Vasopressors, Inotropes, and Receptors……



Vasopressors, Inotropes, and Receptors…….Oh My!!!!!!!

By: JB Topol Pharm.D.

Pharmacy Practice Resident 2008-2009

I believe the most frustrating piece of drug information for me to remember is the pharmacology and cardiovascular effects of the different vasopressors and inotropes. As a student on my ICU rotation at the VA, I learned a lot about how physicians decide on a particular agent and how different patients react differently to each medication. I felt it would be a good review to create charts regarding the different vasopressors/inotropes, their pharmacology, cardiovascular effects, and dosing. It can hopefully serve as a guide and a review for health professionals in an intensive care setting.

I begin with a chart that depicts the different receptors, where they are located, and upon stimulation, what the overall net effect is. I was told in pharmacy school that in order to know how each drug affects the body that you have to understand the physiology behind the particular system being affected. The second chart depicts selected vasopressors/inotropes and the receptors on which they work. Milrinone and Vasopressin do not work within the alpha, beta, and dopamine receptor system. Milrinone, which is a phosphodiesterase inhibitor, causes a vasodilatation and increases the force of contraction. Vasopressin, on the other hand, is a direct vasoconstrictor working at the V1 receptors in the vascular smooth muscle and V2 receptors in the renal tubule causing the kidney to hold onto more water. The final chart depicts the dose and cardiovascular effects of selected vasopressors /inotropes.

I hope this review was helpful and gave each of you a better understanding of the different vasopressors and inotropes. If you ever have questions about different agents and the pharmacology behind them, ask a pharmacist we are here to help.

Adrenergic Receptors: Location and Effect

|Organ: |Receptor |Effect of Stimulation: |

|Heart: | | |

|SA node |β1 and β2 |Increased automaticity |

|AV node |β1 and β2 |Increased automaticity and conduction |

| | |velocity |

|Atria |β1 and β2 |Increased contractility and conduction |

| | |velocity |

|Ventricles |β1 and β2 |Increased automaticity, contractility, and |

| | |conduction velocity |

|Arterioles: | | |

|Coronary |α and β2 |Vasoconstriction (+) and Vasodilatation |

| | |(++) |

|Skin and mucosa |α |Vasoconstriction (+++) |

|Skeletal muscle |α and β2 |Vasoconstriction (++) and vasodilatation |

| | |(++) |

|Cerebral |α |Vasoconstriction (+) |

|Abdominal viscera |α and β2 |Vasoconstriction (+++) and vasodilatation |

| | |(+) |

|Pulmonary |α and β2 |Vasoconstriction (+) |

|Renal |α, β1 and β2 |Vasoconstriction (+++) and vasodilatation |

| | |(+) |

|Veins |α, β1 and β2 |Vasoconstriction (++) and vasodilatation |

| | |(++) |

Vasopressors and Inotropes: Receptor Specificity

|Drug: |α1 |β1 |β2 |Dopaminergic |

|Catecholamines: | | | | |

|Dopamine: | | | | |

|1-3 ug/kg/min |- |+ |- |++++ |

|3-10 ug/kg/min |- |++++ |++ |++++ |

|> 10 ug/kg/min |+++ |++++ |+ |- |

|Dobutamine |+ |++++ |++ |Not Applicable |

|Norepinephrine |++++ |++++ |++ |Not Applicable |

|Epinephrine: | | | |Not Applicable |

|0.01-0.05 ug/kg/min |+ |++++ |++ | |

|>0.05 ug/kg/min | | | | |

| |++++ |+++ |+ | |

|Isoproterenol |No Activity |++++ |++++ |Not Applicable |

|Phenylephrine |+++++ |No Activity |No Activity |Not Applicable |

|Milrinone* |Not Applicable |Not Applicable |Not Applicable |Not Applicable |

|Vasopressin** |Not applicable |Not Applicable |Not Applicable |Not Applicable |

* Milrinone is a phosphodiesterase inhibitor which causes vasodilatation and inotropic effects in the heart

**Vasopressin works on the V1 receptor (vascular smooth muscle) and V2 (renal tubular collecting duct). Direct vasoconstrictor with no effects on the heart.

Vasopressors and Inotropes: Dosing and Cardiovascular Effects

Drug: |Dose: |CO: |TPR |Mean BP |Renal Perfusion |HR |MAP |PCWP | |Dopamine:

1-3 ug/kg/min

3-10 ug/kg/min

> 10 ug/kg/min |

1-20 mcg/kg/min |

NC

↑

↑ |

NC

NC/↓

↑ |

NC

NC

↑ |

↑↑

↑↑

↑↓ |

↑

↑↑

↑↑↑

|

NC

↑

↑ |

NC

NC/↑

↑ | |Epinephrine |0.01-0.05 mcg/kg/min

>0.05 ug/kg/min |NC/↑

↑ |↓

↑ |↑

↑↑ |↑

↑↓ |↑

↑↑ |↑

↑↑ |NC/↓

↑ | |Dobutamine |2-40 mcg/kg/min |↑ |↓ |↑ |NC |↑ |↑ |↓ | |Norepinephrine |0.01-0.3 mcg/kg/min |↓/NC |↑ |↑ |↓ |↓ |↑ |↑ | |Isoproterenol |0.015-0.5 mcg/kg/min |↑ |↓ |↓ |↑-with cardiogenic or septic shock.

↓-normal renal function |↑ |↓ |↓ | |Phenylephrine |10-200 mcg/min |↓ |↑ |↑ |↓ |↓ |↑ |↑ | |Milrinone |LD: 50 mcg/kg over 10 minutes

MD: 0.375-0.75 mcg/kg/min |↑ |↓ |NC |↑ |NC/↑ |NC/↓ |↓ | |NC=No change, TPR=Total Peripheral Resistance, BP=Blood Pressure, HR=Heart Rate, CO=Cardiac Output, MAP=Mean Arterial Pressure, and PCWP=Pulmonary-Capillary Wedge Pressure.

References

1. Overgaard CB, Dzavik V. Inotropes and Vasopressors: Review of Physiology and Clinical Use Cardiovascular Disease. Circulation. 2008;118:1047-1056.

2. London JA, Sena MJ. Pharmacologic Support of the Failing Heart. Surg Clin N Am. 2006;86:1503-1521.

3. Lexi-comp. Available from online. Accessed 12/5/08.

4. Also adapted from ICU dosing card, VA San Diego. Developed by Maria Stubbs, Pharm.D.

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