Chlordiazepoxide and Clidinium
Chlordiazepoxide hydrochloride; Clidinium bromide
Also known as: Librium · Librax · chlordiazepoxidi hydrochloridum · methamino-diazepoxide hydrochloride · NSC-115748 · Ro5-0690
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Behavior indications (thunderstorm/noise phobias) | 2.2-6.6 mg/kg | PO | as needed | — | 🌎 NA |
| Symptomatic treatment of irritable bowel syndrome | 0.1-0.25 mg/kg of clidinium or 1-2 capsules | PO | two times to three times a day | Discontinued in a few days | 🌎 NA |
| Symptomatic treatment of irritable bowel syndrome | 0.44-1.1 mg/kg of clidinium | PO | two to three times a day | 1 day to 2 weeks (some require long-term treatment at 1-2 doses per day) | 🌎 NA |
- Behavior indications (thunderstorm/noise phobias): Chlordiazepoxide alone; start low
- Symptomatic treatment of irritable bowel syndrome: Using the combination product (e.g., Librax). Give when abdominal pain or diarrhea first noticed or if stressful conditions are encountered.
- Symptomatic treatment of irritable bowel syndrome: Using the combination product (e.g., Librax). Use at first signs of cramping or abdominal pain.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| As an anxiolytic | 0.5-1 mg/kg | PO | q12-24h | — | 🌎 NA |
- As an anxiolytic: Chlordiazepoxide alone
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Chlordiazepoxide is a long-acting benzodiazepine primarily used for its anxiolytic and mild sedative properties. Clidinium bromide is a synthetic quaternary ammonium antimuscarinic (anticholinergic) agent that reduces gastrointestinal motility and spasms.
In veterinary medicine, these drugs are occasionally used alone or in combination:
- Chlordiazepoxide alone: Used as an adjunct for behavioral disorders, such as noise phobias in dogs, or intercat aggression and urine spraying in cats.
- Chlordiazepoxide + Clidinium (Librax®): This combination is uniquely positioned to treat stress-induced gastrointestinal disorders, such as Irritable Bowel Syndrome (IBS) in dogs. It addresses both the central anxiety component (via chlordiazepoxide) and the peripheral GI spasms (via clidinium).
Clinical Pearl: Because clidinium is a quaternary amine, it does not readily cross the blood-brain barrier, thereby avoiding the central anticholinergic side effects commonly seen with atropine.
Mechanism of action
The combination product exerts its effects through two distinct mechanisms targeting the central nervous system and the peripheral gastrointestinal tract:
- Chlordiazepoxide (Anxiolytic/Sedative): Binds to the benzodiazepine allosteric site on the GABA-A receptor complex in the CNS → enhances the affinity of the receptor for the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) → increases the frequency of chloride channel openings → neuronal hyperpolarization. This dampens activity in the limbic system, thalamus, and hypothalamus, producing anxiolytic, muscle relaxant, and anticonvulsant effects.
- Clidinium (Antispasmodic): Acts as a competitive antagonist at muscarinic acetylcholine receptors (primarily M3 receptors in the gut) → inhibits parasympathetic nerve impulses → significantly reduces gastrointestinal smooth muscle spasms, motility, and gastric acid secretion.
Safety & warnings
Contraindications
- Known hypersensitivity to benzodiazepines or antimuscarinics
- Coma, shock, or significant respiratory depression
- Aggressive patients (may disinhibit bite inhibition and worsen aggression)
- Tachycardia secondary to thyrotoxicosis or cardiac insufficiency
- Myocardial ischemia
- Gastrointestinal obstructive disease or paralytic ileus
- Severe ulcerative colitis
- Obstructive uropathy
- Myasthenia gravis
- Known or suspected GI infections (may prolong retention of toxins/pathogens)
Adverse effects
- Paradoxical CNS excitement or agitation (especially in dogs)
- Variable sedation and lethargy
- Behavioral changes (irritability, aberrant demeanor in cats)
- Potential hepatotoxicity (idiosyncratic hepatic failure reported with oral diazepam in cats; unknown if chlordiazepoxide shares this risk)
- Dry mouth (xerostomia)
- Constipation or dysphagia
- Urinary retention or hesitancy
- Tachycardia (at higher doses) or initial bradycardia
Precautions
Warning: Use benzodiazepines with extreme caution in aggressive animals, as they may disinhibit anxiety-based bite inhibition, leading to worsened aggressive behavior.
- Hepatic/Renal Impairment: Use cautiously in patients with liver or kidney disease, and in debilitated or geriatric patients.
