Oxytocin

(ox-i-toe-sin)

• Description: Hormonal Agent
• Other Names for this Medication: Pitocin®

Used to cause or increase uterine contractions attime of birth, to manage retained placentas, and to help with milk flow. Must be administered by injection. Oxytocin is not effective when given orally. This drug should ONLY be used by individuals able to adequately monitor the drug’s effects and can assess the animal’s health and reproductive status. Do not use during obstructed labor, if cervix is notready/relaxed, or if vaginal birth is not possible or recommended. Use this medication in your animal only when under close communication with your veterinarian.

How is this medication useful?

The FDA (U.S. Food & Drug Administration) has approved this drug for use in horses, cows, sows, and ewes as an aid to induce or enhance normal labor, to reduce uterine bleeding and/or empty the uterus after birthing, and to induce the flow of milk. The FDA allows veterinarians to prescribe and use products containing this drug in different species or for other conditions in certain situations. You and your veterinarian can discuss why this drug is the most appropriate choice.

Uses/Indications:

Oxytocin has been used in veterinary medicine for induction or enhancement of uterine contractions at parturition, postpartum evacuation of uterine debris or control of uterine bleeding, uterine involution after manual correction of prolapsed uterus in dogs, and treatment of agalactia.

What are the side effects of this medication?

At normal doses, oxytocin rarely causes side effects.

Side effects that usually are not serious include:

• Uterine cramping or discomfort.

If these signs are severe, worsen, or continue to be a problem, contact your veterinarian.

Side effects that may be serious orindicate a serious problem:

• Failure of fetus to be delivered within the expected timeframe as recommended by your veterinarian.
• Failure of milk production.
• Fever.
• Vomiting.
• Seizures.

If you see any of these signs, contact your veterinarian immediately.

Contraindications/Precautions/Warnings:

Oxytocin is considered contraindicated in animals hypersensitive to it or with obstructive dystocia due to abnormal presentation of fetus(es) unless correction is made. It is also contraindicated when female anatomy does not allow vaginal birth. When used prepartum, oxytocin should be used only when the cervix is fully relaxed, either naturally or by prior administration of estrogens (NOTE: Most clinicians avoid the use of estrogens, as natural relaxation is a better indicator of when to induce contractions.)

Oxytocin is ineffective for treatment of primary uterine inertia (uterine muscles do not contract normally at parturition). Correcting hypocalcemia may improve the effectiveness of oxytocin in stimulating uterine contractions.

In humans, oxytocin is contraindicated in patients with significant cephalopelvic disproportion, with unfavorable fetal positions, in obstetrical emergencies when surgical intervention is warranted, with grand multiparity, with uterine hypertonia or severe toxemia, or in which vaginal delivery is contraindicated. This drug should be used with caution in patients with uterine overdistention, previous major cervical or uterine surgery, or cervical carcinoma. Nasally administered oxytocin is contraindicated in pregnancy.

In human medicine, IV oxytocin is considered to be a high-alert medication (ie, medication that requires special safeguards to reduce the risk for errors). Consider instituting practices such as redundant drug dosages, volume checking, and using special alert labels. The National Institute for Occupational Safety and Health (NIOSH) classifies oxytocin as a hazardous drug; personal protective equipment (PPE) should be used accordingly to minimize the risk of exposure. See Controlling Occupation Exposure to Hazardous Drugs for more information.

Adverse Effects:

Oxytocin used appropriately at reasonable doses rarely causes significant adverse effects. Most adverse effects are a result of the drug being used at dosages that are too high (see Overdose/Acute Toxicity) or in patients that should not receive oxytocin (see Contraindications/Precautions/Warnings); adequate physical examination and monitoring of the patient are essential. Most older (ie, higher) dosage recommendations for dogs and cats are obsolete, as mini-doses have been found to improve the frequency of uterine contractility and are less hazardous to the bitch (ie, uterine rupture) and fetus(es) (ie, placental compromise). Hypersensitivity reactions are a possibility with products derived from animal sources. Repeat bolus injections of oxytocin may cause uterine cramping and discomfort.

The human product lists QT interval prolongation and cardiac arrhythmias as possible adverse effects. Water intoxication can occur if the drug is administered too quickly IV and/or if excessively large volumes of electrolyte-free IV fluids are co-administered.

Drug Interactions:

The following drug interactions have either been reported or are theoretical in humans or animals receiving oxytocin and may be of significance in veterinary patients. Unless otherwise noted, use together is not necessarily contraindicated, but weigh the potential risks and perform additional monitoring when appropriate.

• βETA-ADRENERGIC AGONISTS (eg, albuterol, clenbuterol): May reduce effects of oxytocin and delay labor
• DINOPROST: May enhance effects of oxytocin
• MISOPROSTOL: May enhance effects of oxytocin
• NSAIDS (eg, flunixin): Attenuation of oxytocic effects has been demonstrated in postpartum cows.
• VASOCONSTRICTORS (eg, ephedrine, epinephrine): Concurrent use with sympathomimetic agents or other vasoconstrictors increases the risk for hypertension.