Uterine Relaxants (Tocolytics)

For BNS Ist YearDr. Pravin Prasad

Ist Year Resident, MD Clinical PharmacologyMaharajgunj Medical Campus

2nd October, 2015(Asoj 15, 2072); Friday

Drugs used as Tocolytics• Adrenergic agonist: Ritoridine• Calcium channel blockers: Nifedipine• Oxytocin Antagonist: Atosiban• Magnesium sulfate• Miscellaneous: Ethyl alcohol, nitrates, progesterone, general

anaesthetics, indomethacin, Halothane

Ritoridine•Mechanism of action:– β2 selective agonist

• Use:— Supress premature labour— Delay delivery— Treatment beyond 48 hrs not

recommended• Side Effects:

‒ CVS – hypotension, tachycardia,

arrhythmia, pulmonary edema‒ Metabolic – hyperglycaemia,

hyperinsulinemia, hypokalemia‒ Anexity, restlessness, headache‒ Neonate – foetal pulmonary

edema, hypoglycaemia, ileus• Contraindication:

– Mother having diabetes or heart disease, or receiving β blockers or steroids

Nifedipine• Mechanism of Action:• Reduces the tone of myometrium and opposes contraction

• Prominent smooth muscle relaxant action• Side Effects:• Maternal - Tachycardia, Hypotension• Foetal – Foetal Hypoxia due to placental perfusion

Other Tocolytics• Atosiban• Mechanism of Action: Antagonist at the oxytocin receptors• Availability in Nepal (??)

• Magnesium sulfate• Mechanism of Action: Acts as tocolytics by competiting with Ca++ ions for entry

into myocardium through both voltage gated and ligand gated Ca++ channels• Higher risk to be used as tocolytics – increases perinatal mortality• Not recommended

• Halothane• Used as relaxant when external or internal version is attempted

Thank You!!