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SIMPLICIFIED VERSION
ADRENONEGATIVE DRUGS)
SYMPATHOLYTICS
List of drugs
Reserpine
Guanethidine
Mechanism of action
These drugs produce inhibition of releasing of norepinephrine from presynaps, As result, there will be the decreasing of norepinephrine concentration in the synaptic cleft and absence of stimulation of α1, α2, β1, β2- adrenoreceptors.
Pharmacological effects
Previous time you studied the pharmacological effects of Indirect adrenomimetics (see my previous material). For today topic «Sympatholytics» pharmacological effects will be strongly opposite (see table):
| Type of receptors | Organ | Effect |
| Absence of stimulation of α1- adrenoreceptors | Blood vessels | Dilation (due to relaxation of smooth muscles of blood vessels) |
| Absence of stimulation of α2- adrenoreceptors | Blood vessels | Dilation (due to relaxation of smooth muscles of blood vessels) |
| Absence of stimulation of β1- adrenoreceptors | Heart | Decreasing of heart rate, heart contractility, heart conductance and heart excitability |
| Absence of stimulation of β2- adrenoreceptors | Bronchi | Constriction (due to contraction of smooth muscles of bronchi) |
Indications
1. Hypertension (chronic treatment)
Reserpine, Guanethidine → absence of stimulation of α1, α2-adrenoreceptors → dilation of blood vessels + absence of stimulation of β1-adrenoreceptors → decreasing of heart rate and heart contractility = due to dilation of blood vessels and decreasing of heart rate and heart contractility there will be the decreasing of arterial pressure.
2. Tachyarrhythmia (tachycardia)
Reserpine, Guanethidine → absence of stimulation of β1-adrenoreceptors → decreasing of heart rate → inhibition of tachyarrhythmia (tachycardia).
ALFA-ADRENOBLOCKERS
List of drugs
α1, α2-adrenoblockers: phentolamine mesylate
α1- adrenoblockers: prazosin hydrochloride
Mechanism of action
Phentolamine produces direct blockage of α1, α2-adrenoreceptors.
Prazosin produces direct blockage of α1-adrenoreceptors
Pharmacological effects:
Previous time you studied the pharmacological effects of Alfa-adrenomimetics (see my previous material). For today topic «Alfa-adrenoblockers» pharmacological effects will be strongly opposite (see table):
for phentolamine:
| Type of receptors | Organ | Effect |
| Blockage of α1- adrenoreceptors | Blood vessels | Dilation (due to relaxation of smooth muscles of blood vessels) |
| Blockage of α2- adrenoreceptors | Blood vessels | Dilation (due to relaxation of smooth muscles of blood vessels) |
for prazosin:
| Type of receptors | Organ | Effect |
| Blockage of α1- adrenoreceptors | Blood vessels | Dilation (due to relaxation of smooth muscles of blood vessels) |
Indications
1. Relieving of hypertensive crises
Phentolamine → blockage of α1, α2-adrenoreceptors → dilation of blood vessels → decreasing of arterial pressure.
2. Hypertension (chronic treatment)
Prazosin → blockage of α1-adrenoreceptors → dilation of blood vessels → decreasing of arterial pressure.
Date: 2015-12-18; view: 765
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