Does anyone know of a drug that helps annihilate sexual desires in men
? What is your experience with such a drug ?

Prozac, and other antidepressants, tends to curb it significantly -
but I wouldn't say it annihilates it completely.

Reputedly, the British Army used to put bromide in the soldiers' tea
to give this effect but this could be an urban legend.

Have you considered castration?

Although I've never tried it, it might be more effective.

By the way, I am not qualified to give a medical advice.

Depo Provera, the female contraceptive injection, has been used on sex
offenders to 'chemically castrate' them.

http://en.wikipedia.org/wiki/Chemical_castration

http://archive.salon.com/health/sex/urge/2000/05/17/sex_drugs/print.html

Hi,
I think I have the perfect solution for you - but it's a prescription
drug for anxiety-related disorders. The generic name is Clonazepam,
and the brand name is Klonopin in the United States. It almost
prevents erections, and makes you so "weak," you won't have much
sexual desire left. In any case, you'll perform so ridiculously badly,
you won't feel like doing it any more.
Cheers!

Our friend here, Gnossie, asked a similar question some time ago that
received many interesting if not helpful comments:
http://answers.google.com/answers/threadview?id=484089

Probono's advice hasn't changed much.  :-)

I would look into Bromide

About 35 years ago a friend of mine was in a rugby team who played a
prison team, the tea tasted funny and that evening he had a serious
embarrassment with his lass.

Bromide - saltpeter:

http://www.snopes.com/military/saltpetr.htm
http://en.wikipedia.org/wiki/Anaphrodisiac

Not to be recommended, even it works.

Is there an opposite drug or substance that incresaes sexual urges. I
have a "friend" who does  not seem to be overly interestedin sex
leading to partner problems;  who thinks she is the  real problem.This
friend can maintain a "practical" interest for a short while but
wanders back to what is on TV  after only a short priod of time,
leaving the "practical interest"... to wither on the vine so to speak.

 JFM