Drug Monograph
Full clinical overview, indications, dosage references & safety notes.
Drug class: Hormone (uterotonic)
Main indication: Induction or enhancement of uterine contractions; milk letdown
Available forms2 forms · 3 strengths documentedShow all ↓
Injectable
10 units (IU)/mL 1 mL single-dose · 10 and 30 mL multi-dose · Pitocin20 USP units/mL 100 mL vials · generic veterinary
Intranasal
40 units/mL human product
Overview
Oxytocin (Pitocin®) is a naturally occurring hypothalamic hormone used in dogs and cats to induce or enhance uterine contractions during parturition, facilitate postpartum evacuation of uterine contents, promote uterine involution after manual correction of uterine prolapse, and treat secondary agalactia.
Oxytocin facilitates milk ejection but does not stimulate milk production. The response of the uterus to oxytocin increases as pregnancy progresses and is enhanced in the presence of elevated estrogen concentrations and during active labor.
Mechanism of Action (MOA): Oxytocin stimulates uterine contractions by increasing sodium permeability of uterine myofibrils. It also promotes milk letdown by contracting the smooth muscle cells of the mammary gland, and does so if the gland is in the appropriate physiological state. Oxytocin has weak antidiuretic properties, although commercial preparations have virtually none at usual doses.
Indications
Oxytocin is used in dogs and cats to stimulate uterine contractions and facilitate milk ejection when clinically indicated.
- Induction or enhancement of labor: To initiate or strengthen uterine contractions during parturition when appropriate.
- Postpartum uterine evacuation: To assist in the expulsion of retained uterine debris and control postpartum uterine bleeding.
- Uterine involution: To promote uterine involution following manual correction of uterine prolapse.
- Secondary agalactia: To facilitate milk letdown in lactating animals, for feeding of the young or as an adjunct in the treatment of mastitis.
- Acute metritis: To assist evacuation of the uterus as an adjunct to antibiotic and fluid therapy in acute postpartum metritis.
- Retained placenta: To assist expulsion of a retained placenta or retained fetal membranes in an otherwise healthy dog or cat.
- Deficient maternal behavior: To stimulate maternal bonding and behavior in the immediate postpartum period, where it is deficient or poor.
- Uterine evacuation after abortion: To evacuate the uterus after spontaneous abortion in the bitch, where evacuation by uterine contraction alone is the aim.
Dosage (Reference)
Dog
In cases of uterine inertia, calcium is commonly administered before oxytocin to improve uterine contraction strength.
| Clinical use | Route | Dose | Frequency / timing | Notes |
|---|---|---|---|---|
| Uterine inertia | IM | 0.1 units/kg initially | q30–40min | This is an initial dose, not a maximum dose. Older high-dose regimens are no longer recommended because mini-doses improve uterine contraction frequency and reduce uterine rupture and placental compromise. As maximum doses differ between protocols, escalate only within a complete protocol with a clearly defined limit. |
| Uterine inertia | IV | 2 units/dog | q30–60min | Total dose (NOT units/kg). |
| Uterine inertia | SC or IM | 0.25 units/dog | Not more often than hourly | Total dose (NOT units/kg); may increase to a maximum of 4 units/dog. |
| Secondary agalactia | SC | 0.25–1 unit/dog | q2h | Total dose (NOT units/kg). Remove the neonates for 30 minutes after the injection and then encourage suckling, or strip the glands gently; treatment is usually rewarding within 24 hours. |
| Acute metritis (adjunctive therapy) | IM | 0.5–5 units/dog | Within 24 h of parturition | Give with culture-directed, broad-spectrum antibiotics that penetrate the reproductive tract for ≥14 days, plus fluids if dehydrated or in shock. If >24 hours postpartum, consider dinoprost 0.25 mg/kg SC instead. Monitor physical findings, CBC, vaginal cytology, and uterine evacuation by ultrasonography. |
| Acute metritis (alternative per-kilogram protocol) | IM or SC | 0.5-1 U/kg (maximum 5 IU total) | Repeat in 1-2 h | Used where ovariohysterectomy has not been performed and the cervix is open. Efficacy is reduced beyond 48 hours post partum and a higher dose may then be required to attain a similar degree of uterine contraction, still without exceeding the 5 IU total. |
