A brief introduction regarding oxytocics & tocolytics which are the indispensable drugs in obstetrics. It consists of illustrative images, classification of drugs with their dosage, uses & side-effects along with contraindications

1. OXYTOCICS
&
TOCOLYTICS
By: Ankita Priydarshini

2. OXYTOCICS
Oxytocics also called Uterotonics have the
power to stimulate uterine contractions.

4. Mechanism of action :- On uterine oxytocin receptor (T3)
Voltage mediated Ca2+ channels
Physiological uterine contractions
1. Oxytocin

5. Onset :- Half life of 3-4 minutes.
Duration of action :- approx. 20 mins.
Dosage :- Start with low dose (1-2mU/min.) & to escalate by 1-2
MIU/min. at every 20 mins. intervals upto 8mU/min.
ROA :- a). Controlled i.v. infusion
b). Bolus IV or IM - 5-10 units after birth of baby as an
alternative to ergometrine.
c). IM - (synometrine= syntocinon 5U + Ergometrine
0.5mg)
d). Buccal tablets (50IU) or nasal spray (40units/ml)

6. Clinical uses :- a). In the induction of labour
b). to augment uterine contraction during labour
c). to stop PPH
Hazards :- Uterine hyperstimulation, Anti-diuretic effect, Uterine
rupture, anginal pain, hypotension
Contraindications :-
Pregnancy Labour Any time
Grand Multipara All contraindications
in pregnancy
Hypovolemic state
Contracted pelvis Obstructed labour Cardiac disease
H/O C-section or
hysterotomy
Inco-ordinated uterine
contraction
Malpresentation Fetal distress

7. Mechanism of action :- a). directly on myometrium
b). tetanic uterine contractions (US/LS)
Onset :- IV - 1 & half min.
IM - 7 min.
Oral - 10 mins.
DOA :- 3 hours
Dosage :- 0.2mg slow i.v. every 30 mins. (max. 5 doses can be
given within 24 hours)
ROA :- IV, IM, Oral
Clinical Uses :- a). To stop haemorrhage after delivery, abortion or
expulsion of H. mole
b). Prophylactic use in late 2nd or 3rd stage, to hasten
separation of placenta & to minimise blood loss.
2. Methergin

8. Hazards :- Nausea & vomiting
Rise in B.P.
Rarely gangrene of the toe
Intereference with lactation
Contraindications :-
Prophylactic Therapeutic
Suspected pleural
pregnancy
Cardiac disease
Organic cardiac
disease
Severe hypertensive
disorders
Severe pre-eclampsia
& eclampsia
Rh-negative mother

9. 15-methyl PGF 2 alpha ; 1 ml ampoule - 250µg of Prostadin
Mechanism of action :- Change in myometrial permeability &/or
alteration in membrane bound Ca2+
Sensitises myometrium to oxytocin
Dosage :- T2 abortion : 1ml ampoule i.m. every 3 hrs till patient
aborts (max.10 doses)
Prophylaxis of atonic PPH : 0.5-1ml IM
℞ of atonic PPH : 1 ml IM, can be repeated after 30 mins
Clinical Uses :- a). T2 abortion
b). Atonic PPH
Adverse Effects :- Hyperstimulation, Rupture uterus
Contraindications :- Uterine scar
3. Carboprost

10. Prostaglandin derivative - used for cervical ripening
Mechanism of action :- Change in myometrial permeability &/or
alteration in membrane bound Ca2+
Sensitises myometrium to oxytocin
Onset :- Half life- 1-2 mins
Dosage :- Refractory cases of PPH - 600µg - 1000µg (PR)
For induction - 25µg every 4th hourly (max. 8 doses)
Abortion : T1: Mifepristone + Misoprostol
Protocol: Day1 - Mifepristone 600mg orally
Day 3 - Misoprostol 400µg orally
4. Misoprostol

