Can Vyvanse Be Taken In Place Of Focalin XR?

My son takes focalin XR 20 mg. He takes one in the morning and one in the afternoon. I have 2 pills left until Monday when he gets his prescription filled. The reason we ran out early is bc the school has the rest of his medicine and are closed due to Hurricane Michael. They miss d a week of school so I had to use the medicine I had for next week. My question is... I have some of his old vyvanse 30 mg, when I run out of focalin XR can I give him the vyvanse 2 x a day until we get his prescription filled or would it be best to just not give him anything? He had autism and adhd and anxiety