Lorazepam
7-chloro-5-(2-chlorophenyl)-3-hydroxy-1,3-dihydro-2H-1,4-benzodiazepin-2-one
Also known as: Ativan · Lorazepam Intensol · BRN-07599084 · CB-8133 · Ro-7-8408 · Wy-4036 · lorazapamum · anxiedin · azurogen · bonatranquan · delormetazepam · lorazin · lorazon · lorenin · norlormetazepam · novhepar · novolorazem · oChloroxazepam · sinestron · Lorazepamum
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 |
|---|---|---|---|---|---|
| Status epilepticus (alternative to diazepam) | 0.2 mg/kg IV, IM or intranasal once | IV/IM/intranasal | once | — | 🌎 NA |
| Status epilepticus | 0.2 mg/kg IV once, followed by a bolus IV loading dose of levetiracetam at 60 mg/kg | IV | once | — | 🌎 NA |
| Fears, anxieties, phobias | 0.02-0.1 mg/kg PO once daily to three times a day | PO | q8-24h | — | 🌎 NA |
| Anxiolytic | 0.05-0.25 mg/kg PO q12-24h | PO | q12-24h | — | 🌎 NA |
| Fears/anxiety | 0.02-0.5 mg/kg PO q8h | PO | q8h | — | 🌎 NA |
| Fears, anxieties, phobias, aversions | 0.02-0.1 mg/kg q8-24h | PO | q8-24h | — | 🌎 NA |
| Short-term management of anxiety disorders | 0.02-0.1 mg/kg | PO | q12-24h | Short-term | 🌍 EU |
- Fears, anxieties, phobias: May be used on an as needed basis
- Fears/anxiety: The lowest dose and frequency that alleviate the fear should be used
- Fears, anxieties, phobias, aversions: Minimally sedating, may require 4 weeks to peak effect
- Short-term management of anxiety disorders: Start at the lower end of the dose range and gradually increase as needed.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Fears/anxiety | 0.03-0.08 mg/kg PO q12h | PO | q12h | — | 🌎 NA |
| Fears, anxieties, phobias | 0.125 mg-0.25 mg total dose (¼-½ of a 0.5 mg tablet) once to twice a day | PO | q12-24h | — | 🌎 NA |
| Anxiolytic | 0.05-0.25 mg/kg PO q12-24h | PO | q12-24h | — | 🌎 NA |
| Short-term management of anxiety disorders | 0.02-0.1 mg/kg | PO | q12-24h | Short-term | 🌍 EU |
- Fears/anxiety: The lowest dose and frequency that alleviate the fear should be used
- Fears, anxieties, phobias: May be used on an as needed basis
- Short-term management of anxiety disorders: Start at the lower end of the dose range and gradually increase. Monitor closely for signs of hepatotoxicity.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Lorazepam is a potent, intermediate-acting benzodiazepine utilized in veterinary medicine primarily as an anxiolytic for behavioral disorders and as an alternative to diazepam for the management of status epilepticus.
Clinical Pearl: Unlike diazepam, lorazepam undergoes direct glucuronidation without forming active intermediate metabolites. This makes it a significantly safer option for geriatric, obese, or hepatically compromised patients.
- Versatile Administration: It can be administered via multiple routes, including intranasal, intramuscular, and sublingual/buccal, making it highly versatile for emergency seizure management at home or in the clinic.
- Duration: It appears to be as effective as diazepam and may possess a longer duration of anticonvulsant action, though this is not definitively proven in dogs.
Mechanism of action
Lorazepam acts as a positive allosteric modulator at the GABA-A receptor.
- It binds to the benzodiazepine site on the GABA-A receptor complex → enhances the affinity of the receptor for the inhibitory neurotransmitter gamma-aminobutyric acid (GABA).
- This increases the frequency of chloride channel openings → influx of chloride ions → hyperpolarization of the neuronal membrane → decreased neuronal excitability.
- This widespread CNS depression primarily affects the subcortical levels (limbic, thalamic, and hypothalamic), yielding anxiolytic, sedative, skeletal muscle relaxant, and anticonvulsant effects.
- Other postulated mechanisms include antagonism of serotonin and diminished release or turnover of acetylcholine in the CNS.
Safety & warnings
Contraindications
- Hypersensitivity to benzodiazepines
- Severe respiratory insufficiency (unless mechanically ventilated)
- Glaucoma
- Significant liver disease
- Significant kidney disease
- Pregnant animals
- Lactating animals
Adverse effects
- Increased appetite
- Increased activity/excitement (paradoxical reaction)
- Vocalization
- Somnolence
- Lethargy
- Disinhibition (potential emergence of aggression)
- Drowsiness
- Mild transient incoordination (ataxia)
- Tremor and inappetence (associated with acute withdrawal)
Precautions
Withdrawal: When using for negative behaviors, withdraw the drug gradually to avoid a rebound effect. Physical dependency has been induced in dogs; long-term regular usage requires gradual weaning.
