Pitocin

Labor Inducers

Hazardous Drugs Classification
NIOSH 2016 List: Group 3
NIOSH (Draft) 2020 List: Table 2
Observe and exercise appropriate precautions for handling, preparation, administration, and disposal of hazardous drugs.
Use double chemotherapy gloves and a protective gown. Prepare in a biological safety cabinet or compounding aseptic containment isolator with a closed system drug transfer device. Eye/face and respiratory protection may be needed during preparation and administration.

Administer oxytocin by intravenous infusion or intramuscular injection; controlled intravenous (IV) infusion is usually preferred.
Prior to administration, an IV infusion of 0.9% Sodium Chloride or other appropriate IV fluid should be already running for use in case of adverse reactions.
Magnesium sulfate should be readily available for myometrial relaxation, if necessary.
The dosage of oxytocin is determined by the uterine response. Dosage and infusion must be individualized and initiated at a very low level. The manufacturer-supplied information is based upon various regimens and indications for obstetric use.
Visually inspect the parenteral product for particulate matter and discoloration prior to administration whenever solution and container permit.

Intravenous infusion:
The following recommendations for infusion solutions are from the package insert. However, experts recommend that institutions adopt standard oxytocin infusion concentrations to help limit the potential for infusion and dosage errors.
Induction of labor: Dilute 1 mL (10 units) in 1,000 mL of a compatible IV infusion solution. Rotate infusion bottle for thorough mixing. The resultant infusion should contain 10 milliunits/mL.
Control of postpartum uterine bleeding: Dilute 10 to 40 units in a compatible IV solution or to an already infusing compatible IV solution. The maximum concentration is 40 units in 1,000 mL of solution.
Incomplete, inevitable, or elective abortion: Dilute 10 units in 500 mL of a compatible IV solution.
Administer using an infusion pump to ensure accurate dosing. Experts recommend the use of smart infusion pumps with an engaged dose error-reduction system for oxytocin infusions.
When an oxytocin infusion is discontinued, promptly remove and discard any unused portion of the infusion and change the IV line to ensure no residual drug is left in the tubing.
ISMP Safe Practice Recommendations:
Use standardized orders for prescribing oxytocin. Use standard order sets and dose rates.
Standardize to a single concentration/bag size for both antepartum and postpartum infusions.
Communicate orders in terms of dose/rate and align with the smart infusion pump dose error-reduction system (DERS).
Provide oxytocin in a standard ready-to-administer form.
Label both sides of infusion bag.
Conduct a packaging assessment to assure no other look-alike vials or bags prior to purchasing oxytocin vials or premixed infusion bags.
Align the pump drug library with the standardized order set.
Engage end-users when developing or modifying oxytocin order sets in the EHR and smart drug library builds.
Employ barcode scanning technology.
Label and trace infusion lines.
Reduce access to unneeded medications.
Remove oxytocin with discontinued.
Limit verbal orders.
Avoid outdates brand names and drug name abbreviations.
Perform a failure mode effect analysis (FMEA) before implementing changes to oxytocin prescribing, dispensing, preparation, and administration.
Educate and support practitioners, assess competency, support clear communication/documentation, monitor for post-implementation issues, engage patients.

Intramuscular injection:
Inject into a large muscle mass.

cervical laceration / Early / Incidence not known
uterine rupture / Early / Incidence not known
postpartum hemorrhage / Early / Incidence not known
intracranial bleeding / Delayed / Incidence not known
afibrinogenemia / Delayed / Incidence not known
retinal hemorrhage / Delayed / Incidence not known
arrhythmia exacerbation / Early / Incidence not known
fetal death / Delayed / Incidence not known
ocular hemorrhage / Delayed / Incidence not known
coma / Early / Incidence not known
pulmonary edema / Early / Incidence not known
seizures / Delayed / Incidence not known
water intoxication / Delayed / Incidence not known
anaphylactoid reactions / Rapid / Incidence not known

