Methylprednisolone may lower the amount of isoniazid in your blood. This means isoniazid may not work as well as it should against TB. Your doctor may need to watch how you respond to treatment, so do not change or stop either medicine on your own.
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.