The first answer is wrong, the 2 others are just irrelevant.
Urine drinking is basically safe. It's practiced for both sexual and medicinal purposes. It's a pretty common fetish and a lot of people practice it without any damage to their health.
Urine is basically 99% water and 1% mineral and Uric acid, which is, in large dose, poisonous (which is what make urine sterile - it kills germs) As long as you are not drinking gallons of it, you can practice urine drinking without fear.
Read more about it here:
http://en.wikipedia.org/wiki/Urolagnia