multi class comparison

Antiadrenergics: Central vs Alpha-1 vs Beta Blockers

Three antihypertensive families all dial down sympathetic tone — but stop clonidine abruptly and the blood pressure rockets back, stand up too fast after a first dose of prazosin and the patient hits the floor, and give a beta-blocker to an asthmatic and you can trigger bronchospasm. The NCLEX loves making you match the right warning to the right class.

Comparison

Side-by-side3 compared
Comparevs
Dimension
Central α2-Agonists
Alpha-1 Blockers
Beta Blockers
Class & mechanism
  • α2-agonist → ↓ central sympathetic outflow
  • α1 blocker → vasodilation, ↓ SVR
  • β blocker → ↓ HR, contractility, renin
Indications
  • Hypertension
  • Clonidine: also ADHD, opioid withdrawal
  • Hypertension
  • BPH — improves urinary flow
  • Hypertension
  • Angina, post-MI, HF, dysrhythmias
Route & onset
  • PO or transdermal patch (clonidine)
  • PO; first dose at bedtime
  • PO or IV; –olol suffix
Key assessment
  • Monitor blood pressure
  • Sedation, dry mouth
  • Monitor blood pressure
  • Orthostatic BP, fall risk
  • Monitor blood pressure
  • ★Apical pulse — hold if HR <60
Monitoring
  • BP response; methyldopa: LFTs, Coombs
  • BP after first dose & dose ↑
  • HR, BP; glucose in diabetics
Adverse effects
  • Dry mouth, sedation, bradycardia
  • ★First-dose orthostatic syncope
  • Bradycardia, bronchospasm, fatigue
  • ★Masks hypoglycemia signs
Toxicity & antidote
  • ★Rebound HTN if stopped abruptly — taper
  • Profound hypotension; supine, IV fluids
  • Overdose antidote: glucagon
Contraindications & interactions
  • Methyldopa: safe in pregnancy
  • Caution with PDE-5 inhibitors (hypotension)
  • Asthma/COPD (nonselective); AV block
Patient teaching
  • Do not stop abruptly
  • Rise slowly; rotate patch sites
  • Report dizziness when standing up
  • Take first dose at bedtime
  • Do not stop abruptly
  • Report dizziness when standing up
Class & mechanism

Central α2-Agonists

  • α2-agonist → ↓ central sympathetic outflow

Alpha-1 Blockers

  • α1 blocker → vasodilation, ↓ SVR
Indications

Central α2-Agonists

  • Hypertension
  • Clonidine: also ADHD, opioid withdrawal

Alpha-1 Blockers

  • Hypertension
  • BPH — improves urinary flow
Route & onset

Central α2-Agonists

  • PO or transdermal patch (clonidine)

Alpha-1 Blockers

  • PO; first dose at bedtime
Key assessment

Central α2-Agonists

  • Monitor blood pressure
  • Sedation, dry mouth

Alpha-1 Blockers

  • Monitor blood pressure
  • Orthostatic BP, fall risk
Monitoring

Central α2-Agonists

  • BP response; methyldopa: LFTs, Coombs

Alpha-1 Blockers

  • BP after first dose & dose ↑
Adverse effects

Central α2-Agonists

  • Dry mouth, sedation, bradycardia

Alpha-1 Blockers

  • ★First-dose orthostatic syncope
Toxicity & antidote

Central α2-Agonists

  • ★Rebound HTN if stopped abruptly — taper

Alpha-1 Blockers

  • Profound hypotension; supine, IV fluids
Contraindications & interactions

Central α2-Agonists

  • Methyldopa: safe in pregnancy

Alpha-1 Blockers

  • Caution with PDE-5 inhibitors (hypotension)
Patient teaching

Central α2-Agonists

  • Do not stop abruptly
  • Rise slowly; rotate patch sites

Alpha-1 Blockers

  • Report dizziness when standing up
  • Take first dose at bedtime

★ marks the fact that sets a column apart.

Clinical Pearl

Centrally-acting agents (clonidine, methyldopa) AND beta-blockers both rebound if stopped abruptly — always taper. Alpha-1 "-osins" take the first dose at bedtime to dodge orthostatic syncope. Methyldopa is the go-to for HTN in pregnancy; beta-blockers mask hypoglycemia in diabetics.

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