| Uterine prolapse (after manual reduction) | IM | 0.5–5 units/dog | Once, after manual reduction | Perform manual replacement under anesthesia; reduce edema with a hyperosmotic solution if needed |
| Uterine prolapse (alternative protocol) | IM | 5–10 units/dog | Once the uterus is replaced | Perform manual replacement under anesthesia; reduce edema with a hyperosmotic solution if needed |
| Retained placenta or retained fetal membranes | IM | 0.5 IU/kg (maximum 5 IU total) | Within 48 h postpartum | For an otherwise healthy patient. Calcium gluconate 10% 0.5 to 1.5 mL/kg IV slowly over 15 minutes may be given first, watching for bradycardia during the injection; efficacy for retained placenta is questionable and some clinicians add estrogen. Monitor temperature and physical condition afterwards. |
| Deficient maternal behavior | Parenteral (route not specified) | 1–5 units/dog | Immediate postpartum period | Used after cesarean section in particular, where the factors needed during the sensitive period for acceptance of the neonate have waned. A nasal spray is also described, but no intranasal dose is stated. Acepromazine 0.55 to 2.2 mg/kg PO may be added as a dopamine blocker, since prolactin appears to be needed for maternal behavior. Monitor the puppies daily to ensure they are gaining weight. |
| Uterine evacuation after spontaneous abortion | SC | 1 unit/5 kg | q6–24h | Considered only where uterine evacuation solely through uterine contraction is desired. |
Important dosing notes (dogs):
• In canine uterine inertia, 10% calcium gluconate may be given before oxytocin to increase contraction strength. IV regimens include 0.2 mL/kg slowly or 0.5–1.5 mL/kg slowly 10 minutes before oxytocin. SC regimens include 1 mL/5 kg every 4–6 hours or 1 mL/22 kg every 6 hours, with a maximum of 6 mL per site. Follow one complete regimen, avoid IM administration, and monitor heart rate and rhythm; SC administration requires caution because tissue necrosis may occur.
• Dosing frequency depends on labor progression and the selected protocol; the 0.25-unit SC or IM regimen should generally not be repeated more frequently than hourly.
• A larger dose is not a stronger one: high doses can saturate the oxytocin receptors and make the drug ineffective as a uterotonic, and canine myometrium shows markedly reduced responsiveness after high-dose stimulation. If a correctly timed dose fails, reassess rather than escalating automatically.
• Other published canine protocols give 2 to 6 IU/dog IV or IM every 30 minutes for up to three doses, or 5 to 20 units/dog IM or SC repeated every 30 minutes for primary inertia. A microdose protocol of 0.5 to 3 IU IM or SC, repeated every 30 minutes while delivery progresses, is also described.
• For postpartum metritis or retained placenta, efficacy may decline after about 48 hours; in metritis a higher dose may be needed to achieve a similar degree of uterine contraction.
• A single dose of 0.25 to 1 unit SC at the completion of labor may help uterine involution; monitor the dam’s temperature and the character of the postpartum discharge and milk afterwards.
• For simple milk let-down rather than established agalactia – whether the aim is feeding the young or an adjunct in the treatment of mastitis – 2 to 10 IU/dog IV, IM or SC as a single dose is also described, as is 2 to 5 units/dog IM given 15 to 30 minutes before nursing in the early stages of lactation. In established agalactia, metoclopramide 0.1 to 0.2 mg/kg SC every 12 hours can be given alongside the oxytocin to promote milk production.
• In canine uterine inertia, 10% calcium gluconate may be given before oxytocin to increase contraction strength. IV regimens include 0.2 mL/kg slowly or 0.5–1.5 mL/kg slowly 10 minutes before oxytocin. SC regimens include 1 mL/5 kg every 4–6 hours or 1 mL/22 kg every 6 hours, with a maximum of 6 mL per site. Follow one complete regimen, avoid IM administration, and monitor heart rate and rhythm; SC administration requires caution because tissue necrosis may occur.
