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Clonidine

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Subjective Effects

Interactions

Tolerance

Clonidine is a depressant of the arylaminoimidazoline class and an alpha-2 adrenergic receptor agonist. Developed by Boehringer Ingelheim, it entered clinical use in 1966 as a centrally acting antihypertensive. It is also used for ADHD, severe pain, migraine prevention, and withdrawal from substances including alcohol, opioids, and nicotine. Common adverse effects include dry mouth, dizziness, hypotension, and sleepiness; abrupt discontinuation can cause a dangerous rise in blood pressure.

Dosage & Duration

Dosage

Doses are population estimates that vary widely between individuals.

Threshold25 µg

Light25-50 µg

Moderate50-100 µg

Strong100-250 µg

Heavy300+ µg

Duration

Onset15-45 minutes

Peak60-90 minutes

Offset6-8 hours

Total6-8 hours

Subjective Effects

Subjective Effects not written up yet

Pharmacology

Pharmacodynamics

Clonidine primarily acts as an agonist at α2-adrenergic receptors, stimulating the α2A, α2B, and α2C subtypes with similar potency. Presynaptic α2 activation reduces norepinephrine release and sympathetic nervous system signaling, while Gi-mediated inhibition of adenylyl cyclase and potassium channel opening contribute to neuronal hyperpolarization. Clonidine also activates imidazoline I1 receptors, which may contribute to its sympatholytic action, and has peripheral α1-adrenergic agonist activity.

Pharmacokinetics

Oral clonidine has a reported bioavailability of 55-87%, with most estimates around 70-80%. Peak plasma concentrations are generally reported within 60-90 minutes for immediate-release oral clonidine, although a value of 3-5 hours has also been reported. Less than half of an absorbed oral dose is metabolized in the liver, primarily through 4-hydroxylation by CYP2D6, with smaller contributions from CYP1A2 and CYP3A enzymes. Approximately 50% of a dose is excreted unchanged in urine and 20% in feces. The elimination half-life varies from 6-23 hours and is prolonged by poor kidney function, while a 30-minute half-life has been reported after epidural administration.

Interactions

Interactions not written up yet

An unlisted combination is an unknown one, not a safe one. Check a dedicated combination chart before mixing.

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Tolerance

Tolerance not written up yet

Harm Potential

Addiction & Dependence

Psychological

Low

Clonidine is not considered addictive and has low abuse potential, although misuse has been documented among some people with pre-existing substance use disorders.

Physical

Chronic use can produce physical dependence. Abrupt discontinuation may cause withdrawal, including a dangerous rebound increase in blood pressure, so therapy is generally tapered.

Toxicity

Lethal Dosage

Human lethality is rare, with a small number of deaths reported. Cardiorespiratory and central nervous system morbidity from poisoning generally tends to be more severe in young people than in adults.

LD50 Data

Species	Route	Value
rat	oral	126 mg/kg
rat	oral	465 mg/kg
mouse	oral	206 mg/kg

Cardiovascular system

At toxic doses, clonidine can cause serious cardiovascular instability; overdose may produce hypertension followed by hypotension and bradycardia, while severe overdose can cause reversible cardiac conduction defects or dysrhythmias.

Respiratory system

At toxic doses, clonidine can cause respiratory depression, and severe overdose may progress to apnea.

Central nervous system

At toxic doses, clonidine can cause central nervous system depression; severe overdose may progress to coma.

Psychosis Risk

Hallucinations and confusion can occur as severe adverse effects.

Seizure Risk

Seizures can occur in severe clonidine overdose.

History & Culture

Clonidine was patented in 1961. During the early 1960s, Boehringer Ingelheim assigned medicinal chemist Helmut Stähle to develop a peripherally acting α-adrenergic nasal decongestant. Stähle introduced two chlorine substituents onto the phenyl group of an imidazoline structure, an approach…

Legality

By Country

Prescription13

United StatesPrescription only

AustraliaPrescription only

AustriaPrescription only

CanadaPrescription only

FrancePrescription only

GermanyPrescription only

IrelandPrescription only

New ZealandPrescription only

PhilippinesPrescription only

SpainPrescription only

SwitzerlandPrescription only

UkrainePrescription only

United KingdomPrescription only

Not scheduled2

PolandNot scheduled

SwedenNot scheduled

References

Citations

Article Status

Step 1 · Automated synthesis
An autonomous workflow built by Josie Kins compiled this article's foundation from information published across the web.
Step 2 · First-pass reviewPending
Not yet reviewed — this article is pending editorial review by Lyrea.
Step 3 · Citation reviewPending
No one has reviewed this article's citations yet. That second pass checks each claim against the source it cites.

Recent changes7 human edits · latest 24 Jan

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24 January 2026

23:32
Josie Kins · Updated the article · also 1,4-Butanediol, 1B-LSD, 1cP-AL-LAD and 573 more
23:25
Josie Kins · Updated the article · also 1,4-Butanediol, 1B-LSD, 1cP-AL-LAD and 573 more
23:20
Josie Kins · Updated the article · also 1,4-Butanediol, 1B-LSD, 1cP-AL-LAD and 573 more
23:15
Josie Kins · Updated the article · also 1,4-Butanediol, 1B-LSD, 1cP-AL-LAD and 573 more
22:57
Josie Kins · Updated the article · also 1,4-Butanediol, 1B-LSD, 1cP-AL-LAD and 573 more
22:42
Josie Kins · Updated the article · also 1,4-Butanediol, 1B-LSD, 1cP-AL-LAD and 573 more
22:21
Josie Kins · Updated the article · also 1,4-Butanediol, 1B-LSD, 1cP-AL-LAD and 573 more

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