Veterinarian Wendy McCulloch gives deworming medication to Alberta Fergus' cat, Nightmare, on November 4, 2012 in New York City. - 

In the coming weeks, pharmaceutical giant Pfizer is expected to launch a $4 billion stock offering for Zoetis -- its animal health division. The news underscores just how lucrative drugs and vaccines for animals have become.

You can see the financial opportunities at veterinarians offices around the country, like the Ft. Washington Veterinary Hospital in suburban Philadelphia co-owned by Jeffery Berman.

Berman, who provides services such as acupuncture and experimental stem cell treatment, says people spend on their pets.

“I mean, I’ve had people do second mortgages on their homes for animals. I know some who have spent upwards of $60,000 on their pets,” he says.

Businesses, including the pharmaceutical industry, are watching human behavior and responding. Companies like Novartis and Pfizer release new heartworm drugs, painkillers and vaccines each year and they’re getting scooped up.

“If you were to look at the world-wide market, you are looking in the neighborhood of $20 billion in annual sales,” says Damien Conover, director of pharmaceutical research at Morningstar. Conover projects the animal drug business to grow at a “moderate” pace – 5 percent - over the next five years.

That’s not just because people go to the bank to take care of Frisky. A growing demand for meat puts a higher premium on medicine to keep livestock and poultry healthy.

Follow Dan Gorenstein at @dmgorenstein