1. GnRH Agonists - Gonadotropin Releasing Hormone Agonists are considered the safest reversible contraceptives, but dosages and duration of efficacy are not well established for all species; side effects are generally similar to those associated with gonadectomy, especially the potential for weight gain unless diet is controlled.
    Suprelorin® (deslorelin) Implants (F or M)
    Lupron® Depot Injection (F or M)
  2. Ovariohysterectomy or Ovariectomy (F) or Castration (M) are safe and effective methods for preventing pregnancy if permanent sterilization is an option (but see Caution 1 for males).

Guidelines When Progestins Must Be Used

Progestin contraceptives are associated in felids with progressive uterine growth that can result in infertility, infections, and sometimes uterine cancer; mammary tissue stimulation also can result in cancer. 
a) If a progestin is used, treatment should only be short term, because of the increased likelihood of side effects with prolonged exposure.
b) If a progestin is used, treatment should start well BEFORE any signs of proestrus, since the elevated endogenous estrogen can exacerbate side effects of the progestin. 
c) Progestins should not be used in pregnant animals, since they may suppress uterine contractions necessary for normal parturition. Thus, progestins should only be administered to females CONFIRMED non-pregnant.
• MGA Implant (F) - for 2 years, then remove for 1 pregnancy if possible; non-fertile ovulatory cycles do not substitute for pregnancy in reversing deleterious effects on the uterus; not recommended for more than a total of 4 years (F).
• Megestrol acetate (F) - orally for seasonal breeders, but for no more than 2 consecutive seasons. 
• Depo-Provera® injection (F) - 5mg/kg body wt. every 2 months, no more than 2 consecutive seasons.  For felids, Depo-Provera is the least preferable of the progestins due to the unpredictable duration of efficacy and because it has more side effects.


  1. Vasectomy of males will not prevent potential adverse effects to females from prolonged, cyclic exposure to endogenous steroids associated with the obligate hormonal pseudo-pregnancy that follows ovulation in most felids. Endogenous steroids and steroid contraceptives cause similar side effects.
  2. PZP vaccine (F) - efficacy and safety have only been demonstrated in pinnipeds and bears among the carnivores. In other carnivores, there is mounting evidence that anti-PZP antibodies do not cross-react with the sperm receptor on the ovum, or may cause depletion of ovarian oocytes. PZP is contraindicated in species in which pseudopregnancy is common.

Research and Monitoring

  1. Surveillance for deleterious effects
    Contraception Annual Survey
    Tissue Submission Form – Pathology
    Adverse Reactions Report