detailed skeleton plan on PHARMACO-THERAPEUTICS IN OBSTETRICS

1. SKELETON PLAN
PHARMACO-THERAPEUTICS IN OBSTETRICS
OXYTOCICS IN OBSTETRICS
OXYTOCIN
It is synthesized in the supraoptic and paraventricular nuclei of
the hypothalamus with a half-life of 3-4 minutes and duration of
action of approximately 20 minutes
• Mode of action
• preparations used
• effectiveness
• Indications
 Therapeutic
 Diagnostic
• Nurse’s responsibilities
 ¢ Assess
 — Intake output ratio.
 — Uterine contractions and FHR.
 — Blood pressure, pulse and respiration.
 ¢ Administer
 — By IV infusion. Monitor drop rate.
 — Make crash cart available.
 ¢ Evaluate
 — Length and duration of contractions.
 — Notify physician of contractions lasting over 1 minute or
 An absence of contractions.
 ¢ Teach
 — To report increased blood loss, abdominal cramps or

2.  Increased temperature.
ERGOT DERIVATIVES
¢Mode of action:
Ergometrine acts directly on the myometrium
¢ Effectiveness
It is highly effective in hemostasis
¢ Indications:
— Therapeutic:
To stop the atonic uterine bleeding following delivery,
abortion or expulsion of hydatidiform mole.
— Prophylactic:
Against excessive haemorrhage following delivery.
CONTRAINDICATIONS:
Prophylactic:
¢ Suspected plural pregnancy.
¢ Organic cardiac diseases.
¢ Severe pre-eclampsia and eclampsia
¢ Rh- negative mother.
Therapeutic:
¢ Heart disease or severe hypertensive disorders
Hazards:
¢ Common side effects are nausea and vomiting.
¢ Precipitate rise in blood pressure, myocardial
infarction, stroke and bronchospasm because of
vasoconstrictive effect.
¢ Prolonged use may result in gangrene formation of
the toes.

3. ¢ Prolonged use in puerperium may interfere with
lactation
PROSTAGLANDINS
Mechanism of action
¢PGF2α promotes myometrium
contractility
¢PGE2 helps the cervical maturation
Contraindications:
¢ Hypersensitivity to the compound.
¢ Uterine scar.
Preparations
¢ Tablet.
¢ Vaginal suppository
¢ Vaginal pessary
¢ Prostin E2.
¢ Parenteral
Use in obstetrics
¢ Induction of abortion.
¢ Termination of molar pregnancy.
¢ Induction of labour.
¢ Cervical ripening prior to the induction of abortion or
labour.
¢ Acceleration of labour.
¢ Management of atonic PPH.
¢ Medical management of tubal ectopic pregnancy.
ANTI-HYPERTENSIVE THERAPY
METHYLDOPA

4. Mechanism of action
¢ -Drugs of the first choice
¢ -Central and peripheral anti-adrenergic action
¢ -Effective and safe for both mother and fetus.
Contraindications
¢ -hepatic disorders
¢ -psychic patients
¢ -CCF
Dose
¢ -orally 250mg bid may be increased to 1 gm tid
depending upon the response.
¢ -IV infusion 250-500mg
Side effects
-maternal:
¢ postural hypotension
¢ haemolytic anaemia
¢ sodium retention
¢ excessive sedation
¢ coomb’s test may be positive.
-fetal:
¢ intestinal ileus
LABETALOL
Mechanism of action
¢ Combined alpha and beta-adrenergic blocking agents.
Contraindication
¢ hepatic disorders.
Dose

