You are wise to ask this question.  Intal was a popular controller med for asthma in the past, (in fact I was on it in the 1980s) but it is less commonly used today due to much better medicines.  It is a anti-inflammatory medicine, but I rarely ever see it used anymore, especially with adults.

The most common asthma controller medicines used today for asthma are inhaled corticosteroids such as Flovent (a ramp up from Intal). Flovent is much more effective for treating inflammation than Intal (at least most asthma experts conclude this). 

If you continue to have trouble with your asthma despite inhaled corticosteroid use alone, your doctor might prescribe Advair (or Symbicort). Advair (a ramp up from Flovent) is a combination drug with both Flovent and a long acting bronchodilator called Serevent in it.  Advair has been very effective in controlling asthma for many asthmatics, including myself.

There used to be a fear that inhaled corticosteroids had the same side effects as oral corticosteroids (prednisone), but many studies have been done to prove this is not true.  If you take your Flovent or Advair properly, and you rinse really well after each use, side effects from these meds should be rare. 

In my opinion, if Intal is working for you great.  Your doctor may have been wise to have you try it before resorting to inhaled corticosteroids. 

If, as you describe, Intal is not working, you might want to talk with your doctor about other options, such as the Advair you mention.  Either way, it's always a good idea to keep in touch with you physician as I'm sure you are doing. 

Good luck getting your asthma under control.