Drugs used in labour

Oxytocin

Oxytocin is a substance of varied chemical composition that has the ability to stimulate uterine muscle contraction. It is generated in the hypothalamic supraoptic and paraventricular nuclei and stored in a posterior gland, which must release this hormone. Oxytocin has a half-life of 3-4 minutes and an action time of about 20 minutes. The following are crucial oxytocin preparation steps.

1. Oxytocin vs syntonins
2. Prostaglandin
3. Ergo derivatives

Mechanism of Action

The contractile protein oxytocin is assumed to be blind to estrogen-dependent receptors on myometrial cell membrane activity. Oxytocin is also thought to cause the decidua to release prostaglandin. Both of these hormones cause fundal contraction and cervical relaxation.

1. Produce rhythmical contraction of uterine muscles.
2. Stimulates myoepithelial cells and ejects milk.
3. A minimal effect in BP initially lows then rise.

Side effects

Euphoria, constipation, fatigue, dizziness, nausea, vomiting, dry mouth, anxiety, itching, and sweating are all common adverse effects. Loss of appetite, anxiety, abdominal pain, diarrhea, urine retention, dyspnea, and hiccups are less common adverse effects (reported by less than 5% of patients).

Oxycodone can cause shallow breathing, bradycardia, cold clammy skin, apnea, hypotension, miosis, circulatory collapse, respiratory arrest, and death in high dosages, overdoses, or in some people who are not tolerant to opioids.

Indication

• Therapeutic
  - pregnancy
  - labour
  - puerperium
•  Diagnostic
  - oxytocin challenge test
  - oxytocin sensitivity test
• Pregnancy
  Early
  - to inevitable or missed and to expel hydatiform mole.
  - to stop bleeding following an evacuation of the uterus.
  - used as induction of abortion along with other abortifacient agents.
  Late
  - to induce labor
  - to facilitate cervical ripening for effective induction.
• Labour
  - augmentation of labor
  - inactive management of 3rd stage of labor 

Contraindication

• In later months of pregnancy
  - grand multipara
  - contacted pelvis
  - previous history of CS
  - mal presentation
• During labor
  - all contraindication mentioned in pregnancy
  - obstructed labor
  - fetal distress
• Anytime
  - hypovolaemic state
  - cardiac disease
  - placenta previa
  - placenta abruption
  - hypersensitivity reaction.

Methods of Administration

1. Controlled IV infusion for induction of labor.
2. Intramuscular:
   - the preparation used is syntometrine
   - as prophylaxis against hemorrhage alternative to ergometrine.
   - as a routine for active management of the third stage of labor.

Ergot derivatives

Two of the several ergot compounds are widely used. Ergometrine and methargin are the two.

Mechanism of Action

Ergometrine has a direct effect on the myometrium. It stimulates uterine contractions, which occur so often and with increasing severity that the uterus enters a condition of spasm with no respite in between.

Mode of Administration

• Ergometrine and methergine can be used either parenterally or orally to induce tetanic contractions and are best used in the late second stage of labor or after the baby is delivered.
• Syntometrine should always be supplied intravenously and should not be used after one month of manufacture.

Indication

• Therapeutic
  to stop atonic uterine hemorrhage after delivery, abortion, or H mole expulsion
• Prophylactic
  As a preventative measure against excessive postpartum hemorrhage, it may be used after the birth of the anterior shoulder to limit blood loss in the third stage of labor.
• Therapeutic
  - heart diseases
  - the severe hypertensive disorder
  - suspected multiple pregnancies
  - organic cardiac disease
  - Rh-negative mother
  - pregnancy, the first stage of labor

 Danger

• Due to its vasoconstrictive effect, prolonged use may result in toe gangrene.
• Prolonged use during puerperium may interfere with lactation by reducing prolactin levels.

Prostaglandin ( PGs )

Prostaglandin is the term given to the derivative of prostanoic acid. They have the ability to behave as local hormones. In 1935, von Euler described and called prostaglandin.