5. ¢ orally: 100mg tid. Maybe increased up to 800 mg daily.
¢ -IV infusion [hypertensive crisis] 1-2 mg/mt until desired
effect
Side effects
¢ Experience is less compared to methyldopa. efficacy
and safety with short-term use. Appear equal to methyldopa.
PROPRANOLOL
• Mechanism of action
• ¢ Beta-adrenergic receptor blocker
• Contraindication
• ¢ bronchial asthma.
• ¢ renal insufficiency.
• ¢ diabetes.
• ¢ Cardiac failure
• ¢ The drug is better avoided for long-term therapy
• during pregnancy.
• Dose
• ¢ orally: 80-120 mg in divided doses
Side effects
maternal:
¢ severe hypotension
¢ sodium retention
¢ Bradycardia
¢ Bronchospasm
¢ CCF
¢ hypoglycaemia.
fetal:

6. ¢ bradycardia and impaired fetal responses to hypoxia,
IUGR when began in I and II trimesters.
-neonatal: hypoglycaemia
HYDRALAZINE
Mechanism of action
¢ Arteriolar vasodilator.
Contraindication
¢ Because of the variable sodium retention, diuretics should
be used.
Dose
¢ orally: 100mg/day in 4 divided doses.
¢ - IV: 5mg bolus followed by 25g in 200 ml NS at a rate of
2.5 mg/hr to be doubled every 30 mts.
Side effects
¢ -maternal: hypotension, tachycardia, arrhythmia,
palpitation, lupus-like syndrome.
¢ -fetal: reasonably safe.
¢ -neonatal: thrombocytopenia
NIFEDIPINE
Mode of action:
¢ Direct arteriolar vasodilation.
Dose:
¢ Orally 5-10 mg TID.
Contraindications:
¢ Simultaneous use of magnesium sulphate could
be hazardous due to synergic effect.
Side effects:

7. ¢ Flushing
¢ Hypotension
¢ Headache
¢ Tachycardia
¢ Inhibition of labour.
SODIUM NITROPRUSSIDE
Mechanism of action:
¢ Direct vasodilator.
Dose:
¢ Orally 6.25 bid.
Side effects:
¢ Maternal
— Nausea
— Vomiting
¢ Fetal
— Oligohydramnios
— IUGR
— Fetal and neonatal renal failure.
NITROGLYCERINE
Mechanism of action
¢ Release mainly venous but also arteriolar smooth
muscles.
Dose:
¢ Given as IV infusion 5μg/min. to be increased at
every 3-5 min. up to 100μg/min.
Side effects:
¢ Tachycardia

8. ¢ Headache
¢ Methaemoglobinaemia
Diuretics are used in the following conditions during pregnancy.
¢ Pregnancy-induced hypertension with
massive oedema.
¢ Eclampsia with pulmonary oedema.
¢ Severe anaemia in pregnancy with heart
failure.
¢ Prior to blood transfusions in severe
anaemia.
¢ As an adjunct to certain antihypertensive
drugs, such as hydralazine or dioxide
FUROSEMIDE
Mechanism of action
¢ Acts o loop of the Henle by increasing excretion of
sodium and chloride.
Dose
¢ 40 mg tab, daily following breakfast for 5 days a
week. In acute conditions, parentally 40-120 mg
daily.
Contraindications:
¢ Hypersensitivity
HYDROCHLOROTHIAZIDE
Mechanism of action:
¢ Acts on distal tubule by increasing excretion of
water, sodium, chloride and potassium. It is used in
oedema and hypertension.

9. Dose:
¢ PO 25-100 mg/day.
Side effects:
¢ Polyuria, glycosuria, frequency.
¢ Nausea, vomiting, anorexia.
¢ Rash, urticaria, fever.
¢ Increased creatinine, decreased electrolytes.
TOCOLYTIC AGENTS
¢ Betamimetics
¢ prostaglandin synthetase inhibitors
¢ magnesium sulphate
¢ calcium channel blockers
¢ oxytocin receptor antagonists
¢ nitric oxide donors
¢ antibiotics.
BETAMIMETICS
• Commonly used drugs:
• ¢ Terbutaline
• ¢ Ritodrine
• ¢ Isoxsuprine
• Mechanism of action:
• ¢ Activation of the intracellular enzymes [adenylate
• cyclase, cAMP, protein kinase] reduces intracellular
• free calcium [Ca++] and inhibits the activation of MLCK
Dose:
¢ Ritodrine is given by IV infusion, 50μg/min. and
increased by 50μg every 10 min. until contractions

