Dogs taking chemotherapy drugs excrete residues from the drugs in their bodily fluids, but what sorts of risks do these residues pose?

A recently published German study on cytotoxic drug residues in dog urine attempts to answer that question. A team of researchers at the Hannover University of Veterinary Medicine Small Animal Hospital studied urine samples from client-owned dogs with lymphoma or mast cell tumors that were being treated with standard chemotherapy protocols.

The team collected urine samples before, directly after and for several days after administration of chemotherapy drugs. They tested for the residues of vincristine, vinblastine, cyclophosphamide, and doxorubicin, with varying results.

Median concentration of residues (µg/L)

“At the moment it is unclear whether the residue concentrations that we have measured in the urine of the dogs in our study are high enough to pose a risk to people and/or animals,” said co-author Daniela Simon, Dr.med.vet., DECVIM-CA (Internal Medicine & Oncology). “To clarify this, more studies – i.e. mutagenicity assays – will be necessary in the future. Until this aspect is clarified protective measures should be instituted when handling a dog’s urine for the described time periods in order to rule out any hazard risk.”

Simon said the study could be useful to veterinarians in terms of educating clients about how long the powerful cytotoxic drugs stay in their pets systems.

“We can better inform our clients on the residue aspect of chemotherapy treatment and advise them on the use of protective measures during the residue excretion period,” Simon said. “In this, the safety of cytotoxic treatment is improved for veterinarians, patients and owners as well as their close surroundings.”

Colorado State University’s Animal Cancer Center advises its clients not to handle any kind of excretions from a pet within a day of administration. According to the site:

“Do not handle feces, urine or vomitus unless absolutely necessary within 24 hours of the chemo administration. If your pet has an “accident”, wear gloves and clean the area with disposable items (paper towels, baby diapers, etc.) and dispose in the trash. Wash your hands thoroughly when you are finished cleaning. In general, it is recommended that clothing/ bedding which is soiled by feces, urine or vomitus within 24 hours of chemotherapy administration should be washed twice in hot water.”

Simon said the most surprising thing from the study was the duration of measurable urinary doxorubicin residues was longer than have expected. According to the study, doxorubicin remained measurable in low concentrations up to 21 days after administration.

The study, “Drug Residues in Serum of Dogs Receiving Anticancer Chemotherapy,” appears in the “Journal of Veterinary Internal Medicine.”