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Clonidine: Uses, Dosage & Safety Information

Clonidine

Clonidine
Clonidine HCL Tablets-0.1 mg Teva
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Clonidine

Clonidine hydrochloride
Clonidine is a centrally acting drug for high blood pressure whose main hazard is stopping it. Sudden withdrawal can cause a rapid rebound in blood pressure with raised catecholamines, and rare deaths have been reported, so it is tapered over 2 to 4 days and continued until 4 hours before surgery. It is prescription-only.
  • ActiveIngredient: Clonidine hydrochloride
  • DosageForm: Tablet
  • Dosage: 0.1 mg, 0.2 mg, 0.3 mg
  • Indications: Hypertension
  • Manufacturer: Multiple ANDA holders
  • Storage: Store at 20–25°C, protect from light and moisture
  • Drug Status: Prescription Only
Drug Status: Prescription Only
Description

What is Clonidine?

Stopping is the hazard
Sudden cessation of clonidine has, in some cases, produced nervousness, agitation, headache and tremor followed by a rapid rise in blood pressure, with rare cases of hypertensive encephalopathy, stroke and death. The risk is greater at higher doses and with a beta-blocker, so the dose is reduced over 2 to 4 days rather than stopped.1

Clonidine acts in the brain rather than on blood vessels: it stimulates alpha-adrenoreceptors in the brain stem, which reduces sympathetic nerve output to the heart, kidneys and blood vessels. Peripheral resistance, heart rate and blood pressure fall, while kidney blood flow and filtration remain essentially unchanged.

It works quickly after a dose, and beyond a certain blood level a higher dose does not lower pressure further. Tolerance can develop in some patients, making reassessment of treatment necessary; the figures are in the clinical details.1

This page covers the immediate-release tablets for high blood pressure. Extended-release clonidine for ADHD is a separate product, Kapvay. The original Catapres tablets were approved in 1974 and have been discontinued; generic tablets remain on prescription.2

▶Clinical detailspharmacokinetics
Pharmacokinetic Figures From the
MeasureValue
Bioavailability70% to 80%; not affected by food or race
Peak plasma level1 to 3 hours after a dose
Elimination half-life12 to 16 hours; up to 41 hours in severe kidney impairment
Elimination40% to 60% of the absorbed dose in urine unchanged within 24 hours; about 50% metabolised in the liver
DistributionCrosses the placenta; passes into breast milk
DialysisOnly a minimal amount removed by routine haemodialysis

Source: 1

General Instructions

How to Take Clonidine

How the dose is set

Treatment usually starts at 0.1 mg twice daily, morning and bedtime, and may be increased by 0.1 mg a day at weekly intervals. Most people take 0.2 mg to 0.6 mg a day in divided doses; 2.4 mg a day is the maximum effective dose and is rarely used. Taking the larger share at bedtime may reduce dry mouth and drowsiness.1

The tablets are usually taken twice a day, in the morning and at bedtime. Taking the larger share of the daily amount at bedtime may reduce the dry mouth and drowsiness that occur while the body adjusts. Food does not affect absorption.

Do not stop without advice

Do not interrupt or stop clonidine unless your doctor tells you to. When treatment ends, the dose is reduced over 2 to 4 days. If you also take a beta-blocker and both are being stopped, the beta-blocker is withdrawn several days before clonidine is tapered.1

Before an operation

Clonidine is continued until 4 hours before surgery and restarted as soon as possible afterwards, with blood pressure monitored during the operation.1

Alertness and eyes

Clonidine can cause sleepiness, dizziness or blurred focusing; alcohol, barbiturates and other sedatives add to this. If you wear contact lenses, it may dry your eyes.

Side Effects

What Are the Side Effects of Clonidine?

The labelling reports its commonest effects as approximate counts per 100 patients, notes that they appear to be dose-related, and says most are mild and tend to diminish with continued therapy.1

The Most Frequent Effects
FrequencyEffectLabelled figure
Very commonDry mouthAbout 40 in 100
Very commonDrowsinessAbout 33 in 100
Very commonDizzinessAbout 16 in 100
Very commonConstipationAbout 10 in 100
Very commonSedationAbout 10 in 100

Source: 1

Reported Without a Rate
FrequencyEffectWhat the labelling says
Frequency not stated in labellingSlow heart rate, heart block, faintingLess frequent reports; causal relationship not established in many cases because of other medication
Frequency not stated in labellingLow mood, disturbed sleep, vivid dreams, hallucinationsLess frequent reports, with the same caveat
Frequency not stated in labellingRebound after stopping: nervousness, agitation, headache and tremor with a rapid rise in blood pressure and plasma catecholaminesOccurred in some cases after sudden cessation; more likely after higher doses or with continued beta-blocker treatment
Labelling calls it rareHypertensive encephalopathy, cerebrovascular accident and death after withdrawalRare instances reported

Source: 1

Seek immediate medical attention if:
  • A sudden severe headache with agitation or tremor after missing doses
  • Blood pressure rising sharply above your usual readings
  • Confusion, visual disturbance or weakness on one side
  • Fainting, or a pulse persistently below 50 beats per minute
Uses

What is Clonidine Used For?

