My LO isn't on Singulair but he is on Albuterol and Flovent, there kind of the same. He has been on them for almost three weeks now and his breathing is just now getting better. His pulmo said to give them 2-4 weeks to start working to there full potential.
Her nurse said to give it at least a month to see results. These things take awhile because they have to build up in their system. I started seeing results probably at about 3 weeks.
Re: LOs that are on Singulair...