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):

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:

for prazosin:

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: 649