Uterine Stimulants

Uterine Stimulants:

These are the medications, which come in a variety of chemical forms, that cause an increase in uterine contraction. Other names for them include oxytocin, ecbolics, and abortifacients. The following medications are a part of this group.

• Oxytocin
• Methargine
• Ergotamine
• Prostaglandin

Oxytocins

Along with ADH, it is produced by the posterior pituitary gland. It intensifies uterine contractions, followed by full relaxation. It causes the lower portion of the uterus to relax, allowing the fetus to be expelled while increasing the contraction of the top section (fundus and body).

Note: Estrogen increase where as Progesterone decrease the sensitivity of uterus to Oxytocin.

Mechanism of Action:

• Binds to voltage gated calcium channel to uterus. 
• Increase the Entry of Calcium into myometrium.
• Increase the fundal Contraction (100-200 fold) and relaxation of Cervix during labour. 

Note: It also increase Ixal PG's production which further stimulate uterine contraction.

Preparation Used:

Synthetic Oxytocin

• Syntocinon (ampula containing 5IU / M * L ) (Pitocin) (10IU / M * L)
• Sand 02 (Combination of Syntocinon 5 units and (Synometrine) Ergometrine 0.5 mg
• Desamine - Oxytocin (Bucal tablets containing 50 IU)
• Oxytocin Nasal Solution (40units / M * L)

Indication:

• Diagnostic use:
  • Contraction Speed Test (CST)
  • Oxytocin sensitivities (OST)
• Therapeutic use:
  • Pregnancy
    • Early
      • To accelerate abortion
      • To stop bleeding following Evacuation of uterus.
    • Later
      • To induce labour.
• Labour: Management of 3 stage of labour.
• Puerperium: To minimize blood loss and to control post partum hemorrhage.
• Ejection of milk from Breast (By Contraction of myoepithelial cell) after delivery.

Adr

• Sinus bradycardia
• Fetal hypercapnia
• Low apgar score (5 min)
• Fetal death
• Tachycardia
• Premature CNS damage
• Perinatal hepaticnecrosis
• Fetal hypoxia
• Neonatal seizure

Danger of Oxytocin:

The risk is greatest when the medication is used toward the end of pregnancy or during labor. Oxytocin's risk is divided into two categories.

• Maternal
  • Uterine Hyperstimulation
  • Water intoxication
  • Antidiuresis
  • Uterine rupture
  • Hypotension
• Fetal
  • Fetal distress.

Contraindication:

• Cephalopelvic disproportion.
• Unfavourable fetal position or presentation.
• Obstretic Emergency that favor Surgery.
• Fetal distress.
• Where adequate uterine activity fails to achieve statisfactory progress.
• Hyperactive or Hypertonic uterus.
• Contraindicated Vaginal delivery eg. Invasive Cervical, Carcinoma, active herpes genitals, total placentaprevia prolapse of cord.
• Hypersensitivity.

Cautions:

• If uterine hyperactivity occurs, discontinue immediately.
• Intravenous preparation should be administered by trained person.
• Risk of severe water intoxication on prolonged administered due to antidiuretic effects.
• Restricted fluid intake may be warranted.
• Uterine hypertonicity, spasm, rupture of the uterus and titanic contraction may occur fro high dose.
• IM not recommended for labour induction.

Dosage form and Route of Administration

• Postpartum Hemorrhage.
  • 10 units IM after delivery of placenta.
  • Add 10-40 units; not to exceed 40 units; to 1000 ml of nonhydrating IV solution and infuse at necessary rate to control uterine atony.
• Labour induction
  • 0.5-1 m Unit/min IV, titrate 1-2 unit/ming 15-60 min until Contraction pattern reached that is similar to normal labour. (Usually 6 m units/min); may decrease the dose after desired frequency of contraction reached and labour has progressed to 5-6 cm dilation.
• Incomplete Abortion
  • 10-20 mUnit/min; not Exceed 50units / 12 hr.

*Note: 1 unit=1000 milliunits. (mIU)

Pregnancy category: X

Observation during Oxytocin Infusion:

• Rate of flow of infusion.
• Uterine Contraction.
• Peak intrauterine pressure.
• FHR monitoring.
• Assesment of progress of labour.

Pharmacokinetics/ Pregnancy Category:

• Duration: 2-3 hr (IM), 1 hr (IV)
• VD: 0.3 kg
• Metabolism: Rapidly metabolized in the liver and plasma
• Excreation : Urine (Small amounts)
• Half life: 1-6 min, decreased in late pregnancy and during lactation.

Nursing Consideration:

Asses the following:

• 1/0 ratio
• Vital sign: BP, Pulse, Respiration
• Uterine Contraction and FSH in every 30 min Watch for changes that may indicate Haemorrhage.
• Respiratory rule, rhythm, depth and notify prescribe of abnormalities.
• Lengths, intensity, duration of contraction notify of contraction lasting over 1 min or absence of contraction turn patient on her side, discontinue.
• FSH, fetal distress, watch for acceleration, notify prescriber.

*Note: Oxytocin→ Outsrison in - milk from Breast

Bonding Hormone that is released by both male and female but female release more than male so, that strong bonding character in female.