uterine contractions / Early / Incidence not known
hematoma / Early / Incidence not known
bleeding / Early / Incidence not known
premature ventricular contractions (PVCs) / Early / Incidence not known
hypertension / Early / Incidence not known
fetal bradycardia / Delayed / Incidence not known
blurred vision / Early / Incidence not known
hyperbilirubinemia / Delayed / Incidence not known
jaundice / Delayed / Incidence not known

vomiting / Early / Incidence not known
nausea / Early / Incidence not known

Use of oxytocin requires an experienced clinician who is trained in the administration and complications of the drug. Oxytocin use also requires a specialized care setting where intensive care and surgical facilities are immediately available. Furthermore, according to the manufacturer, oxytocin should only be used when induction of labor is necessary for medical reasons. It should not be used for elective induction of labor as available data are insufficient to evaluate the risk-benefit ratio in this indication. When oxytocin is used for induction or reinforcement of already existent labor, patients should be carefully selected. Pelvic adequacy must be considered and maternal and fetal conditions evaluated prior to initiation. The use of oxytocin is contraindicated in the following circumstances: where there is significant cephalopelvic disproportion, in unfavorable fetal positions or presentations which are undeliverable without conversion prior to delivery (i.e., transverse lies), in obstetrical emergencies where the benefit-to-risk ratio for either the fetus or the mother favors surgical intervention, in fetal distress where delivery is not imminent, where adequate uterine activity fails to achieve satisfactory progress, where the uterus is already hyperactive or hypertonic, and in cases where vaginal delivery is contraindicated (i.e., invasive cervical cancer, active herpes infection, total placenta previa, vasa previa, and cord presentation or prolapse of the cord). Except in unusual circumstances, oxytocin should be avoided when the following conditions or situations are present: evidence of fetal distress, hydramnios, fetal prematurity, abnormal fetal position (including unengaged head), partial placenta previa, borderline cephalopelvic disproportion, overdistention of the uterus, grand multiparity, any condition in which there is a predisposition for uterine rupture, such as a previous major surgery of the uterus or cervix (including cesarean section), overdistension of the uterus, past history of uterine sepsis or of traumatic delivery, or in any condition presenting as an obstetric emergency requiring surgical intervention. Due to the variability of the combinations of factors which may exist in these conditions, the definition of unusual circumstance must be left to the judgement of the physician. The decision can only be made by carefully weighing the potential benefits which oxytocin can provide in a given case against rare but definite potential for the drug to produce hypertonicity or tetanic spasm. During oxytocin administration, uterine contractions, fetal and maternal heart rate, maternal blood pressure, and, if possible, intrauterine pressure should be continuously monitored to avoid complications. Only intrauterine pressure recording can accurately measure the intrauterine pressure during contractions. A fetal scalp electrode provides a more dependable recording of the fetal heart rate than any external monitoring system. If uterine hyperactivity occurs, oxytocin administration should be immediately discontinued; oxytocin-induced stimulation of the uterine contractions usually decreases soon after discontinuance of the drug.

Pitocin

Rx

Parenteral hormone with all the naturally occurring actions of endogenous oxytocin released from the posterior pituitary
Used clinically to induce labor and to aid in the delivery of the placenta (third stage of labor)
Also used to control postpartum bleeding

0.5 to 2 milliunit/minute continuous IV infusion, initially. Titrate by 1 to 2 milliunits/minute every 15 to 60 minutes until the desired contraction pattern has been established. Once the desired frequency of contractions is obtained and labor has progressed to 5 to 6 cm dilation, reduce the dose similarly. Low-dose regimens and less frequent increases in dose are associated with decreased uterine hyperstimulation.

0.5 to 2 milliunit/minute continuous IV infusion, initially. Titrate by 1 to 2 milliunits/minute every 15 to 60 minutes until the desired contraction pattern has been established. Once the desired frequency of contractions is obtained and labor has progressed to 5 to 6 cm dilation, reduce the dose similarly. Low-dose regimens and less frequent increases in dose are associated with decreased uterine hyperstimulation.

6 milliunits/minute continuous IV infusion, initially. Titrate by 3 to 6 milliunits/minute every 15 to 60 minutes until the required contraction pattern is established. Reduce the incremental increase if uterine hyperstimulation occurs. Max: 40 milliunits/minute.