• Dosing frequency depends on labor progression and the selected protocol; the 0.25-unit SC or IM regimen should generally not be repeated more frequently than hourly.
• A larger dose is not a stronger one: high doses can saturate the oxytocin receptors and make the drug ineffective as a uterotonic, and canine myometrium shows markedly reduced responsiveness after high-dose stimulation. If a correctly timed dose fails, reassess rather than escalating automatically.
• Other published canine protocols give 2 to 6 IU/dog IV or IM every 30 minutes for up to three doses, or 5 to 20 units/dog IM or SC repeated every 30 minutes for primary inertia. A microdose protocol of 0.5 to 3 IU IM or SC, repeated every 30 minutes while delivery progresses, is also described.
• For postpartum metritis or retained placenta, efficacy may decline after about 48 hours; in metritis a higher dose may be needed to achieve a similar degree of uterine contraction.
• A single dose of 0.25 to 1 unit SC at the completion of labor may help uterine involution; monitor the dam’s temperature and the character of the postpartum discharge and milk afterwards.
• For simple milk let-down rather than established agalactia – whether the aim is feeding the young or an adjunct in the treatment of mastitis – 2 to 10 IU/dog IV, IM or SC as a single dose is also described, as is 2 to 5 units/dog IM given 15 to 30 minutes before nursing in the early stages of lactation. In established agalactia, metoclopramide 0.1 to 0.2 mg/kg SC every 12 hours can be given alongside the oxytocin to promote milk production.
Cat
In uterine inertia, calcium is often given before oxytocin because calcium strengthens uterine contractions, whereas oxytocin increases their frequency.
| Clinical use | Route | Dose | Frequency / timing | Notes |
|---|---|---|---|---|
| Uterine inertia | IM | 0.1 units/kg initially | q30–40min | This is an initial dose, not a maximum dose. Older high-dose regimens are no longer recommended because mini-doses improve uterine contraction frequency and reduce uterine rupture and placental compromise. As maximum doses differ between protocols, escalate only within a complete protocol with a clearly defined limit. |
| Uterine inertia | IV | 2 units/cat | q30–60min | Total dose (NOT units/kg). |
| Uterine inertia | SC or IM | 0.25 units/cat | Not more often than hourly | Total dose (NOT units/kg); may increase to a maximum of 4 units/cat. |
| Secondary agalactia | SC | 0.25–1 unit/cat | q2h | Remove the kittens for 30 minutes, then encourage suckling or gently strip the glands; response usually occurs within 24 hours |
| Acute metritis (adjunctive therapy) | IM | 0.5–5 units/cat | Within 24 h of parturition | Give with culture-directed, broad-spectrum antibiotics that penetrate the reproductive tract for ≥14 days, plus fluids if dehydrated or in shock. If >24 hours postpartum, consider dinoprost 0.25 mg/kg SC instead. Monitor clinical findings, CBC, vaginal cytology, and uterine evacuation by ultrasonography. |
| Acute metritis (alternative per-kilogram protocol) | IM or SC | 0.5-1 U/kg (maximum 5 IU total) | Repeat in 1-2 h | Use only when ovariohysterectomy has not been performed and the cervix is open. Efficacy declines after 48 hours; higher doses may be required, without exceeding 5 IU total. |
| Uterine prolapse (after manual reduction) | IM | 0.5–5 units/cat | Once, after manual reduction | Replace under general or epidural anesthesia; reduce marked edema with 50% dextrose or mannitol. Episiotomy may be required. |
| Uterine prolapse (alternative protocol) | IM | 5–10 units/cat | Once the uterus is replaced | Under anesthesia, lubricate and replace the uterus, flushing the horn with pressurized sterile saline; reduce edema first with mannitol or hypertonic saline if needed. |
| Retained placenta or retained fetal membranes | IM | 0.5–1 IU/cat | Within 48 h postpartum | For otherwise healthy queens. Calcium gluconate 10% at 0.5–1.5 mL/kg IV over 15 minutes may be given first; monitor for bradycardia. Efficacy is questionable, and estrogen is sometimes added. Monitor temperature and clinical condition. |
| Deficient maternal behavior | Parenteral (route not specified) | 1–5 units/cat | Immediate postpartum period | Used mainly after cesarean section when the maternal-acceptance period has waned. Intranasal use is described without a stated dose. Acepromazine 0.55–2.2 mg/kg PO may support prolactin-mediated maternal behavior; monitor kittens’ daily weight gain. |
Important dosing notes (cats):
• 10In feline uterine inertia, 10% calcium gluconate 0.5–1 mL/cat IV over 10 minutes may be given before oxytocin. Other regimens include 0.2 mL/kg slowly IV or 1 mL/5 kg SC every 4–6 hours, with 1 mL/22 kg SC every 6 hours and a maximum of 6 mL per site also described. Follow one complete regimen, avoid IM administration, and monitor heart rate and rhythm. Use cautiously because strong contractions may increase the risk of uterine rupture.
