2. Alfa-adrenomimetics

List of drugs

α₁, α₂- adrenomimetics: Norepinephrine bitartrate

α₁- adrenomimetics: phenylephrine hydrochloride

α₂- adrenomimetics: naphazoline hydrochloride

Mechanism of action

Phenylephrine produces direct stimulation of α₁-adrenoreceptors.

Naphazoline produces direct stimulation of α₂-adrenoreceptors

Pharmacological effects:

for phenylephrine:

Type of receptors	Organ	Effect
Stimulation of α1- adrenoreceptors	Eye	Dilation of pupil (midriasis)
	Blood vessels	Constriction (due to contraction of smooth muscles of blood vessels)

for naphazoline:

Type of receptors	Organ	Effect
Stimulation of α2- adrenoreceptors	Blood vessels	Constriction (due to contraction of smooth muscles of blood vessels)

Indications

1. Acute hypotension (circulatory collapse) – relieving

Phenylephrine → stimulation of α₁-adrenoreceptors → constriction of blood vessels → increasing of arterial pressure

2. Rhinitis

Naphazoline → stimulation of α₂-adrenoreceptors → constriction of blood vessels → decreasing of running nose

3. Beta-adrenomimetics

List of drugs

β₁, β₂- adrenomimetics: isoprenaline sulfate

β₁- adrenomimetics: dobutamine hydrochloride

β₂- adrenomimetics: fenoterol, salbutamol

Mechanism of action

Isoprenaline sulfate produces direct stimulation of β₁, β₂- adrenoreceptors.

Dobutamine produces direct stimulation of β₁- adrenoreceptors.

Fenoterol, salbutamol produce direct stimulation of β₂- adrenoreceptors

Pharmacological effects:

for isopreneline:

Type of receptors	Organ	Effect
Stimulation of β1- adrenoreceptors	Heart	Increasing of heart rate, heart contractility, heart conductance and heart excitability
Stimulation of β2- adrenoreceptors	Bronchi	Dilation (due to relaxation of smooth muscles of bronchi)
	Uterus	Relaxation (due to relaxation of smooth muscles of uterus)
	Mast cells	Inhibition of degranulation (i.e. inhibition of releasing of histamine from mast cells)

for dobutamine:

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

for fenoterol, salbutamol:

Type of receptors	Organ	Effect
Stimulation of β2- adrenoreceptors	Bronchi	Dilation (due to relaxation of smooth muscles of bronchi)
	Uterus	Relaxation (due to relaxation of smooth muscles of uterus)
	Mast cells	Inhibition of degranulation (i.e. inhibition of releasing of histamine from mast cells)

Indications

1. Acute heart failure

Dobutamine → stimulation of β₁- adrenoreceptors → increasing of heart rate, heart contractility, heart conductance and heart excitability → relieving of acute heart failure

2. Bronchospasm (prophylaxy and relieving)

Isopreneline, Fenoterol, Salbutamol → stimulation of β₂- adrenoreceptors → dilation of bronchi → prophylaxy and relieving of bronchospasm

3. Relaxation of uterus to prevent preterm labor (delivery) of child.

Isopreneline, Fenoterol, Salbutamol → stimulation of β₂- adrenoreceptors → relaxation of uterus → prevention of preterm labor (delivery) of child.