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Hemodynamic effects of guanfacine in essential hypertension
Insights
Guanfacine, a central alpha-adrenergic receptor stimulant, reduced heart rate and pulmonary capillary wedge pressure after a single dose. Long-term use significantly lowered blood pressure and systemic vascular resistance in patients with essential hypertension.
Area of Science:
- Cardiovascular medicine
- Pharmacology
Background:
- Essential hypertension is a common cardiovascular condition.
- Central alpha-adrenergic receptor agonists are used to manage hypertension.
- Understanding the hemodynamic effects of guanfacine is crucial for its clinical application.
Purpose of the Study:
- To evaluate the acute and long-term hemodynamic effects of guanfacine in patients with essential hypertension.
- To elucidate the hemodynamic mechanisms underlying guanfacine's antihypertensive action.
Main Methods:
- Hemodynamic parameters were assessed before and after a single dose of oral guanfacine.
- Hemodynamic parameters were reassessed after a six-week course of daily guanfacine administration.
- Measurements included blood pressure, heart rate, pulmonary capillary wedge pressure, and pulmonary arterial pressure.
Main Results:
- A single dose of guanfacine decreased heart rate and pulmonary capillary wedge pressure, as well as pulmonary arterial pressure.
- Long-term administration of guanfacine significantly reduced systemic blood pressure, heart rate, and systemic vascular resistance.
- Pulmonary artery systolic pressure, mean right atrial pressure, and stroke volume index increased after long-term treatment.
Conclusions:
- Guanfacine exerts both acute and long-term hemodynamic effects in patients with essential hypertension.
- The primary mechanism for the long-term antihypertensive effect of guanfacine appears to be a reduction in systemic vascular resistance.
Abstract:
Hemodynamic evaluation of three men and eight women aged 20 to 58 years (mean, 44 years) with essential hypertension was performed before and after a single dose of guanfacine and before and after long-term administration of the drug, which is a stimulant of central alpha-adrenergic receptors. Mean (+/- SE) recordings of blood pressure before catheterization were 168/115 +/- 6/3 mmHg when supine and 168/112 +/- 8/4 mmHg when standing. Within two hours of oral administration of 3 mg of guanfacine, the heart rate decreased from a mean of 77 +/- 2 to 69 +/- 3 beats/min (P less than 0.05), and the pulmonary capillary wedge pressure (PCWP) decreased from a mean of 9 +/- 1 to 6 +/- 1 mmHg (P less than 0.02). The mean readings of pulmonary arterial pressure also decreased, as follows: systolic, from 22 +/- 2 to 18 +/- 0.14 mmHg (P less than 0.05); diastolic, from 9 +/- 1 to 7 +/- 1 mmHg (P less than 0.05); and mean, from 15 +/- 1 to 12 +/- 2 mmHg (P less than 0.05). No changes were observed in systemic blood pressure, the cardiac index, systemic vascular resistance, or total pulmonary vascular resistance. After a six-week course (mean dosage, 3.9 +/- 0.57 mg/day), the following variables decreased significantly: systemic blood pressure--systolic, diastolic, and mean, both supine and standing (P less than 0.001); heart rate (P less than 0.001); and systemic vascular resistance (P less than 0.01). The PCWP reached values similar to those measured during the control phase. Increases were noted in pulmonary artery systolic pressure (P less than 0.05), mean right atrial pressure (P less than 0.01), and in the stroke volume index (P less than 0.05). It is likely that the main hemodynamic mechanism underlying the long-term antihypertensive effect of guanfacine is a decrease in systemic vascular resistance.