Prevalence of G6PD deficiency versus oxidizing drugs: a survey in the tertiary care hospital
ABSTRACT
Background: G6PD deficiency is distributed worldwide including India and is involved in accidental hemolysis and anemia by inadvertent use of oxidizing drugs. Awareness of community wise occurrence of G6PD deficiency can help in screening beforehand.
Methods: On 150 community wise classified, non-anemic, non- hemolysed (in recent past) visitors of pathological laboratory attached to C U Shah Medical College, Surendranagar, Gujarat, Crayman’s hemoglobin colorimetric kit (item no 700540) was used to estimate normal or below normal status of G6PD.
Results: 10 people (6.6% of population) were found deficient – 7 (4 male + 3 female) from Harijan community, 2 (1 male + 1 female) from Rabbari community and 1 (1 male + 0 female) from Lohana community.
Conclusions: While applying oxidizing drugs in a person of Harijan community (prevalence 7 out of total 26, i.e. 27%), extra caution is required, esp. if a person otherwise vulnerable (e.g. alcoholic). For other less represented communities, larger stratified sampling is required.
Keywords: G6PD deficiency, Oxidizing drug, Dapsone, Aspirin, Alcohol, Isoniazid
INTRODUCTION
The third world countries spend 30-40% of their total health budget on drugs, some of which are useless and expensive and double their expenditure every 4 years, while, GNP (gross national product) doubles only every 16 years.15 That’s why now the individual concerns for potency or cost of treatment, and even more precisely, efficacy or safety of a drug is being rationalized as overall risk-benefit ratio on individual level or cost-affectivity analysis on the mass scale.
In today’s scenario, irrational prescribing has become a global phenomenon20 to estimate which, pharmaco-epidemiology is the study of the use and effects / side effects of drugs in large numbers of people with the purpose of supporting the rational and cost-effective use of drugs in the population, thereby improving health outcomes.30 The basis of pharmacoepidemiological variations can be exogenous like ecological, cultural, food pattern and life style or endogenous like immunity, inborn errors and congenital anomalies. Concerning endogenous problems, incidence and prevalence tend to be used interchangeably.
Most endogenous differences are finally located in genetic make-up (e.g. iatrogenic hemolysis finally being traced to G6PD deficiency). Concerning drug elimination (metabolism as well as excretion), genetic polymorphism is widely known.21 These individually inherited differences in drug metabolism such as acetylator status (e.g. sulfonamides and sulfones which require acetylation) play a significant role in determining whether a drug will be hemolytic in G6PD deficient person.2 Racial difference in the incidence of iatrogenic hemolysis was established as early as 1952.9 Thus G6PD deficiency is known since 5 decades.4 Presently >0.4 billion people in the world, i.e. 7.5% of the total human population, show this deficiency.17
The enzyme G6PD is also known as NADP+ oxidoreductase, (international code EC 1.1.1.49).6 Normal G6PD activity is inversely proportional to RBC’s age index. Thus hemolytic susceptibility is directly proportional to the RBC aging as G6PD also has a half-life. Contextually RBCs are classified as nascent (reticulocytes), recent (<10 day), juvenile (10-30 days), mature (30-60 days), aged (60-90 days) and senescent (> 100 days) - also denoted by age index I to VI. The
deleterious effect is not immediate and is initially nullified by the little amount of glutathione already available till the total capacity of antioxidant mechanism is used up.
When G6PD deficiency is relatively mild (as in the class III G6PDA-), the hemolytic anemia is self-limited because only the older RBCs are destroyed and young RBCs/ reticulocytes have normal or near normal enzyme activity2 to protect themselves from oxidative stress. Thus hemolysis starts 2-3 days after the administration of the oxidant drug. Young RBCs/ reticulocytes, which are normally <3% of total RBC count, have normal or near normal enzyme activity2 and their compensatory excess after recent hemolysis can interfere with the screening results. By the same token, this belated start of hemolysis is self-limiting within a week even if the drug is continued further and hemoglobin level returns back to normal by 3rd - 4th week as compensatory production of new reticulocyte cells which are now far more than original “<3%” and would not be as much deficient in G6PD. If the G6PD variant is highly defective, even the slightest oxidative stress, as seen in the routine life, is enough to precipitate hemolysis in such case withdrawal of the drug is necessary. In patients with severely deficient forms (e.g. Mediterranean variant), hemolysis continues as long as the administration of drug continues because even the younger RBCs are deficient enough.2
Hemolytic anemia after administration of the antimalarial drug primaquine (also known as plasmoquine and plasmochin) was reported as early as 1926.3 A long list of drugs thought to cause hemolysis evolved with time. A list of unsafe drugs is given in the Table 1.
Table 1: Drugs and chemicals that should be avoided by persons with G6PD deficiency.
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