Can you combine felony drug charges in 2 different states?

The answer to your question cannot be fully determined based on the facts that you have stated. If he has charges from either state based on different actions (for example, AR is claiming he sold or possessed drugs on a certain date in AR, while TN is claiming he sold or possessed drugs on a certain date in TN), then they may be separate and distinct charges. In that situation, both states may prosecute him. If he is convicted and receives a jail or prison sentence, then the latter sentence may be concurrent or consecutive to the former sentence. If the charges are based on a conspiracy that spanned both states, he can still be subject to prosecution by both states, but his lawyer in one state could push for charges being dropped in that state if he is being prosecuted in the other. Tennessee Rule of Criminal Procedure 18 gives the state vast discretion to prosecute an individual who either commits an offense (or part of an offense) within TN, or someone who simply is found in TN even though the offense was committed completely outside of TN (so long as TN nonetheless has jurisdiction).