J.,
I am a Registered Respiratory therapist along with Registered Polysomnographer.. Which means I also do sleep studies on people. I love to work with children and especially asthmatics. First thing which I believe is that there are doctors that specialize for a reason and even though family doctors are good there is always someone better. So if your son is not under the care of a Pulmonologist (Lung Dr) and even more so Pediatric one then I would see about consulting with one.
A lot of asthmatics are being mistreated by family Dr's, because there lack of knowledge on the subject. Also children that tend to have behavior problems are being tested by means of sleep studies. The reason being that when kids do not get quality sleep they have behavior problems such as being hyper.
A big population of ADHD children is not being treated for various sleep disorder breathing problems. Which most are due to enlarged tonsils or the anatomy of their airways. Which can be easily treated and corrected with surgery and without surgery.
Asthmatics that are uncontrolled are often having problems when they are sleeping as well and that is a way that they are sorted out on the severity scale for asthma.
Yes medications can cause side effects but the same time pregnant women can take their asthma medication safely during pregnancy. I don’t believe that a behavior problem could be coming from those medications.
I really think you should consider other options and see a pediatric lung doctor or talk with your family doctor about an evaluation of your son's sleep and possibly changes in medications. Depending where you live a children’s hospital might have and asthma program or clinic and they also can also aid your quest