Acute hemolytic anaemia due to phenazopyridine hydrochloride in G-6-PD deficient subject

Review and drug therapy implications of glucose-6-phosphate dehydrogenase deficiency

PURPOSE

The pathophysiology, diagnosis, and medication-use implications of glucose-6-phosphate dehydrogenase (G6PD) deficiency, the most common enzyme deficiency in humans, are reviewed.

SUMMARY

Originally identified as favism in patients who experienced hemolysis after ingestion of fava beans, G6PD deficiency results from an X-linked chromosomal mutation that leads to reduced activity of the enzyme responsible for the final step of the pentose phosphate pathway, through which reduced nicotinamide adenine dinucleotide phosphate required for protection of cells from oxidative stress is produced. G6PD deficiency affects about 400 million people worldwide. Diagnosis of G6PD can be made through detection of enzymatic activity (by spectrophotometric testing, fluorescence testing, or formazan-based spot testing) or molecular analysis to detect known mutations of the gene encoding G6PD. Most individuals with G6PD deficiency are asymptomatic throughout life. Symptoms of acute hemolysis associated with G6PD deficiency include anemia, fatigue, back or abdominal pain, jaundice, and hemoglobinuria. The most common precipitators of oxidative stress and hemolysis in G6PD deficiency include medication use and infection.

CONCLUSION

G6PD deficiency should be considered in patients who experience acute hemolysis after exposure to known oxidative medications, infection, or ingestion of fava beans. A diagnosis of G6PD deficiency is most often made through enzymatic activity detection, but molecular analysis may be required in females heterozygous for the disorder. When clinically feasible, rasburicase, primaquine, dapsone, pegloticase, and methylene blue should not be used until a G6PD diagnostic test has been performed.

Identification of New FLT3 Inhibitors That Potently Inhibit AML Cell Lines via an Azo Click-It/Staple-It Approach

Acute myeloid leukemia (AML) is an aggressive malignancy with only a handful of therapeutic options. About 30% of AML patients harbor mutated FLT3 kinase, and thus, this cancer-driver has become a hotly pursued AML target. Herein we report a new class of FLT3 inhibitors, which potently inhibit the proliferation of acute myeloid leukemia (AML) cells at nanomolar concentrations.

Medications and glucose-6-phosphate dehydrogenase deficiency: an evidence-based review

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common human enzyme defect and one of the most common genetic disorders worldwide, with an estimated 400 million people worldwide carrying a mutation in the G6PD gene that causes deficiency of the enzyme. Although drug-induced haemolysis is considered the most common adverse clinical consequence of G6PD deficiency, significant confusion exists regarding which drugs can cause haemolytic anaemia in patients with G6PD deficiency. In the absence of consensus among physicians, patients are subject to conflicting advice, causing uncertainty and distress. In the current review we aimed, by thorough search of the medical literature, to collect evidence on which to base decisions either to prohibit or allow the use of various medications in patients with G6PD deficiency. A literature search was conducted during May 2009 for studies and case reports on medication use and G6PD deficiency using the following sources: MEDLINE (1966-May 2009), PubMed (1950-May 2009), the Cochrane database of systematic reviews (2009), and major pharmacology, internal medicine, haematology and paediatric textbooks. After assessing the literature, we divided medications into one of three groups: medications that should be avoided in individuals with G6PD deficiency, medications that were considered unsafe by at least one source, but according to our review can probably be given safely in normal therapeutic dosages to individuals with G6PD deficiency as evidence does not contravene their use, and medications where no evidence at all was found to contravene their use in G6PD-deficient patients. It is reasonable to conclude that, over time, many compounds have been wrongly cited as causing haemolysis because they were administered to patients experiencing an infection-related haemolytic episode. We found solid evidence to prohibit only seven currently used medications: dapsone, methylthioninium chloride (methylene blue), nitrofurantoin, phenazopyridine, primaquine, rasburicase and tolonium chloride (toluidine blue). Regarding all other medications, our review found no evidence to contravene their use in normal therapeutic doses to G6PD-deficient patients. There is a need for evidence-based global consensus regarding medication use in G6PD-deficient patients.

Heinz-body hemolytic anemia associated with phenazopyridine and sulfonamide

A 27-year-old white woman developed Heinz-body hemolytic anemia following multiple courses of oral phenazopyridine and trimethoprim-sulfamethoxazole. Her diagnosis was supported by the finding of bite cells on peripheral blood smear. The patient's rapid recovery and reversal of abnormal laboratory parameters were consistent with an acquired hemolytic disorder. This case should sensitize the clinician to the development of drug-induced oxidative hemolysis, its clinical features, and its reversibility. It is also important that the clinician recognize those drugs capable of causing this disorder and appreciate the methods available to establish the diagnosis.