Thank you for your inquiry.
The question you asked might receive different answers from different allergists-immunologists. It is an issue about which there are no data upon which to formulate a strategy. Therefore the answer I give you is based solely upon my personal approach, and, as noted, this may differ from other knowledgeable and well-qualified allergists-immunologists, and pulmonologists as well.
I use narcotic cough suppressants in asthmatics in a fashion similar to how I would use them in non-asthmatics, with two exceptions.
I would not use a codeine cough suppressant unless I was reasonably certain that the cough was not due to the asthma itself. If I felt that the cough was related to the asthma (e.g., cough-variant asthma or cough associated with an asthmatic flare), I would treat the asthma itself without a codeine cough suppressant.
If, however, I was fairly certain that the cough was unrelated to asthma (e.g., related to an acute bronchitis), I would have no reluctance in prescribing a codeine cough suppressant in the same manner as I would in a non-asthmatic.
The other exception to the rule, however, is of course an obvious one - I would not use a narcotic cough suppressant in a patient who was having a moderate to severe episode of asthma during which one would not wish to suppress the cough, or suppress in any way the respiration.
However, I would not consider a diagnosis of asthma per se an absolute contraindication to the administration of codeine/narcotic cough suppressants.
Thank you again for your inquiry and we hope this response is helpful to you.
Phil Lieberman, M.D.