3. Beta-adrenoblockers

List of drugs

β₁, β₂-adrenoblockers: propranolol hydrochloride

β₁-adrenoblockers: metoprolol, atenolol, nebivolol

Mechanism of action

Propranolol produces direct blockage of β₁, β₂-adrenoreceptors.

Metoprolol, atenolol and nebivolol produce direct blockage of β₁-adrenoreceptors.

Pharmacological effects:

Previous time you studied the pharmacological effects of Beta-adrenomimetics (see my previous material). For today topic «Beta-adrenoblockers» pharmacological effects will be strongly opposite (see table):

for propranolol:

Type of receptors	Organ	Effect
Blockage of β1- adrenoreceptors	Heart	Decreasing of heart rate, heart contractility, heart conductance and heart excitability
Blockage of β2- adrenoreceptors	Bronchi	Constriction (due to contraction of smooth muscles of bronchi)

for metoprolol, atenolol and nebivolol:

Type of receptors	Organ	Effect
Blockage of β1- adrenoreceptors	Heart	Decreasing of heart rate, heart contractility, heart conductance and heart excitability

Indications

1. Hypertension (chronic treatment)

Propranolol, metoprolol, atenolol, nebivolol → blockage of β₁-adrenoreceptors → decreasing of heart rate and heart contractility → decreasing of arterial pressure.

2. Tachyarrhythmia (tachycardia)

Propranolol, metoprolol, atenolol, nebivolol → blockage of β₁-adrenoreceptors → decreasing of heart rate → inhibition of tachyarrhythmia (tachycardia).

3. Angina pectoris

Propranolol, metoprolol, atenolol, nebivolol → blockage of β₁-adrenoreceptors → decreasing of heart rate and heart contractility → decreasing of heart work → decreasing in oxygen demand for myocardium → decreasing of ischemia of myocardium → decreasing of constricting pain in the chest (angina pectoris).

Side effects:

Propranolol can produce bronchospasm due to blockage of β₂- adrenoreceptors.

SIMPLICIFIED VERSION

General anesthetics

List of drugs

Inhalation anesthetics: Diethyl ether, Halothane, Nitrous oxide

Intravenous anesthetics: Thiopental sodium, Ketamine, Sodium oxybate

Mechanism of action

Inhalation anesthetics produce two activities:

1. change the physicochemical properties of neuronal membranes thus resulting in decrease of excitability of neurons;

2. potentiate GABAergic inhibition of central nervous system.

The mechanism of action of intravenous anesthetics you should not study.

Pharmacological effects

These drugs induce the inhibition of central nervous system below normal state and produce the general anaesthesia (narcosis).

Indications

General anesthesia is essential to surgical practice, because it renders patients analgesic, amnesic, and unconscious, while causing muscle relaxation and suppression of undesirable reflexes.

1. Induction to anaesthesia: using of intravenous anesthetics before applying of inhalation anesthetics (Thiopental sodium, intravenous Ketamine).

2. Basal anaesthesia: using of intravenous anesthetics along with inhalation anesthetics (Thiopental sodium, intramuscular Ketamine, Sodium oxybate)

3. Mixed anaesthesia: combined using of inhalation anesthetics (e.g. Halothane + Nitrous oxide)

All of these approaches we need to use for decreasing of side effects of narcosis, producing more deeper anaesthesia etc.

Side effects:

Diethyl ether produces the irritative action on the upper respiratory tract (up to respiratory arrest) and on the cardiac system (up to cardiac arrest)

Ketamine can induce the postoperative hallucinations.

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