“It is Mexico where Nembutal is most readily available,” says “The Peaceful Pill Handbook,” a book that lays out methods to end one’s life. Co-written by Philip Nitschke, founder of Exit International, an Australian group that helps people who want to end their lives early, the book is banned in Australia and New Zealand. In the United States, though, it is only a few mouse clicks away online.  The book, as well as seminars that Mr. Nitschke offers, lays out strategies for dying. The most trouble-free and painless form of suicide, he contends, is to buy Mexican pentobarbital, which goes by brand names like Sedal-Vet, Sedalphorte and Barbithal.  Those in search of the drug, so-called death tourists, scout out the veterinary pharmacies that abound in Tijuana. The shelves are fully stocked with tick medication for dogs, vitamins for horses and an array of bottles and boxes that make little sense to anyone but a veterinarian.  Mr. Nitschke’s book, however, provides glossy photos of the many versions of pentobarbital that are most suitable for suicide. Buying pentobarbital can be as easy as showing the pictures to a clerk and paying as little as $30 for a dose.  Pet shop clerks throughout Tijuana acknowledge that foreigners regularly inquire about the drug. “We’ve probably had 100 people come in asking for the drug in the last couple years,” said Pepe Velazquez, a veterinarian and owner of El Toro pharmacy.  Until El Norte, a regional newspaper, published an article recently that detailed how easy it was to buy pentobarbital — and how foreigners intended to use it — many store owners and clerks said they assumed the customers were using the drug to end the lives of their animals.  “We didn’t have any idea what they were doing,” said a sales clerk at a pet shop called California. “It’s for animals. Everything here is for animals. We thought they were giving it to their animals.”  It turns out that they were buying it for human consumption. Mr. Nitschke estimates that 300 members of his group, most of them from Australia but some from the United States and Europe, have bought the drug in Mexico in recent years. Some save it for when their health fails to the point that they no longer wish to live. In a few instances, buyers took the drug while in Mexico.  “To witness it, it looks as peaceful as can be,” Mr. Nitschke said of death by pentobarbital. “I usually recommend that they take it with their favorite drink since it has a bitter taste. I’ve never seen anyone finish their whiskey or Champagne. There isn’t enough time to give a speech. You go to sleep and then you die.”  But now that word is out that the drug is being used for human consumption, local authorities are seeking to clamp down on unauthorized purchases. Shops are now supposed to sell the drug only to licensed veterinarians who present a prescription.  Don Flounders, 78, has mesothelioma, a rare and deadly form of cancer usually linked to asbestos exposure. He had no problem getting pentobarbital when he traveled from Australia to Los Angeles in January and then crossed the border to Tijuana.  “I went into the first shop that was advertised as being a vet, and I showed the photo and they handed it over,” he said in a telephone interview from Australia. Getting it home was more of a challenge. It is illegal to bring pentobarbital into the United States, and Exit International says United States customs officers have seized the drug from at least three of its members. The group says no members have been caught with the drug by Australian customs officers.  But once he was home, Mr. Flounders, who advocates for euthanasia, talked to a television news crew about his purchase. He was filmed taking a bottle to a friend, Angie Belecciu, 56, who is dying of cancer and who helped to finance his trip to Mexico.  Both of their houses were later searched by the Australian Federal Police. Assisted suicide is illegal in Australia.  “It was an affront,” Mr. Flounders said of the raid. “I’m 78, and my wife is 85. I’ve got this incurable disease, and when four very big policemen came marching up the front steps it was very disconcerting.”  Neither Mr. Flounders nor Ms. Belecciu has used the pentobarbital, and charges have not been filed against either of them.  Another Australian who bought the drug in Mexico, Caren Jenning, was convicted in June of accessory to manslaughter because a friend, Graeme Wylie, who had advanced Alzheimer’s disease and had long expressed a desire to end his life, used it to commit suicide two years ago.  Also convicted of manslaughter in the case was Shirley Justins, Mr. Wylie’s partner, who opened a bottle of Nembutal purchased by Ms. Jenning and told him that if he took it he would die.  “The whole issue was whether this man had the mental capacity at the time he took the drug to end his life,” said Sam Macedone, Ms. Jenning’s lawyer. The court was apparently swayed by the prosecution’s argument that Mr. Wylie had such severe dementia that he was unable to make an informed decision to take his life.  Ms. Jenning has cancer, Mr. Macedone said. She faces up to 25 years in prison but probably has less than a year to live, he said. If he lodges an appeal, Mr. Macedone said, it will probably not be resolved until after her death.  He said it was terribly sad “that we put someone like this through all that when all she did was help a friend get where he wanted to go.”  Assisted suicide has emerged as an issue in Mexico, where the Senate voted in April to allow doctors to withdraw life-sustaining medicines from some patients but not to actively take steps to cause death. Euthanasia is also strongly opposed by the Catholic Church.  “It’s awful to me,” Mr. Velazquez, the Tijuana veterinarian and pharmacy owner, said of euthanasia. “I think people should live as long as God decides.”  All the publicity over the unauthorized use of pentobarbital has made it somewhat harder to find along Mexico’s northern border. “Oh, no, we don’t have that,” said a clerk at El Grano de Oro, the answer given by workers approached at six veterinary shops in Tijuana’s tourist zone on a recent afternoon.  At the seventh shop, however, just a few blocks off Avenida Revolución, the clerk said the drug was in stock. She reached up to a shelf behind her and pulled down a box of Sedalphorte, one of the brands Mr. Nitschke recommends. The package bore photos of a dog and a cat and said in bold letters that it could be sold only with a prescription.  Asked if she would sell it, the clerk gave a confused look. “Of course,” she said, ringing up a bottle for $45.  A version of this article appears in print on , on Page A5 of the New York edition with the headline: In Tijuana, A Market For Death In a Bottle. Order Reprints| Today's Paper|Subscribe
One contraband product trumps all others: a drug popular with people seeking a painless way to end their lives.