Pharmacodynamics and mechanism of action
This drug is a domestic pharmacological development. The basis of its therapeutic action is rooted in the interference with the function of adrenergic synapses. Proxodolol has a combined mechanism of action:
- First, it exhibits pronounced non-selective $\beta$-blocking activity. This means that the drug blocks both $\beta_1$- and $\beta_2$-adrenoceptors in various organs and tissues.
- Second, this activity is complemented by weak $\alpha$-blocking action.
It is precisely this combination of effects that determines the breadth of the drug's application, as well as the specifics of its adverse reactions upon entering the systemic circulation.
Application in ophthalmology
In ophthalmology, Proxodololum is used topically, in the form of eye drops. The main indication for its prescription is open-angle glaucoma, a disease accompanied by an increase in intraocular pressure.
The mechanism of pressure reduction is local and specific: due to the local blockade of $\beta$-adrenoceptors of the eye, the drug causes a significant suppression of aqueous humor production. The decrease in the volume of intraocular fluid naturally leads to a drop in pressure.
The pharmacokinetics of local formulations is quite convenient for patients: a clinically significant pressure-lowering effect persists for 8–12 hours after a single instillation (instilling) of the drug into the conjunctival sac.
Systemic use
For systemic therapy, the drug is available in two main dosage forms: tablets for oral administration and solution for parenteral administration.
The choice of form and route of administration depends on the clinical objective:
- Long-term treatment: Used in cardiology as a potent antihypertensive (for sustained blood pressure reduction) and antianginal (for the prevention of myocardial ischemia episodes) agent.
- Emergency care: The parenteral solution is used intravenously. The main goal of such therapy is the rapid and effective cessation of a hypertensive crisis.
Safety profile and contraindications
Like any non-selective $\beta$-blocker, proxodolol has a number of systemic side effects. Upon entering the systemic circulation (including through partial absorption of eye drops), the following adverse reactions may occur:
- Cardiovascular system: bradycardia (pronounced decrease in heart rate) and hypotension.
- Smooth muscle: increased bronchial tone and increased myometrial tone (the muscular layer of the uterus).
Important: Due to its ability to increase bronchial tree tone (a consequence of $\beta_2$-receptor blockade), the drug has an absolute contraindication — bronchial asthma. The prescription of proxodolol to such patients is strictly prohibited due to the high risk of developing life-threatening bronchospasm.
Remember the contraindication through the letter "A": Proxodolol blocks two (dvA in Russian) types of beta-receptors, so it is strictly prohibited in Asthma.
Class and exam questions
What is the mechanism of action of proxodolol?
The drug is a non-selective $\beta$-blocker, the action of which is complemented by weak $\alpha$-blocking activity.
How does proxodolol work in open-angle glaucoma?
Upon instillation of eye drops, it blocks the $\beta$-receptors of the eye, which inhibits the production of aqueous humor and reduces intraocular pressure for 8–12 hours.
Is the drug used in emergency situations?
Yes, proxodolol solution is administered intravenously for the rapid relief of a hypertensive crisis.
Why is bronchial asthma an absolute contraindication?
Due to the non-selectivity of its action, the drug causes an increase in bronchial tone, which in patients with asthma can provoke severe bronchospasm.
What else to study on this topic
- Comparative characteristics of $\beta$-blockers in ophthalmology
- Mechanisms regulating aqueous humor production
- Pathophysiology of hypertensive crisis development and the choice of drugs for its management
- The role of $\alpha$- and $\beta$-receptors in regulating the tone of bronchial and myometrial smooth muscle
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