The document discusses various drugs used in obstetrics including oxytocics like oxytocin and ergot derivatives, antihypertensives like methyldopa and labetalol, anticonvulsants like magnesium sulfate, analgesics and anesthetics. It provides details on the mechanisms of action, indications, contraindications and side effects of these drug classes and some commonly used medications. The nurse's responsibilities in administering and monitoring patients on these drugs are also outlined.

1. Drugs in Obstetrics
By: Maj Saminder Malik

2. Drugs in Obstetrics
1. Oxytocics
2. Epidosin
3. Antihypertensives
4. Anticonvulsants
5. Analgesia & anesthesia

3. Oxytocic in Obstetrics
Power to excite uterine muscle contractions
1. Oxytocin
2. Ergot Derivatives
3. Prostaglandins

4. Oxytocin
It is synthesized in the supra-optic and para ventricular nuclei of
the hypothalamus
A half life of 3-4 min and duration of action of approx. 20 min
Stimulates amniotic and decidual prostaglandin production
Bound intracellular calcium (mobilize from the sarcoplasmic
reticulum to activate the contractile protein)
Stimulate myoepithelial cells of mammary glands for milk
ejection
Anti diuretic action

5. Oxytocin (preparations)
Synthetic oxytocin (5IU/ml)
Syntometrine (5+0.5mg)
Desamino oxytocin ( buccal tablets; 50IU)
Oxytocin nasal solution (40U/ml)

6. Indications
Pregnancy, labor , puerperium
To accelerate abortion, expedite H. Mole
To stop bleeding following evacuation of the uterus
Adjunct to induction of abortion along with other abortifacient agents
To induce and augment labor
Active management of third stage of labor
To minimize & control blood loss & control PPH
To facilitate cervical ripening for effective induction
Diagnostic of Contraction Stress Test & Oxytocin Sensitivity Test

7. Contraindications
Grand multipara
Obstructed labor
Fetal distress
Cardiac patient
Previous history of anaphylactic shock

8. Adverse effects
Maternal
Uterine hyper stimulation
Uterine rupture
Water intoxication
Hypotension
Anti diuresis
Amniotic fluid embolism
Fetal : fetal distress, fetal hypoxia, fetal death

9. 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

10. Nurse’s responsibilities
Evaluate:
length and duration of contractions
Notify physician of contractions lasting over 1 min or
absence of contractions
Teach:
To report increased blood loss, abdominal cramps or
increased temperature

11. Ergot derivatives
Preparation Ampoules Tablet
Ergometrine (ergonovine) 0.25mg or
0.5mg
0.5mg
Methergine(methylergonovi
ne)
0.2mg 0.5-1mg
Syntometrine (Sandoz) 0.5mg
ergometrine
0.5-1mg +5 U
syntometrine

12. Onset of action
Routes Ergometrine methergine
IV 45-60sec 5min
IM 6-7min 7min
Oral 10min 10min

13. Mode of action
Acts directly on myometrium
Excites powerful frequent uterine
contractions with increasing intensity
without any relaxation in between
both upper & lower uterine segment

14. Indications
Prophylaxis & treatment of atonic PPH
First trimester MTP
Following LSCS/ Hysterotomy

15. Contraindications
Before birth of anterior shoulder
Before second twin is born
Heart disease in pregnancy
PIH/ Chronic hypertension
Rh negative patient
Vascular diseases

16. Ergot derivatives
Common side effects are nausea and vomiting
Precipitate rise of BP, myocardial infarction, stroke and bronchospasm
because of vaso-constrictive effect
Prolonged use may result in gangrene formation of the toes
Prolonged use in puerperium may interfere with lactation
Caution: ergometrine should not be used during pregnancy, first stage
of labor, second stage of labor, second stage prior to crowning of the
head an din breech delivery prior to crowning