Mechanism of Action

When taken at the appropriate amount, both PGE2 and PGF2 alpha have an oxytocin impact on the pregnant uterus. A change in myometrial cell membrane permeability and/or an adjustment in membrane-bound cu++ are the most likely mechanisms of action. PGs also make the myometrium more sensitive to oxytocin. PGEs are at least 5 times more potent than PGF2 alpha. PGF2 alpha mostly acts on the myometrium, whereas PGE2 primarily acts on the cervix due to its collagenolytic characteristic.

Indication in Obstetrics

• indication of abortion
• termination of molar pregnancy
• induction of labor
• cervical ripening prior to induction of abortion or labor
• medical mgmt of tubal ectopic pregnancy

Contraindications

1. Absolute contraindications
   - hypersensitivity of compound
   - asthma
   - acute PID
2. Relative contraindications
   - peptic ulcer
   - cardiovascular diseases
   - jaundice
   - renal disease
   - uterine scar

Advantages of using Prostaglandin

1. It has a strong oxytocin effect when used during pregnancy. As such, it can be employed independently, most notably in the successful induction of abortion.
2. It is more powerful than oxytocin.
3. It has no antidiuretic properties.

Disadvantages

1. It is expensive and not commonly available.
2. An extensive cervical laceration may develop when administered as an abortifacient.
3. The uterine hyperactivity may persist even after the medication is stopped.

Pethidine

It has a powerful sedative effect but little analgesic efficacy. Pethidine is typically used in the first stage of labor when the discomfort of labor becomes regular, frequent, and painful contractions. The first dose is 50 mg IM, and it is repeated as soon as the impact of the first dose begins to wear off, without waiting for the re-establishment of labor pain. Nausea, vomiting, and delayed stomach emptying are all adverse effects of pethidine.

Penazocin

It is given Intramuscularly in a dose of 30-40 mg. Its duration is shorter and causes some respiratory depression. Iy also causes drug dependence. Naloxone is an efficient and reliable antagonist.

1. Regional anesthesia
   A regional anesthetic cannot guarantee a painless delivery or make labor pleasant when the pain is intense. When comprehensive pain relief is required during delivery, the epidural analgesic is the safest and simplest technique for obtaining it.

2. Epidosin
   Epidosin is an injectable medication that promotes cervical dilatation and effacement. Epidotic can be administered if the cervix is 3 cm dilated. On the closed O, inject epidosin IM or IV and repeat every half hour up to 3 ampoules. If the progress is not satisfactory, it can be increased to 10 ampoules.

3.  Respiratory stimulants

4. Nikethamide
   It works similarly to Doxapram. It can be given parenterally or orally. It has a lower therapeutic index than doxapram, increasing the likelihood of central excitation.

Mechanism of action

Respiratory stimulants either act directly on the medulla's central respiratory center or indirectly on the chemoreceptor.

Indication

• intrauterine hypoxia
• neonatal asphyxia
• respiratory depression

Dose

Injection of 375 mg into an umbilical vein. If administered intravenously, arterial spasms and thrombosis may occur.

Nursing consideration

• Throughout therapy, keep an eye on the baby's breathing rate and volume.
• Overdosage symptoms include arrhythmia, hyperpyrexia, and convulsions.

Doxapram

It is a pyrrolidinone monohydrate. It is a central and respiratory stimulant with a short half-life. It exerts pressure and may stimulate catecholamine release.

Mechanism of Action

Respiratory stimulants either act directly on the medulla's central respiratory center or indirectly on the chemoreceptor.

Indication

• intrauterine hypoxia
• neonatal asphyxia
• respiratory depression
• chronic pulmonary disease

Preparation

• It is usually available in the form of injections such as; a Doxapram injection of 20mg/ml

Adverse effects

CNS: CNS stimulation, seizure, confusion.

CVS: hypertension, tachycardia, chest pain.

GIT: nausea, vomiting

Genitourinary: urinary retention

Miscellaneous: hiccups, rebound hypoventilation.

Nursing consideration

• Throughout therapy, keep an eye on the baby's breathing rate and volume.
• Overdosage symptoms include arrhythmia, hyperpyrexia, and convulsions.