Page 514 - WSAVA2018
P. 514

 25-28 September, 2018 | Singapore
S. Romagnoli1
1Department of Animal Medicine, Production and Health, University of Padova, Agripolis, Legnaro, 35020 (PD), Italy
Reproductive hormones are readily available to veterinarians working with dogs and cats, both as small animal as well as large animal drugs. The increased importance of companion animals as family members has caused a differentiation of reproductive presenting complaints, from mostly castration a few decades ago to preventing and interrupting pregnancies, inducing heat, blocking the oestrus cycle, causing reversible sterility, treating uterine diseases or neutering-induced conditions or mammary hypertrophy and the like. These presenting complaints require in general a high degree of confidence with the clinical use of reproductive hormones, some of which have been improperly used for decades such as progestogens1, 2. This paper
will review the most common clinical indications
and applications in small animals of prostaglandins, antiprolactinics, progestogens and estrogens.
Several prostaglandin F2alpha (PGF) compounds
have been available for over 30 years as veterinary compounds for use in food animals and horses. Their luteolytic and uterotonic actions make them unique and very useful in small animals for several indications related to pregnancy termination and treatment of uterine conditions. Recently, the use of prostaglandin E1 (PGE1) products such as misoprostol has become popular for their uterotonic properties.
Early pregnancy termination in bitches only (not in queens)
The abortifacient efficacy of PGF involves induction of luteolysis, stimulation of uterine contraction and cervical dilation. Initially it was thought that these actions could be achieved using dosages of 250 mcg/kg 3, but it was later demonstrated that lower doses could bejust as effective4. In dogs, the progesterone (P4) necessary
to support pregnancy is entirely secreted from the corpora lutea throughout gestation. PGF will induce luteolysis and decrease P4 concentrations to nearly non-detectable levels very easily after day 25 or 30 but also as early as day 10 following onset of diestrus5. The later in the cycle PGF is administered the easier and more rapid the induction of luteolysis. Use of PGF requires subcutaneous administration 2 or 3 times a day, for 6-9 days or longer, until pregnancy termination
can be confirmed by ultrasound 6-9. The dosage varies depending on the type of PGF: natural PGF should be administered using a maximum dosage of 50-80 mcg/kg twice or 3 times daily (TID with 50 mcg/kg, BID with 80 mcg/kg), starting gradually with 1/3 to 1⁄2 the dose for the first day (or the first 2 administrations) 6,10. Cloprostenol should be used at a dose of 1-2.5 mcg/kg once daily and alphaprostol should be used at the dose of 20 mcg/kg twice daily. Side effects (which include emesis, salivation, defecation, urination and slight tachypnea) are dose dependent (i.e. displayed in 80% of bitches using doses of 250 mcg/kg natural PGF and only in 20% of bitches using doses of 50 mcg/kg natural PGF) and self-limiting, decreasing in intensity with repeated dosing. PGF do not appear to be working during the first half of diestrus in queens.
Late pregnancy termination in bitches and queens
Canine late pregnancy termination is generally adopted as a treatment when either a mismating was not observed, the female was not in the ovulatory phase
or fertility of the male is unknown. Dosage of PGF compounds is the same as for early abortion, the only difference being that treatment must be continued
until verification of efficacy by ultrasound as partial abortion of litters can occur if treatment is discontinued prematurely. With most dosages, 9 or more days may
be required to complete fetal expulsion, although 5 to 7 days is usually sufficient 8. Cloprostenol at the dose of 2.5 mcg/kg subcutaneously, administered three times, at 48 h intervals, starting at day 30 of pregnancy shows a high efficacy in termination of pregnancy. Cloprostenol
at even lower doses (1.0 mcg/kg) has been used in combination with a dopamine agonist treatment to terminate pregnancy shortly after implantation (which
in bitches and queens occurs around 15-18 days after ovulation) starting around day 23 from ovulation 11. Mismated queens can be treated with natural PGF at a dose of 2 mg/cat IM once a day, beginning at day 33 of pregnancy, as this will induce luteolysis and terminate pregnancy by expulsion of fetuses in pregnant cats. Side effects are milder than in dogs and included prostration, vomiting and diarrhea. Cloprostenol has been used in queens with success (and with fewer side effects than
in bitches) at the dose of 5 mcg/kg in combination with cabergoline administered once daily from mid pregnancy on 12.
Uterine evacuation (including treatment of open cervix pyometra) in bitches and queens
The mioconctracting action of PGF compounds is well known, and can become useful when dealing with
cases of open-cervix pyometra or late abortions with incomplete fetal expulsion 13. Dosage are the same
as listed above. We frequently use PGF compounds combined with aglepristone (see paper on clinical use of aglepristone) when late pregnant bitches are presented

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