17. Ergot derivatives
Nurse’s responsibilities:
Assess : Blood pressure, pulse and respiration
Watch for signs of hemorrhage
Administer: orally or IM in deep muscle mass
Have emergency cart readily available
Evaluate: therapeutic effect – decreased blood loss
Teach : to report increased blood loss, abdominal cramps, headache,
sweating, nausea, vomiting or dyspnea

18. Prostaglandins
Mechanism of action:
increases intramyometrial calcium concentration &
enhance uterine contraction.
Act on G protein coupled receptors & activate
calcium channels
PGF2α promotes myometrial contractility
PGE2α helps cervical maturation

19. Prostaglandins
Routes Availability Preparation Dose
Vaginal
route
Dinoprostone (prostin E2) Vaginal tablet 3mg in post. Fornix.
Repeat dose after 6-8
hrs. Max dose 6mg
Releasing dinoprostone Vaginal pessary 10mg over 24hrs.
Removed when cervix is
ripe
Prostin E2 (cerviprime) Vaginal gel 0.5mg at/below internal
os
Parenteral PGE2 IV 1mg/ml
PGF2a (dinoprost
tromethamine)
IM 5mg/ml
Methyl analogue of PGF2a
(carboprost)
IM 250mcg/ml
Methyl ester of PGE1
(misoprost)
tablets

20. Contraindications
Hypersenstivity to the compound
Uterine scar
Active cardiac, pulmonary, renal or hepatic
disease, hypotension (PGE2)
Bronchial asthama (PGF2a)

21. Side effects
Nausea, vomiting
Tachycardia
Bronchospasm
Cervical lacerations
hyper stimulation

22. Prostaglandins - uses
Powerful oxytocic effect irrespective of period of pregnancy.
In later months it can be used for acceleration of labor
It has got no anti diuretic effect
Termination of molar pregnancy
Induction of abortion, labor & augmentation
Cervical ripening prior to the induction of abortion or labor
Management of atonic PPH
Medical managemnt of tubal ectopic pregnancy

23. Nurses' responsibility
Monitor for hypersensitivity reaction
Maintain asepsis
After instillation of cerviprime gel patient should
lie in bed for half an hour. Max. 3 instillations can
be done at the interval of 6-8hrs

24. Epidosin (valethamate bromide)
Used in active management of labor
Facilitate dilataion and effacement of cervix
Anticholinergic, spasmolytic action on
smooth muscles

25. Indications
Acceleration of first stage of labor
Dilataion of cervix in labor
Spasmodic dysmenorrhea

26. Route of administration & dose
SC/IM/ IV/Orally
Dose: >3-4cm dilated cervix in labor
1ampoule = 8mg IM/IV 3doses every 20min
Side effects mild tachycardia

27. Anti-hypertensive therapy
Sympathom
imetics
Adrenergic
receptor
blocking
agent
Vasodilators Calcium
channel
blockers
Methyldopa Labetalol Hydralazine Nifedipine

28. Methyldopa
Drug of first choice
Central and peripheral anti-adrenergic action
Effective and safe for both mother and fetus
Dose: Orally 25omg BD may be increased o 1gm tds
depending upon the response
IV infusion 250 – 500 mg

29. Methyldopa
Contraindications: hepatic disorders
Psychic patients
CCF
Side effects: Maternal hypotension
Hemolytic anemia
Sodium retention
Excessive sedation
Fetal intestinal ileus

30. Labetalol
Mechanism of action: combined alpha and beta adrenergic
blocking agents
Contraindication: hepatic disorders
Dose: orally 100mg tds. May be increased upto 800mg daily
IV infusion (hypertensive crisis) 1-2 mg/ ml until desired effect
Side effects: experience is less compared to methyldopa. Efficacy
and safety with short term use. Appear equal to methyl dopa

31. 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 25mg in 200 ml NS at a rate of 2.5 mg/hr to be
doubled every 30 min
Side effects: maternal : hypotension, tachycardia, arrhythmia,
palpitation, lupus like syndronme
Neonatal : thrombocytopenia

