M. Herron
When is Full Chemical Restraint Indicated?
Marked fear at any point or moderate fear in response to minimal handling.
- Marked fear: Alligator rolling, flinching and vocalizing with minimal touch, releasing anal glands, urinating, flailing, panicked attempts to flee during exam, in addition to moderate fear signs. These patients should be given CR for any and all procedures until (if/when) patient can be desensitized/counter-conditioned to be more accepting of handling.
- Moderate fear: Cowering, crouching, urinating, tail tucked, head turned away, avoiding eye contact, ears pinned back, displaying several oral displacement behaviors (harsh panting, lip licking, yawning, lip smacking). May be able to “talk these patients off the ledge” using food for counterconditioning, minimal restraint, environmental modification and handling tools; if not then opt for chemical restraint.
Severely fractious behavior at any point or moderately fractious behavior in response to minimal handling.
- Severely fractious: Barking/lunging upon clinician’s entrance or when within immediate radius, attempts to bite, hackles up, snarling, air snapping, tail up, ears forward. These patients should be given CR for any and all procedures until (if/when) patient can be desensitized/counter-conditioned to be more accepting of handling.
- Moderately fractious: Growls, snarls, freezes with “whale eye” at any touch, may show more defensive postures while growling and showing teeth (ears back, tail tucked, cowering). May be able to “talk these patients off the ledge” using food for counterconditioning, minimal restraint, environmental modification and handling tools; if not then opt for chemical restraint.
Known history of displaying moderate–marked fear or fractious behavior during a specific procedure. For example, a patient who shows this behavior during a previous toenail trim, rectal exam, ear cleaning, bandage change, urinary catheterization, blood draws, etc., should have CR before such procedures.
Prior to painful or socially invasive procedure, or combination of procedures, which may adversely affect the future behavior of a patient in the clinic setting. For example, CR should be given prior to pelvic radiographs, wound repair/debridement, and abdominal FNAs.
When Should CR Be Administered?
Ideally, injection should be given prior to the patient’s becoming highly aroused, agitation or fractious. If the procedure is not essential, you can plan for CR on a subsequent visit.
Oral Premedications
Oral anxiolytics/sedatives can be used as the sole method of anxiety reduction for mildly fearful patients. They can also be used prior to administration of injectable chemical restraint to reduce stress during the injection and to increase the safety of giving the injection. Oral medications should be administered at least 90 minutes prior to patients getting into the car/carrier to come to the vet clinic. Any new medication should be tested by the owner at home a few days before their scheduled visit to assess for adverse effects and ensure adequate dosing.
Table 1. Trazodone
Dose
|
Dogs: 4–18 mg/kg PO; not exceeding 300 mg/dose Cats: 50–100 mg/cat
|
Class
|
Serotonin 2A antagonist/reuptake inhibitor (SARI)
|
MOA
|
Some selective inhibition of 5HT reuptake, antagonizes 5HT2A receptors, releasing 5HT1A
|
Onset of action
|
60–120 minutes
|
Duration of action
|
About 8 hours
|
Contraindications
|
Use caution in patients with severe systemic disease
|
Drug interactions
|
Do not combine with MAOIs, slight caution with other SRIs
|
Side effects
|
Likely: sedation Possible: GI upset/bleed, agitation, urinary incontinence, changes in appetite
|
Shortcut dosing:
Dogs <40 lb: Start at a calculated dose between 4–6 mg/kg
Dogs >40 lb: Start at 100 mg titrated as needed up to 300 mg/dog
Table 2. Clonidine
Dose
|
Dogs: 0.01–0.05 mg/kg PO Cats: 5–10 µg/kg PO
|
Class
|
Alpha-2 agonist
|
MOA
|
Slows release of NE in CNS, decreasing anxiety, HR, BP, pupil dilation
|
Onset of action
|
30–90 minutes
|
Duration of action
|
6–8 hours
|
Contraindications
|
Cardiovascular disease, severe renal disease, hypotensive patients
|
Drug interactions
|
Beta-blockers may enhance bradycardia, other antihypertensive drugs (Ace?)
|
Side effects
|
Likely: sedation, mild hypotension Possible: agitation, GI upset, collapse, bradycardia
|
Table 3. Gabapentin
Dose
|
Dogs: 10–50* mg/kg PO Cats: 50–200 mg/cat PO
|
Class
|
GABA analogue; anticonvulsant
|
MOA
|
Not well understood; blocks release of excitatory NTs (substance P, glutamate, NE)
|
Onset of action
|
60–90 minutes
|
Duration of action
|
6–8 hours
|
Contraindications
|
Caution in patients with renal insufficiency
|
Drug interactions
|
Antacids block absorption
|
Side effects
|
Likely: sedation
|
Caution: human Neurontin® oral solution contains xylitol.