6 milliunits/minute continuous IV infusion, initially. Titrate by 3 to 6 milliunits/minute every 15 to 60 minutes until the required contraction pattern is established. Reduce the incremental increase if uterine hyperstimulation occurs. Max: 40 milliunits/minute.

10 to 40 units in 500 to 1,000 mL of dextrose or electrolyte solution continuous IV infusion; adjust infusion rate to sustain uterine contraction and control uterine atony.

10 units IM as a single dose after delivery of the placenta.

10 to 20 milliunits/minute via continuous IV infusion. Do not exceed 30 units in a 12-hour period. Intravenous oxytocin is usually safe and effective for inducing labor for near term fetal demise, but is less effective remote from term.

Protocols may vary slightly by institution. Following baseline monitoring for 20 to 30 minutes, initiate at a low dose (e.g., 0.5 to 2.33 milliunits/minute) via continuous IV infusion to the mother. Double the infusion rate every 10 to 30 minutes until the frequency of the contractions are 3 within a 10-minute period (1 contraction every 3 to 4 minutes) and the duration is 40 to 60 seconds. When the desired number of contractions is obtained, record fetal heart rate and contractions until sufficient, then discontinue the infusion. Compare baseline and oxytocin-induced recordings.

†Indicates off-label use

Specific guidelines for dosage adjustments in hepatic impairment are not available; it appears that no dosage adjustments are needed.

Specific guidelines for dosage adjustments in renal impairment are not available; it appears that no dosage adjustments are needed.

