Jeanette Loeb knows just how troublesome pets can be. Her Labrador retriever once chewed up and swallowed his entire leash, leaving just a little stub that was still attached to his collar.

Naturally, surgery followed, and Ms. Loeb was introduced to the shockingly high cost of pet maintenance.

However, it was some time later, when both her son and her dog were being treated with amoxicillin, that she realized something was amiss. Astonishingly, she was paying more for her dog’s medication than for her son’s.

Being a woman of vision, Ms. Loeb responded to that particular nuttiness by investing in and becoming Co-CEO of PetCareRx, a company that is revolutionizing the distribution of medications for animals.

PetCareRx is an online discounted dispenser of medications and other products for pets. It was founded in 2000 by Blake Brosnan, who was joined in 2001 by Ms. Loeb and one of her former Goldman Sachs partners, David George. The latter two individuals serve as co-chairmen and co-CEOs.

Other than a healthy disgust with the high prices being charged for pet medicines, Ms. Loeb and Mr. George brought with them many years in the service of Goldman Sachs. This training has led them to build PetCareRx the right way, according to Ms. Loeb, investing in systems and software that will serve them well into the future.

Considering the opportunity, that seems a wise choice. Consulting firm McKinsey has estimated that medications sold for pets amounted to $2.4 billion in 2002, at factory prices. It further forecasts growth in the sector at 12% to 15% per year; other sources put the growth rate as high as 20% per year. These figures suggest a retail market today in excess of $5 billion.

Most of these sales are made by local veterinarians, and are included in the overall care of the pet. Ms. Loeb and Mr. George are trying to change that, by discounting prices (up to 90% lower in some cases) and by providing helpful services to pet owners at the same time.

Here is how it works: Pet owners can order medications from PetCareRx online, or by telephone, but must have a prescription. If they do not, PetCareRx will call the customer’s vet and ask for the prescription over the telephone. Information about the pet will be recorded, and the owner will be reminded on a timely basis when and if the prescription needs to be refilled.

Veterinarians are not universally happy about this arrangement. Selling medications is a sizable business – perhaps accounting for 15%-20% of the typical vet’s revenues – and profitable. However, Ms. Loeb makes the case that by reminding owners of their pets’ needs, they are encouraging regular visits to the vets for shots and checkups, which might otherwise be skipped.

To her, it’s a symbiotic relationship. To some vets, it is a dead loss, and they occasionally refuse to give out the prescription.

Not all of the industry’s concerns about the upstart vendor have been about money. Some have questioned the reliability of online dispensing and the supervision given to drug sourcing.

In part, these concerns have echoed problems which have arisen at other online discounters, including PetMed Express and Savemax. One drug company has sued these vendors, charging that they illegally sold foreign versions of medicines.

According to Ms. Loeb, these concerns have typically abated as PetCareRx has become better known. The oversight at its warehousing and dispensing facility on Long Island is intense. Nothing can be brought in from a foreign country illegally for example, since every pallet in the receiving area is inspected thoroughly.

Similarly, it would be virtually im possible for a mistake to occur in the filling of orders, since the meds come with an attached photo of the pill and the order is checked numerous times. The serial number of the individual filling the order is on the bill, further ensuring accountability.

To its credit, PetCareRx has not been charged with a single violation of its pharmacy license.

Is Ms. Loeb happy to have traded the status due the first woman partner at Goldman Sachs for life as an Internet retailer? You bet. Though she occasionally pines for the support systems available at a large firm, (PetCareRx has only 40 employees) she is energized by the opportunity she sees ahead.

For sure, the world of pet ownership has changed. As people age, and suffer the pangs of isolation, it appears they turn to their dogs and cats for comfort. Pets are considered members of the family; one survey indicated that a dog or cat is often greeted first, before a spouse, when the breadwinner returns home.

Whereas in earlier times an ailing animal was often put to sleep, the veterinary world of today has built an entire industry on maintaining dogs and cats with chronic problems.

The pharmaceutical industry has climbed on board, making an increasing number of human medications available to pets. As a result, dogs and cats are being treated by doting owners for all kinds of ailments once exclusive to humans, such as depression and senility. (Can insomniac turtles be far behind?)

One of the largest areas of growth is obesity. Just like humans, dogs and cats are spending too much time sitting around watching TV and eating too much. Now there are medications that can help. (Whatever happened to a run in the park?)

Though Ms. Loeb will not reveal revenue or profit figures for the closely held company, some indication of success is that sales have expanded tenfold in the past three years. The company is profitable, and it already has hundreds of thousands of customers.

Ms. Loeb and her partners intend to keep the business simple. They don’t want to compete with Petco, for example, which supplies pet products of all kinds. Their focus is medicines, and they see plenty of room for growth as they loosen the grip that vets currently have on the market.

She does have to be a little careful about alienating her own vet. Last week her dog ate her husband’s underwear, another trip to the emergency room.