Pha - Autonomic Nervous System Drugs

Scopolamine is more potent than atropine in affecting the eye and glands, but less potent in affecting the heart, lungs, and gastrointestinal system. It is used for the prevention of motion sickness. In low doses, it can cause CNS depression, while in high doses, it has similar side effects to atropine. It should not be used in individuals who are hypersensitive to belladonna (plant) or barbiturates.

Adrenergic antagonists are drugs that block the action of adrenergic receptors, preventing the binding of neurotransmitters such as norepinephrine and epinephrine. In this case, the correct answer suggests that the drugs listed, including Phenoxybenzamine, Phentolamine, Prazosin, Doxazosin, Labetalol, Propranolol, Timilol, and Metoprolol, all belong to the class of adrenergic antagonists. These drugs block the binding of norepinephrine and epinephrine to the postsynaptic adrenergic receptors, thereby reducing the effects of the sympathetic nervous system.

The drugs listed in the question, Atropine, Scopolamine, and Oxybutynin, are all examples of cholinergic antagonists. Cholinergic antagonists block the action of acetylcholine, a neurotransmitter that is involved in the transmission of nerve impulses. These drugs are commonly used to treat conditions such as overactive bladder, motion sickness, and certain eye conditions. The side effects described, "Red as a beet, hot as an oven, dry as a bone, mad as a hatter," are commonly associated with cholinergic antagonists due to their effects on the autonomic nervous system.

Atropine is a medication that acts on various organs in the body. At low doses, it can cause bradycardia (slow heart rate), while at high doses it can cause tachycardia (fast heart rate). It also has bronchodilatory effects and decreases secretions, GI motility, salivation, and sweating. Atropine can also cause mydriasis, which is the dilation of pupils. Clinically, it is used as a preanesthetic to prevent respiratory secretions, and low doses can be used for tachycardia while high doses can be used for bradycardia. However, it is important to note that atropine can cause side effects such as dry mouth, urinary retention, and tachycardia. It is contraindicated in patients with glaucoma, BPH, obstructive bowel disease, and asthma.

Direct sympathomimetics increase the effect of the agonist by binding directly to the postsynaptic axon receptor and mimicking the effects of the neurotransmitter NE. They manipulate adrenergic receptors to produce a sympathomimetic response.

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Methyldopa is a medication that is metabolized to alpha-methylnorepinephrine, which acts as a potent alpha-2 agonist. This mechanism of action leads to a decrease in sympathetic outflow, resulting in a rapid decrease in blood pressure. Methyldopa is primarily used for the treatment of hypertension. However, it can also cause side effects such as sedation, mild orthostatic hypotension, coombs positive RBC (which can cause allergies), and rebound hypertension.

Amphetamine/Methamphetamine enters the presynaptic terminal and displaces norepinephrine (NE) from storage vesicles. This leads to vasoconstriction, an increase in cardiac contraction, and a reflex bradycardia due to increased mean artery pressure (MAP). In the CNS, it causes wakefulness and euphoria. However, it also has unwanted side effects such as hypertension, cerebral hemorrhage, convulsions, tremor. It is used for conditions like narcolepsy, attention deficit disorder (ADD), and Parkinson's disease.

The correct answer is "Cholinergic Agonist" because the drugs listed - Carbachol, Bethanechol, and Pilocarpine - are all known to stimulate or activate cholinergic receptors in the body. Cholinergic agonists mimic the effects of acetylcholine, a neurotransmitter involved in various bodily functions including muscle contractions, digestion, and the regulation of heart rate. These drugs are commonly used to treat conditions such as glaucoma, urinary retention, and dry mouth.

The given correct answer suggests that the drugs listed in the question bind to alpha-1, alpha-2, beta-1, and beta-2 receptors. This means that they directly stimulate these receptors, leading to the activation of second messengers that mediate the various effects associated with each receptor. These drugs are classified as direct sympathomimetics because they directly mimic the effects of the sympathetic nervous system.

Clonidine is a potent alpha-2 agonist that decreases preganglionic sympathetic outflow, leading to a decrease in blood pressure. It is used for the treatment of hypertension. However, it can cause side effects such as orthostatic hypotension, sedation, and rebound hypertension. Therefore, Clonidine is the correct answer.

Epinephrine is a medication that acts as an alpha and beta receptor agonist. It has vascular effects such as vasoconstriction through alpha-1 receptors and vasodilation through beta-2 receptors. It also has cardiac effects including increased heart rate and increased contractility through beta-1 receptors. In terms of pulmonary effects, epinephrine causes bronchodilation through beta-2 receptors and decreased secretions through alpha-1 receptors. Additionally, epinephrine is often injected with local anesthetics to delay distribution away from the injection site through vasoconstriction.

