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Haemodynamic effects of guanfacine
British Journal of Clinical Pharmacology
|January 1, 1980
Summary
Guanfacine initially increases blood pressure and resistance, then decreases them, affecting cardiac output and heart rate. This study details its haemodynamic effects during rest and exercise for up to 20 hours.
Area of Science:
- Pharmacology
- Cardiovascular Physiology
Background:
- Guanfacine is an alpha-2 adrenergic agonist with known hypotensive effects.
- Its detailed haemodynamic profile, especially under varying physiological conditions, requires further elucidation.
Purpose of the Study:
- To investigate the haemodynamic mechanism of action of intravenous guanfacine (4 mg).
- To assess its effects on blood pressure, cardiac output, heart rate, and pulmonary arterial pressure at rest and during exercise for up to 20 hours.
Main Methods:
- Direct blood pressure measurement.
- Swan-Ganz thermodilution method for cardiac output and pulmonary arterial pressure.
- Assessment in resting conditions and during exercise.
Main Results:
- Initial increase in blood pressure, peripheral resistance, and pulmonary arterial pressure, with decreased heart rate and cardiac output (alpha-sympathomimetic effect).
- Subsequent decrease in blood pressure due to reduced cardiac output, followed by decreased peripheral resistance and increased cardiac output after 3 hours.
- Reduced blood pressure during exercise after 3 hours, attributed to decreased peripheral resistance.
- Sustained reduction in heart rate at rest.
Conclusions:
- Guanfacine exhibits a biphasic haemodynamic effect, initially sympathomimetic, followed by vasodilation and reduced cardiac work.
- The drug effectively reduces blood pressure and heart rate during rest and exercise, with potential side effects including fatigue, drowsiness, and bradycardia.