Phenytoin may make your body break down the vitamin D3 in this medicine faster than usual. Barbiturates and glucocorticoid medicines (steroids) can do the same. If you take both, tell your doctor or pharmacist so they can keep an eye on it.
These medicines are often taken together with some care. Your doctor may change a dose, space them apart or check on you more often. Make sure your doctor and pharmacist know you take both.