Selling pet products to humans is big business. Last year, according to the American Pet Products Association, owners spent nearly $70 billion on their pets.

While much of that money is spent on pet paraphernalia, some of the biggest, and most unexpected, costs are for drugs and medical procedures as pets live longer and occupy a more central role in homes. By one estimate, owners spend $9,000 to more than $13,000 for medical treatments over their pets’ lifetimes.

“Things have changed dramatically over the past 30 to 40 years with how people are viewing pets,” said Dr. Craig A. Clifford, a medical oncologist and director of clinical studies at Hope Veterinary Specialists in Malvern, Pennsylvania. “Thirty years ago, we called it the Snoopy generation, where the dog lived outside and wasn’t a big part of the family.”

Now, Clifford said, we live in the Brian generation, a reference to the dog on “Family Guy,” who walks on his hind legs, martini in paw, and chats with his family. “People are eating dinner with them and having cocktails with them,” he said, with a laugh. “That’s a paradigm shift about how pets are perceived.”

That kind of relationship can lead to some difficult decisions. While a new collar may be a happy expense, emergency surgery to remove a sock lodged in a dog’s intestine is not. And the cost for such surgery can stretch to many thousands of dollars, blowing up a monthly budget.

Consider Lord Tigglesworth, known as Tiggy to family and friends.

He was living a fine feline existence, as a fat cat with doting parents in Wilmington, Delaware. A few months ago, he began vomiting and eating less. Claire Anderson and Andrew Logan,his owners (or pet parents, as some call themselves), began to worry. At first, they thought he just needed some teeth removed, so they had that done.

“He was incredibly low maintenance in terms of any health stuff,” Anderson said of her 8-year-old cat. “He had lost 7 pounds, and he only weighed 18 pounds to begin with. When he lost the weight, that’s when I knew it was more.”

It turned out that Lord Tigglesworth had cancer in his gastrointestinal tract. The treatment was effective, but he still didn’t eat. And giving him a pill — not an easy feat with any cat — was stressful for him and his owners.

The couple’s veterinarian prescribed an ointment, Mirataz, a drug that was originally used to treat depression in humans but has a side effect of increasing appetite. Logan said he and his wife had already spent $6,000 on Lord Tigglesworth’s care, so they didn’t flinch at paying about $30 for a two-week supply.

“It’s been pricey,” Logan said. “But if you were to annualize this over our time together, it’s been cheap.”

Unlike humans, only about 10 percent of dogs and 5 percent of cats are covered by medical insurance, according to a survey by the American Pet Products Association. And since 2015, the costs of veterinary services have risen over 10 percent for medical treatments and 5 percent for regular checkups, according to the Nationwide/Purdue University Veterinary Price Index.

“It’s not what veterinarians are charging,” said Dr. Carol McConnell, vice president and chief veterinary officer for Nationwide. “It’s more what consumers are choosing to pay.”

Mirataz is made by Kindred Biosciences, a small pet pharmaceutical company in Burlingame, California. The company introduced the drug, its first, in August because 9 million cats in the United States have unintended weight loss but only a third of them are treated with appetite stimulants, Kindred’s chief operating officer, Denise Bevers, said.

One reason is the difficulty of giving pills or compounded liquids to cats. Kindred formulated the appetite stimulant so an owner can rub it into the cat’s ear while both are relaxing.

The pet pharma field has been growing at an estimated rate of 5 percent a year, to nearly $6 billion in 2016, the latest figure available. Companies producing drugs for pets include Zoetis, which was spun out from Pfizer in 2013; Elanco, formerly part of Eli Lilly; and Merck Animal Health.

While there are more cats than dogs in the United States — 94 million vs. 89 million — dog owners are a richer market for several reasons. Dogs are generally outside more than cats. They’re active with other dogs, which means they get hurt. Dogs are also liable to bring diseases inside through fleas and ticks, or to eat something that gives them a parasite.

But veterinarians note that dogs are also easier to treat. Have a pill? Cover it in peanut butter or wrap it in deli meat and chances are the dog will scarf it down in seconds.

Try to give a cat a pill and the race is on to catch the feline before she disappears under a couch for the rest of the night.

The big drugmakers have released drugs to deal with common ailments — fleas and ticks and itchy skin, known as contact dermatitis. But they have had to be price sensitive in a way they are not with human drugs.

Dr. Elaine Wexler-Mitchell, a veterinarian who owns the Cat Care Clinic in Orange, California, said she often cut up a human pill for her feline patients, recalling that a lot of owners didn’t want to use a hypothyroidism drug made specifically for cats because it was more expensive. A three-month supply was $35.

Pet insurance would seem an answer to this. The industry grew 17.5 percent last year, but to only 1.83 million pets, according to the North American Pet Health Insurance Association. (The first pet policy in the United States was issued in 1982 by Veterinary Pet Insurance for the dog portraying Lassie, the canine star.)

Nationwide, which acquired Veterinary Pet Insurance in 2009, assesses the costs of pet insurance in much the same way it assesses cars: different rates for different breeds, ages and geography.

The monthly cost to insure a 1-year-old Labrador retriever in New York City ranges from $36.65 for a basic, high-deductible emergency plan to $111.19 for whole pet insurance, which covers 90 percent of all preventive and medical care. In Manhattan, Kansas, insuring the same dog ranges from $26.65 to $72.51 a month.

A 1-year-old shorthair cat costs $20.15 to $49.10 a month in New York and $14.66 to $32.02 a month in Manhattan, Kansas.

“The cost of care for us is also related to age,” McConnell said. “It’s the reverse of the car — the older the animal gets, the more it costs.”

But policies like that are intended to cover all veterinary expenses — well visits, emergencies, dental work and prescriptions — and not single out a service the way human health insurance does.

Still, the ultimate arbiters for many of these treatments are not the specialists but the neighborhood veterinarians. And sometimes they say enough is enough.

“Zoetis has done a lot for allergies, and Merck has a new flu vaccine out,” said Dr. Nolan Zeide, a veterinarian at Bull’s Head Pet Hospital in Stamford, Connecticut. “With new drugs, we look at the practicality of it and how safe it is. Then we ask: ‘How much is this going to cost? Is it going to be of good benefit to you, or it’s going to be a waste of your money?’”

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