Sex and Pain

A reader writes in with this question

I have a question that I’ve asked a few friends about, but I thought I’d try your blog.  A good friend of mine, (LDS woman, married, kids) recently mentioned that she was having painful intercourse problems, and asked if I knew of any good books or resources to address it.  Her general problem as told to me is a really painful bladder irritation caused by sex, that lasts for hours and hours afterwards — requiring drugs to knock her out if she wants to sleep.  Also there are related psychological issues for both her and her husband.

I made some general suggestions (was it a bladder infection, a muscle cramp issue, etc.).  But I’m no sex expert or doctor.  I’ve asked a few folks, and gotten some good suggestions.  (One person suggested that it might be cystitis.)  I’ve passed on these suggestions to her — cystitis, lubrication, varying positions.  And of course, I’ve told her to go see her doctor.

I thought folks on your blog might have additional insights.  Are there known issues that might cause painful sex?  What things should my friend (or for that matter, people in general) be aware of?  Thanks!