Osteomalcia is adverse effect of:

Phenytoin produces osteomalacia, hypocalcaemia- due to altered metabolism of vitamin D and inhibition of intestinal absorption of calcium. Phenytoin also reduces target tissue sensitivity to vitamin D. Osteomalacia is the softening of the bones caused by impaired bone metabolism primarily due to inadequate levels of available phosphate, calcium, and vitamin D, or because of resorption of calcium. The impairment of bone metabolism causes inadequate bone mineralization. REF KD TRIPATHI 8TH ED.