Prostaglandins

Prostaglandins are the derivatives of Prestanoic Acid from which they derive their name. They have the property of acting as 'local Hormones. Prostaglandins were first described by Von Euler in 1935. These are important factors, which initiate and maintain labor. The major site of synthesis of Prostaglandin is Amnion, Chorion, decidual cell, and myometrium.

Synthesis is triggered by a rise in estrogen level, glucocorticoids, mechanical stretching in late pregnancy, an increase in cytokines infection, vaginal examination, and rupture of the membrane. Prostaglandins enhance gap formation.

Chemistry

    PGs are 20-Carbon Carboxylic acids with a cyclopentane ring which are formed from polyunsaturated fatty acid. Out of many, PGE1, PGE2 and PGF2a are mainly used in labor.

Note: Specific PG is named with a Letter (which indicates the type of ring Structure) followed by a number (which Indicates the number of double bonds In Hydrocarbon structure).

Mechanism of Action

• Phospholipase A_{2} in the Lysosomes of the fetal membrane near term Act directly at the Sarcoplasmic reticulum
• Esterified arachidonic acid
• Formation of free arachidonic acid
• Synthesis of PG
• PG*E_{2} and PGF2a diffuse in the myometrium
• Inhibit intracellular CAMP generation.
• Increase local free Calcium ion
• Uterine Contraction

Indication

• To induce childbirth (particular) or abortion (PGF2 or PGF2 with or without mifepristone.
• To prevent the closure of patent ductus arteries in newborns with particular Cyanotic heart defect (PGE1).
• To prevent and treat PVD.
• As a vasodilator in Severe Raynauld Phenomenon.
• In pulmonary HTN.
• In the treatment of Glaucoma.
• To treat Erectile dysfunction or in Penile rehabilitation following Surgery (PGE1 as a / alprostadil).
• To stop atonic uterine bleeding following delivery or abortion.
• Medical management of tubal Ectopic pregnancy.

Symptoms 

• Nausea, GI upset
• Diarrhea
• Bronchospasm
• Chills
• Vomiting
• Pyrexia, hot flashes
• Tachy cardia
• Cervical laceration
• Risk of uterine rupture.
• Tachysystole of uterus.
• Mild pelvic pain or menstrual-type cramps.
• Warm feeling in the vagina
• Blurred vision
• Bleeding from the vagina.
• Back pain
•  Hypotension
• Skin discoloration, hearing impairment

Contraindication

• HSN.
• Bronchial Asthama (PGE2α)
• History of cesarean section
• Cases of fetal distress
• Uterine scar
• Hypotension (PGE2)
• CPD present
• History of difficult labor
• 6 or more previous pregnancies
• Malpresentation
• Active Cardiac, pulmonary, renal, or Hepatic disease.

Doses and Route of Misoprostol

Dose for Cervical Ripening:

• Before Surgical abortion: 400 mcg vaginally 3 to 4 hrs before suction Curettage.

Dose for Medical Abortion:

• 1st trimester of pregnancy: 400 mcg orally once a single dos PO 48 hrs after mifepristone administration.
• In failed pregnancy or fetal death: 800 mcg vaginally once or twice.
• 2nd trimester of pregnancy: 600 mcg vaginally, 36 to 48 hrs after mifepristone administration, followed by 400 mcg.
• 3rd trimester of pregnancy (fetal death): 100 mcg vaginally every 12 hrs.

Dose for labor induction:

• 25 mcg vaginally every 4 to 6 hrs. 50 mcg orally

Dose for Postpartum Bleeding

• 400 to 600 mcg orally, before delivery of Placenta.

Preparation:

• Vaginal tablet: Containing 3 mg dinoprostone (PGE)
• Vaginal Pessary: (releasing dinoprostone 10 mg over 24 hrs).
•  Dinoprostone Gelugs500 ug into Cervical Canali below the level of the internal OS.
• PGE (IV): Contain 1mg / m * L v. PGE2a: Containing 5mg / m * L
• Carbopost: Containing 250mg / m * L

Pharmacokinetics

• Absorption: Rapidly absorbed.
• Distribution: (Unknown) Action is local.
• Metabolism: Metabolished by Enzyme in lungs, kidney, liver, and spleen.
• Excretion: Urine, feces.

Nursing Consideration

• Explain the purpose of medication and vagina exam.

Abortifacient

• Instruct pt to notify health Care Professional immediately if fever and chills, foul-smelling vaginal discharge, lower abdominal pain or increased bleeding,
• Provide Emotional Support through the therapy.

Cervical Ripening

• Inform the patient that she may Experience a warm fever in her vagina during administration. •
• Advise patient to notify health Care Professional if Contraction becomes prolonged.
• Pt should remain Supine for 15-30 min after administration to minimize leakage from Cervical Canal.
• Monitor vital signs and report wheezing, chest pain, dyspnea, and significant change in BP and pulse, notify the physicians.