Pharmacology trans - Sympathetic Depressants / Alpha Adrenoceptor Blockers

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Questions and Answers

Which of the following represents a common adverse effect associated with Silodosin?

Increased appetite

Hypertension

Abnormal ejaculation (correct)

Skin rash

Silodosin is primarily indicated for the treatment of which condition?

Benign Prostatic Hyperplasia (correct)

Chronic Kidney Disease

Hypertension

Congestive Heart Failure

What is a contraindication for the use of Silodosin?

Concurrent use of nitrates

Administration of CYP3A4 inhibitors (correct)

Daily aspirin use

Chronic Antacid therapy

Which condition is Silodosin less likely to exacerbate when compared to other medications?

Hypertension Signup and view all the answers

What effect might result from the use of Silodosin in patients with specific contraindications?

Floppy Iris Syndrome Signup and view all the answers

The 'first dose effect' of Silodosin is characterized by what?

Sudden drop in blood pressure Signup and view all the answers

What is the most common undesirable effect of methyldopa at the onset of treatment?

Sedation Signup and view all the answers

Which group of patients should methyldopa be given with caution?

Patients with a history of depression Signup and view all the answers

What is the primary therapeutic use of methyldopa?

Hypertension Signup and view all the answers

What effect can long-term treatment with methyldopa lead to?

Persistent mental lassitude Signup and view all the answers

What type of drug is Guanfacine categorized as?

Second-line drug for ADHD Signup and view all the answers

What physiological response can occur after the abrupt cessation of methyldopa?

Activation of RAAS Signup and view all the answers

Which of the following is a common side effect associated with both methyldopa and clonidine?

Mental depression Signup and view all the answers

In which age group is methyldopa most effective when used for ADHD?

Children ≤ 12 years old Signup and view all the answers

What is a possible side effect of methyldopa related to salivation?

Dry mouth Signup and view all the answers

What is the effect of α1 receptor blockers on smooth muscle tone in the prostate?

Decrease smooth muscle tone Signup and view all the answers

What occurs as a result of presynaptic α2 receptor blockade?

Increased norepinephrine release Signup and view all the answers

Which receptors aid in the facilitation of insulin release when α2 receptors are blocked?

β2 receptors Signup and view all the answers

What is the main result of α1 receptor blockade on urine outflow?

Increased urine flow Signup and view all the answers

What impact do catecholamines have on glucose output from the liver?

Increase glucose output Signup and view all the answers

What effect does α1 receptor blockade have on radiating smooth muscles?

Dilation and miosis Signup and view all the answers

What is one of the consequences of α2 receptor blockade in the pancreas?

Increased insulin release Signup and view all the answers

How does presynaptic α2 receptor blockade influence the baroreceptor reflex?

Increases heart rate Signup and view all the answers

What is a consequence of α1 receptor blockade on nasal mucous membranes?

Nasal congestion Signup and view all the answers

What is the primary mechanism of action of guanfacine?

Stimulates α2A receptors in the brainstem Signup and view all the answers

Which of the following is an occasional adverse effect of guanfacine?

Nightmares Signup and view all the answers

What metabolic process is guanfacine primarily subjected to?

Liver metabolism Signup and view all the answers

What is one consequence of prolonged use of guanfacine?

Positive Coombs test Signup and view all the answers

Which adverse effect can guanfacine lead to due to inhibition of dopaminergic mechanisms?

Decreased libido Signup and view all the answers

What type of drug is methyldopa considered when treating hypertension?

Preferred drug during pregnancy Signup and view all the answers

Which condition may require dose adjustment for guanfacine?

Hepatic cirrhosis Signup and view all the answers

What is a common adverse effect associated with the use of guanfacine?

Dry mouth (xerostomia) Signup and view all the answers

What is a potential consequence of discontinuing guanfacine?

Sudden increase in blood pressure Signup and view all the answers

What are EPS observed with guanfacine attributed to?

Depleted dopamine and catecholamine levels Signup and view all the answers

Which medication is a selective α1A receptor blocker primarily used for lower urinary tract symptoms?

