Adrenergic Agonists Lecture Notes

A collection of vocabulary flashcards covering the classification, mechanisms, therapeutic uses, and adverse effects of direct-acting, indirect-acting, and mixed-action adrenergic agonists.

Noncatecholamines

Drugs that lack catechol hydroxyl groups on the benzene ring, have a longer duration of action (not substrates for COMT), better CNS penetration, and are active orally.

Positive chronotropic effect

An increase in heart rate, typically produced by stimulation of $\beta_1$ receptors in the heart.

Positive inotropic effect

An increase in the force of heart contraction, often caused by $\beta_1$ receptor activation.

Direct-acting adrenergic agonists

Drugs that bind directly to adrenergic receptors on the postsynaptic membrane and do not require the release of norepinephrine from presynaptic terminals.

Anaphylactic shock

A life-saving indication for Epinephrine, which reverses bronchoconstriction, vasodilation, and increased vascular permeability in type I hypersensitivity reactions.

Baroreceptor reflex

The mechanism where a sharp rise in blood pressure activates the vagus nerve via the brainstem, leading to decreased heart rate (reflex bradycardia).

Extravasation

The leakage of a drug, such as norepinephrine, outside the vein into surrounding tissue, which can cause severe local vasoconstriction and tissue necrosis.

Phentolamine

An $\alpha$-blocker used specifically to treat and reverse local tissue necrosis caused by the extravasation of norepinephrine.

Isoproterenol

A direct-acting synthetic catecholamine that acts as a nonselective $\beta$ agonist ($\beta_1$ and $\beta_2$) with negligible $\alpha$ activity.

Dopamine

An endogenous catecholamine and precursor to norepinephrine that activates D1, $\beta_1$, and $\alpha_1$ receptors in a dose-dependent manner.

Fenoldopam

A selective peripheral dopamine D1 receptor agonist used in the intravenous treatment of hypertensive emergencies.

Dobutamine

A synthetic catecholamine and primarily a $\beta_1$ agonist used as an inotrope to increase cardiac output without significant vascular resistance changes.

Rhinitis medicamentosa

A condition of rebound nasal congestion caused by the use of oxymetazoline for more than 3 days due to receptor downregulation.

Phenylephrine

A selective $\alpha_1$ adrenergic receptor agonist that causes vasoconstriction and reflex bradycardia, used for hypotension and as a nasal decongestant.

Midodrine

A prodrug converted to the selective $\alpha_1$ agonist desglymidodrine, used to treat orthostatic hypotension.

Clonidine

A central $\alpha_2$ adrenergic agonist that acts in the brainstem to decrease sympathetic outflow, used for hypertension and withdrawal symptoms.

Short-acting $\beta_2$ agonists (SABAs)

Drugs like albuterol that primarily stimulate $\beta_2$ receptors on bronchial smooth muscle to produce rapid bronchodilation for acute symptoms.

Terbutaline

A selective $\beta_2$ agonist used as a bronchodilator and off-label as a tocolytic to suppress preterm labor for a short duration.

Long-acting $\beta_2$ agonists (LABAs)

Maintenance medications like salmeterol and formoterol that provide prolonged bronchodilation; they must be combined with inhaled corticosteroids in asthma patients.

Mirabegron

A $\beta_3$ agonist that relaxes the detrusor muscle of the bladder to treat overactive bladder.

Amphetamine

An indirect sympathomimetic that enters nerve terminals through NET and causes the massive release of norepinephrine via reverse transport.

Cocaine

An indirect-acting agent that blocks the norepinephrine transporter (NET), preventing reuptake and prolonging sympathetic stimulation.

Cheese reaction

A hypertensive crisis caused when individuals taking MAO inhibitors consume tyramine-rich fermented foods, leading to massive norepinephrine release.

Mixed-action adrenergic agonists

Drugs like ephedrine and pseudoephedrine that work by both increasing norepinephrine release and directly stimulating adrenergic receptors.