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Letter to the editor
Editor, – We read with interest the comment about primaquine phosphate ('New drugs' Aust Prescr 1999;22:70). We would like to comment on the statement'... but all patients should be tested for glucose-6-phosphate dehydrogenase deficiency'.
Although, when circumstances permit, it is always preferable to test for glucose-6-phosphatedehydrogenase deficiency (G6PD) before prescribing primaquine phosphate (and other drugs liable to cause haemolysis in G6PD-deficient patients), the following points weigh against routine testing in a developing country like India.
- Although G6PD deficiency is not uncommon in India, it is less common than in some parts of the world like Mediterranean Africa, the Middle East and South-East Asia. Severe deficiency is still less common.
- G6PD deficiency is an X-linked recessive trait. Like other X-linked recessive disorders males are affected while females are carriers. Homozygous females would be extremely rare. In carrier females, the likelihood of severe haemolysis is remote as the extent of deficiency would seldom exceed50% of normal.
- G6PD deficiency testing is not universally available.
- The average cost of this test is Indian Rs.250 (approximately US$ 5.95) while the cost of one course of primaquine phosphate for radical cure (at 15 mg base daily in an adult for 14 days) is Indian Rs.36 (approximately US$ 0.86). The cost of the test is a strong disincentive, even when facilities for testing are available.
In this scenario Indian practitioners have, for years, been prescribing primaquine phosphate for radical cure of vivax malaria without routine testing for G6PDdeficiency beforehand and no great harm seems to be done. However, patients are warned to report immediately if signs of haemolysis such as unusually dark urine or unusual pallor or tiredness are noted, so that the drug may be withdrawn. In the National Malaria Control Program a course of primaquine phosphate is recommended in confirmed cases of vivax malaria without mandatory G6PD testing. Incidentally, it is a moot point how 'radical' can the 'radical cure' of vivax malaria be, when almost the entire population of the country is residing in an endemic area and is therefore always susceptible to re infection.
It would be interesting to know the comments of your other readers on these observations.
Community Development Medicinal Unit