Buspirone will take 6 weeks to reach its maximum effect. It is not a fast acting drug ( as compared to a benzo like Valium or Xanax) and should not be taken "as needed". It is a maintenance drug for anxiety. Perhaps you could call your Pdoc and leave a message asking if you can go up on the Celexa ( avoiding a visit if you have an established relationship) and then see if the combined effect doesn't provide you some relief.