Dopamine
Dopamine is a neurotransmitter, known for being the neurotransmitter that makes us feel good. Dopamine plays an important role in our cognitive, emotional and behavioural functioning.
Dopamine is produced in the brain and helps with the transmission of signals within the brain. In addition, it is responsible for motor functions such as smooth and controlled movements or even motivation and reward systems.
Dopamine is synthesized in the central nervous system as well as the peripheral nervous system and binds to G protein-coupled receptors [1, 2]. Dopamine is used in treating a wide range of conditions, most famously Parkinson’s disease [1, 3]. PD is a neurodegenerative disease caused by the loss of dopaminergic neurons in the basal ganglia, leading to a loss of motor control.
However, it can be used for diseases like prolactinoma which is a disease characterized by an excess of prolactin hormone [4]. Not only that, dopamine treatment is showing potential as an antitumor agent against malignant melanoma [5].
In addition to these, dopamine treatment has been used to manage acute congestive heart failure due to its cardiovascular and renal effects [6].
While dopamine is beneficial in treating these conditions, it does not do so without side effects. Long-term use of dopamine-based treatments can lead to motor fluctuations or can diminish the quality of life among patients [7, 8].
Dobutamine
Dobutamine is a synthetic catecholamine. It was developed as a selective positive inotropic drug for short-term parental administration.
Normally, it includes two isomers: alpha- and beta-adrenergic receptors and the effects are mediated by adrenergic receptor stimulation and mild stimulation of beta-2 and alpha-1 receptors [9, 10].
Dobutamine is used for short-term management of heart failure. It increases cardiac output, and reduces systemic vascular resistance. Further, it lowers central venous and pulmonary artery wedge pressures. In addition, it also improves renal blood flow and relieves signs and symptoms of congestive heart failure [9].
Dobutamine is used to improve ventricular function and cardiac performance in patients in whom ventricular dysfunction has caused a reduced stroke volume and cardiac output, a mild to moderate drop in systemic blood pressure, diminished organ and tissue perfusion, and elevated ventricular filling pressures [10].
It has been used successfully in several circumstances, such as after cardiac surgery, in patients with myocardial infarction, and in various shock states [9]. Dobutamine may also benefit normotensive patients with cardiac decompensation due primarily to loss of ventricular contractility or when left ventricular afterload reduction is needed [11].
Dobutamine vs Dopamine: Comparisons
When comparing dobutamine and dopamine, there are several ways we can compare the two.
Dopamine is a natural molecule, a neurotransmitter naturally found in the brain, while dobutamine is a synthetic drug.
Both dopamine and dobutamine act by stimulating the beta-1 adrenergic receptors. Stimulation of these receptors leads to increased myocardial contractility and stroke volume which in turn leads to an increase in cardiac output [12, 13, 10].
But unlike dopamine, dobutamine has a lesser effect on alpha-1 - 1 adrenergic receptors.
As both of these drugs act on the alpha 1 adrenergic receptors, they both have effects on heart rate, in particular increase in heart rate[14]. Although we observe a more robust effect with dopamine.
When comparing their inotropic action (contractility affecting actions) dopamine is indirectly mediated via noradrenaline release while dobutamine is direct. This means that dopamine effects may be attenuated with time due to noradrenaline depletion, while the effects of dobutamine are maintained [15].
We can also look at the hemodynamic, renal, or pulmonary effects of both dopamine and dobutamine:
Hemodynamic effects:
- Both drugs generally increase cardiac output and stroke volume.
- Dopamine tends to increase mean arterial pressure more than dobutamine.
- Dobutamine often decreases or maintains left ventricular filling pressure, while dopamine may.
Renal effects:
- Dopamine typically produces greater diuresis and natriuresis compared to dobutamine.
- At low doses, dopamine may increase renal blood flow more than dobutamine.
Pulmonary effects:
- Dopamine may increase pulmonary artery pressure more than dobutamine, potentially aggravating pulmonary cong.
Efficacy in specific populations:
- In preterm infants with hypotension, dopamine was more effective in raising blood pressure than dobut.
- In patients after cardiac surgery, dobutamine may be preferable due to less impact on coronary bloo.
Conclusion
In conclusion, while both dopamine and dobutamine can increase cardiac output, they do so through different mechanisms and have different effects on blood pressure and heart rate. The choice between the two will depend on the specific needs of the patient.