Labelled Indication
IndicationWho it coversWhat the labelling records
High blood pressureAdults, alone or with other blood pressure medicinesLowers blood pressure through reduced sympathetic output; slows the pulse in most patients without altering the normal response to exercise

Source: 1

The tablets have a single indication. Because postural reflexes stay intact, dizziness on standing is described as mild and infrequent.

The labelling adds three limits on who benefits. In high blood pressure caused by phaeochromocytoma, no therapeutic effect can be expected. Safety and effectiveness in children have not been established in adequate trials. And tolerance to the blood-pressure effect may develop in some patients over time.

Clonidine also reduces plasma renin activity and the excretion of aldosterone and catecholamines, and it briefly stimulates growth-hormone release without raising it long term; how these actions relate to its blood-pressure effect has not been fully worked out.

Its effect on the circulation changes over time. Lying down after a first dose, cardiac output falls by 15% to 20% with no change in peripheral resistance; tilted upright, output falls less and resistance drops. With long-term use, cardiac output tends to return to normal while peripheral resistance stays lower.1

Safety Advice

Interactions Alcohol:

Unsafe
Clonidine may increase the sedating effect of alcohol, and both together can impair alertness.

Interactions Other Medications:

Unsafe
The most serious combination listed is with beta-blockers (major): raises the likelihood and severity of the withdrawal reaction if clonidine is stopped. Every other combination, with its effect, is in the Interactions table.

Special Groups Pregnancy:

Consult your doctor
No adequate studies exist in pregnancy and clonidine crosses the placenta; the labelling allows use only if clearly needed.

Special Groups Breastfeeding:

Consult your doctor
Clonidine passes into breast milk, and the labelling advises caution when it is given to a nursing woman.

Special Groups Elderly:

Use with caution
Older adults may benefit from a lower starting dose.

Special Groups Children:

Consult your doctor
Safety and effectiveness in children have not been established, and children are especially exposed to withdrawal if vomiting interrupts doses.

Effects on Activities Driving:

Unsafe
Clonidine can cause sleepiness, dizziness or problems focusing the eyes. Do not drive until you know how it affects you.

Effects on Activities Operating Machinery:

Unsafe
The same applies, and more so with alcohol or sedatives. Kidney guidance is in the Dosage table.
Concerns

Important Safety Concerns and Considerations

Rebound Hypertension and Withdrawal Syndrome

This is a major safety concern with clonidine therapy. Abrupt cessation, especially after prolonged use of higher doses, can cause a rapid, potentially life-threatening rise in blood pressure. Symptoms may include nervousness, agitation, headache, tremors, tachycardia, and chest pain. This rebound phenomenon means clonidine should generally be discontinued by gradual dose reduction under a physician’s direction.

Cardiovascular Effects

Clonidine can cause symptomatic bradycardia (slow heart rate) and hypotension (low blood pressure), particularly at the initiation of therapy or with dose increases. Patients with pre-existing conduction abnormalities, heart disease, or those taking other heart rate-lowering medications may require closer monitoring. Symptoms like lightheadedness, fainting, or excessive fatigue should be reported promptly.

Central Nervous System Depression

Sedation is a very common effect. When combined with other CNS depressants (alcohol, opioids, sedatives), these effects can be additive and may be dangerous, leading to profound sedation and impaired breathing in severe cases.

Dermatological Reactions

With the transdermal patch, localized skin reactions (redness, itching) are common. Contact sensitization (allergic contact dermatitis) can also occur, which may require discontinuation of the patch formulation.

Warnings

Critical Warnings for Clonidine Use

Clonidine hypersensitivity

Contraindicated in known hypersensitivity to clonidine.1

Withdrawal

Sudden cessation can be followed by a rapid rise in blood pressure with raised plasma catecholamines; hypertensive encephalopathy, stroke and death have rarely been reported. The risk is greater at higher doses and with a beta-blocker. A rebound rise can be reversed with oral clonidine or intravenous phentolamine. Children are particularly exposed, because vomiting illnesses can suddenly stop them taking doses.1

Heart rhythm

Clonidine can worsen sinus node dysfunction and atrioventricular block, especially with other sympatholytic drugs. Severe bradycardia needing intravenous atropine, isoproterenol and temporary pacing has been reported.

