Oxytocin

(oxytocin)

Brand

Veterinary: Oxytocin

Veterinary Availability:

Vials: 20 USP Units/mL in 10mL, 30mL, and 100mL

Brands

Human: Pitocin, Syntocinon

Human Availability:

Vials: 10 Units/mL in 1 & 10mL
Syntocinon Nasal Spray 40 Units/mL *Note: not practical to use in rats.

Pharmacology

Oxytocin is a synthetic compound. It is identical to the natural hormone which is found in the posterior pituitary. It causes potent and selective stimulation of uterine and mammary gland smooth muscle.

The name oxytocin means, “rapid birth”, because of the ability it has to contract the pregnant uterus (Bergersen, Pharmacology in nursing, fourteenth edition, page 603).

Oxytocin stimulates the contraction of the uterus by increasing sodium permeability of uterine myofibrils. It also has the ability to cause contraction of the myoepithelial cells which surround mammary alveoli and facilitate milk ejection.

Even though oxytocin has only weak antidiuretic properties, water intoxication can occur if it is administered at a rapid rate, and/or if excessively large volumes of electrolyte-free intravenous fluids are administered ⁽¹⁾

Oxytocin is destroyed in the GI tract and must be given either IV, IM, SQ, or by nasal spray.

This drug is distributed in extracellular fluid, metabolized in the liver and kidneys and excreted unchanged in small amounts in the urine.

Indications

Used to induce or continue labor in normal presentation, to evacuate uterus, or to control bleeding following delivery.

Drug Interactions or Contraindications

Avoid using vasoconstrictors with oxytocin as it can result in hypertension.
Oxytocin is contraindicated when dystocia present due to abnormal presentation without making correction.
Prior to initiating oxytocin it is recommended to treat any signs of hypoglycemia and/or hypocalcemia/

Adverse Reactions

Relatively safe margins at reasonable dosage.

CNS: subarachnoid hemorrhage, seizures

CV: increases heart rate, blood pressure, systemic venous return, cardia output, arrhythmias

GU: impaired uterine blood flow, pelvic hematoma, tetanic uterine contractions, uterine rupture, postpartum hemorrhage

Dosage Recommendations

1 unit/kg, SQ, IM, (rats) ²⁶^, ³⁴

or

0.2 units/kg to 3 units/kg, SQ, IM, IV ¹^, ²⁶^, ³⁴^, ³⁵^, ⁴¹^, ⁴²^, ⁴⁴

Considerations

Check solution to be sure it is clear and free of sediment.
Store at refrigerated temperatures less than 25 degrees centigrade and protect from freezing.

References

Plumb, D. C. (2008). Plumb’s veterinary drug handbook (6th ed.). Stockholm, Wis.: PharmaVet
Oxytocin – A Hormone of Affiliation: https://www.rmca.org/Articles/oxytocin.htm