5. Adrenergic drugs

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Questions and Answers

What is the primary clinical use of Midodrine?

Control of bradycardia

Treatment of orthostatic hypotension (correct)

Management of asthma

Treatment of hypertension

Which α2 selective agonist is NOT mentioned in the context of treating hypertension?

Methyldopa

Clonidine

Guanfacine

Salmeterol (correct)

Which of the following is a major side effect common with α2 selective agonists?

Sedation (correct)

Dry cough

Tachycardia

Hypotension

What physiological effect does Epinephrine primarily induce through β2 receptor activation?

Bronchodilation Signup and view all the answers

What is the primary action of dopamine in the treatment of cardiogenic shock?

Activation of β1 receptors Signup and view all the answers

Which drug is a synthetic, direct-acting catecholamine that functions primarily as a β1 agonist?

Dobutamine Signup and view all the answers

Which of the following agents is a long-acting β2 agonist used for bronchodilation?

Salmeterol Signup and view all the answers

What is the action of Mirabegron in managing overactive bladder?

Increasing bladder capacity Signup and view all the answers

Which of the following is NOT a treatment indication for Epinephrine?

Chronic obstructive pulmonary disease (COPD) Signup and view all the answers

Which drug is indicated for rapid-acting vasodilation in severe hypertension?

Fenoldopam Signup and view all the answers

What is the primary difference in function between epinephrine and norepinephrine in the human body?

Epinephrine acts as a hormone, while norepinephrine acts as a neurotransmitter. Signup and view all the answers

Which of the following drugs is classified as a catecholamine?

Dopamine Signup and view all the answers

How are catecholamines typically metabolized in the body?

By catechol-O-methyltransferase (COMT) in the synaptic space and MAO intraneuronally. Signup and view all the answers

Which characteristic of catecholamines limits their ability to penetrate the CNS?

Their polar nature. Signup and view all the answers

What common effect is associated with the consumption of tyramine in patients on MAO inhibitors?

Intensified sympathomimetic effects and increased blood pressure. Signup and view all the answers

Which of the following statements about non-catecholamines is true?

They lack catechol hydroxyl groups and are not inactivated by COMT. Signup and view all the answers

What is the action of oxymetazoline as an adrenergic drug?

It is a synthetic agonist that directly stimulates α1 and α2 receptors. Signup and view all the answers

Which of the following is true regarding the action of indirect-acting agonists such as cocaine?

They can block the reuptake of norepinephrine from the synaptic cleft. Signup and view all the answers

What is a common use for phenylephrine in medical treatments?

As a nasal decongestant due to its α1 agonistic properties. Signup and view all the answers

Study Notes

Catecholamines

Contain the 3,4-dihydroxybenzene group
Examples: epinephrine, norepinephrine, isoproterenol, dopamine, and dobutamine
Activate α or β receptors
Metabolized by COMT (synaptic space) and MAO (intraneuronally)
Brief effect when given parenterally, no effect orally
Polar, therefore do not penetrate the CNS

Non-Catecholamines

Lack catechol hydroxyl groups
Not inactivated by COMT
Examples: phenylephrine, ephedrine, amphetamine
Longer half-lives

Indirect-Acting Agonists

Block reuptake (cocaine)
Cause release of norepinephrine (amphetamine)
Example: tyramine (naturally occurring, can be found in foods)
In patients with MAO inhibitors, the sympathomimetic effect of tyramine may be greatly intensified, leading to increased blood pressure

Directly Acting Sympathomimetics

α1-receptor agonists:
- Phenylephrine: not inactivated by COMT, longer duration of action, raises blood pressure, used as nasal decongestant
- Midodrine: selective α1-receptor agonist, used in treatment of orthostatic hypotension
α2 selective agonists:
- Clonidine, methyldopa, guanfacine, guanabenz: useful in the treatment of hypertension, clonidine and guanfacine are also used for treatment of attention deficit disorders
- Sedation is a major side effect
- Newer α2 agonists (moxonidine, rilmenidine) with fewer CNS side effects are available for the treatment of hypertension

Side Effects of Nonselective Adrenergic Agonists

Bronchodilation (β2)
Hyperglycemia (β2, increased glycogenolysis, increased glucagon release, decreased insulin release)
Lipolysis (increased cAMP, activates hormone-sensitive lipase)

Epinephrine

Used for:
- Bronchospasm
- Anaphylactic shock
- Cardiac arrest
- Local anesthesia
- Intraocular surgery (mydriasis)

Dopamine

Activates β1 in the heart
Dilates renal and splanchnic arterioles
Used for:
- Cardiogenic and septic shock
- Hypotension
- Severe heart failure
- Bradycardia

Fenoldopam

Agonist of peripheral D1 receptors
Used as a rapid-acting vasodilator to treat severe hypertension

Dobutamine

Synthetic, direct-acting catecholamine
Acts as β1 agonist

Short-Acting β2 Agonists

Albuterol, levalbuterol, metaproterenol, terbutaline
Bronchodilators
Tremor is a common side effect
Should not be used with MAO inhibitors

Long-Acting β2 Agonists

Salmeterol, formoterol, arformoterol, and indacaterol
Not used as monotherapy

Mirabegron

β3 agonist
Relaxes detrusor smooth muscle
Increases bladder capacity
Used for patients with overactive bladder

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Description

This quiz covers the pharmacological properties and effects of catecholamines, non-catecholamines, and indirect-acting agonists. It examines their mechanisms of action, examples, and clinical implications. Test your knowledge on the various types of sympathomimetics and their roles in medicine.

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