· Oxytocics table
· Tocolytic table
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Mechanism of action (MoA) and adverse effects (AE) |
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Oxytocin |
· Bind oxytocin receptor, a Gq G protein coupled receptor (GPCR) · ↑IP3 -> ↑ICF [Ca2+] (also ↑DAG) · At low dose: intermittent contraction · At high dose: tonic contraction · Receptors upregulated from from 36/40 · AE: N&V, vasodilatation, slightly ADH effect on kidney (V2) -> H2O reabsorption, hyponatraemia |
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Carbetocin |
· Synthetic analogue of oxytocin |
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Ergometrine |
· Oxytocic mechanism unclear · Causes tonic contraction at any dose cf. oxytocin · Known receptor effects: o α1: ↑SVR, ↑BP, risk of APO (contra-indicated in pre-eclampsia) o 5HT2 agonist: N&V o DA agonist: N&V |
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Misoprostol |
· PGE1 analogue · Binds PGE2-R -> multiple G protein-coupled receptor subtypes · AE: diarrhoea |
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PGF2α |
· MoA: binds Gq protein-coupled receptor -> ↑ICF Ca2+ · AE: bronchoconstriction, hypertension, nausea |
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Mechanism of action and adverse effects: |
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Terbutaline |
· β2 agonist / Gs GPCR -> ↑cAMP -> ↑inhibition of MLCK · AE: ↑HR (cardiac B2) ↓K+ (↑Na+K+ATPase activity), lactic acidosis (β2 liver and skeletal muscle), tremor (β2 skeletal muscle) |
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Nifedipine |
· Inhibit L-Ca2+ -> ↓ICF [Ca2+] · AE: reflex ↑HR, peripheral oedema |
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GTN |
· Prodrug · Reacts with endothelial ICF sulfhydryl groups -> NO -> activate GC -> ↑cGMP -> ↑MLCP activity, ↑Ca2+ reuptake, ↑K+ efflux · AE: ↓BP (vascular SM), reflex HR, flushing, headache, metHbaemia (bad in foetus) · Note tachyphylaxis (depletion of sulfhydryl groups) |
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Atosiban |
· Nonapeptide · Competitive antagonist at oxytocin receptor · AE: headache, nausea&vomiting |
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Volatile anaesthetics |
· Inhibit L-Ca2+ -> ↓ICF [Ca2+] · Note ↑risk sedated neonate · ↑Risk PPH if GA Caesarean · Supplement with N2O · AE: maternal and foetal anaesthesia, respiratory and cardiovascular depression, nausea and vomiting |