Dobutamine is the correct answer because it has a strong effect on beta-1 receptors, making it the drug of choice to stimulate the heart. It has a minor effect on heart rate but improves the efficiency of the heart. It does not have any pulmonary effects and is a synthetic derivative of dopamine but does not affect dopamine receptors.

Propranolol is a non-selective beta blocker that acts on both beta-1 and beta-2 receptors. It decreases the force and rate of heart beating, reducing the oxygen demand of the heart and also decreases the release of renin. It is used in the treatment of hypertension, angina pectoris, supraventricular tachycardia, ventricular arrhythmias, myocardial infarction, and migraine prophylaxis. However, it can have side effects such as suppressing a failing heart, CNS sedation and depression, rebound hypertension, and impotence. It is contraindicated in patients with asthma.

Metoprolol is the correct answer because it has the same actions as propranolol, such as treating hypertension, angina pectoris, and myocardial infarction, but with less bronchospasm in asthmatics. It also has lower toxicity compared to propranolol, making it a safer option. This makes metoprolol a suitable choice for patients with asthma.

Bethanecol is the correct answer because it is a muscarinic receptor agonist that can stimulate M1, M2, and M3 receptors. It is used clinically to induce evacuation of a non-obstructed bladder and increase GI motility after surgery. However, it is contraindicated in patients with bradycardia, parkinsonism, epilepsy, and hypo/hypertension. Carbachol and pilocarpine are also muscarinic receptor agonists, but they are not specifically indicated for the clinical uses mentioned in the question.

Oxybutynin is the correct answer because it has a direct antispasmodic effect on smooth muscle. It is used for relieving bladder spasms that result in urinary leakage and incontinence. Some of the side effects of oxybutynin include decreased sweating, rash, decreased lacrimation, and mydriasis. There are no special notes mentioned about oxybutynin.

Pilocarpine is the correct answer because it is a muscarinic receptor agonist that can activate M1, M2, and M3 receptors. It is used clinically for various purposes including the cystic fibrosis sweat test, glaucoma (to induce miosis or constriction of the pupil), and xerostomia (to treat dry mouth). However, it is contraindicated in patients with bradycardia, parkinsonism, epilepsy, and hypo/hypertension.

Phenylephrine is the correct answer because it is a medication that acts as an alpha-adrenergic agonist. It causes intense vasoconstriction, leading to an increased mean arterial pressure (MAP). It also decreases heart rate due to a reflex reaction to the increase in arterial pressure. Phenylephrine does not have any pulmonary effects. It is used to treat supraventricular tachycardia (SVT) and is included in cold remedies as a nasal decongestant because it causes nasal vasoconstriction.

Albuterol is a beta-2 adrenergic agonist that works by stimulating beta-2 receptors in the smooth muscles of the airways, causing bronchodilation. It does not have any direct cardiac effects, but it may cause reflex tachycardia as a result of its vasodilatory effects. It is commonly used to treat acute asthma exacerbations.

Carbachol is the correct answer because it is a cholinergic agonist that acts on both muscarinic (M1, M2, M3) and nicotinic receptors. It is commonly used in clinical settings for conditions such as glaucoma, miosis for surgery, and cataract surgery. It is contraindicated in situations where constriction is undesirable.

Dopamine is the correct answer because it acts on dopamine receptors and beta-1 receptors. At low doses, it constricts blood vessels in sites other than the kidneys or brain, while at high doses, it constricts all blood vessels. Dopamine also increases contractility and systolic blood pressure. It does not have any pulmonary effects. Dopamine is commonly used to treat shock related to underperfusion and reflex vasoconstriction.

Prazosin is the correct answer because it is an alpha-1 receptor antagonist. Alpha-1 receptors are found in smooth muscle, including the blood vessels, and their blockade leads to vasodilation. Prazosin is commonly used in the treatment of hypertension. One of the side effects of prazosin is postural hypotension, especially with the first dose. There are no special features or unique characteristics mentioned for prazosin.

Norepinephrine is the correct answer because it is an alpha-1 agonist, leading to intense vasoconstriction and an increase in mean artery pressure (MAP). It does not bind to beta-2 receptors, so there is no beta-2 effect. Norepinephrine is used in septic shock when intense vasoconstriction is needed to combat the drop in blood pressure.

Mixed sympathomimetics are drugs that have both direct and indirect sympathomimetic effects. They can displace norepinephrine (NE) from storage vesicles and also bind to adrenergic receptors. This means that they can increase the release of NE from storage vesicles and also directly stimulate adrenergic receptors. Ephedrine is an example of a mixed sympathomimetic drug.