32. Nifedipine
Mode of action: direct arteriolar vasodilator
Dose: orally 5-10 mg td
Contraindications: simultaneous use of magnesium sulphate
could be hazardous due to synergic effect
Side effects: flushing, headache, hypotension, tachycardia,
inhibition of labor

33. Tocolytic agents
Prevention of preterm labor
Delays labor by 48-72 hrs
Give time to administer steroids, treat infection
1. Beta 2 adrenergic receptor agonists
2. Prostaglandin synthetase inhibitors
3. Calcium channel blockers
4. Antagonists (atosiban)

34. Betamimetics
Commonly used:
Terbutaline
Ritodrine
Isoxuprine
Mechanism of action: Activation of the
intracellular enzymes( acetylate cyclase, cAMP,
protein kinase) reduces intracellular free
calcium and inhibits the activation of MLCK

35. Betamimetics
Dose: ritodrine is given by infusion 50mcg/min and
increased by 50 mcg every 10min until contractions cease.
Maximum dose of 200mcg /min till 12-48 hrs may be
given. Infusion is continued for about 12 hours after
contraction ceases. DO NOT USE SALINE TO MAKE
INFUSION
Terbutaline: has longer life and has fewer side effects
subcutaneous injection of 0.025mg every 3-4 hours is
given

36. Betamimetics
Isoxuprine: is given a IV drip 100mg in 5%D. Rate 0.2
mcg/minute. To continue for at least 2 hours after contraction
ceases. Maintenance Is by IM 10mg six hourly for 24 hours,
tab 10mg 6-8hourly
Side effects: maternal headache, palpitation, tachycardia,
pulmonary edema, hypotension, cardiac failure,
hyperglycemia, ARDS, Hyper-insulinemia, lactic academia,
hypokalemia, even death
Neonatal hypoglycemia, IVH

37. PG synthetase inhibitor -
Indomethacine
Reduces synthesis of PGs thereby reduces
intracellular free ca, activation of MLCK and
uterine contractions
Dose: loading dose 50mg PO or PR followed by
25mg evry 6 hours for 48 hrs
Side effects: Maternal heart burn , GI bleeding,
asthma, thrombocytopenia, renal injury

38. Calcium Channel blockers
Nifedipine
MgSo4
Mechanism: nifedipine blocks the entry of calcium inside the cell.
Compared to beta-mimetics, effects are less. It is equally effective to
Mg SO4
Dose: oral: 10 -20 mg every 6-8hrs
Side effects: maternal hypotension, headache, flushing, nausea

39. Magnesium Sulphate
Inhibition to calcium ion
Contraindication: myasthenia gravis, impaired renal
function
Side effects: Maternal: flushing, perspiration,
headache, muscle weakness, pulmonary edema rarely
Neonatal Lethargy hypotonia respiratory depression
rerely

40. Oxytocin antagonists - Atosibvan
It blocks myometrial oxytocin receptors
Dose: IV infusion 300mcg/min, initial bolus may be
needed
Side effcts: nausea, vomiting, platelet dysfunction
Fetal oligohydramnios, IVH, NEC

41. Anticonvulsants – MgSo4
Mode of action: it decreases the acetylcholine release from the nerve
endings
Dose: IM loading dose 4gm IV ( 20% solution) over 3-5min to follow
10gm deep IM, 5gm in each buttock. Maintenance dose: 5gm deep IM
on alternate buttocks every 4 hours (pritchard’s regimen)
IV loading dose: 4-6 gm. IV over 15-20min. Maintenance dose: 1-
2gm/hr IV infusion (Zuspan regimen)
Maintenance dose to be continued for 24hrs after the last seizure
Side effects: relatively safe and is drug of choice. Muscular paresis
(diminished knee jerks), respiratory failure. Renal function to be
monitored.
Antidote: injection of calcium gluconate 10% 10ml IV

