Oxytocin

Oxytocin is a peptide hormone used for its effects on uterine contraction and milk ejection. Veterinary applications include selected nonobstructive dystocia, postpartum uterine management and impaired milk letdown. It also has a specialized equine reproductive role in protocols intended to prolong luteal activity and suppress estrous behavior.

Group

Uterotonic hormone

Mechanism of Action

Oxytocin activates G-protein-coupled receptors on uterine myometrial and mammary myoepithelial cells. Increased intracellular calcium promotes contraction, supporting uterine evacuation or expulsion of milk already present in the mammary gland. Its effects on the equine uterine prostaglandin–luteal signaling system depend on cycle timing and can be used in selected protocols to prolong luteal function.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Primary uterine inertia	5–20 IU/animal	IM, SC	Every 0.5 h	Repeat according to labor response; label alternative is 5-30 IU/dog.
Primary uterine inertia	5–30 IU/animal	IM, SC		Separate manufacturer-label alternative; monitor closely.
Milk letdown	2–5 IU/animal	IM	Once	Give 15-30 minutes before nursing.
Uterine contraction augmentation	0.5–3 IU/animal	SC, IM	Every 0.5–1 h	Use uterine and fetal monitoring; rule out obstruction.
Low-dose uterine inertia protocol	0.25 IU/animal	SC, IM	As needed	Maximum 4 IU/dose; Start at this total amount, titrated to contractions, generally no more often than hourly; described maximum 4 IU per bitch/queen. High doses or IV bolus may cause tetany and fetal compromise.
Secondary agalactia	0.25–1 IU/animal	SC	Every 2 h	Remove neonates for 30 minutes then encourage suckling. Combined lactation plan may include metoclopramide 0.1-0.2 mg/kg SC every 12 hours.
Acute postpartum metritis adjunct	0.5–5 IU/animal	IM		Within 24 hours of birth; antimicrobial and supportive care are also required.
Uterine involution after prolapse reduction	0.5–5 IU/animal	IM
Uterine involution after prolapse reduction	5–10 IU/animal	IM

Cats

Use / stage	Dose	Route	Schedule	Instructions
Uterine inertia	2.5–3 IU/animal	IM, IV	Every 0.5–1 h	Maximum 3 IU/dose; Repeat at 30-60 minute intervals, up to three times.
Low-dose uterine inertia protocol	0.25 IU/animal	SC, IM	As needed	Maximum 4 IU/dose; Start at this total amount, titrated to contractions, generally no more often than hourly; described maximum 4 IU per bitch/queen. High doses or IV bolus may cause tetany and fetal compromise.
Secondary agalactia	0.25–1 IU/animal	SC	Every 2 h	Remove neonates for 30 minutes then encourage suckling. Combined lactation plan may include metoclopramide 0.1-0.2 mg/kg SC every 12 hours.
Acute postpartum metritis adjunct	0.5–5 IU/animal	IM		Within 24 hours of birth; antimicrobial and supportive care are also required.
Uterine involution after prolapse reduction	0.5–5 IU/animal	IM
Uterine involution after prolapse reduction	5–10 IU/animal	IM

Cattle

Use / stage	Dose	Route	Schedule	Instructions
Uterine contraction	30 IU/animal	IM	Every 0.5 h	Repeat if needed; manufacturer alternative is 100 IU/cow.
Uterine contraction	100 IU/animal	IM		Manufacturer-label alternative.
Retained placenta	20 IU/animal	IM	Every 2–4 h	First dose immediately after calving.
Milk letdown	10–20 IU/animal	IV, IM

Horses

Use / stage	Dose	Route	Schedule	Instructions
Uterine contraction	20 IU/animal	IM		Mares; manufacturer-label alternative is 100 IU.
Uterine contraction	100 IU/animal	IM		Manufacturer-label alternative for mares.
Retained placenta	30–40 IU/animal	IM	Every 1–1.5 h
Retained placenta infusion	Reference only	IV		Mares: add 80-100 IU to 500 mL saline and give IV; no infusion time or rate is specified.
Estrous behavior suppression	60 IU/animal	IM	Every 12–24 h	Mares on days 7-14 after ovulation.

