Canine Estrus Control/Drug Therapy

Question 1

Why is Megestrol Acetate (Ovaban®) contraindicated in the queen?

Answer 1

causes diabetes mellitus

Question 2

T/F: In order to be effective, Megestrol Acetate (Ovaban®) must be used within the first three days of estrus

Answer 2

False

• In order to be effective, Ovaban® must be used within the first three days of proestrus
• Next estrus cycle will be 4-6 weeks earlier

Question 3

T/F: Use of Depo-Provera® may predispose bitches to CEH and pyometra

Answer 3

True

Medroxyprogesterone acetate (MPA), commonly known as Provera ® or Depo-Provera®, is used to suppress the heat cycle in female dogs

Question 4

In the bitch, progesterone needs to be in a range of ___ ng/mL or lower to consider supplementing

Answer 4

In the bitch, progesterone needs to be in a range of 3 ng/mL or lower to consider supplementing

Question 5

If you’re going to supplement progesterone in a pregnant bitch, you should ideally wait until 45 days of pregnancy or (at a minimum) avoid the first trimester (21 days). Why?

Answer 5

to avoid masculinization of female pups or maintain a physiologic concentration of P₄

Remove Progesterone 2 to 3 days prior to due date to allow cervix to relax adequately. Any progestagen can masculinize the female fetuses

Question 6

T/F: Progesterone supplementation during pregnancy can feminize male fetuses

Answer 6

False

Progesterone supplementation during pregnancy can masculinize female fetuses

Question 7

What does Mibolerone (Cheque®) do?

Answer 7

prolongs interestrus interval (IEI)

prevents LH release by negative feedback, thereby preventing estrus

• Androgenic compound
• Not approved for use in breeding bitches
• Generally not recommended due to safety/efficacy issues

Question 8

Deslorelin is a(n) ______ analogue. It down-regulates the pituitary-gonadal axis

Answer 8

Deslorelin is a GnRH analogue. It down-regulates the pituitary-gonadal axis

• It can be used for long or short term suppression of reproductive function of dogs and in situations where a reduced Testosterone level is required, such as controlling antisocial behavior and treating prostatic enlargement
• Approved in ferrets

Question 9

“Mismating” shots can be given to cause “tubular lockage” and disrupt/alter the uterine environment. They must be given within ____ hours of breeding to be effective

Answer 9

72 hours

• Estrogen - within 72 hours of breeding - while still in estrus
  
  • Take cytology to confirm estrus/sperm
• Causes “tubular lockage” and disrupts/alters uterine environment
• 25% incidence of pyometra - side effect
• Only ~38% of dogs become pregnant from one mating – so may want to delay drugs until ~30 day ultrasound

Question 10

What is the main sign of estrogen toxicity seen in dogs and ferrets?

Answer 10

bone marrow suppression/aplasia

Question 11

T/F: Mismating shots must be administered within 63 days of breeding

Answer 11

False

Mismating shots must be administered within 72 hours of breeding

Question 12

T/F: Multiple small injections of prostaglandin will lyse the CL of the bitch or the queen

Answer 12

True

• Side effects seen with smooth muscle contractions but minimize over time
  
  • Luteolytic dose only 5 fold from the LD 50
• May get drop in blood pressure (some need IV fluids to stabilize), vomiting, diarrhea, salivation and panting
• Used for treatment of pyometra, retained placenta, mismating, collection of males
  
  • Best accomplished during 2nd trimester after pregnancy diagnosis

Question 13

Bromocriptine and Cabergoline are _______ inhibitors

Answer 13

prolactin

• Prolactin is luteotropic in bitch and queen during the 2nd trimester. CL’s lyse in response to lowered prolactin levels
  
  • Cabergoline is a serotonin antagonist
  • Bromocryptine is a dopamine agonist

Question 14

Before mid-gestation, what drug(s) is/are most commonly used to induce abortion in the bitch?

Answer 14

Lutalyse®

Question 15

After mid-gestation, what drug(s) is/are most commonly used to induce abortion in the bitch?

Answer 15

Bromocriptine + Lutalyse®

• Bromocryptine 10 mcg/kg PO TID plus Lutalyse ® 0.1mg/kg SQ TID (less side effects with low dose)
• Side effects lessen with subsequent doses
• Takes 10-12 doses before abortion is complete
• Recheck with U/S to ensure abortion complete

Question 16

What drug is used to induce estrus when a bitch does not come back into estrus for a prolonged period?

Answer 16

Cabergoline (Dostinex®)

• Prolactin inhibition may shorten anestrus
• 70% will induce within 14 days
• Make sure low P4 before start and had normal (5 mo) interestrous interval
• Can take 7 to 50 days though – be prepared for expense if longer time interval
• Look for bleeding and vulvar edema to start cytologies/Progesterone measurements or check cytology and vag speculum q7d until in proestrus
• May get coat color changes esp with tx beyond 3 weeks but will go away when next sheds

Question 17

What is the drug of choice for treatment of unwanted uterine contractions in the bitch?

Answer 17

Terbutaline (β₂ agonist)

• Progesterone will also decrease uterine contractions if Terbutaline not totally effective
• Avoid high Terbutaline dosages as may cause cardiac effects
• Look for dead pup, infection or inflammation as cause of abnormal contractions

Question 18

This drug is used for a bitch that whelps with little to no milk:

Answer 18

Domperidone

• ↓ dopamine & ↑ prolactin*
• ↑ milk production*

Question 19

Which of the following drugs would be appropriate to give in a protocol to induce an abortion in a bitch at around 45 days of gestation?

• Estrogen
• Testosterone
• Bromocriptine
• Domperidone

Answer 19

Bromocriptine