Dopamine is a precursor of norepinephrine, i.e., dopamine can be chemically converted into norepinephrine at the synapse, and both are vasoactive drugs, and both can be used to treat shock. The roles of the two are described as follows: 1. Low concentrations of dopamine can dilate renal blood vessels, mesentery, coronary arteries of the heart. And high concentration of dopamine can agonize cardiac β1 receptor, so that myocardial contractility is enhanced, cardiac output increases, at the same time can constrict blood vessels, peripheral resistance increases, which can play a role in raising blood pressure and anti-shock. Its common adverse reactions are dyspnea, chest pain, headache and so on. Pheochromocytoma patients are prohibited to use these drugs. 2. Norepinephrine can agonize α-receptor, constrict blood vessels and increase peripheral resistance. In addition, norepinephrine can also weakly agonize β1 receptor, strengthen myocardial contractility, increase cardiac output, maintain and rebound blood pressure, so as to achieve the effect of anti-shock. It should be noted that overdose of norepinephrine can cause cardiac arrhythmia and even lead to death, and other adverse reactions are common, such as drug leakage leading to local tissue necrosis and skin rash. Dopamine and norepinephrine are prescription drugs and should never be used without authorization. If you feel unwell, please consult a doctor and follow strictly the doctor’s instructions for standardized treatment.