Clonidine
Clonidine hydrochloride (imidazoline derivative)
Also known as: Duraclon · Jenloga · Catapres-TTS · ST-155 · clonidini hydrochloridum · Adesipress-TTS · Arkamin · Aruclonin · Atensina · Barclyd · Cantanidin · Caprysin · Catanidin · Catapresan · Catapressan · Clonistada · Clonnirit · Dispaclonidin · Dixarit · Epiclodina · Glausine · Haemiton · Menograine · Mirfat · Normopresan · Paracefan · Tenso-Timelets · Clonidina · Clonidine hydrochloride · Clonidinum
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Audited v13 dosing evidence
Structured calculator evidenceAdjunctive antidiarrheal therapy for refractory cases of inflammatory bowel disease (extra-label)
Verified clinician required
- q8-12h
NA
Governing clinical context (2)
- ■ This medicine may be given with or without food. If your animal vomits or acts sick after receiving this medicine on an empty stomach, try giving the next dose with food or a small treat. If vomiting continues, contact your veterinarian.
- Clonidine tablets should be stored in tight, light-resistant containers at room temperature, 25°C (77°F); excursions from 15°C to 30°C (59°F-86°F) are permitted. The preservative-free injection for epidural use should be stored at controlled room temperature, 20°C to 25°C (68°F-77°F). Because it contains no preservative, unused portions of the injection should be discarded.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Clonidine is a central alpha-2 adrenergic agonist traditionally used in veterinary medicine as a diagnostic agent for growth hormone (GH) deficiency or pheochromocytoma in dogs. It also serves as an adjunctive treatment for refractory inflammatory bowel disease (IBD), particularly in cats, and as an epidural adjunct for severe pain or surgical anesthesia.
Clinical Pearls (Pharmacology Enrichment):
- While the monograph highlights its diagnostic and gastrointestinal uses, clonidine is increasingly utilized off-label in modern veterinary behavioral medicine to manage fear-based anxiety, noise phobias, and situational panic in dogs.
- It provides anxiolysis and sedation by dampening sympathetic arousal, often without the profound ataxia seen with other sedatives.
- Because of its cardiovascular effects, it requires careful patient selection and dose titration.
Mechanism of action
Clonidine acts centrally at the brain stem, stimulating alpha-2 adrenoreceptors.
- Cardiovascular/Sympathetic: Stimulation of presynaptic alpha-2 receptors (e.g., in the locus coeruleus) → decreases norepinephrine release → reduces sympathetic outflow from the CNS → decreased peripheral resistance, heart rate, and blood pressure.
- Endocrine: Stimulates GHRH (Growth Hormone Releasing Hormone) → transient release of Growth Hormone (GH).
- Analgesia: Stimulates presynaptic and postjunctional alpha-2 adrenoreceptors in the dorsal horn of the spinal cord → blocks pain signal transmission to the brain.
- Gastrointestinal: Alpha-2 stimulation alters enteric nervous system tone, increasing fluid absorption and decreasing motility, aiding in refractory IBD.
Safety & warnings
Contraindications
- Known hypersensitivity to clonidine
- Severe cardiovascular disease (use with extreme caution)
- Renal disease (use with extreme caution)
Adverse effects
- Transient hyperglycemia
- Dry mouth
- Constipation
- Aggressive behavior
- Hypotension
- Collapse
- Bradycardia
- Transient sedation
- Rebound hypertension (if withdrawn abruptly)
Precautions
Clonidine has a narrow margin of safety. It should be used with caution in patients with severe cardiovascular disease, including conduction disturbances or heart failure. Use very cautiously in patients with renal failure. Abrupt withdrawal, especially when used with beta-blockers, may cause rebound hypertension.
Drug interactions
Possible additive hypotensive effects
May enhance bradycardia. If discontinuing, beta-blocker should be stopped first, then clonidine tapered to avoid rebound hypertension.