Ephedrine is a medication that works by displacing norepinephrine (NE) from storage vesicles and binding to adrenergic receptors. This mechanism of action leads to vasoconstriction, resulting in an increased mean arterial pressure (MAP) through the activation of alpha-1 receptors. In terms of cardiac effects, ephedrine is similar to epinephrine but does not cause a change in heart rate. It also has stimulating effects on the central nervous system. Ephedrine is commonly used to treat narcolepsy and can cause bronchodilation, making it useful in the treatment of asthma and nasal congestion. Additionally, it is used to dilate pupils.

Central Adrenergic Nerve Blockers, such as Clonidine and Methyldopa, bind to alpha-2 receptors on neurons and prevent the release of NE (norepinephrine) from nerves. This action leads to a decrease in sympathetic outflow from the central nervous system, resulting in a decrease in blood pressure. These drugs are commonly used to treat hypertension and other conditions related to increased sympathetic activity.

Phenoxybenzamine is the correct answer because it is an alpha-blocker that acts on both alpha-1 and alpha-2 receptors. It causes vasodilation and blocks sympathetic outflow from the brain, making it effective in treating hypertension and pheochromocytoma. However, it can also cause side effects such as postural hypotension, reflex tachycardia, and sexual dysfunction.

Salmeterol is a beta-2 agonist that works by binding to and activating beta-2 adrenergic receptors in the smooth muscles of the airways. This leads to bronchodilation, making it an effective treatment for asthma and chronic obstructive pulmonary disease (COPD). Unlike other beta-2 agonists, such as albuterol, salmeterol has a long duration of action, allowing for twice-daily dosing. It does not have significant cardiac effects, but it may cause reflex tachycardia as a result of its vasodilatory effects. Therefore, the correct answer is salmeterol.

Indirect sympathomimetics increase the effect of the agonist by working on the presynaptic axon and increasing the release of neurotransmitters like NE. They manipulate adrenergic receptors to enhance the sympathetic response.

Levalbuterol is a beta-2 agonist that works by causing vasodilation and bronchodilation. It does not have any cardiac effects, but it may cause reflex tachycardia. What sets levalbuterol apart from albuterol is that it has fewer cardiac side effects.

Labetalol is the correct answer because it is a non-selective beta blocker with alpha-1 blocking activity. It decreases blood pressure by blocking the alpha-1 receptors, without causing reflex tachycardia due to its beta-1 blocking activity. Labetalol is commonly used to treat hypertension. However, it is contraindicated in patients with asthma or bradycardia. Side effects of labetalol include suppression of a failing heart, impotence, and orthostatic hypotension.

Doxazosin is a medication that belongs to the class of drugs known as alpha-1 blockers. It acts on the alpha-1 receptors and causes vasodilation, which helps in reducing blood pressure. It is commonly used in the treatment of hypertension (HTN) and benign prostate hyperplasia (BPH). In addition to its vasodilatory effects, doxazosin also relaxes smooth muscle in the bladder neck, making it useful in relieving symptoms associated with BPH. One of the side effects of doxazosin is postural hypotension, especially with the first dose. It does not have any special features that distinguish it from other alpha-1 blockers.

Timilol is a beta-blocker that acts on both beta-1 and beta-2 receptors. It decreases inotropy and chronotropy, reducing the workload and oxygen demand of the heart. It also decreases the release of renin, which helps to lower blood pressure. Timilol is clinically used for the treatment of hypertension, myocardial infarction, and migraine prophylaxis. Additionally, it can decrease intraocular pressure, making it useful in the treatment of glaucoma. However, timilol is contraindicated in patients with asthma due to its potential to cause bronchoconstriction. Some of the side effects of timilol include suppression of a failing heart, CNS sedation and depression, rebound hypertension, and impotence.

Isoproterenol is the correct answer because it is a beta-adrenergic agonist that primarily acts on beta-2 receptors, causing intense vasodilation and stimulating the heart. It is the most potent bronchodilator and is used to prevent bronchospasm. It does not have any alpha-adrenergic effects.

Phentolamine is the correct answer because it is an alpha-blocker that acts on both alpha-1 and alpha-2 receptors. It is used in the clinical setting for the treatment of pheochromocytoma, a tumor in the adrenal glands, to control hypertension. Its main action is vasodilation, which helps to lower blood pressure. However, it can also cause side effects such as tachycardia, arrhythmias, and hypotensive episodes. Phentolamine does not have any special features distinguishing it from other alpha-blockers.