Acetaminophen; Chlorpheniramine; Dextromethorphan; Phenylephrine: (Major) The administration of prophylactic vasopressors with oxytocin can cause severe, persistent hypertension, as the 2 drugs may have a synergistic and additive vasoconstrictive effect. This interaction was noted when oxytocin was given 3 to 4 hours after prophylactic vasoconstrictor in conjunction with caudal anesthesia. The incidence of such an interaction may be decreased if vasopressors are not administered prior to oxytocin.
Acetaminophen; Chlorpheniramine; Phenylephrine : (Major) The administration of prophylactic vasopressors with oxytocin can cause severe, persistent hypertension, as the 2 drugs may have a synergistic and additive vasoconstrictive effect. This interaction was noted when oxytocin was given 3 to 4 hours after prophylactic vasoconstrictor in conjunction with caudal anesthesia. The incidence of such an interaction may be decreased if vasopressors are not administered prior to oxytocin.
Acetaminophen; Dextromethorphan; Guaifenesin; Phenylephrine: (Major) The administration of prophylactic vasopressors with oxytocin can cause severe, persistent hypertension, as the 2 drugs may have a synergistic and additive vasoconstrictive effect. This interaction was noted when oxytocin was given 3 to 4 hours after prophylactic vasoconstrictor in conjunction with caudal anesthesia. The incidence of such an interaction may be decreased if vasopressors are not administered prior to oxytocin.
Acetaminophen; Dextromethorphan; Phenylephrine: (Major) The administration of prophylactic vasopressors with oxytocin can cause severe, persistent hypertension, as the 2 drugs may have a synergistic and additive vasoconstrictive effect. This interaction was noted when oxytocin was given 3 to 4 hours after prophylactic vasoconstrictor in conjunction with caudal anesthesia. The incidence of such an interaction may be decreased if vasopressors are not administered prior to oxytocin.
Acetaminophen; Guaifenesin; Phenylephrine: (Major) The administration of prophylactic vasopressors with oxytocin can cause severe, persistent hypertension, as the 2 drugs may have a synergistic and additive vasoconstrictive effect. This interaction was noted when oxytocin was given 3 to 4 hours after prophylactic vasoconstrictor in conjunction with caudal anesthesia. The incidence of such an interaction may be decreased if vasopressors are not administered prior to oxytocin.
Acetaminophen; Phenylephrine: (Major) The administration of prophylactic vasopressors with oxytocin can cause severe, persistent hypertension, as the 2 drugs may have a synergistic and additive vasoconstrictive effect. This interaction was noted when oxytocin was given 3 to 4 hours after prophylactic vasoconstrictor in conjunction with caudal anesthesia. The incidence of such an interaction may be decreased if vasopressors are not administered prior to oxytocin.
Articaine; Epinephrine: (Moderate) Oxytocin may potentiate the pressor effects of epinephrine. Severe hypertension has been reported when oxytocin was given 3 to 4 hours after prophylactic administration of a vasoconstrictor in conjunction with caudal block anesthesia.
Brompheniramine; Dextromethorphan; Phenylephrine: (Major) The administration of prophylactic vasopressors with oxytocin can cause severe, persistent hypertension, as the 2 drugs may have a synergistic and additive vasoconstrictive effect. This interaction was noted when oxytocin was given 3 to 4 hours after prophylactic vasoconstrictor in conjunction with caudal anesthesia. The incidence of such an interaction may be decreased if vasopressors are not administered prior to oxytocin.
Brompheniramine; Phenylephrine: (Major) The administration of prophylactic vasopressors with oxytocin can cause severe, persistent hypertension, as the 2 drugs may have a synergistic and additive vasoconstrictive effect. This interaction was noted when oxytocin was given 3 to 4 hours after prophylactic vasoconstrictor in conjunction with caudal anesthesia. The incidence of such an interaction may be decreased if vasopressors are not administered prior to oxytocin.
Bupivacaine; Epinephrine: (Moderate) Oxytocin may potentiate the pressor effects of epinephrine. Severe hypertension has been reported when oxytocin was given 3 to 4 hours after prophylactic administration of a vasoconstrictor in conjunction with caudal block anesthesia.
Carboprost Tromethamine: (Major) Carboprost tromethamine may augment the activity of other oxytocics. Augmentation can result in uterine hypertonus with subsequent uterine rupture, particularly in the absence of adequate cervical dilation. The concurrent use of carboprost tromethamine and other oxytocic drugs is not recommended.
Chlorpheniramine; Dextromethorphan; Phenylephrine: (Major) The administration of prophylactic vasopressors with oxytocin can cause severe, persistent hypertension, as the 2 drugs may have a synergistic and additive vasoconstrictive effect. This interaction was noted when oxytocin was given 3 to 4 hours after prophylactic vasoconstrictor in conjunction with caudal anesthesia. The incidence of such an interaction may be decreased if vasopressors are not administered prior to oxytocin.