10. cease. The maximum dose of 350μg/ min. may be given.
Infusion is continued for about 12 hours after
contraction ceases.
¢ Terbutaline has the longer half-life and has fewer side
effects. Subcutaneous injection of 0.25 mg every 3-4
hours is given.
¢ Isoxsuprine has given an IV drip 100 mg in 5D. Rate 0.2
μg/minute. To continue for at least 2 hours after
contraction ceases. Maintenance is by IM 10mg six
hourly for 24 hours, tab 10 mg 6-8 hourly.
INDOMETHACIN
Mechanism of action:
¢ Reduces synthesis of PGs thereby reduces intracellular
free Ca++, activation of MLCK and uterine contractions.
Dose:
¢ Loading dose, 50 mg P.O. or .P.R. followed by 25mg
every 6 hrs for 48 hours.
Side effects:
¢ Maternal
¢ Heartburn
¢ G.I. bleeding
¢ Asthma
¢ Thrombocytopenia
¢ Renal injury.
CALCIUM CHANNEL BLOCKERS
• ¢ Nifedipine
• ¢ Nicardipine

11. • Mechanism of action:
• ¢ Nifedipine blocks the entry of calcium inside the cell.
• Compared to β- mimetics, effects are less. It is
• equally effective to MgSO4.
• Dose:
• ¢ Oral 10-20 mg every 6-8 hours.
MAGNESIUM SULPHATE
Mechanism of action:
¢ inhibition of calcium ion
Contraindications:
¢ Myasthenia gravis
¢ Impaired renal function
Dose:
¢ Loading dose: 4-6 gm I.V. over 20-30 min. followed
by an infusion of 1-2 gm/hr to continue tocolysis for
12 hours after contractions have stopped.
Side effects:
¢ Maternal
¢ Flushing
¢ Perspiration
¢ Headache
¢ Muscle weakness
¢ Pulmonary oedema rarely
¢ Neonatal
¢ Lethargy
¢ Hypotonia
¢ Respiratory depression rarely.

12. OXYTOCIN ANTAGONISTS:
¢ Atosiban
Mechanism of action:
¢ It blocks myometrial oxytocin receptors.
Dose:
¢ I.V.infusion 300μg/min. the initial bolus may be needed.
Side effects:
¢ Nausea
¢ Vomiting
¢ Chest pain
ANTICONVULSANTS
1. MAGNESIUM SULPHATE:
¢ Mode of action:
¢ It decreases the acetylcholine release from the
nerve endings.
¢ Dose:
¢ IM – loading dose: 4 gm IV [20% solution] over 3-5
min. to follow 10 gm deep IM, 5gm in each
buttock. Maintenance dose: 5gm deep IM on
alternate buttocks every 4 hrs.
¢ IV- loading dose: 4-6 gm IV over 15-20 min.
maintenance dose: 1-2 gm/hr. IV infusion.Side effects:
¢ MgSO4 is relatively safe and is the drug of choice.
Muscular paresis[ diminished knee jerks],
respiratory failure. Renal function to be monitored.
Antidote:
¢ Injection of calcium gluconate 10% 10 ml IV.

