A variety of physiological responses of the body are dependent on the production and secretion of hormones. Epinephrine, which is also known as adrenaline, is one such hormone that is secreted by the adrenal glands. Adrenal glands, also known as the anti-stress glands, secrete various hormones that determine the body's response to stress. Cortisol, aldosterone, epinephrine and norepinephrine are some of the vital hormones that are produced by the adrenal glands. While cortisol is secreted in response to stress, secretion of epinephrine is associated with the fight-or-flight response that is triggered when one perceives a threat. Under such circumstances, a variety of bodily changes take place. The constriction and dilation of blood vessels, increase in the flow of blood to the heart and increased heart rate are the effects of epinephrine that bring about the physiological response in such situations. Epinephrine reversal, as the name suggests, refers to the fall in the blood pressure that is produced by epinephrine following the administration of a class of drugs called alpha-blockers. Scroll down to find out more about this phenomenon of epinephrine or adrenaline reversal.
Effects of Epinephrine
As mentioned earlier, the release of epinephrine into the bloodstream helps in facilitating the fight-or-flight response. People who suffer from epinephrine deficiency, may be administered epinephrine shots in order to correct the imbalance that may be caused due to the decreased secretion of this neurotransmitter. It may also help in alleviating the symptoms of anaphylaxis, a condition wherein a severe allergic reaction may give rise to a life-threatening situation. However, the physiological responses that result from the activation of the adrenergic receptors in the body, can sometimes give rise to certain distressing symptoms, in people who are suffering from certain ailments.
Since an overdose can give rise to certain side effects, doctors take into account various factors while recommending the dosage of epinephrine. Any medical condition that one may be suffering from, must be considered. Increased heart rate, high blood pressure, tremors, anxiety and palpitations are some of the side effects of epinephrine that one may experience if epinephrine is administered in excessive amounts. Under such circumstances, doctors may recommend the use of pharmacological agents that may help in blocking the action of epinephrine. These pharmacological agents are referred to as alpha-blockers.
Epinephrine Reversal Effect
The effects of epinephrine manifest when this hormone or neurotransmitter attaches itself to the adrenergic receptors located in the body. Alpha receptors and beta receptors are the subtypes of these adrenergic receptors. In fact, epinephrine is sometimes referred to as an adrenergic transmitter. When epinephrine binds to the beta receptor sites located in various parts of the body, one may experience an increase in the heart rate along with an increase in the force of heart contractions. On the other hand, the activation of alpha-receptor sites causes constriction of small blood vessels. The reversal of the pressor effects of epinephrine is induced through the administration of alpha-blockers. Since release of epinephrine causes an increase in blood pressure, the reversal effect refers to the drop in blood pressure that occurs as a reaction to alpha-blockers.
Wondering why does the administration of alpha-blockers cause a drop in the blood pressure? Alpha-blockers, also known as alpha-adrenergic blocking agents, refer to a class of drugs that prevent epinephrine from binding to the alpha-receptors. The physiological responses that are associated with the binding of epinephrine to these receptors include constriction of blood vessels along with tightening of certain muscles in the arterial walls. When one takes these drugs, the effects of epinephrine are reversed. Thus administration of alpha-blockers prevents the small blood vessels from getting constricted. This allows the blood vessels to stay relaxed which in turn helps in lowering the blood pressure. Thus, an alpha-blocker acts as an agent that reverses the pressor effects of epinephrine, and helps in preventing the fight-or-flight response, that could prove fatal for people suffering from certain medical conditions. Phentolamine and Phenoxybenzamine are both alpha-blockers that may be used for altering the pressor effect of epinephrine.
Reversal of epinephrine is a phenomenon that is usually seen in people who are being treated for high blood pressure. Administration of alpha-blockers helps in inducing the process of epinephrine reversal, thereby causing a drop in the blood pressure. Thus, administration of these drugs can help in alleviating the symptoms that one may experience during a hypertensive emergency.