These drugs have a dual mechanism of action. They lower BP in two ways:
1. They block the alpha receptor, causing the vessels to dilate and the pressure to drop.
2. They directly relax vascular smooth muscle. Around the blood vessels, there’s smooth muscle surrounding it. If the muscle around it relaxes, it causes the blood pressure to go down. So it does it in two ways, by blocking the alpha receptor and relaxing the smooth muscle. When you relax the smooth muscle, the baroreceptors get stimulated and the heart speeds up but there is no rebound tachycardia because they don’t work on the autonomic nervous system at all.
There’s a caution for a patients first dose of their lifetime: They could have syncope, meaning they faint. So they should take this first dose ever at night time, so they are sleeping and the caution is to get out of bed slowly.
- Prostate Hypertrophy: The vast majority of patients on these drugs are not for hypertension but for their enlarged prostate gland so it will shrink it so they could urinate.
Alpha Adrenegric Blocking Agents
Hint: They all end in -azosin, YAY!
- Prazosin (Minipres) – p.o.
- Terazosin (Hytrin) – p.o.
- Doxazosin (Cardura) – p.o.