Anti-hypertensive drugs ( alpha1-blocker and alpha2-agonist )
Alpha1-blockers:
Drugs:
- Prazosin
- Doxazosin
- Terazosin
Mechanism of action:
These drugs reduce peripheral vascular resistance and arterial blood pressure by dilating arterial and venous smooth muscle.
Pharmacological action:
Prolonged use of these drugs does not cause tachycardia because these drugs cause a slight change in cardiac output and renal blood flow.
The uses:
These drugs are used in refractory cases, and this may be due to side effects.
The side effect:
- Reflex tachycardia
- Postural hypotension
Alpha2-agonist:
Drugs:
- Clonidine
- Methyldopa
Mechanism of action:
The alpha2-agonist inhibits sympathetic vasomotor centers and reduces sympathetic outflow to the periphery. Thus, these drugs reduce blood pressure, so they are used in the treatment of patients with hypertension.
Pharmacological action:
These drugs do not reduce renal blood flow or glomerular filtration (as a reminder, alpha1-antagonist drugs do little to change renal blood flow).
The uses:
- Clonidine and methyldopa are both used in patients with hypertension and complicated by renal disease.
- Methyldopa is used in the management of hypertension in pregnant women.
The side effect:
- Dry mouth
- Constipation
- Sedation
- Drowsiness
When suddenly stopping the use of clonidine, the patient may get rebound hypertension, so the patient must slowly stop using clonidine when the need to stop clonidine.