Obstetrics is one of my favorite parts of my career. Delivering fetuses can however be difficult, even under the best of circumstances. One of the most important tools we have to aid us in managing labor and delivery is oxytocin. Oxytocin is a drug that stimulates uterine muscle contraction by acting on receptors in uterine muscle1.
I commonly use this drug as an aid for the delivery of puppies. Once a dog starts pushing or after the water breaks a puppy should be delivered within about 20 minutes. If a puppy isn’t delivered in twenty minutes we suggest a full exam. If the cervix is open, I will administer oxytocin to help deliver the puppies. If the cervix is closed the uterus may rupture as the mother pushes.
We normally dose the oxytocin according to the size of the patient, by intramuscular injection. The injections are administered about every 30-45 minutes. If no puppies are delivered after about four injections we usually suggest a cesarean. I also give oxytocin after a caesarian to encourage the uterus to contract down so that there is less chance of bleeding.
Oxytocin can also be used in cows, sheep and goats and llamas. The difference with these animals is that I generally only give oxytocin after I deliver the fetuses. Most of these fetuses need repositioning which is challenging, if oxytocin is administered the uterus contracts even more powerfully, making repositioning more difficult. I administer a single intramuscular injection of oxytocin after delivery to help expel the placenta and to encourage the uterus to contract down. This also decreases the incidence of uterine prolapse. If treating a patient that has already prolapsed I administer oxytocin to try to get the uterus to shrink, making it easier to replace inside of the patient.
Horses are more sensitive to the effects of oxytocin than most other species and develop abdominal pain after administration. I give an injection after I have delivered the foal so that the mare will pass the placenta. It is important that horses deliver their placentas within two to four hours, if they do not they can develop painful feet and uterine infections. There are two methods to administer oxytocin to horses, by intramuscular injection or as a slow intravenous drip. I usually give and intramuscular injection. Since horses usually develop abdominal pain after administration of oxytocin I give pain and anti-inflammatory medications concurrently.
As you can see oxytocin is a very effective drug when used in the correct situation. It must be used with caution and only after a thorough exam by your veterinarian and under his or her direct supervision.
1. Saunders Handbook of Veterinary Drugs third edition small and large animals; By Mark G. Papich page 575