Pharmacology · MU Sofia

68. Uteroactive drugs.

Covers drugs that influence uterine contractions, split into oxytocics such as oxytocin, misoprostol and ergometrine, and tocolytics such as nifedipine and terbutaline. Walks through their mechanisms, a pharmacokinetics table comparing routes, onset, metabolism, half-life and excretion, side effects, drug interactions, therapeutic uses, and pregnancy and lactation considerations, ending with recap questions.

Inside: 9 sections · 4 labelled pictures · 1 table · 10 flashcards · 2 min

Topic 67 of 93 in the MU Sofia syllabus for Pharmacology (Dental Medicine, Year 3). The free AceMed note covers it in 9 sections, about 274 words (2 min of reading), with 10 flashcards.

In this note

  1. Uteroactive Drugs
  2. Classification
  3. Pharmacodynamics
  4. Pharmacokinetics
  5. Side Effects
  6. Drug Interactions
  7. Therapeutic Uses
  8. Pregnancy and Lactation Considerations
  9. Recap Questions

Uteroactive Drugs

Uteroactive drugs are medications that influence uterine contractions. They are widely used in obstetrics to manage labor, delivery, postpartum hemorrhage, and preterm labor.

Classification

  • Oxytocics (Stimulate uterine contractions):
  • Oxytocin
  • Misoprostol
  • Ergometrine
  • Tocolytics (Inhibit uterine contractions):
  • Nifedipine
  • Terbutaline

Pharmacodynamics

  • Oxytocin: Binds to oxytocin receptors → ↑ intracellular calcium → uterine smooth muscle contraction
  • Misoprostol: Prostaglandin E1 analog → activates prostaglandin receptors → ↑ calcium → uterine contraction
  • Ergometrine: Acts on α-adrenergic, serotonin, and dopamine receptors → powerful sustained uterine contraction
  • Nifedipine: Calcium channel blocker → ↓ calcium influx → relaxation of uterine muscle
  • Terbutaline: β2-adrenergic agonist → ↑ cAMP → relaxation of uterine smooth muscle

Side Effects

  • Common:
  • Nausea, vomiting
  • Flushing, headache
  • Abdominal discomfort
  • Rare/Severe:
  • Uterine rupture (especially with oxytocics)
  • Severe hypotension (nifedipine, ergometrine)
  • Arrhythmias
  • Allergic reactions
  • Excessive bleeding

Drug Interactions

  • Nifedipine:
  • Potentiates effects of other antihypertensives
  • Metabolism affected by CYP3A4 inducers/inhibitors
  • Terbutaline:
  • ↓ efficacy with beta-blockers
  • ↑ cardiovascular risk with other sympathomimetics
  • Ergometrine:
  • Risk of hypertension with vasoconstrictors
  • ↑ toxicity with macrolides (e.g. erythromycin)

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