Patients are advised to take them separately to prevent potential drug-drug interactions. It occurs when a compound affects the activity of a drug when both are taken together.
If one increases the effect of another, an overdose may occur or the side effects profile may be intensified. Similarly, if the efficacy of a drug is reduced, it will not elicit a therapeutic response and can be dangerous in some instances (e.g. diabetes).
However, there remains a possibility that they may generate enhanced results when taken together, than when taken alone, but more extensive research is warranted for it to be conclusive. Therefore, there is no harm heeding your physician’s advice and remember to take them two hours apart.