• Older, higher dose recommendations for dogs and cats are now regarded as obsolete: mini-doses improve the frequency of uterine contractions and are less hazardous to the dam (uterine rupture) and to the fetuses (placental compromise).
• A larger dose is not a stronger one: high doses can saturate the oxytocin receptors and make the drug ineffective as a uterotonic. If a correctly timed dose fails in a queen, reassess rather than escalating automatically.
• Other published feline protocols give 2 to 4 IU/cat IV or IM every 30 minutes for up to two doses, or 2.5 to 3 units/cat IM or IV repeated up to three times every 30 to 60 minutes, with a maximum of 3 units per cat. A microdose protocol of 0.5 to 1 IU/queen SC or IM, given 15 to 30 minutes after calcium, is also described, as is a single dose of 0.25 to 1 unit in the queen.
• A single dose of 0.25 to 1 unit SC at the completion of labor may help uterine involution; monitor the dam’s temperature and the character of the postpartum discharge and milk afterwards.
• For simple milk let-down rather than established agalactia – whether the aim is feeding the young or an adjunct in the treatment of mastitis – 1 to 10 IU/cat IV or IM as a single dose is also described. In established agalactia, metoclopramide 0.1 to 0.2 mg/kg SC every 12 hours can be given alongside the oxytocin to promote milk production.
• 10In feline uterine inertia, 10% calcium gluconate 0.5–1 mL/cat IV over 10 minutes may be given before oxytocin. Other regimens include 0.2 mL/kg slowly IV or 1 mL/5 kg SC every 4–6 hours, with 1 mL/22 kg SC every 6 hours and a maximum of 6 mL per site also described. Follow one complete regimen, avoid IM administration, and monitor heart rate and rhythm. Use cautiously because strong contractions may increase the risk of uterine rupture.
• Older, higher dose recommendations for dogs and cats are now regarded as obsolete: mini-doses improve the frequency of uterine contractions and are less hazardous to the dam (uterine rupture) and to the fetuses (placental compromise).
• A larger dose is not a stronger one: high doses can saturate the oxytocin receptors and make the drug ineffective as a uterotonic. If a correctly timed dose fails in a queen, reassess rather than escalating automatically.
• Other published feline protocols give 2 to 4 IU/cat IV or IM every 30 minutes for up to two doses, or 2.5 to 3 units/cat IM or IV repeated up to three times every 30 to 60 minutes, with a maximum of 3 units per cat. A microdose protocol of 0.5 to 1 IU/queen SC or IM, given 15 to 30 minutes after calcium, is also described, as is a single dose of 0.25 to 1 unit in the queen.
• A single dose of 0.25 to 1 unit SC at the completion of labor may help uterine involution; monitor the dam’s temperature and the character of the postpartum discharge and milk afterwards.
• For simple milk let-down rather than established agalactia – whether the aim is feeding the young or an adjunct in the treatment of mastitis – 1 to 10 IU/cat IV or IM as a single dose is also described. In established agalactia, metoclopramide 0.1 to 0.2 mg/kg SC every 12 hours can be given alongside the oxytocin to promote milk production.
