Sympathomimetic-like agents produce an effect that mimics the stimulation of the sympathetic nervous system, which is primarily concerned with stimulating the body's 'fight-or-flight response'. During times of emergency, the sympathetic nervous system releases neurotransmitters from the adrenal gland, causing an increased heart rate, sweating, breathing rate, and decreased digestion. This is similar to epinephrine, norepinephrine, or dopamine. These drugs stimulate the same response by copying the action of norepinephrine or stimulating its release. They can act by stimulating the heart through the activation of beta-adrenoceptors, such as isoproterenol, which cause vascular smooth muscle contraction, as well as activation of alpha-adrenoceptors (for example noradrenaline and norepinephrine) to cause vasoconstriction. They can also directly activate postsynaptic receptors, block the breakdown and reuptake of certain neurotransmitters, or by stimulating the production and release of catecholamines. They can also act indirectly by blocking and reversing norepinephrine transporter activity. This is a protein that clears noradrenaline and adrenaline from the extracellular space converting into cells, causing the signaling effects to cease.
Prescription and Parenteral Agents:
Sympathomimetic-like agents have a wide range of uses. They can treat low blood pressure by acting on the alpha-adrenergic receptors which causes central vasoconstriction. Drugs like Provigil and Nuvigil are used to treat sleep disorders like fatigue, narcolepsy, and sleep apnea. can be used to relieve some of the symptoms of Parkinson's disease. Other sympathomimetics can be used as an appetite suppressant to treat people who are morbidly obese, although this is only effective as a short term solution as the appetite suppressing effects only last for a few weeks. They can also be used to treat hypertensive crisis, cardiac arrest, and even delay premature labor.
Because of wide range of uses for this class of drugs, side effects can vary depending on the kind of drugs used. Long term use has been shown to increase mortality in heart failure patients. Most of these drugs are only used for short-term cardiovascular treatment with clinical supervision and monitoring because of these potential side effects. Common side effects include:
More serious side effects include:
Sympathomimetics can interact with Digoxin, increasing the risk of cardiac dysrhythmias. If combined with Doxapram, there may be additive pressor effects. If combined with Dronabinol, it can cause hypertension, tachycardia, or cardiotoxicity. Combination with Linezolid may reverse the enhancement effects of the sympathomimetic agent. They can also interact with Procarbazine, which has monoamine oxidase inhibitory activity. These interactions are all ranked as severe. If combined with amphetamines, they can potentiate the activity of the sympathomimetic agent, but this is more moderate. Isocarboxazid, Phenelzine Sulfate, Tranylcypromine Sulfate, Selegiline, and Rasagiline Mesylate are also not advised for coadministration. Sympathomimetics can also have a minor effect on glycemic control if combined with drugs in the following categories: Sulfonylureas, Insulin, Biguanides, Meglitinides, and Glitazones. This can include drugs like Metformin, Pioglitazone, Glimepiride, and Glipizide. If combined with Thyroid Products, they can increase the risk of coronary insufficiency if given to patients with coronary heart disease. They are also warned against combining with MAO Inhibitors. If used concurrently with tricyclic antidepressants, they can potentiate the effects of catecholamines. Sympathomimetics are also known to have high abuse potential and are warned against long-term use for this reason.
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