Asthma
"I have had asthma for 40 plus years, which became progressively worse until I was having an asthma attack every day and using at least one salbutamol  inhaler every week. My preventative meds were 1000mg beclamethasone and 100mg of salmeterol per day.  I had broken sleep every night, waking to use my inhaler.  My Doctor prescribed Montelukast and from the first night my asthma was almost entirely gone. Ten years on I very rarely use my reliever, at most three to four times a year!!! It has been a miracle drug to me, the only down side is that I believe my temper is probably worse.  Not terrible but a much shorter fuse and more explosive."