical Pearl:** G6PD deficiency screening is mandatory before prescribing primaquine, especially in endemic malaria regions. Chloroquine and quinine are safe alternatives in G6PD-deficient patients. **Warning:** Glucose-6-phosphatase deficiency (von Gierke disease) causes glycogen storage disease, not hemolysis with primaquine — do not confuse the enzyme names.