Chemical Castration and Contraception

Non-surgical spay/neuter options

Several studies have established that surgical sterilisation raises significant health risks, particularly when performed at an early age; the most problematic of which is delayed closure of bony growth plates resulting in abnormal skeletal development that increases the incidence of orthopaedic problems such as hip dysplasia and patellar luxation.

Further studies have revealed that whilst spay surgery carries a high rate of complications, around 20%, such as infection, haemorrhage and even death, and that it the lack of oestrogen created leads to around 20-30% of spayed bitches developing urinary incontinence,  waiting to spay until after the age of six can increase longevity by 30%. Neutered males have an increased risk of prostate cancer (4 times the risk), both sexes have an increased risk of Osteosarcoma (bone cancer), haemagiosarcoma, hypothyroidism (triple the risk), obesity (3 times the risk), diabetes, urinary tract infections (3-4 times the risk), urinary tract cancer (double the risk), urinary incontinence and cognitive dysfunction in older pets. Behavioural studies have shown increased fearfulness, noise phobias and aggression.

If surgical sterilisation comes with all of the above risks, what about the new option of chemical castration?

According to chemical castration with Neutersol, recently renamed Zeuterin and released onto the market in February of this year, is FDA approved as 99.6% effective, and can be used on males between 3 and 10 months old.  The chemical is injected into each testes and the amount provided is dependent on their diameter. Apparently it does not have a significant effect on testosterone production, and does not appear to effect behaviour and the animal may succumb to irritation and inflammation at the injection site. Zeuterin contains Zinc Gluconate and L-Arginine and works by destroying existing spermatozoa in both the seminiferous tubules and the epididymis, resulting in the collapse of the empty tubules, leaving scar tissue to block any further transport (Ark Sciences, 2014).

The side effects are listed as:

  • Scrotal pain one to three days after injectionPicture1
  • Mild, temporary swelling
  • Scrotal irritation or dermatitis
  • Low white blood cell count
  • Anorexia
  • Lethergy
  • Diarrhea

There are also contraceptives available to bitches, in drop or pill form. Mibolerone is a drop given daily for 30 days prior to the heat cycle, with side effects such as:

  • Liver damage
  • Infertility
  • Increased risk of vaginal infection and indoor wetting
  • Body odour
  • Skin problems
  • Vaginal distortion
  • Personality and behaviour changes

Ovaban is a pill to be administered at the beginning of the heat cycle, with side effects listed as:

  • Uterine infections
  • Mammarian cancer
  • Breast enlargement
  • Weight gain
  • Changes in coat

The question then becomes a philosophical one, which only the owner can answer, are you happy to take the risk, or simply separate your pets for 3 weeks once or twice a year?

We recommend reading: The Spay Neuter Health Denigration & checking out Voss Pets

Ark Sciences (2014) Zeuterin. [Online] Available from: (accessed 31/07/2014)

Image rights — All Critters Pet Hospital (2014) Zeuter vs Neuter tOnline] Available from: (accessed 31/07/2014)


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