Tamsulosin Signup and view all the answers

What is the primary mechanism of action of prazosin in relation to blood pressure?

Vasodilation via α1 receptor blockade Signup and view all the answers

What is the first dose effect associated with α1 receptor blockers?

Postural hypotension and syncope Signup and view all the answers

Which of the following treatments involves the use of non-selective α1ABD receptor blockers?

Mild to moderate hypertension with BPH Signup and view all the answers

Which of the following is an adverse effect of alfuzosin?

Prolongation of QT interval Signup and view all the answers

What is the effect of quinazolines on lipid profiles?

No change or potential improvement in plasma lipid profiles Signup and view all the answers

What characteristic is true for selective α1A receptor blockers compared to non-selective blockers?

Less likelihood of causing tachycardia Signup and view all the answers

Which mechanism contributes to a decrease in blood pressure with α1 receptor blockade?

Reduction in central sympathetic outflow Signup and view all the answers

What should be limited when starting the administration of prazosin to minimize side effects?

Initial minimum effective dose Signup and view all the answers

Which pharmacological agent is used for short term treatment of congestive heart failure?

Prazosin Signup and view all the answers

Study Notes

Mechanism of Action

Blockade of α1 adrenoceptors provides relief for benign prostatic hypertrophy (BPH) symptoms.
Presynaptic α2 receptor blockade leads to increased norepinephrine release from sympathetic nerves.
Increased norepinephrine stimulates cardiac β1 receptors and activates baroreceptor reflex, resulting in elevated heart rate (HR).

Effects of α1 Receptor Blockade

α1A receptors are abundant in prostate and lower urinary tract tissue.
Administration of α1 receptor blockers reduces smooth muscle tone and relaxes muscle in the prostate and bladder neck, facilitating urine flow.
Blockade results in mydriasis (pupillary dilation) and nasal congestion.

α2 Receptor Blockade Effects

Promotes unopposed insulin release from pancreatic β islet cells.
Inhibits glucose release from the liver, as catecholamines usually increase liver glucose output via β and some α receptors.
Stimulation of GI smooth muscle occurs, leading to increased gastric acid secretion.

Adverse Effects of Methyldopa

Common side effects include sedation, dry mouth, and mental lassitude, especially at treatment onset.
Serious effects include mental depression and impaired concentration, necessitating caution in patients with a history of depression.
Positive Coombs test in 10-20% of patients due to autoantibodies; may include rare cases of hemolytic anemia and hepatotoxicity.

Therapeutic Uses of Methyldopa

Considered the preferred antihypertensive for pregnant women due to its safety and efficacy profile for both mother and fetus.
Not a first-line choice for hypertension treatment in the general population.

Chemistry and Pharmacokinetics

Metyrosine inhibits tyrosine hydroxylase to treat excessive sympathetic stimulation.
Prazosin, doxazosin, and terazosin are notable selective α1 receptor blockers.
Selective α1A blockers include tamsulosin, silodosin, and alfuzosin, primarily for BPH management.

First Dose Effect

Significant postural hypotension and syncope can occur with initial doses of α1 receptor blockers, typically within 30-90 minutes after administration.
Risk factors include rapid dose increases and concurrent antihypertensive medications.

Cardiovascular Effects

α1 receptor antagonism leads to vasodilation, decreasing blood pressure by reducing total peripheral resistance (PVR) and venous return.
Quinazolines may improve lipid profiles and glucose metabolism in hypertensive patients.

Common Considerations and Precautions

Monitor patients for sedation and drowsiness; dose adjustments may be required in those with hepatic impairment.
Guanfacine and clonidine are alternative medications with similar mechanisms but differing side effect profiles.
Contraindications may include concurrent use with CYP3A4 inhibitors, risking intraoperative floppy iris syndrome and QT interval prolongation.

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Description

This quiz explores the mechanisms and effects of α1 and α2 receptor blockade in pharmacology. Understand how these actions relate to conditions like benign prostatic hypertrophy (BPH) and their broader physiological impacts. Test your knowledge on how these receptors affect various bodily systems.