Allergy after the patch

People sensitised to the clonidine skin patch may develop a generalised rash on the tablets, and those allergic to the patch may react to the tablets with rash, hives or angioedema.

Phaeochromocytoma

In high blood pressure caused by phaeochromocytoma, clonidine has no therapeutic effect.

See Interactions for the full list.

Dosage

Dosage

Clonidine Tablets
FormulationActive IngredientsClinical Note
Immediate-release tablets 0.1 mg, 0.2 mg, 0.3 mgClonidine hydrochlorideExtended-release clonidine for ADHD is a different product
Renal impairmentClonidine hydrochlorideMay benefit from a lower starting dose, with careful monitoring; no supplemental dose after routine dialysis
Age 65 and overClonidine hydrochlorideMay benefit from a lower starting dose
Hepatic impairmentClonidine hydrochlorideNot addressed in the labelling

Source: 15

Exceeding the dose
Overdose can cause an early rise in blood pressure, then low blood pressure, slow heart rate, slowed breathing, low body temperature, drowsiness and small pupils; large overdoses can cause conduction problems, apnoea, coma and seizures, usually within 30 minutes to 2 hours. There is no specific antidote. As little as 0.1 mg has caused toxicity in children, so keep tablets out of their reach and seek urgent help after any overdose.1
Interactions

What Does Clonidine Interact With?

Interactions by Severity
Interacting SubstanceEffect and RiskSeverityDocumentation
Beta-blockersA withdrawal reaction is more likely if clonidine is stopped while a beta-blocker continues; the beta-blocker is withdrawn several days firstMajorGood — labelled warning
Diltiazem or verapamilSinus bradycardia requiring hospital admission and a pacemaker has been reportedMajorFair — case reports
Digitalis, calcium channel blockers and other drugs affecting sinus or AV node functionAdditive slowing of heart rate and conduction; heart rate is monitoredMajorGood — labelled interaction
Tricyclic antidepressantsThe blood-pressure effect of clonidine may be reduced, needing a higher doseModerateGood — labelled interaction
NeurolepticsDizziness on standing, low blood pressure on standing and fatigue may appear or worsenModerateGood — labelled interaction
Alcohol, barbiturates and other sedating drugsIncreased central nervous system depressionModerateGood — labelled interaction
High-dose intravenous haloperidolHigh intravenous doses of clonidine may add to its arrhythmia risk; relevance for oral tablets not establishedMinorPoor — observational suggestion

Source: 1

FAQs
Yes. Decreased sexual activity, loss of libido and erectile dysfunction are listed among its adverse reactions. Discuss them with your doctor rather than stopping the tablets, because stopping suddenly carries its own risk.
The labelling lists a transient rise in blood glucose and weight gain among less common reactions, along with breast enlargement in men.
Tell your doctor promptly. The labelling notes that children with vomiting illnesses are especially prone to high blood pressure episodes when they suddenly cannot take their doses, and the same interruption applies to adults.
Catapres tablets, approved in 1974, have been discontinued; generic clonidine tablets are available on prescription. A Catapres-TTS skin patch is a separate product that remains available.
No. The labelling says to continue it to within 4 hours of surgery and resume it as soon as possible afterwards, because stopping suddenly can cause a rebound rise in blood pressure.
Evidence and Reported Data

Evidence Scope

What we know
  • Clonidine lowers blood pressure by reducing sympathetic output from the brain stem, with an effect beginning within an hour of a dose.1
  • Abrupt stopping can produce a rapid rebound in blood pressure, and rare deaths have been reported.
  • Raising plasma levels above the effective range does not add blood-pressure lowering.
What remains uncertain
  • How often withdrawal reactions occur. The labelling describes them as occurring in some cases and gives no rate.
  • How the blood-pressure effect relates to its other actions. Its effects on renin, aldosterone and catecholamines have not been tied to the blood-pressure fall.
  • Who develops tolerance. Tolerance may develop in some patients, and the labelling does not say who.
  • How it performs in children. Safety and effectiveness have not been established in adequate trials.
  • What spontaneous reports can establish. Reporting is voluntary and skews toward serious, unexpected or newsworthy events, entries reach the database at least three months late, and no count of treated patients exists — so the report figures below cannot give an incidence.

Reports in the FDA Adverse Event Reporting System

As of the data cut of 30 July 2026, the FDA Adverse Event Reporting System held 5,514 reports listing clonidine hydrochloride among the medicines taken. The ten reactions named most often in those reports are below.