May exacerbate the actions of other CNS depressant drugs
Possible additive bradycardia
May decrease the antihypertensive effects of clonidine
May block the antihypertensive effects of clonidine
Increased central nervous system depression and hypotension
Additive sedation, bradycardia, and respiratory depression
Additive hypotensive and bradycardic effects; may exacerbate rebound hypertension upon withdrawal
Additive lowering of blood pressure
Monitoring
- Growth Hormone (GH) levels and adverse effects (when used for diagnostics)
- Blood pressure
- Heart rate
- Efficacy and adverse effect profile (when used for ongoing diarrhea treatment)
- Degree of sedation
- Behavioral response
- Plasma IGF-1 or GH levels (when used diagnostically)
Pharmacokinetics
Half-life
Absorption
Well absorbed after oral administration in humans (peak plasma 3-5 hours). After epidural administration, maximal analgesia occurs within 30-60 minutes.
Distribution
Widely distributed into body tissues; tissue concentrations are higher than in plasma. Enters the CSF, but brain concentrations are low compared with other tissues. In cats, exhibits a two-compartment open model and penetrates tissues rapidly.
Metabolism
Metabolized in the liver; one active metabolite (p-hydroxyclonidine) has been identified.
Elimination
Up to 60% of a dose is eliminated unchanged in the urine. Elimination may be prolonged with higher dosages (dose-dependent elimination kinetics) or in renal dysfunction.
Overdose
Clonidine has a narrow margin of safety.
- Clinical Signs: Hypotension, bradycardia, vomiting, weakness, depression, lethargy, tachycardia, ataxia, and hypertension. Rarely, seizures or respiratory depression.
- Toxicity Values: LD50 for oral clonidine in rats is 465 mg/kg; mice 206 mg/kg.
- Treatment: For large overdoses, gut evacuation using standard protocols (use emetics cautiously as consciousness may deteriorate rapidly). Symptomatic and supportive care. Fluids and pressors (e.g., dopamine) for hypotension. IV atropine for bradycardia. Atipamezole or yohimbine may be used to reverse cardiovascular effects, but multiple doses may be required as signs can last up to 48 hours.
Available products
Formulations
- Epidural injection
- Oral tablets
- Oral modified-release tablets
- Transdermal patch
- Injectable: 150 μg/ml solution
- Oral: 25 μg tablets
Human-labeled
- Clonidine HCl Injection for epidural use: 100 micrograms/mL & 500 micrograms/mL preservative-free (Duraclon)
- Clonidine HCl Oral Tablets: 0.1 mg, 0.2 mg & 0.3 mg (Catapres, generic)
- Clonidine HCl Oral Modified-release Tablets: 0.1 mg (Jenloga)
- Clonidine HCl Transdermal: 0.1 mg/24hrs, 0.2 mg/24hrs, & 0.3 mg/24hrs (Catapres-TTS-1, 2, or 3)
- Catapres 150 μg/ml injectable solution
- Catapres 25 μg oral tablets
Regulatory status
POM (Prescription Only Medicine)
POM-V
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Tablets should be stored in tight, light-resistant containers at room temperature (15-30°C / 59-86°F). Preservative-free injection for epidural use should be stored at controlled room temperature (25°C); unused portions must be discarded.
Client information
Purpose: Your veterinarian has prescribed clonidine to help manage your pet's condition, which may include severe diarrhea, pain management, or off-label use for severe anxiety and phobias.
- Strict Dosing: Clonidine has a narrow margin of safety. Give the exact dose prescribed. Never give more than directed.
- Side Effects: Watch for signs of profound lethargy, weakness, pale gums, or unexpected behavioral changes (such as aggression). Contact your veterinarian if these occur.
- Do Not Stop Abruptly: Do not suddenly discontinue this medication without consulting your veterinarian, as it can cause a dangerous spike in blood pressure (rebound hypertension).
- Accidental Ingestion: Keep out of reach of all pets and children. If an overdose occurs, seek emergency veterinary care immediately.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.