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Medicine (MD/DO)
Adrenergic Receptor Pharmacology
Alpha-2 Agonists (Sympathoplegics)

Alpha-2 Agonist Mnemonic by Picmonic

Struggling with alpha-2 agonists? Picmonic makes it easy! Learn how these drugs work with our engaging mnemonics, characters, stories, and quizzes. Master alpha-2 agonists and ace your exams!

Alpha-2 Agonists (Sympathoplegics)

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Alpha-2 Agonists (Sympathoplegics)

Afro (2) Tutu Dragonist
α2 agonists are a class of medication which act on α2 adrenergic receptors to yield a decreased sympathetic outflow centrally. By decreasing sympathetic outflow, these drugs treat hypertensive symptoms. Clonidine, is a commonly used antihypertensive drug which can lead to rebound hypertension if therapy is abruptly ceased. α-Methyldopa is another antihypertensive agent, which is particularly helpful in pregnancy, as it treats pregnancy-induced hypertension and pre-eclampsia. Along with its α2 agonist activity, it also works by interrupting dopamine formation. This drug, however, may result in a Coomb's+ hemolytic anemia.

Drugs of this class are used to treat hypertension, as they reduce peripheral resistance by stimulating presynaptic α2 adrenoreceptors in the central nervous system.

Renal disease

These drugs may be used in patients with renal disease as they do not cause a decrease in blood flow to the kidney.

Centrally acting Alpha-2 Agonist
C-Brain on Afro (2) Tutu Dragonist

The primary mechanism of action of alpha-2 agonists is stimulation of presynaptic alpha-2 receptors in the central nervous system. Drugs of this class are centrally acting and decrease sympathetic outflow, as they activate medullary presynaptic α2 adrenoceptors. Remember that α2 activation decreases sympathetic outflow.


Clonidine activates α receptors, which causes inhibition of norepinephrine release from synaptic vesicles. Clonidine is frequently administered with a diuretic, and may produce side effects of lethargy, dry mouth and constipation.

Rebound Hypertension
Bouncing Hiker-BP

An adverse side effect of clonidine includes severe rebound hypertension in the case of abrupt withdrawal.

Afro Metal-dough-boy

Methyldopa decreases total peripheral resistance by reducing sympathetic outflow from the CNS. It is used to treat moderate or mild hypertension and can be used together with a diuretic for increased effect.


This drug may be used to treat hypertension during pregnancy.

Coombs (+) Hemolytic Anemia
Positive-Comb Hemolysing-RBCs from Anemia-Anemone

Methyldopa usage may lead to drug-induced immune-mediated hemolysis, leading to a positive direct Coombs test.

SLE Like Syndrome
Dressed like a Loopy-butterfly

Patients taking methyldopa may develop an SLE-like syndrome, with symptoms like fever, pericarditis, arthralgias and malaise, with positive anti-nuclear antibodies.


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