Retrograde ejaculation occurs when the semen that would normally exit the body via the urethra, is redirected to the urinary bladder.
Here's an imagined conversation between Chuck Lorre and his doctor:
Doctor: Any other physical problems lately?
Me: Well, yeah... frequent urination. Very annoying.
Doctor: Oh, that's just a result of your prostate getting larger as you get older.
Me: It could be a result of your index finger.
Doctor: Hey, I don't enjoy that part of the exam either.
Me: So you say, but you do it every time.
Doctor: If you're interested, there's a new drug you can try that will help with the frequent urinating.
Me: Oh yeah, I think I saw a commercial. Bunch of middle-aged guys driving in a convertible, drinking bottles of water and celebrating not having to pee. Made me weep for the Age of Aquarius.
Doctor: Huh. Well, I don't watch much TV.
Me: Thanks. I support your profession.
Doctor: Would you like to try some free samples?
Me: Maybe. Are there any side effects?
Doctor: Not really. Occasional retrograde ejaculation.
Me: I'm sorry, what?
Doctor: The ejaculation reverses direction and goes into the bladder.
Me: I think I'm okay peeing a lot.
Doctor: Are you sure?
Me: Positive. In fact I'm peeing right now.
Retrograde ejaculation is a common side effect of medications such as Tamsulosin that are used to relax the muscles of the urinary tract for various purposes.
Chuck Lorre: #179: retrograde ejaculation, a side-effect of a drug to prevent the frequent need for urination.
Mayo Clinic: Retrograde ejaculation
Wikipedia: Retrograde ejaculation