Warnings & Precautions
Oxytocin should only be used in appropriately selected patients after careful assessment of the dam and fetus(es). Improper use may result in serious maternal or fetal complications.
- Hypersensitivity: Contraindicated in animals with a known hypersensitivity to oxytocin.
- Obstructive dystocia: Contraindicated when dystocia is caused by abnormal fetal presentation unless correction has been made.
- Anatomical obstruction: Do not use when maternal anatomy does not allow vaginal delivery.
- Cervical relaxation required: Before parturition, oxytocin should only be administered when the cervix is fully relaxed naturally or following prior estrogen administration.
- Primary uterine inertia: Oxytocin is often ineffective when used alone for primary uterine inertia. In dogs, 5–20 units IM or SC every 30 minutes has been described, or it may be given 15–30 minutes after calcium.
- Hypocalcemia: Correct hypocalcemia before administering oxytocin, as this may improve uterine contractility and treatment response.
- Patient monitoring: Careful physical examination and monitoring are essential during treatment to reduce the risk of maternal and fetal complications.
- Hazardous drug handling: Oxytocin is classified by NIOSH as a hazardous drug; appropriate personal protective equipment should be used during handling.
- Closed cervix: A closed cervix is an absolute contraindication, not merely a reason to wait.
- Other contraindications: Also contraindicated with fetal stress, longstanding in-utero fetal death, uterine rupture and uterine torsion.
- Uterine overdistention and previous surgery: Human labeling advises caution where the uterus is overdistended, where there has been previous major cervical or uterine surgery, and where cervical carcinoma is present.
- A further reason to rule out obstruction: Oxytocin may cause premature placental separation, which is part of why it must not be used in obstructive dystocia.
- Use in pregnancy: Do not administer to a pregnant animal except to induce parturition. In human labeling there is no known indication in the first trimester other than in relation to spontaneous or induced abortion, and nasally administered oxytocin is contraindicated in pregnancy.
- Who should not handle it: Those trying to conceive, and anyone who is pregnant or breastfeeding, should take particular care when handling oxytocin.
- When to stop and operate: In the bitch, consider cesarean section if more than three doses of oxytocin per fetus are needed, if more than four fetuses remain, or if uterine inertia does not respond to oxytocin at all. In either species, persistent or worsening fetal bradycardia with a poor response to medication is itself an indication to operate.
Drug Interactions
The following interactions have been reported or are considered theoretically significant in patients receiving oxytocin. Concurrent use is not always contraindicated but may require additional monitoring.
- Beta-adrenergic agonists (e.g., albuterol, clenbuterol): May reduce the effects of oxytocin and delay labor.
- Dinoprost: May enhance the effects of oxytocin.
- Misoprostol: May enhance the effects of oxytocin.
- NSAIDs (e.g., flunixin): Listed as an interaction that may reduce the uterotonic effects of oxytocin, although the attenuation behind that listing was demonstrated in postpartum cows rather than in dogs or cats.
- Vasoconstrictors (e.g., ephedrine, epinephrine): Concurrent use may increase the risk of hypertension; severe hypertension has been described, and some sources advise avoiding the combination altogether.
Side Effects & Overdose
Side Effects
Oxytocin is generally well tolerated when used appropriately. Most adverse effects occur when excessive doses are administered or when the drug is used in inappropriate patients.
- Uterine cramping and discomfort: May occur following repeated bolus injections.
- Hypersensitivity reactions: Possible, particularly with products derived from animal sources.
- QT interval prolongation and cardiac arrhythmias: Listed as possible adverse effects on the human product label.
- Water intoxication: May occur if oxytocin is administered too rapidly IV and/or with excessive volumes of electrolyte-free IV fluids.
- Premature placental separation: May occur, which is part of why the drug is avoided where dystocia may be obstructive.
- Uterine rupture and placental compromise: Excessive dosing risks both – the first in the dam, the second in the fetuses – which is why the smaller mini-doses have been found less hazardous.
Overdose
Overdose can result in excessive uterine stimulation and serious maternal or fetal complications. The severity of effects depends on the stage of parturition and fetal position.
