*2.3.1 Pathophysiology of drug induced megaloblastic anemia*

Megaloblastic anemia is most frequently brought on by cobalamin (vitamin B12) or folate insufficiency (vitamin B9). For the development of healthy cells, such as the precursors of red blood cells, these two vitamins act as building blocks. Since most dietary causes of folate and vitamin B12 deficiency may be resolved, drugs have emerged as a more significant contributor to megaloblastic anemia. Megaloblasts-inducing medications are frequently employed in clinical settings, although the caused changes to DNA synthesis pathways aren't always welcomed. The most crucial biochemical process during DNA synthesis is the synthesis of thymidine, which is a component of DNA but not RNA. As a result, it is susceptible to drug inhibition. Through the methylation of pyrimidine, which is a folate and vitamin B12 dependent process, thymidine is produced. Megaloblastosis is brought on by medications that physically destroy vitamins, compete with reducing enzymes, or obstruct folate or vitamin B12 absorption, transport, or delivery.
