A bottle of the liquid sedative Pentobarbital Sodium is pictured at a veterinary supply shop in the northern border city of Nuevo Laredo, in the Mexican state of Tamaulipas, May 29, 2008. Elderly foreign tourists are tapping Mexican pet shops for a drug used by veterinarians to put cats and dogs to sleep that has become the sedative of choice for euthanasia campaigners. Tourists from as far as Australia have traveled to Mexico to buy liquid pentobarbital, which causes a painless death in humans in less than an hour, right-to-die advocates say. Picture taken May 29, 2008. REUTERS/Tomas Bravo (MEXICO)