Pharmacological Action of Sympathomimetic drugs
- increases the heart rate, force of myocardial contraction and cardiac output which is associated with increased metabolism by the myocardium, increased oxygen consumption and thus decreasing cardiac efficiency.
- constrict the blood vessels of skin and mucous membranes.
- Constriction predominates in cutaneous and mucous membranes which occur through both α1 and α2 receptors.
- dilates the blood vessels of the skeletal muscles
- Blood pressure:
- decrease in total peripheral resistance.
- simultaneously lowers the blood pressure by its peripheral action.
- rise in systolic blood pressure is often followed by decrease in blood pressure
- mean blood pressure rises with increase in pulse pressure.
- causes rise in systolic, diastolic and mean blood pressure
- causes relaxation of smooth muscles of GIT and reduce its motility.
- cause bronchodilatation
Action on CNS:
- do not produce any marked CNS effects because they do not cross blood brain barrier