May ventolin be taken together with a beta blocker? what are the consequences if i already take both of them together?

Asthma?: Most beta blockers work 12-24 hours but if you have asthma then you should be avoiding beta blockers if you can or have your doctor measure your lung via puulmonary function test if it affects you. Recent data still shows that it can exacerbate asthmatic attacks but if you have tolerated it for a long time then your md will weight the risk and benefit.

Ventolin: If you are taking ventolin for bronchospasm then do not take betablockers. You should talk to your physician either to decrease the dose to a minimal dose or stop it (if possible). Otherwise, broncodilator, ventolin will not be effective. It is not going to improve your shortness of breath.