Prazosin

Definition

Prazosin is an alpha-1 adrenergic receptor antagonist that is primarily used to treat hypertension, benign prostatic hyperplasia, and post-traumatic stress disorder. It works by blocking the action of norepinephrine, a neurotransmitter that normally stimulates alpha-1 receptors, leading to vasodilation and reduced blood pressure.

5 Must Know Facts For Your Next Test

1. Prazosin is primarily used to treat hypertension, benign prostatic hyperplasia, and post-traumatic stress disorder.
2. Prazosin works by blocking the action of norepinephrine on alpha-1 adrenergic receptors, leading to vasodilation and a reduction in blood pressure.
3. Prazosin has a longer half-life and longer duration of action compared to other alpha-1 blockers, such as terazosin and doxazosin.
4. Prazosin can cause orthostatic hypotension, especially when starting treatment or increasing the dose, due to its vasodilatory effects.
5. Prazosin has also been used off-label to treat nightmares associated with post-traumatic stress disorder, as it can help reduce the physiological symptoms of fear and anxiety.

Review Questions

• Explain how prazosin works to lower blood pressure.
  • Prazosin is an alpha-1 adrenergic receptor antagonist, which means it blocks the action of norepinephrine on these receptors. Norepinephrine normally stimulates alpha-1 receptors, leading to vasoconstriction and an increase in blood pressure. By blocking this effect, prazosin causes vasodilation, which reduces peripheral resistance and lowers blood pressure.
• Describe the additional uses of prazosin beyond the treatment of hypertension.
  • In addition to treating hypertension, prazosin is also used to manage benign prostatic hyperplasia and post-traumatic stress disorder. For benign prostatic hyperplasia, prazosin's alpha-blocking effects help to relax the smooth muscle in the prostate, improving urine flow. For PTSD, prazosin has been found to be effective in reducing the frequency and intensity of nightmares, as it can help to reduce the physiological symptoms of fear and anxiety associated with traumatic memories.
• Analyze the potential side effects of prazosin and explain how they relate to the drug's mechanism of action.
  • One of the primary side effects of prazosin is orthostatic hypotension, or a sudden drop in blood pressure when standing up. This is directly related to prazosin's mechanism of action as an alpha-1 adrenergic receptor antagonist. By blocking the vasoconstrictor effects of norepinephrine, prazosin causes vasodilation, which can lead to a significant decrease in blood pressure, especially when transitioning from a seated or lying position to standing. This effect is most pronounced when starting treatment or increasing the dose of prazosin, and patients must be monitored closely for this potential side effect.

Related terms

Alpha-1 Adrenergic Receptors: Alpha-1 adrenergic receptors are G-protein coupled receptors that, when activated by norepinephrine or epinephrine, cause vasoconstriction and an increase in blood pressure.

Norepinephrine:

Norepinephrine is a neurotransmitter and hormone that acts on both alpha and beta adrenergic receptors, leading to increased heart rate, blood pressure, and other physiological effects.

Vasodilation:

Vasodilation is the widening of blood vessels, which decreases peripheral resistance and lowers blood pressure.