[Bartholow]

As usual, ante and bring-in are a factor. Also, am I to read this that the 5 was the bring-in and open-completed?

Either way, in the games I've played the 5 and 8 usually won't fold after putting in a full bet. If you've seen them fold in these type situations that of course changes things. If you had aces or kings it would still be worth reraising in the hopes that one or both would bail, but with a hand like yours that REALLY wants to be headsup things are a lot trickier. I'd be tempted to fold if the Q is particularly likely to have a good hand, or if the ante is small or medium sized. Probably neither of those is the case, so I might call hoping to thin the field later (probably 5th) and get some REAL dead money in the pot. And if things come bad just fold 5th instead.