What's the best time to take paxil (paroxetine) while using montelukast?

Anytime: It doesn't really matter - if Paxil (paroxetine) makes you sleepy then go ahead and take it at night (when you probably take the motelukast). If it doesn't make you drowsy then take it in the morning.

Any time: There is no need to take them at separate times, etc. There are no interactions between the Paxil (paroxetine) and Montelukast. The most important thing is to take them both regularly, so whatever time of day is easiest to remember is the time you should take them each day.

Whenever you'd like: There are no drug to drug interactions that are of significance and so it should be just fine to take these drugs at whatever time you'd like relative to when one is taken or the other.