Order a six-pack of Comfortis tablets from 1-800-PetMeds, and the pills come in an orange bottle with the name of the online drug store and “America’s Largest Pet Pharmacy” printed on the cap.

The box supplied by the manufacturer of the flea-killing drug for dogs and cats is not included.

The pills are repackaged for “branding” purposes, to place the pharmacy’s name on the product, according to Menderes “Mendo” Akdag, President and CEO of PetMed Express, owner of 1-800-PetMeds.

Repackaging is a common pharmacy practice also when dispensing drugs in doses fewer than provided by the manufacturer, Akdag added, but he acknowledged that the pharmacy may repackage drugs regardless of the number of doses ordered.

Elanco Animal Health, maker of Comfortis, believes there’s another reason PetMed Express is taking the tablets out of their original box: to elude tracking. Elanco deploys a “track and trace” system to monitor whether its products are carried by unauthorized dealers such as PetMed Express.

Like most veterinary pharmaceutical companies, Elanco has a policy of selling its animal-health products only through licensed veterinarians who treat patients. Unlike most veterinary pharmaceutical companies, Elanco tries to enforce that policy by using tracking technology on every drug package.

“The reason they (repackage) is to try to evade that,” Elanco spokeswoman Colleen Parr Dekker said.

Elanco’s assertion is driven by its knowledge of a long-evolving practice in the pet parasite industry known as gray-market diversion. In the context of veterinary medicine, diversion is the sales of pet drugs and therapeutics outside of official manufacturer-to-veterinarian channels.

The unauthorized sales aren’t necessarily illegal, hence the market is deemed “gray” rather than “black.”

Where the unauthorized sellers obtain their supplies is a subject of much debate and secrecy. Some veterinarians are known to resell products to brokers. Some pharmaceutical companies are suspected of facilitating diversion to boost sales, even as they publicly decry the practice.

Elanco, to demonstrate its commitment to veterinarians, touts "track and trace" technology as a means of deterring diversion. But the system isn’t foolproof. Practicing diversion and impeding it, it seems, is an ever-changing game.

Inside 1-800-PetMeds bottles, the pills are still contained in Elanco-supplied blister packs. Parr Dekker suggested that the blister packs may be trackable. “We’re continuing to do new system upgrades and (use) new methodology,” she said.

Another Elanco anti-parasite drug, Trifexis, also is repackaged by the unauthorized pharmacy, she said.

PetMed Express CEO Akdag declined to comment on Elanco’s suspicions that the pharmacy is trying to outwit the tracking system.

He noted that PetMed Express repackages drugs other than Elanco brands but would not name them. He said only: “The Elanco products, we don’t sell that many, so we break it all down. If it’s a high-volume brand, it’s not as convenient for us to break it down.”

Akdag added, “We are considering sometime in the future breaking down everything for branding.”

Parr Dekker acknowledged that Elanco doesn’t have direct knowledge of PetMed Express’s motives for repackaging. But she said it’s a logical deduction: “They’re not an authorized dealer of the product.”

She added that Costco, a big-box retailer and another unauthorized seller, also repackages Comfortis and Trifexis.

Vic Curtis, senior vice president of pharmacy at Costco Wholesale, said the company had no comment. “Typically you don’t see Costco in the press much in any regard,” Curtis said in a telephone message left in response to inquiries from the VIN News Service. “We just kind of do our thing and don’t really feel the need to talk much in the press.”

Elanco’s website lists six authorized distributors of its animal health products. All are veterinary suppliers, not retail stores or pharmacies.

Parr Dekker said Elanco sells its drugs through veterinarians only to ensure that pet owners are receiving appropriate guidance and support. “Our concern is, has the consumer had that conversation with the veterinarian about, ‘Is this the right product for my pet?’ ” she said.

Veterinarian-exclusive sales policies have come under criticism of their own. Critics say the policies hinder competition and consumer choice. The Federal Trade Commission (FTC) hosted a workshop last fall to explore the issue. To date, the FTC has not stated an opinion.

Regarding repackaged drugs, Parr Dekker said Elanco is concerned that product instructions, product support contact information and expiration dates may be missing. “Once it’s removed from the packaging, we don’t have any way of knowing that the consumer is getting what they need,” she said.

The U.S. Food and Drug Administration (FDA) had no definitive comment on whether drug repackaging is permissible or problematic.

“Unfortunately, it isn’t a simple answer,” said Siobhan DeLancey, a spokeswoman for the FDA’s Center for Veterinary Medicine. “There are a lot of factors that have to be taken into account, and we wouldn’t want to speculate on any one particular case …”

She added, “We don’t have any advice about this practice at this time.”

At Pasco Animal Hospital in New Port Richey, Fla., Dr. Geoffrey Adams provides written prescriptions for clients who wish to purchase drugs from Internet pharmacies. When he learned from Elanco about the repackaging issue, he began adding to prescriptions: “To be dispensed in the original packaging only.”

“This is the only way to verify that the product is what it claims it to be,” Adams explained on a message board of the Veterinary Information Network (VIN), an online community for the profession.

Initially, the caveat caused some blowback. “PetMeds has retaliated by telling our clients that we have declined the prescription. Understandably, clients are calling us a lot and are quite upset about this,” Adams wrote in June. “However, once we explain the situation, they seem pretty receptive to going through the sources we trust — price-matched, of course.”

Adams then figured out how to avoid future misunderstandings. He reported a few weeks later, “We are warning clients ahead of time now so it won’t be a problem again.”

There's one other thing veterinary clients might want to know when considering their pet-medication purchase: According to Parr Dekker, drugs purchased from unauthorized sellers aren't guaranteed by Elanco.