Mechanism of action
The pharmacological effects of hexoprenaline are due to the selective stimulation of $eta_2$-adrenoreceptors. In the smooth muscle of the uterus (myometrium) and bronchi, this leads to the activation of adenylate cyclase, accumulation of cAMP, and a decrease in the cytoplasmic concentration of free calcium. As a result, myometrial tone and contractile activity decrease. Furthermore, stimulation of $eta_2$-receptors prevents mast cell degranulation, inhibiting the release of inflammatory mediators, and helps improve mucociliary clearance.
Pharmacological effects and kinetics
Hexoprenaline belongs to short-acting $eta_2$-adrenoreceptor agonists (effect lasts 4–6 hours). The drug is characterized by a short latent period: the onset of bronchodilating or tocolytic effect is observed within 2–5 minutes after administration, and the maximum effect develops within 40–60 minutes. The drug effectively dilates the bronchi and decreases uterine contractility, making it a frequent tool in emergency situations.
Indications for use
In clinical practice and obstetrics, hexoprenaline is prescribed for:
- Inhibiting labor contractions and preventing preterm birth;
- Managing the threat of miscarriage;
- Eliminating excessive labor activity;
- Treating and preventing acute bronchospasm attacks (as a representative of bronchodilators).
Specific features of use and fetal effects
Routes of administration depend on the clinical situation: routinely, the drug is used orally in tablets, and in emergency cases, intravenously.
In obstetrics, hexoprenaline (along with fenoterol) is considered the drug of choice because it carries a lower risk of adverse fetal effects compared to salbutamol. Nevertheless, drugs of this group cross the placental barrier and can cause fetal tachycardia and arrhythmia.
Administration and dosage
Orally, the single dose (SD) is 0.0005 g (500 mcg tablets). For emergency inhibition of labor contractions, the ampoule solution (10 mcg) is pre-diluted in 10 mL of 0.9% sodium chloride solution and administered intravenously slowly over 5–10 minutes.
Hexoprenaline = Gynipral: "Gyni" saves from preterm birth (reduces uterine tone), while having a short duration of action (4–6 hours) and a mild profile for the fetus.
Class and exam questions
To which pharmacological group does hexoprenaline belong?
Hexoprenaline belongs to selective beta-2-adrenomimetics (agents regulating the functions of the peripheral nervous system).
Why is hexoprenaline preferred over other beta-2 agonists in obstetrics?
Hexoprenaline and fenoterol carry a lower risk of developing fetal tachycardia and arrhythmia compared to salbutamol.
How to properly administer hexoprenaline to inhibit contractions?
The ampoule contents (10 mcg) are diluted in 10 mL of 0.9% sodium chloride solution and administered intravenously slowly over 5–10 minutes.
What else to study on this topic
- Comparative pharmacodynamics of selective and non-selective beta-adrenoreceptor agonists
- Classification of tocolytic agents by mechanisms of action
- Side effects of beta-2 receptor stimulation on the maternal cardiovascular system
- Pharmacokinetics of short-acting and long-acting bronchodilators
- Features of transplacental drug transfer
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