13. DIAZEPAM
mode of action:
¢ central muscle relaxant and anticonvulsant.
Dose:
¢ 20-40 mg IV
Side effects:
¢ Maternal:
¢ Hypotension
¢ Fetal
¢ Respiratory depression
¢ Hypotonia
¢ Thermoregulatory problem
PHENYTOIN
Mode of action:
¢ Centrally acting anticonvulsant
Dose:
¢ 10 mg/ kg IV at the rate not more than 50 mg/ min
followed 2 hrs later by 5 mg/kg. In epilepsy 300-
400 mg daily orally in divided doses.
Side effects:
¢ Maternal
¢ Hypotension
¢ Cardiac arrhythmias
¢ Phlebitis at the injection site.
¢ Fetal
¢ Fetal hydantoin syndrome

14. ANTICOAGULANTS:
HEPARIN
Mechanism of action:
¢ It inhibits the action of thrombin
Dose:
¢ 5000-10000 I.U. to be administered parenterally [SC or IV].
¢ Low molecular weight heparin is 2500 IU
Side effects:
¢ Maternal:
¢ Haemorrhage
¢ Urticarial
¢ Thrombocytopenia
¢ Osteopenia.
¢ Fetal
¢ It does not cross the placenta
WARFARIN
Mechanism of action:
¢ Interferes with synthesis of vit K dependent factors.
Dose:
¢ 10 mg orally
Side effects:
¢ Maternal
¢ Haemorrhage
¢ Fetal
¢ Contradi’s syndrome [skeletal and facial anomalies]

15. ¢ Optic atrophy
¢ Microcephaly
¢ Chondrodysplasia punctate.
ANALGESIA AND ANAESTHESIA IN
OBSTETRICS
1. SEDATIVES AND ANALGESICS
¢ OPIOID ANALGESICS:
¢ PETHIDINE
Mechanism of action:
¢ Inhibits ascending pain pathways in CNS, increase
pain threshold and alters pain perception.
Indications:
¢ Moderate to severe pain in labour, postoperative pain,
abruption placentae, pulmonary oedema.
Dose:
¢ Injectable preparations contain 50mg/ml can be
administered SC, IM, IV. Its dose is 50-100 mg IM
combined with promethazine.
PETHIDINE
Contraindications:
Should not be used IV within 2 hrs and IM within 3 hrs of an
expected time of delivery of the baby, for fear of birth asphyxia.
It should not be used in cases of preterm labour and when the
respiratory reserve of the mother is reduced
Side effects:
¢ Maternal
¢ Drowsiness
¢ Dizziness

16. ¢ Confusion
¢ Headache
¢ Sedation
¢ Nausea
¢ Vomiting
¢ Fetal
¢ Respiratory depression
¢ Asphyxia
FENTANYL
Mechanism of action:
¢ Inhibits ascending pathways in CNS, increases pain
threshold and alters pain perception.
Indications:
¢ Moderate to severe pain in labour, postoperative
pain an adjunct to the general anaesthetic.
Dose:
¢ 0.05 to 0.1 mg IM q1-2 hrs prn. Available in
injectable form, 0.05 mg/ml.
¢ Side effects:
¢ Dizziness
¢ Delirium
¢ Euphoria
¢ Nausea
¢ Vomiting
¢ Muscle rigidity
¢ Blurred vision
PENTAGON

17. • ¢ dose of 30-40 mg
• ¢ Naloxone is an efficient and reliable antagonist.
• Adverse effects
• ¢ Neonate respiratory depression secondary to the
• medication crossing the placenta and affecting
• the fetus.
• ¢ Unsteady ambulation of the client.
• ¢ Inhibition of the mother’s ability to cope with the
• the pain of labour.
Tranquillizers
• ¢ DIAZEPAM: Usual dose is 5-10 mg.
• ¢ MIDAZOLAM: Dose of 0.05 mg/kg is given
• intravenously
• ¢ COMBINATION OF NARCOTICS AND
• Tranquillizers
• ¢ BUTORPHANOL and NALBUPHINE
INHALATIONAL METHODS
• ¢ Nitrous oxide and air
• ¢ Premixed nitrous oxide and oxygen
• ¢ Trichloroethylene
• ¢ Methoxyflurane, isoflurane, enflurane
EPIDURAL AND SPINAL REGIONAL
ANALGESIA
• Adverse effects
• ¢ nausea and vomiting.
• ¢ Inhibition of bowel and bladder elimination
• sensations.

