clonidine
Brand: Catapres, Kapvay, Duraclon
Beers Criteria Prototype Drug
Drug Class: central alpha-2 agonist
Drug Family: antihypertensive
Subclass: imidazoline/alpha-2 agonist
Organ Systems: cardiovascularcns
Mechanism of Action
Stimulates presynaptic alpha-2 receptors in the brainstem (nucleus tractus solitarius), reducing sympathetic outflow and decreasing norepinephrine release; reduces heart rate, BP, and peripheral resistance.
alpha-2 adrenergic receptor (presynaptic)imidazoline receptor
Indications
- hypertension
- ADHD (Kapvay)
- opioid/alcohol withdrawal adjunct
- cancer pain (epidural, Duraclon)
- menopausal hot flashes
- Tourette syndrome
Contraindications
- anticoagulation (epidural use)
- simultaneous beta-blocker use when considering withdrawal
Adverse Effects
Common
- sedation
- dry mouth
- constipation
- bradycardia
- hypotension
Serious
- rebound hypertension on abrupt withdrawal
- severe bradycardia with beta-blockers
Pharmacokinetics (ADME)
| Absorption | 75-95% oral bioavailability |
| Distribution | crosses BBB readily (lipophilic) |
| Metabolism | hepatic 50% |
| Excretion | renal 40-60% unchanged |
| Half-life | 12-16 hours |
| Onset | 30-60 min |
| Peak | 2-4 hours |
| Duration | 6-12 hours (oral) |
| Protein Binding | 20-40% |
| Vd | 2.1 L/kg |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| beta-blockers | withdrawal of clonidine while on beta-blocker causes severe rebound hypertension | major |
| CNS depressants | additive sedation | moderate |
| TCAs | TCAs antagonize antihypertensive effect | moderate |
Nursing Considerations
- Never abruptly discontinue — taper over 1-2 weeks to prevent rebound hypertension
- Discontinue beta-blocker first, then taper clonidine if stopping both
- Transdermal patch (Catapres-TTS) changes weekly — remove old patch before applying new
- Sedation is prominent; warn patients about driving
- Avoid in elderly (Beers criteria concern)
Clinical Pearls
- Rebound hypertension on withdrawal can exceed pretreatment levels — dangerous
- Patch formulation provides smoother 24h delivery
- Useful adjunct in opioid/alcohol withdrawal (reduces adrenergic symptoms)
Safety Profile
Pregnancy use-with-caution
Lactation avoid
Renal Adjustment Required
Hepatic Adjustment Not required
TDM Not required
Concordance Terms
Cross-referenced clinical concepts — click any term to see all content where it appears.