Chlorpheniramine; Dihydrocodeine; Phenylephrine: (Major) The administration of prophylactic vasopressors with oxytocin can cause severe, persistent hypertension, as the 2 drugs may have a synergistic and additive vasoconstrictive effect. This interaction was noted when oxytocin was given 3 to 4 hours after prophylactic vasoconstrictor in conjunction with caudal anesthesia. The incidence of such an interaction may be decreased if vasopressors are not administered prior to oxytocin.
Chlorpheniramine; Phenylephrine: (Major) The administration of prophylactic vasopressors with oxytocin can cause severe, persistent hypertension, as the 2 drugs may have a synergistic and additive vasoconstrictive effect. This interaction was noted when oxytocin was given 3 to 4 hours after prophylactic vasoconstrictor in conjunction with caudal anesthesia. The incidence of such an interaction may be decreased if vasopressors are not administered prior to oxytocin.
Codeine; Phenylephrine; Promethazine: (Major) The administration of prophylactic vasopressors with oxytocin can cause severe, persistent hypertension, as the 2 drugs may have a synergistic and additive vasoconstrictive effect. This interaction was noted when oxytocin was given 3 to 4 hours after prophylactic vasoconstrictor in conjunction with caudal anesthesia. The incidence of such an interaction may be decreased if vasopressors are not administered prior to oxytocin.
Dextromethorphan; Diphenhydramine; Phenylephrine: (Major) The administration of prophylactic vasopressors with oxytocin can cause severe, persistent hypertension, as the 2 drugs may have a synergistic and additive vasoconstrictive effect. This interaction was noted when oxytocin was given 3 to 4 hours after prophylactic vasoconstrictor in conjunction with caudal anesthesia. The incidence of such an interaction may be decreased if vasopressors are not administered prior to oxytocin.
Dextromethorphan; Guaifenesin; Phenylephrine: (Major) The administration of prophylactic vasopressors with oxytocin can cause severe, persistent hypertension, as the 2 drugs may have a synergistic and additive vasoconstrictive effect. This interaction was noted when oxytocin was given 3 to 4 hours after prophylactic vasoconstrictor in conjunction with caudal anesthesia. The incidence of such an interaction may be decreased if vasopressors are not administered prior to oxytocin.
Diclofenac; Misoprostol: (Major) In certain cases, oxytocin can be used in combination with other oxytocics for therapeutic purposes. However, in the augmentation of labor, oxytocin administration is usually withheld until after the last dose of intravaginal misoprostol. There is a risk of severe uterine hypertony occurring, with possible uterine rupture or cervical laceration when misoprostol and oxytocin are used at the same time. These products should be used concomitantly only under adequate supervision, with particular attention to ensure adequate cervical dilation has occurred.
Dinoprostone, Prostaglandin E2: (Contraindicated) Dinoprostone is contraindicated in patients receiving intravenous oxytocic agents. Following dinoprostone use, a specific wash-out period is recommended before the use of oxytocin; see specific product information for the specific recommendations as they differ. These products should be used sequentially only under adequate obstetric supervision. Following the removal of the dinoprostone vaginal insert, an interval of at least 30 minutes is recommended prior to the use of another oxytocic agent. For the sequential use of oxytocin following dinoprostone gel administration, a dosing interval of 6 to 12 hours is recommended. Concomitant use of dinoprostone vaginal suppositories with other oxytocic agents is also not recommended. Serious side effects may occur if these agents are used concurrently. There is a risk of severe uterine hypertony occurring, with possible uterine rupture or cervical laceration.
Diphenhydramine; Phenylephrine: (Major) The administration of prophylactic vasopressors with oxytocin can cause severe, persistent hypertension, as the 2 drugs may have a synergistic and additive vasoconstrictive effect. This interaction was noted when oxytocin was given 3 to 4 hours after prophylactic vasoconstrictor in conjunction with caudal anesthesia. The incidence of such an interaction may be decreased if vasopressors are not administered prior to oxytocin.
Dopamine: (Moderate) Monitor blood pressure during concomitant use of dopamine and oxytocin due to the risk for severe hypertension. Severe hypertension has been reported when oxytocin was given 3 to 4 hours after prophylactic administration of a vasoconstrictor in conjunction with caudal anesthesia.
Ephedrine: (Moderate) Carefully monitor blood pressure in patients who have received ephedrine and oxytocin. Serious hypertension has been reported when oxytocin was given 3 to 4 hours after prophylactic administration of a vasoconstrictor in conjunction with caudal anesthesia. Some patients have experienced a stroke.
Ephedrine; Guaifenesin: (Moderate) Carefully monitor blood pressure in patients who have received ephedrine and oxytocin. Serious hypertension has been reported when oxytocin was given 3 to 4 hours after prophylactic administration of a vasoconstrictor in conjunction with caudal anesthesia. Some patients have experienced a stroke.
