Simplicified version

3. (Adrenopositive drugs)

1. Indirect adrenomimetics

List of drugs

Ephedrine hydrochloride

Mechanism of action

These drugs increase the releasing of norepinephrine from presynaps. As result there will be the accu­mulation of norepinephrine in the synaptic cleft and stimulation of α₁, α₂, β₁, β₂- adrenoreceptors.

Pharmacological effects

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

Indications

1. Acute hypotension (circulatory collapse) – prevention

Ephedrine → stimulation of α₁, α₂-adrenoreceptors → constriction of blood vessels → increasing of arterial pressure.

2. Bronchospasm (prophylaxis)

Ephedrine → stimulation of β₂- adrenoreceptors → dilation of bronchi → prophylaxis of bronchospasm

3. Rhinitis (including allergic rhinitis)

Ephedrine → stimulation of α₁, α₂-adrenoreceptors → constriction of blood vessels → decreasing of running nose

and

Ephedrine → stimulation of β₂- adrenoreceptors → inhibition of degranulation of mast cells → inhibition of allergic component of rhiniris.

NB! Repeated administration of ephedrine produce tachyphylaxis - rapid development of tolerance (i.e. absence of effect).

2. Direct adrenomimetics

1. Mixed action Adrenomimetics

List of drugs

Epinephrine hydrochloride

Dopamine hydrochloride

Mechanism of action of epinephrine: direct stimulation of α₁, α₂, β₁, β₂- adrenoreceptors.

Pharmacological effects of epinephrine:

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

Indications for epinephrine:

1. Bronchospasm (relieving).

Epinephrine → stimulation of β₂- adrenoreceptors → dilation of bronchi → relieving of bronchospasm

2. Hypoglycemic coma

Epinephrine → α₁, α₂, β₁, β₂- adrenoreceptors → increasing of the glucose level in the blood (due to disruption of glycogen in the liver etc.) → relieving of hypoglycemic coma.

3. Anaphylactic (allergic) shock

Epinephrine → stimulation of β₂- adrenoreceptors → inhibition of degranulation of mast cells → relieving of anaphylactic (allergic) shock.

Side effects:

Epinephrine can produce cardiac arrhythmias.

Mechanism of action of dopamine: mostly direct stimulation of D₁-receptors (dopamine receptor type 1) and α₁- adrenoreceptors.

Pharmacological effects of dopamine: iincreasing of heart contractility + dilation of blood vessels.

Indications for dopamine:

1. Shocks of different aetiology (e.g. cardiogenic shock etc.)