Male dogs can breathe a sigh of relief. The days of removing their testicles to stop them breeding or to curb aggressive behaviour may be numbered. A contraceptive implant that halts testosterone and sperm production for months at a time is expected to gain European approval within weeks, while steps are being taken to enable the drug to be sold in the US.
Both egg and sperm production are controlled by the release of sex hormones from the pituitary gland, which is in turn controlled by gonadotrophin releasing hormone (GnRH).
The implant, developed by Peptech in Macquarie Park, Australia, contains a drug called deslorelin or Suprelorin, which binds to GnRH receptors and overstimulates them so that they become desensitised to the hormone. As well as making the dogs temporarily infertile, deslorelin blocks testosterone production, curtailing aggressive behaviour. 鈥淚t鈥檚 reversible,鈥� says Katie Yeates of Peptech. 鈥淚t gives you the option of breeding later.鈥�
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A six-month implant was launched in Australia in late 2004, where it costs between AUS$60 and AU$90 a dose ($52 to $77). Peptech recently launched a 12-month implant and is now developing similar implants for cats and female dogs.
David McDowell, veterinary consultant for the UK鈥檚 Royal Society for the Prevention of Cruelty to Animals, says while oral contraceptives have been used in female cats for years, long-term use may stimulate breast tumours or uterus infections. Although the new implants work through a different mechanism, he fears similar side effects may be associated with long-term use in dogs. 鈥淧rovided owners use them within the manufacturers鈥� guidelines, we would welcome the new drug,鈥� he says. 鈥淗owever, if dog owners don鈥檛 want to use their pet for breeding, we believe neutering is the best option.鈥�
The European Medicines Agency recommended in March that the European Commission authorise the marketing of Suprelorin later this month.
Last week, Daniela Braga of the Assisted Fertilization Center in Sao Paolo, Brazil, and colleagues told a meeting of the European Society for Human Reproduction and Embryology in Lyon, France, that they have used the drug as an alternative to surgical sterilisation in female cattle and to time their pregnancies for when pastures are available.
