] Called Neutersol, it's a shot administered directly into
] the testicles of puppies at the right age for neutering.
] The ingredients -- the amino acid l-arginine and a zinc
] salt -- cause the testicles and prostate to atrophy.
]
] The alternative, surgically removing the testicles,
] guarantees sterility. In a study of 224 dogs, Neutersol
] did almost as well: Semen analysis showed only one
] sterilization failure, said Dr. Melanie Burson of the
] Food and Drug Administration.

CNN.com - FDA approves shot to neuter puppies - May. 20, 2003