Administration Warning: Injectable lorazepam must NOT be given intra-arterially; arteriospasm may occur resulting in necrosis.
Pregnancy: Designated FDA Category D in humans (evidence of fetal risk), but animal studies suggest relative safety at usual dosages. High doses just prior to delivery can cause 'floppy infant' syndrome.
Drug interactions
Additive CNS effects
Decreased renal clearance of lorazepam
Increased CNS depression, irrational behavior
Decreased sedation from lorazepam
Increased lorazepam serum concentration
Inhibits the metabolism of lorazepam, potentially leading to increased plasma concentrations and prolonged sedation.
May inhibit the metabolism of lorazepam, increasing the risk of toxicity.
Additive CNS depression and sedation.
Monitoring
- Clinical efficacy (seizure control or anxiety reduction)
- Adverse effects (CNS depression, paradoxical excitation, ataxia)
- Behavioral changes (watch for paradoxical aggression or extreme sedation)
- Liver enzymes (ALT, AST, ALP, Bilirubin), especially in cats
- Appetite and water intake
Pharmacokinetics
Half-life
Absorption
In humans, absolute bioavailability is ~90% orally. Rapidly and completely absorbed after IM dosing. Sublingual has similar bioavailability to oral, but peaks sooner. In dogs, intranasal administration reaches 30 ng/mL in 3-9 minutes.
Distribution
High affinity for benzodiazepine receptors in the CNS. Brain concentrations may persist longer than serum levels. Small amounts are distributed into milk.
Metabolism
Converted into inactive glucuronide forms in the liver in most species. Lack of active metabolites makes it safer for patients with liver dysfunction.
Elimination
Dogs: Primary elimination route is via urine. Cats: Elimination is ~50% in urine (primarily as glucuronide) and 50% in feces.
Overdose
Overdoses of lorazepam are generally limited to CNS depression (confusion, lethargy, somnolence, decreased reflexes).
- Severe Toxicity: Very large overdoses can cause ataxia, hypotension, coma, and rarely death.
- Treatment: Standard protocols for removing/binding the drug in the gut (if orally ingested) and supportive systemic measures. Forced diuresis with IV fluids/electrolytes and mannitol may enhance excretion in patients with normal renal function.
- Antidote: Flumazenil may be considered for adjunctive treatment of serious overdoses, but it does not replace supportive therapy. Caution: Flumazenil is not recommended in patients with seizure disorders as it may induce seizures.
- Note: Analeptic agents (CNS stimulants like caffeine) are generally not recommended.
Available products
Formulations
- Concentrated Oral Solution
- Injection
- 1 mg oral tablets
- 2 mg/ml oral suspension
- 4 mg/ml injectable solution
Human-labeled
- Lorazepam Tablets: 0.5 mg, 1 mg, & 2 mg
- Lorazepam Concentrated Oral Solution: 2 mg/mL
- Lorazepam Injection: 2 mg/mL & 4 mg/mL
- Ativan 1 mg tablets
- Intensol 2 mg/ml oral suspension
- Lorazepam 4 mg/ml injectable solution
Regulatory status
POM (Prescription Only Medicine). Subject to national controlled substance regulations.
POM-V / POM. Controlled Drug Schedule 4 Part 1.
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Tablets should be stored in well-closed containers at room temperature (20-25°C). Oral solution and injection should be stored refrigerated (2-8°C) and protected from light. Injection must be diluted just prior to IV use with an equal volume of D5W, normal saline, or sterile water. Do not use if discolored or if a precipitate forms.
Client information
Lorazepam is a medication used to help control seizures or manage severe anxiety and phobias in pets.
- Appetite Changes: This medication may increase your pet's appetite. Diligent food restriction may be required to prevent unwanted weight gain.
- Behavioral Shifts: Watch for changes in activity levels. It can cause either sleepiness/lethargy or, conversely, increased activity, excitement, and vocalization.
- Do Not Stop Abruptly: Do not stop treatment suddenly without your veterinarian's guidance. Animals receiving this medication regularly for a prolonged period may develop withdrawal signs if not properly 'weaned off'.
- Liver Health: Although liver toxicity has not yet been reported in animals receiving lorazepam, a similar drug (diazepam) has rarely caused liver toxicity in cats. If you notice vomiting, lack of appetite, or yellowing of the whites of the eyes or gums, contact your veterinarian immediately.
- Administration Tip: The tablets are relatively tasteless and readily disintegrate in saliva. If pilling is difficult, place the tablet inside the patient's cheek and follow in a minute or so with a small treat to facilitate swallowing.
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.