- Hypertonic or tetanic uterine contractions: May lead to tumultuous labor.
- Uterine rupture: Can occur following excessive uterine stimulation.
- Fetal injury or death: May result from prolonged or excessive uterine contractions.
- Clinical signs of water intoxication: Listlessness, depression, coma, seizures, and death in severe cases.
- Management: Discontinue oxytocin therapy and restrict water access until clinical signs resolve. Severe intoxication may require osmotic diuretics with or without furosemide.
Key Notes
Practical clinical points for the use of oxytocin in dogs and cats:
- Parenteral administration required: Oxytocin is destroyed in the gastrointestinal tract and cannot be given by mouth; it must be given by a parenteral route.
- Rapid onset of action: Uterine response occurs almost immediately after IV administration and typically within 3–5 minutes after IM injection.
- Short duration: Reported duration of effect in dogs is approximately 13 minutes after IV administration and 20 minutes after IM or SC administration.
- Does not increase milk production: Oxytocin promotes milk ejection only and has no galactopoietic activity.
- Intranasal absorption is variable: Although intranasal administration is possible, absorption may be erratic.
- Crosses the placenta: Small quantities are believed to enter the fetal circulation.
- Rapid elimination: Oxytocin has a plasma half-life of 1 to 6 minutes in most mammals and is rapidly metabolized by the liver and kidneys and by circulating oxytocinase, with very small amounts excreted unchanged in the urine.
- When to give it: The most effective moment is as uterine inertia begins to develop, before contractions stop completely. Where uterine monitoring is used, calcium and oxytocin are given only after 8 to 12 hours of an established stage I contraction pattern and only if inertia is detected as stage II labor is anticipated; premature administration gives a suboptimal response.
- What a non-response means: In a bitch, failure to respond to oxytocin or absence of a Ferguson reflex makes uterine inertia more likely than an obstructive dystocia, unless it has been obstructed for several hours.
- Monitoring after the birth: After a dystocia or a cesarean section, monitor the dam’s temperature and the character of the vaginal discharge daily for 5 to 7 days, watching for metritis.
- Pregnancy and nursing: Used as indicated, oxytocin is not expected to present a risk of fetal abnormality; small quantities may appear in maternal milk but are unlikely to have significant effects, although milk flow may be altered.
- Storage and stability: Store below 25°C, protected from light, and do not freeze; some manufacturers recommend refrigeration at 2 to 8°C and the UK formulary says to store it in a refrigerator, so follow the label on the product in use. Some products have been shown to remain stable for up to five years when stored below 26°C.
- How potency is expressed: One unit is equivalent to 2 to 2.2 micrograms of pure hormone. Potency is standardized against vasopressor activity and expressed in USP Posterior Pituitary Units.
- Why water intoxication needs a large dose: Commercial preparations are highly purified and have virtually no antidiuretic or vasopressor activity at usual doses; the veterinary label specifies less than 0.4 units of pressor activity per mL. Water intoxication is therefore a hazard of large or prolonged dosing rather than of ordinary use.
- What it can be mixed with: Reportedly physically compatible with most commonly used IV fluids and with calcium salts, cefazolin, clindamycin, dexamethasone sodium phosphate, famotidine, ketamine, lidocaine, metoclopramide, metronidazole, midazolam, ondansetron and penicillin G, and reportedly incompatible with ampicillin sodium, diazepam, pantoprazole and sulfamethoxazole/trimethoprim. Compatibility depends on pH, concentration, temperature and diluent, so consult a compatibility reference or a pharmacist.
- Making up an IV dose: It can also be given intravenously after dilution in water for injection.
- How much is actually known: Evidence for oxytocin in nonobstructive small-animal dystocia is mostly anecdotal rather than trial-based. A canine report gives a failure rate of 54.3% for medical treatment attempts, and in one feline emergency cohort 104 of 386 oxytocin-treated queens went on to cesarean section.
- Where it does not work on its own: Oxytocin is generally not successful for subinvolution of placental sites, and it is typically not effective as sole treatment for uterine inertia – in inertia it is given 15 to 30 minutes after calcium rather than alone.
