Tocolytics are agents which decrease uterine tone. Tocolytics include:

All tocolytics are discussed in more detail elsewhere - this covers just the mechanism of action of their uterine effects.

Drug β2-agonists Ca2+-channel antagonists COX Inhibitors
Example Salbutamol, Terbutaline Nifedipine Indomethacin
Mechanism of Action Activate GPCR, ↑ cAMP, which activates protein kinase A and leads to inhibition of myosin light chain kinase and relaxation Block L-type Ca2+ channels, causing relaxation Inhibit prostaglandin synthesis, which are vital for uterine contraction


  1. Diaz, A. Describe the mechanism of action and side effects of three classes of drugs that are used to increase uterine tone, and three classes of drugs used to decrease uterine tone. Primary SAQs.
Last updated 2019-07-18

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