Midodrine
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Sympathomimetics and Sympatholytics (New)
- Isoproterenol
- Dobutamine
- Norepinephrine
- Alpha-Methyldopa
- Midodrine
- Clonidine & Guanfacine
- Phenylephrine
- Epinephrine
- Dopamine
Summary
Midodrine is a drug primarily used to treat low blood pressure. As a sympathomimetic drug, it works by activating alpha-1 receptors. This results in vasoconstriction, which causes an increase in blood pressure. This also slows the heart rate as a compensatory response. Clinically, midodrine is used to treat autonomic dysfunction and orthostatic hypotension. Side effects of midodrine include supine hypertension.
Key Points
- Midodrine
- Drug Class
- Sympathomimetic
- mimics the action of endogenous hormones on adrenergic receptors
- Sympathomimetic
- Site of Action
- Activates Alpha-1 (Alpha-1 Agonist)
- Physiologic Effects
- Vasoconstriction
- ↑ BP
- This is usually caused by arterial vasoconstriction and increased vascular resistance
- ↓ HR
- Due to compensatory baroreceptor reflex in response to increased blood pressure
- -/↓ CO
- Venous constriction increases venous return to the heart, which can increase cardiac output
- Decreased HR however works to decrease cardiac output, so the effect may be no change at all
- Conflicting studies here show that midodrine may even increase basal cardiac output
- Clinical Use
- Treats Orthostatic Hypotension
- Alpha 1-mediated venous vasoconstriction helps maintain venous return despite the effects of gravity from standing up
- Treats Autonomic Insufficiency
- Treats Orthostatic Hypotension
- Side Effects
- May exacerbate supine hypertension
- Since activation of alpha-1 receptors leads to vasoconstriction, which increases blood pressure
- May exacerbate supine hypertension
- Drug Class