Epinephrine: (Moderate) Oxytocin may potentiate the pressor effects of epinephrine. Severe hypertension has been reported when oxytocin was given 3 to 4 hours after prophylactic administration of a vasoconstrictor in conjunction with caudal block anesthesia.
General anesthetics: (Major) Adverse cardiovascular effects can develop as a result of concomitant administration of oxytocin with general anesthetics, especially in those with preexisting valvular heart disease. Cyclopropane, when administered with or without oxytocin, has been implicated in producing maternal sinus bradycardia, abnormal atrioventricular rhythms, hypotension, and increases in heart rate, cardiac output, and systemic venous return. In addition, halogenated anesthetics decrease uterine responsiveness to oxytocics (e.g., oxytocin) and, in high doses, can abolish it, increasing the risk of uterine hemorrhage. Halothane is a potent uterine relaxant. Enflurane displaces the myometrial response curve to oxytocin so that at lower concentrations of enflurane oxytocin will restore uterine contractions. However, as the dose of enflurane progresses (somewhere between 1.5 to 3% delivered enflurane) the response to oxytocin is inhibited. It is not clear if other halogenated anesthetics would interact with oxytocics in this manner.
Guaifenesin; Phenylephrine: (Major) The administration of prophylactic vasopressors with oxytocin can cause severe, persistent hypertension, as the 2 drugs may have a synergistic and additive vasoconstrictive effect. This interaction was noted when oxytocin was given 3 to 4 hours after prophylactic vasoconstrictor in conjunction with caudal anesthesia. The incidence of such an interaction may be decreased if vasopressors are not administered prior to oxytocin.
Lidocaine; Epinephrine: (Moderate) Oxytocin may potentiate the pressor effects of epinephrine. Severe hypertension has been reported when oxytocin was given 3 to 4 hours after prophylactic administration of a vasoconstrictor in conjunction with caudal block anesthesia.
Methohexital: (Major) Adverse cardiovascular effects can develop as a result of concomitant administration of oxytocin with general anesthetics.
Methylergonovine: (Major) Methylergonovine and oxytocin both control uterine atony, and if used in combination there may be a risk of severe uterine hypertony, with possible uterine rupture or cervical laceration.
Midodrine: (Major) The administration of prophylactic vasopressors with oxytocin can cause severe, persistent hypertension, as the 2 drugs may have a synergistic and additive vasoconstrictive effect. This interaction was noted when oxytocin was given 3 to 4 hours after prophylactic vasoconstrictor in conjuction with caudal anesthesia. The incidence of such an interaction may be decreased if vasopressors are not administered prior to oxytocin.
Misoprostol: (Major) In certain cases, oxytocin can be used in combination with other oxytocics for therapeutic purposes. However, in the augmentation of labor, oxytocin administration is usually withheld until after the last dose of intravaginal misoprostol. There is a risk of severe uterine hypertony occurring, with possible uterine rupture or cervical laceration when misoprostol and oxytocin are used at the same time. These products should be used concomitantly only under adequate supervision, with particular attention to ensure adequate cervical dilation has occurred.
Norepinephrine: (Moderate) The administration of prophylactic vasopressors with oxytocin can cause severe, persistent hypertension, as the 2 drugs may have a synergistic and additive vasoconstrictive effect. This interaction was noted when oxytocin was given 3 to 4 hours after prophylactic vasoconstrictor in conjunction with caudal anesthesia. The incidence of such an interaction may be decreased if vasopressors are not administered prior to oxytocin.
Phenylephrine: (Major) The administration of prophylactic vasopressors with oxytocin can cause severe, persistent hypertension, as the 2 drugs may have a synergistic and additive vasoconstrictive effect. This interaction was noted when oxytocin was given 3 to 4 hours after prophylactic vasoconstrictor in conjunction with caudal anesthesia. The incidence of such an interaction may be decreased if vasopressors are not administered prior to oxytocin.
Prilocaine; Epinephrine: (Moderate) Oxytocin may potentiate the pressor effects of epinephrine. Severe hypertension has been reported when oxytocin was given 3 to 4 hours after prophylactic administration of a vasoconstrictor in conjunction with caudal block anesthesia.
Promethazine; Phenylephrine: (Major) The administration of prophylactic vasopressors with oxytocin can cause severe, persistent hypertension, as the 2 drugs may have a synergistic and additive vasoconstrictive effect. This interaction was noted when oxytocin was given 3 to 4 hours after prophylactic vasoconstrictor in conjunction with caudal anesthesia. The incidence of such an interaction may be decreased if vasopressors are not administered prior to oxytocin.
Succinylcholine: (Moderate) Concomitant use of succinylcholine and oxytocin may prolong neuromuscular blockade.

