If the debt is immediate and he has no excess money to pay his debt, then he is considered (from the ones in debt), but if the debt is deferred, and when the debt has matured and he has the money to pay back his debt, then it is not permissible to take Zakat.
إذا كان الدين حالا وليس عنده مال زائد عن حاجته يقضي به دينه فهو من الغارمين، اما اذا كان الدين مؤجلا، وحينما يحل الدين يجد ما يسدد به الدين فلا يجوز أن يأخذ من الزكاة