Most Frequently Named Reactions in
Reaction as codedReports naming it
Hypertension733
Headache686
Off label use644
Pain608
Fatigue605
Hypersensitivity508
Drug ineffective507
Nausea450
Infusion related reaction425
Hepatic enzyme increased418

Source: 4

What these numbers are, and what they are not

Four distinctions matter, and collapsing any two of them produces a false statement:

  • These are reports mentioning the active ingredient, submitted voluntarily by clinicians, patients and manufacturers.
  • They are not events shown to have been caused by the drug. A report records that something happened to someone taking the medicine, nothing more; most reports list several medicines.
  • They are not product-specific or brand-specific. The query is by active ingredient and covers every product containing it.
  • They are not a frequency or a risk estimate. There is no denominator: the number of people who took the drug without reporting anything is unknown.

See Evidence Scope above for the limitations of postmarketing data.

Who was this medicine studied in?

No FDA Drug Trials Snapshot exists: Catapres tablets were approved in 1974, and the programme began publishing in 2015.32 The current labelling reports pharmacological and haemodynamic studies rather than outcome trials, and gives no breakdown of trial participants by age, sex or ethnicity; it records that race does not affect the pharmacokinetics.1

Who this is and is not appropriate for

Typically considered for: adults with high blood pressure who can take doses reliably, including through illness, and who will not stop suddenly.

Not appropriate for: anyone with known hypersensitivity to clonidine; high blood pressure from phaeochromocytoma; caution with sinus node disease or AV block, and in children.

Where to report and verify

Routing to Official Registries
What you needWhere to go
Report a side effectFDA MedWatch
Pregnancy-specific dataMotherToBaby
Full prescribing informationDailyMed
Verify a pharmacy websiteFDA BeSafeRx · LegitScript
References

References

  1. FDA Prescribing Information, clonidine hydrochloride tablets (Unichem, ANDA 078895, reference standard) — Indications, Contraindications, Warnings, Precautions, Drug Interactions, Adverse Reactions, Overdosage, Dosage and Administration, Clinical Pharmacology, Pharmacokinetics
    Label effective 2026-03-30 · Accessed 2026-09-26
    Used for: the indication; mechanism, onset and haemodynamics; pharmacokinetics; doses and kidney adjustment; the withdrawal warning and its management; perioperative use; heart rhythm, patch allergy and phaeochromocytoma precautions; the interactions; the adverse reactions; pregnancy, nursing and paediatric use; overdose; and patient counselling.
    dailymed.nlm.nih.gov — DailyMed
  2. Drugs@FDA — application records for Catapres tablets (NDA 017407) and Catapres-TTS (NDA 018891)
    Records accessed 2026-09-26
    Used for: the 1974 approval and discontinuation of Catapres tablets, and the continued availability of the Catapres-TTS patch.
    accessdata.fda.gov — Drugs@FDA
  3. FDA — Drug Trials Snapshots programme scope
    Programme current · Accessed 2026-09-24
    Used for: confirmation of when the programme began publishing, used to explain the absence of a Snapshot for this molecule.
    fda.gov — Drug Trials Snapshots
  4. openFDA — FDA Adverse Event Reporting System, drug event API query for clonidine hydrochloride
    Data cut 2026-07-30 · Accessed 2026-09-24
    Used for: the report total and the ten most frequently coded reaction terms shown in the aggregates section, retrieved by active ingredient at the stated data cut.
    open.fda.gov — drug adverse event API
  5. FDA Orange Book — clonidine hydrochloride
    Current edition · Accessed 2026-09-28
    Used for: reference-standard and generic availability.
    accessdata.fda.gov — Orange Book

How this page was sourced

The withdrawal description is reported with the physiological finding attached — raised plasma catecholamines — because it distinguishes this reaction from a return of untreated hypertension, and the distinction changes how urgently it is treated.

The perioperative instruction is given as the labelling words it, since a four-hour limit before surgery is specific enough that paraphrasing it would lose the point.

The leading FAERS term is the treated condition itself, which is flagged in Evidence Scope so the table is not mistaken for a ranking of harms.

Review cycle. Clinical review completed 28 September 2026. Next review due by 28 September 2027, or earlier if the labelling is revised.

Disclaimer

Disclaimer: The information on this site is provided for informational purposes only and is not medical advice. It does not replace professional medical consultation, diagnosis, or treatment. Do not self-medicate based on the information presented on this site. Always consult with a doctor or other qualified healthcare professional before making any decisions about your health.