This Morning Our Dog Was Very Restless, Wandering Around, Tail

This morning our dog was very restless, wandering around, tail between his legs, not settling down as he usually does, he is on medication for leishmania grade 2, usually takes his medication okay followed by a treat , but this morning wouldn't take his treat. He is finally settled after a couple of hours, but this isn't usual behaviour for him, any ideas please? Thank you