42. MgSo4 – Toxic levels
Normal = 0.8 – 1mmol/L
Therapeutic levels = 1.7 – 3.5 mmol/L
Prolonged PR interval & wide QRS = 3.5-5mmol/L
Loss of tendon reflexes = 5-7.49mmol/L
Respiratory paralysis = 7.5 – 11.9mmol/L
Cardiac arrest = >12mmol/L

43. MgSo4 - side effects
Flushing & lethargy
Generalized muscle weakness
Pulmonary oedema
Cardiac arrest & death
Newborn respiratory depression
hyporeflexia

44. Diazepam
Central muscle relaxant & anticonvulsant
Dose: 20-40mg IV
Side effects: Maternal – Hypotension
Fetal - Respiratory Distress, hypotonia,
thermoregulatory problem

45. Analgesia & anesthesia in obstetrics
Sedatives and analgesics
Opioid analgesics

46. Pethidine
Dose: injectable preparations contains 50 mg/ml can be
administered SC, IM, IV .its dose is 50-100mg IM combined
with promethazine.
Contradictions: should not be used IV within 2hrs and IM
within 3 hrs. of expected time of delivery of the baby, for fear
of birth asphyxia. It should not be used in cases of preterm
labor and when respiratory reserve of the mother is reduced
Side effects: M: drowsiness, dizziness, confusion, headache,
sedation, nausea, vomiting

47. Fentanyl
Inhibits ascending pathways in CNS. Increases
pain threshold and alters pain perception.
Indications: moderate to severe pain in labor,
postoperative pain , and adjunct to GA
Dose: 0.5-1mg IM per1-2hrs available in
injectable form 0.05mg/ml
Side effects: dizziness, delirium, euphoria,
nausea, vomiting, muscle rigidity, blurred vision

48. Pentazocin
Dose: 30-40mg
Naloxone is an efficient & reliable antagonist
Adverse effects: neonate respiratory depression
secondary to the medication crossing to the
placenta and affecting the fetus.
Unsteady ambulation of the client
Inhibition of the mother’s ability to cope with the
pain of labor

49. Tranquilizers
Diazepam – usual dose is 5-10mg
Midazolam – dose of 0.05mg/kg is given IV
Combination of narcotics & tranquilzers
Butorphanol and nalbuphine

50. Inhalational methods
Nitrous Oxide and air
Premixed nitrous oxide and oxygen
Trichloroethylene
Methoxyflurane, isoflurane , enflurane

51. Epidural and spinal regional
analgesia
Adverse effects:
Nausea & vomiting
Inhibition of bladder & bladder elimination sensations
Bradycardia or tachycardia
Hypotension
Respiratory depression
Allergic reaction and pruritis

52. Pudendal block
It consists of a local anesthetic such as
lidocaine (xylocaine) or bupivacaine (Marcaine)
being administered transvaginally into the space
in front of the pudendal nerve

53. Epidural anaesthesia
Epidural block consists of a local anesthetic
bupivacaine (Marcaine) along with an analgesic
morphine (duramorph) or fentanyl (sublimaze)
injected into the epidural space at the level of 4th
or 5th vertebrae
Adverse effects : maternal hypotension, fetal
bradycardia, inability to feel the urge to void,
loss of bearing down refl;ex

54. Spinal block
Spinal block consist of a local anesthetic injected
into the subarachnoid space into the spinal fluid at
3rd, 4th, 5th lumbar interspace, alone or in
combination with an analgesic such as fentanyl
Adverse effects: maternal hypotension, fetal
bradycardia, loss of bearing fown reflex

55. Para-cervical block
It consists of lidocaine (xylocaine) being injected
into the cervical mucosa early in labor during the
1st stage to block the pain of uterine contractions
Adverse effects include fetal bradycardia.
Improper technique can result in serious toxicity

56. General Anesthesia
100% oxygen is administered by tight mask fit for more than 3 min.
Induction of anaesthesia is done with the injection of thiopentone
sodium 200 – 250mg as a 2.5% solution IV followed by refrigerated
suxamethonium 100mg.
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 4mg or Atracurium 25mg)