18. • ¢ Bradycardia or tachycardia.
• ¢ Hypotension.
• ¢ Respiratory depression.
• ¢ Allergic reaction and pruritus.
PUDENDAL BLOCK
It consists of a local anaesthetic such as lidocaine(Xylocaine) or
bupivacaine (Marcaine) being administered transvaginally into
the space in front of the pudendal nerve.
EPIDURAL ANAESTHESIA
• The epidural block consists of a local anaesthetic bupivacaine
(Marcaine) along with an analgesic morphine (Duramorph) or
fentanyl (Sublimaze) injected into the epidural space at the level
of the fourth or fifth vertebrae.
• Adverse effects
• Maternal hypotension.
• Fetal bradycardia.
• Inability to feel the urge to void.
• Loss of the bearing down reflex.
SPINAL BLOCK
• The spinal block consists of a local anaesthetic injected into
the subarachnoid space into the spinal fluid at the third, fourth,
or fifth lumbar interspace, alone or in combination with an
analgesic such as fentanyl.
• Adverse effects
• Maternal hypotension.
• Fetal bradycardia.
• Loss of the bearing down reflex.
PARACERVICAL BLOCK

19. • It consists of lidocaine (Xylocaine) being injected into the
cervical mucosa early in labour during the first stage to block the
pain of uterine contractions.
• Adverse effects include fetal bradycardia.
• Improper technique can result in serious toxicity.
GENERAL ANAESTHESIA
• 100% oxygen is administered by tight mask fit for more than
3 minutes.
• Induction of anaesthesia is done with the injection of
thiopentone sodium 200- 250 mg as a 2.5 % solution IV., followed
by refrigerated suxamethonium 100 mg.
• the patient is intubated with cuffed ET tube.
• Anaesthesia is maintained with 50% NO2, 50% oxygen and a
trace of halothane.
• Relaxation is maintained with non-depolarizing muscle
relaxant [ vecuronium 4 mg or atracurium 25 mg].
FETAL HAZARDS ON MATERNAL
MEDICATION DURING PREGNANCY
• Mechanism of teratogenicity
• ¢Folic acid deficiency.
• ¢Epoxides or arena oxides
• ¢Environmental and genes
• abnormalities.
• ¢Maternal disease and drugs
• ¢Homebox genes
Maternal-fetal drug transfer and the hazards
• ¢ before D 31:
• Teratogen produces an all or none effect.
• ¢ D31-d71:

20. • It is the critical period for organ formation.
• ¢ After D 71:
• The development of other organs continues.
MATERNAL DRUG INTAKE AND
BREASTFEEDING
Transfer of drugs through breast milk depends on
following factors:
¢ Chemical properties
¢ Molecular weight
¢ Degree of protein binding
¢ Ionic dissociation
¢ Lipid solubility
¢ Tissue pH.
¢ Drug concentration.
¢ Exposure time.
DRUGS IDENTIFIED AS HAVING EFFECT ON
LACTATION AND THE NEONATE
¢ Bromide: Rash. Drowsiness, and poor feeding.
¢ Iodides: Neonatal hypothyroidism
¢ Chloramphenicol: Bone marrow toxicity
¢ Oral pill: Suppression of lactation.
¢ Bromocriptine: Suppression of lactation.
¢ Ergot: Suppression of lactation.
¢ Metronidazole: Anorexia, blood dyscrasias, irritability,
weakness,
neurotoxic disorders.
¢ Anticoagulants: Haemorrhagic tendency.

21. ¢ Isoniazid: Anti-DNA activity and hepatotoxicity.
¢ Anti-thyroid drugs and radioactive iodine: Hypothyroidism and
goitre, agranulocytosis.
¢ Diazepam, opiates, phenobarbitone: Sedation effect with the
poor
sucking reflex.