(Mongabay) Authorities are considering banning the use of a human contraceptive injection for animals backed by calls from animal rights activists and vets, after a state-sanctioned chemical sterilization program drew serious criticism.

The medroxyprogesterone acetate contraceptive injection, popularly sold under the brand name Depo-Provera, is intended for humans and had come under the spotlight when the government attempted to introduce it to stray dogs (Canis lupus familiaris)as a pilot project.The drug has often been surrounded in controversy due to its safety risks. In the United States, the Food and Drug Administration has issued a “black box warning” on the contraceptive, citing that it may lead to bone density loss among humans.Vets and animal rights activists say the repercussions of using the injection on animals are even worse.

The Veterinary Drug Control Authority (VDCA), which falls under the purview of the Department of Animal Production and Health, has not banned the use of this contraceptive for animals.The Public Health Veterinary Services office estimates Sri Lanka’s stray dog population to be around 3-4 million.Hemali Kothalawala, the director general of the Department of Animal Production and Health, said in the past, the VDCA has granted approval to import that jab only under “special circumstances” if it is to be used on animals.

However, the National Medicines Regulatory Authority has granted approval to import the injection to be used on humans. Animal rights activists say the injections imported for humans are illegally used by quack vets on dogs.

“We are considering proposals to prohibit the use of this injection on animals. This has many harmful side effects. We will make a final decision in the near future,” Kothalawala told Mongabay.She added that until a final decision is made, anyone importing the injection for the purpose of using it on animals will have to obtain the approval of the VDCA.

Calls to ban the injection came after the Public Health Veterinary Services officeannounced a pilot project on Jan. 5 to carry out chemical sterilization on 50,000 free-roaming dogs.The program was aimed at achieving zero dog-mediated human rabies deaths by 2025, in line with the United Nations Sustainable Development Goals.

“The Depo-Provera vaccines were to be given to us as a grant by the World Health Organization,” L.D. Kithsiri, the director of Public Health Veterinary Services, told Mongabay.

Over the years, the Public Health Veterinary Services Office has adopted two approaches to combat rabies. The options are to administer rabies vaccines or perform clinical sterilization on female dogs — a process during which the animal’s reproductive organ is removed to permanently stop it from reproducing.

“We wanted to introduce chemical sterilization because we have not received enough funds from the government to carry out clinical sterilization,” Kithsiri said.

He said the Public Health Veterinary Services Office has received only around 69 million rupees ($190,000) for clinical sterilization in 2023, and that allocation is enough to perform the surgery on only 25,000 dogs.

“In 2022, the number of dog-mediated human rabies deaths was 28. Each year, around 20-30 deaths occur due to rabies. We need to perform the surgery on at least 100,000 dogs every year to achieve our target of no rabies deaths,” Kithsiri added.

The proposed chemical sterilization program sparked serious concerns from animal rights activists and vets who pointed out that the injection can have life-threatening implications when given to dogs.

The injection requires repeated dosing and has to be given to dogs after assessing the exact phase of their reproductive cycle. The Sri Lanka Veterinary Association (SLVA)had written to the health ministry highlighting that it is not practical to monitor the reproductive cycle of stray dogs, which had been chosen for the pilot project.

“It [the injection] requires repeated dosing for long-term suppression of reproduction. Therefore, administering Depo-Provera to stray animal population control is limited,” SLVA said in its letter seen by Mongabay.

The injection should not be given to female dogs when their estradiol hormone levels have been elevated or when they are not in anestrus — the non-breeding period of a dog’s six-month heat cycle, according to research published in The Blue Cross, the annual bulletin of the Nepal Veterinary Students Association.