Oxytocin/Pitocin Intramuscular Inj Sol: 1mL, 10U
Oxytocin/Pitocin Intravenous Inj Sol: 1mL, 10U

No specific maximum dosage limit recommendations are available. Dosage regimens of oxytocin depend upon the patient's age, sex, weight, condition being treated, product chosen, and the prescribing clinician's judgment. Therefore, doses may vary widely and must be carefully individualized.

Synthetic oxytocin elicits the same pharmacological response produced by endogenous oxytocin, with cervical dilation, parity, and gestational age as predictors of the dose response to oxytocin administration for labor stimulation. Oxytocin increases the sodium permeability of uterine myofibrils, indirectly stimulating contraction of the uterine smooth muscle. The uterus responds to oxytocin more readily in the presence of high estrogen concentrations and with the increased duration of pregnancy. There is a gradual increase in uterine response to oxytocin for 20 to 30 weeks gestation, followed by a plateau from 34 weeks of gestation until term, when sensitivity increases. Women who are in labor have a greater response to oxytocin compared to women who are not in labor; only very large doses will elicit contractions in early pregnancy. In the term uterus, contractions produced by exogenous oxytocin are similar to those that would occur during spontaneous labor. Oxytocin increases the amplitude and frequency of uterine contractions, which transiently impede uterine blood flow and decrease cervical activity, causing dilation and effacement of the cervix.
 
Oxytocin causes contraction of the myoepithelial cells surrounding the alveolar ducts of the of the breast. This forces milk from the alveolar channels into the larger sinuses, and thus facilitates milk ejection. While oxytocin possesses no galactopoietic properties, if it is absent the milk-ejection reflex in the breast fails.
 
Oxytocin causes dilation of vascular smooth muscle, thus increasing renal, coronary, and cerebral blood flow. Blood pressure usually remains unaffected, but with the administration of very large doses or high concentration solutions blood pressure may decrease transiently. This transient decrease in blood pressure leads to reflex tachycardia and an increase in cardiac output; any fall in blood pressure is usually followed by a small, but sustained, increase in blood pressure.
 
Oxytocin does possess antidiuretic effects, but they are minimal. If oxytocin is administered with an excessive volume of electrolyte-free IV solution and/or at too rapid a rate, the antidiuretic effects are more apparent and water intoxication can result.
 
Oxytocin appears to have important roles in sexual function and bonding responses in both males and females.

Oxytocin administered effectively by parenteral injection. Steady-state is usually achieved in plasma by 40 minutes after parenteral administration. Oxytocin's plasma half-life is between 1 and 6 minutes. The drug distributes throughout the extracellular fluid, with minimal amounts reaching the fetus. Oxytocinase, a glycoprotein aminopeptidase that is capable of degrading oxytocin, is produced during pregnancy and is present in the plasma. Enzyme activity increases gradually until term approaches when there is a sharp rise in plasma levels and activity is high in the plasma, placenta, and uterus. After obstetric delivery, the enzyme activity declines. Oxytocinase most likely originates from the placenta and regulates the amount of oxytocin in the uterus; there is little or no degradation of oxytocin in men, nonpregnant women, or cord blood. Oxytocin is rapidly removed from the plasma by the liver and the kidneys, with only small amounts being excreted unchanged in the urine. Oxytocin is metabolized in the lactating mammary gland and is distributed into breast-milk.
 
Affected cytochrome P450 (CYP450) isoenzymes and drug transporters: None

Chymotrypsin, present in the GI tract, destroys oxytocin, rendering oral administration ineffective.

When administered by IV infusion, the uterus responds almost immediately to oxytocin, with response subsiding in about an hour.

When oxytocin is administered by IM injection, the uterus responds within 3 to 5 minutes, with response subsiding in approximately 2 to 3 hours.

Oxytocin is indicated during pregnancy to induce labor; it precipitates uterine contractions. There are no known indications for use of oxytocin in the first and second trimester of pregnancy other than in relation to spontaneous or induced abortion. Based on the wide experience with this drug and its chemical structure and pharmacological properties, it would not be expected to present a risk of fetal abnormalities when used as indicated.

Endogenous oxytocin is involved in the process of lactation and therefore, oxytocin has been used in mothers having difficulty with engorgement and breast-feeding. Because several small studies have failed to show a beneficial effect, oxytocin is not used for this indication. Oxytocin is excreted in the breast-milk, but is not expected to have adverse effects in the infant.