Singulair and intense headaches

I took this medicine only twice, and both times suffered the most intense headaches I have ever had - what I would imagine a migrane might feel. I was also incredibly hyper and agitated from the medicine - I will NEVER take this again...

I am a paediatrician in private practice. I recently put an 8yr old boy with moderte to severe asthma on singulair. He is also epileptic and is on lamictin. After starting the singulair he experienced intense headaches, dizziness and blurred vision.
The headches were associated with vomiting. I have subsequently stopped the singulair but was really surprised by these side effects. Could it be related to his epilepsy? I have been using singulair for many years but this is the first case that I have seen with these side effects.