Sheep

Use / stage	Dose	Route	Schedule	Instructions
Uterine contraction	5–10 IU/animal	IM		Sows and small ruminants; manufacturer-label alternative is 30-50 IU/animal.
Uterine contraction	30–50 IU/animal	IM		Separate manufacturer-label alternative.
Postpartum metritis adjunct	5–10 IU/animal	IM	Every 6–8 h	Up to 3 days

Goat

Use / stage	Dose	Route	Schedule	Instructions
Uterine contraction	5–10 IU/animal	IM		Sows and small ruminants; manufacturer-label alternative is 30-50 IU/animal.
Uterine contraction	30–50 IU/animal	IM		Separate manufacturer-label alternative.
Postpartum metritis adjunct	5–10 IU/animal	IM	Every 6–8 h	Up to 3 days
Post-manipulation uterine bleeding	10–20 IU/animal	IV		May repeat SC after 2 hours.

Pigs

Use / stage	Dose	Route	Schedule	Instructions
Uterine contraction	5–10 IU/animal	IM		Sows and small ruminants; manufacturer-label alternative is 30-50 IU/animal.
Uterine contraction	30–50 IU/animal	IM		Separate manufacturer-label alternative.
Uterine contraction augmentation	10 IU/animal	IM	Every 0.5 h	Do not repeat sooner than 30 minutes.
Obstetrical use	30–50 IU/animal	IV, IM, SC
Postpartum metritis adjunct	5–10 IU/animal	IM	Every 6–8 h	Up to 3 days
Milk letdown	5–20 IU/animal	IV

Llamas

Use / stage	Dose	Route	Schedule	Instructions
Retained placenta	5–10 IU/animal	IM	Every 0.1666666667 h	Only gentle traction; forceful traction can cause prolapse.

Alpacas

Use / stage	Dose	Route	Schedule	Instructions
Retained placenta	5–10 IU/animal	IM	Every 0.1666666667 h	Only gentle traction; forceful traction can cause prolapse.

Birds

Use / stage	Dose	Route	Schedule	Instructions
Uterotonic treatment	0.5 IU/kg	IM	Every 1 h	Repeat after 60 minutes if required.

Reptiles

Use / stage	Dose	Route	Schedule	Instructions
Egg binding	1–10 IU/kg	IM		In a calcium-correction protocol. Exclude obstructed passage to avoid oviduct rupture; less reliable in lizards.

Indications

Treatment of selected nonobstructive dystocia caused by uterine inertia in dogs, cats and other veterinary patients.
Support of postpartum uterine contraction or uterine clearance in selected reproductive cases, including some mares with delayed clearance.
Stimulation of milk letdown when milk is present but ejection is inadequate.
Selected adjunctive management of postpartum uterine atony or associated bleeding.
Specialist prolongation of luteal activity to suppress estrous behavior in mares.

Contraindications

Do not induce contractions with an unrelaxed cervix, obstructed delivery or abnormal fetal presentation.
Pregnancy except when parturition is intentionally induced.

Interactions

Beta-adrenergic agonists oppose uterine contraction.

Adverse effects

Excessive or poorly timed uterine contractions may compromise delivery and fetal wellbeing.

Toxicity

Excessive uterine stimulation can cause tetany, rupture, placental compromise or fetal death. Prolonged high-dose infusion with electrolyte-free fluid may cause water intoxication and neurologic signs.

Preparations

Preparation	Form	Strength	Route
Oxytocin injection 10 IU/mL	Injection	10 IU / mL	IM, IV, SC
Oxytocin injection 20 IU/mL	Injection	20 IU / mL	IM, IV, SC

Monitoring and Administration

Check fetal position and cervical relaxation before administration; monitor labor progression and fetal stress. Pregnant handlers should avoid accidental exposure.

Retained-placenta efficacy varies; use the species-specific regimen rather than extrapolating a per-kg amount.