Alpha-2 Agonists: Central

Question 1

Clonidine (Catapres)

Indications and MOA

Answer 1

• used for HTN, ADHD
• HTN: stimulates alpha-2 receptors in the brain stem, activating an inhibitory neuron, resulting in reduced sympathetic outflow from CNS, decreasing peripheral resistance, HR, BP, and renal vascular resistance
• ADHD: MOA unknown; thought that it regulates activity in the prefrontal cortex responsible for emotions, attention, and behaviors

Question 2

Clonidine (Catapres)

Caution and Contraindications

Answer 2

• do not stop abruptly; must taper
• caution with severe coronary insufficiency
• avoid in those at risk of or with history of bradycardia
• caution in renal impairment
• caution in cerebrovascular disease
• caution in pregnancy
• avoid in lactation
• caution in elderly patients
• approved for pediatrics

Question 3

Clonidine (Catapres)

Adverse Drug Effects

Answer 3

• drowsiness, xerostomia, headache, fatigue, dizziness, skin rash, bradycardia, nightmares, constipation, impotence

Question 4

Methyldopa (Aldomet)

Indications and MOA

Answer 4

• used for HTN
• MOA: stimulation of central alpha-2 receptors by methyldopa’s metabolite alpha-methylnorepinephrine produces a decrease in sympathetic outflow to the heart, kidney, and blood vessels
• patients can build a tolerance to dose over a period of 2-3 months; may have to increase dose or add on med

Question 5

Methyldopa (Aldomet)

Caution and Contraindications

Answer 5

• caution with severe coronary insufficiency
• avoid in those at risk of or history of bradycardia
• caution in renal impairment
• avoid in active liver disease
• caution in cerebrovascular disease
• compatible in pregnancy
• avoid in lactation
• caution in elderly patients
• no longer recommended in pediatrics
• avoid use with beta blockers (bradycardia)

Question 6

Methyldopa (Aldomet)

Adverse Drug Effects

Answer 6

• edema, sedation, bradycardia, hypotension, skin rash, myalgias, elevated LFTs
• hemolytic anemia (rare), hepatotoxicity (rare)