A GP have me 8 Singulair tablets to trial for my 4 year old daughter to see if her night time cough would improve....(to determine if she may be asthmatic like me.) A month back I gave her a tablet at bedtime over 4 nights or so. She had a virus at the time, so I didn't think too much about her waking in the middle of the night very distressed, inconsolable etc. Tonight I gave her a tablet before bed, as her cough was quite persistent & I thought it may help her sleep. Well, she's woken up twice in the last 2 hours crying in her sleep and very distressed. Exactly the same way she did a month ago. I've just done a search of side effects and found this web page. Very interesting....I think the drug has definitely caused her to have night terrors and definitely won't be giving it to her again!!!