- Working Animals: Benzodiazepines may impair the abilities of working or service animals.
- Autonomic Neuropathy: Use antimuscarinics with extreme caution.
- Pregnancy: Benzodiazepines are potentially teratogenic (FDA Category D). Use during the first trimester only if benefits clearly outweigh risks.
- Nursing: Distributed into milk and may cause CNS effects in nursing neonates.
Drug interactions
Pharmacologic effects of digoxin may be increased; clidinium may also increase serum levels of slow-dissolving digoxin.
Additive CNS depression and sedative effects.
May interfere with benzodiazepine metabolism in the liver, causing increased or prolonged effects.
May induce hepatic microsomal enzymes and decrease the pharmacologic effects of benzodiazepines.
May decrease the metabolism of chlordiazepoxide, leading to excessive sedation.
May decrease the metabolism of chlordiazepoxide, leading to excessive sedation.
May decrease the metabolism of chlordiazepoxide, leading to excessive sedation.
May decrease the metabolism of chlordiazepoxide, leading to excessive sedation.
May decrease chlordiazepoxide metabolism. Additionally, increased gastric pH from clidinium may decrease GI absorption of ketoconazole (administer clidinium 2 hours after ketoconazole).
May decrease the metabolism of chlordiazepoxide, leading to excessive sedation.
May decrease the metabolism of chlordiazepoxide, leading to excessive sedation.
May enhance the anticholinergic activity and toxicity of clidinium.
Antimuscarinics may aggravate signs of amitraz toxicity, leading to hypertension and further inhibition of peristalsis.
May decrease PO absorption of clidinium; give at least 1 hour prior to oral antacids.
Long-term use concurrently with antimuscarinics may increase intraocular pressure.
Clidinium and other antimuscarinics may antagonize the prokinetic actions of metoclopramide.
Monitoring
- Clinical efficacy (reduction in anxiety, resolution of GI spasms/diarrhea)
- Adverse effects (excessive sedation, paradoxical excitement, anticholinergic signs)
- Baseline and periodic liver function tests in cats (due to idiosyncratic hepatotoxicity risks associated with oral benzodiazepines)
Pharmacokinetics
Absorption
Chlordiazepoxide is rapidly absorbed following oral administration. Clidinium is incompletely absorbed from the small intestine.
Distribution
Chlordiazepoxide is highly lipid soluble, widely distributed, fairly highly bound to plasma proteins, and readily crosses the blood-brain barrier. Clidinium is completely ionized in vivo and does not appreciably cross into the CNS or the eye.
Metabolism
Chlordiazepoxide is metabolized in the liver to several active metabolites (desmethyldiazepam, desmethylchlordiazepoxide, oxazepam) which have considerable half-lives. Clidinium is metabolized principally in the liver.
Elimination
Both drugs and their metabolites are eliminated primarily in the urine.
Overdose
Overdoses of chlordiazepoxide alone are generally limited to significant CNS depression (confusion, coma, decreased reflexes). Hypotension, respiratory depression, and cardiac arrest are possible but rare.
Treatment:
- Standard protocols for acute oral toxicity (gastric decontamination, binding agents like activated charcoal).
- Supportive systemic measures (fluids, cardiovascular support).
- Flumazenil may be considered as a specific reversal agent for severe benzodiazepine-induced CNS depression.
- Analeptic agents (CNS stimulants like caffeine) are generally not recommended.
Available products
Formulations
- Oral Capsules
Human-labeled
- Chlordiazepoxide HCl Oral Capsules: 5 mg, 10 mg & 25 mg
- Chlordiazepoxide HCl 5 mg and Clidinium Br 2.5 mg Capsules (Librax®)
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Chlordiazepoxide HCl capsules/tablets and combination capsules should be stored at room temperature in tight, light-resistant containers.
Client information
- Administration: Give exactly as directed by your veterinarian. If using for stress-related diarrhea, give at the first sign of cramping or stressful events.
- Behavioral Changes: In some animals (especially dogs), this medication can cause paradoxical excitement or agitation instead of calming them. Notify your veterinarian immediately if your pet's behavior worsens or if they become aggressive.
- Side Effects: May cause dry mouth (ensure fresh water is always available), constipation, or mild sleepiness.
- Cats: Watch closely for loss of appetite, vomiting, lethargy, or yellowing of the eyes/gums, as oral anti-anxiety medications in this class can rarely cause liver issues in cats.
- Safety: Keep strictly out of reach of children and other pets. Store in a tightly closed container.
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.