11. Clinical Uses :- a). Induction of labour
b). Induction of abortion (MTP & missed abortion)
c). Termination of molar pregnancy
d). Management of atonic PPH
e). Medical management of tubal ectopic
pregnancy
Hazards :- Tachysystole of uterus
Meconium passage
Uterine rupture
As an abortifacient - extensive cervical lacerations may
occur
Contraindications :- Hypersensitivity to the compound
Uterine scar - known to cause rupture
Active cardiac, pulmonary, renal or hepatic disease

12. Preterm labour & delivery can be delayed by drugs in order to improve
the perinatal outcome & thus reduce perinatal morbidity & mortality
significantly.
TOCOLYTICS

14. Mechanism of action of Tocolytic drugs

15. E.g. - Nifedipine, Nicadipine, Verapamil
Mechanism of action :- It blocks the entry of calcium inside the
cell
Doses :- Oral 10-20mg every 3-6 hours
Side effects & precautions :- Maternal : Hypotension
Headache
Flushing & nausea
Combined therapy with Beta mimetic
or MgSO4 should be avoided
1. Calcium Channel Blocker

16. Mechanism of action :- Acts by competitive inhibition of Ca2+ ion
either at the motor end place at the cell membrane reducing calcium
influx.
es acetylcholine release & its sensitivity at motor end plate.
Direct depressant action on uterine muscle.
Doses :- Loading dose 4-6g IV (10-20% solution) over 20-30 mins
followed by an infusion of 1-2g/hr to continue tocolysis for 12
hrs after the contractions have stopped. Tocolytic effects is poor.
Side effects & precautions :- It is relatively safe.
Common maternal side effects are flushing, perspiration, headache,
muscle weakness, rarely pulmonary oedema.
Neonatal side effects are lethargy, hypotonia, rarely respiratory
depression.
Contraindications : Pts with myasthenia gravis & impaired renal
function.
2. Magnesium Sulphate

17. Mechanism of action :- es synthesis of PGs thereby es intracellular
free Ca++, activation of MLCK & uterine contractions.
Doses :- Loading dose 50mg PO or PR followed by 25mg every 6
hrs for 48 hrs.
Side effects & precautions :- Maternal : Heart burn, asthma, GI
bleeding, thrombocytopenia, renal injury.
Contraindications : Hepatic disease, active peptic ulcer, coagulation
disorders.
Fetal & neonatal side effects : Constriction of dusts arteriosus,
oligohydramnios, Neonatal pulmonary hypertension, IUGR
3. Indomethacin
Cyclo-oxygenase inhibitor) [ Suldinac another NSAID is also
used as it has less placental transfer]

18. Mechanism of action :- Activation of intracellular enzymes
(adenylate cyclase, cAMP, Protein kinase, es intracellular free Ca++
( Ca++) & inhibits activation of MLCK ( ) Reduced
interaction of actin & myosin smooth muscle relaxation.
Doses :- Ritodrine is given IV infusion, 50µg/min & is increased by
50µg every 10 mins until contraction cease. Infusion is continued for
about 12hrs after contractions cease.
Terbutaline has longer 1/2 life & has fewer side effects.
Subcutaneous injection of 0.25mg every 3-4 hrs is given.
Side effects :- Maternal : Headache, palpitation, tachycardia,
pulmonary oedema, hypotension, cardiac failure, ARDS, lactic
acidaemia & even death. Fetal: Tachycardia, heart failure, IUFD.
Neonatal : Hypoglycaemia & intraventricular haemorrhage.
4. Betamimetics
E.g. - Terbutaline, Ritodrine, Isoxsuprine (Effective for 48 hrs to
allow time for steroids & antibiotics to work

19. Mechanism of action :- blocks myometrial oxytocin receptors. It
inhibits intracellular Ca++ release, release of PGs & thereby
inhibits myometrial contractions.
Doses :- IV infusion 300µg/min. Initial bolus may be needed.
Side effects :- Nausea, vomiting, chest pain (rarely).
5. Oxytocin Antagonists
E.g. - Atosiban

20. Mechanism of action :- Smooth muscle relaxant
Doses :- Patches
Side effects :- May cause cervical ripening, Headache
6. Nitric Oxide (NO) Donors
E.g. - Glyceryl trinitrate (GTN)