Terbutaline, Ritodrine

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Summary

Terbutaline and Ritodrine are beta-2 agonists. They are primarily used as tocolytics to slow or prevent uterine contractions by relaxing the uterine smooth muscle. This relaxation of the uterus delays the onset of labor. Since terbutaline and ritodrine are beta-2 agonists, they can also cause bronchodilation, which may be useful in treating severe acute asthma.

Key Points

  • Terbutaline and Ritodrine
    • Mechanism:
      • B2 agonist
        • Given IV or subcutaneously, so relatively short-acting
    • Effects
      • Uterine relaxation
      • Bronchodilation
        • Not the primary focus of these drugs (in contrast vs. albuterol/salmeterol)
        • B2 agonists activate adenylyl cyclase to ↑ cAMP in bronchial smooth muscle, leading to smooth muscle relaxation and dilation of the airways.
    • Indications:
      • Tocolysis
        • Slow or prevent uterine contractions by relaxing the uterine smooth muscle to delay the onset of labor, particularly premature labor.
      • Severe acute asthma
    • Adverse effects:
      • Due to B1 activation
        • Tremor
        • Tachyarrhythmias
      • Due to B2 activation:
        • Hypokalemia
      • Increased risk of neonatal hemorrhage, hypoglycemia, hypocalcemia, and ileus.