Table 4. Lorazepam
Dose
|
Dogs: 0.05–0.5 mg/kg PO Cats: 0.05–0.25 mg/kg PO
|
Class
|
Benzodiazepine
|
MOA
|
Potentiates GABA activity
|
Onset of action
|
30–60 minutes
|
Duration of action
|
6–8 hours
|
Contraindications
|
Severe respiratory insufficiency, aggressive patients
|
Drug interactions
|
Caution with other CNS depressants
|
Side effects
|
Likely: increased appetite, sedation Possible: ataxia, aggression, paradoxical excitation
|
Caution: diazepam (benzodiazepine) has been associated with acute hepatic necrosis after PO administration in cats. No active liver metabolites in lorazepam—risk should be lower.
Table 5. Acepromazine
Dose
|
Dogs: 0.55–2.2 mg/kg PO Cats: 1.1-2.2 mg/kg PO
|
Class
|
Phenothiazine tranquilizer; antipsychotic
|
MOA
|
Block postsynaptic dopamine receptors in CNS, depressing RAS (alertness)
|
Onset of action
|
30–90 minutes
|
Duration of action
|
8–12 hours
|
Contraindications
|
Seizures?, severe cardiovascular disease, hypotensive patients, aggressive patients?
|
Drug interactions
|
Antacids block absorption, caution with other CNS depressants
|
Side effects
|
Likely: sedation, hypotension Possible: collapse, seizures, bradycardia, agitation, noise sensitivity
|
Best used in combination with an anxiolytic drug—does not provide anxiolysis.
Common oral premed cocktails for dogs:
Trazodone + clonidine
Trazodone + gabapentin
Trazodone + acepromazine
Trazodone + clonidine + gabapentin
Trazodone + acepromazine + gabapentin
*Lorazepam can be added to any of the above combinations in non-fractious patients. All are safe premeds for injectable sedation in healthy dogs.
Oral premed cocktails for cats:
Lorazepam + acepromazine
Acepromazine + gabapentin
Lorazepam + gabapentin
Chemical Restraint—Injectables
Table 6. Dexdomitor® (dexmedetomidine)
Dose
|
Dogs: 4–20 µg/kg IM, 40 µg/kg OTM Cats: 10–40 µg/kg IM or OTM
|
Class
|
Alpha-2 agonist
|
MOA
|
Very specific for alpha-2 receptors in CNS, causing major CNS depression
|
Onset of action
|
5–15 minutes (IM); 30–60 minutes (OTM)
|
Duration of action
|
45–60 minutes
|
Contraindications
|
Cardiovascular disease, severe renal disease
|
Drug interactions
|
Caution with high doses of acepromazine and CNS depressants
|
Side effects
|
Bradycardia, vasoconstriction, hypothermia, pale mm, respiratory depression
|
Reverse dexmedetomidine with half volume of atipamezole to volume of dexmedetomidine administered IM.
Table 7. Torbugesic® (butorphanol)
Dose
|
0.1–0.5 mg/kg IM, IV, or SC—dogs and cats
|
Class
|
Opiate partial agonist
|
MOA
|
Partially agonizes/antagonizes µ and opioid receptors, subcortical and spinal analgesia
|
Onset of action
|
3 minutes (IV)–15 minutes (IM, SC)
|
Duration of action
|
1–4 hours
|
Contraindications
|
Severe renal insufficiency, severely debilitated patients
|
Drug interactions
|
May enhance CNS depressant effects of other CNS depressants; will partially reverse full opioid agonists
|
Side effects
|
Sedation, mild bradycardia, mild respiratory depression, mild ataxia
|
Table 8. Ketamine
Dose
|
1–5 mg/kg IM—dogs and cats
|
Class
|
Dissociative general anesthetic
|
MOA
|
NMDA receptor antagonist
|
Onset of action
|
5–10 minutes
|
Duration of action
|
1 hour
|
Contraindications
|
Hypertensive patients, CHF; caution in epileptic patients
|
Drug interactions
|
Caution with other CNS depressants
|
Side effects
|
Anesthesia, respiratory depression, seizures, dysphoria, myoclonic jerking
|
Table 9. Acepromazine
Dose
|
1–5 mg/kg IM—dogs and cats
|
Class
|
Dissociative general anesthetic
|
MOA
|
NMDA receptor antagonist
|
Onset of action
|
5–10 minutes
|
Duration of action
|
1 hour
|
Contraindications
|
Hypertensive patients, CHF; caution in epileptic patients
|
Drug interactions
|
Caution with other CNS depressants
|
Side effects
|
Anesthesia, respiratory depression, seizures, dysphoria, myoclonic jerking
|
Table 10. Midazolam
Dose
|
0.2–0.4 mg/kg IM or IV—dogs and cats
|
Class
|
Benzodiazepine
|
MOA
|
Potentiates GABA activity;
|
Onset of action
|
3–5 minutes
|
Duration of action
|
1–2 hours
|
Contraindications
|
Severe respiratory insufficiency, aggressive patients
|
Drug interactions
|
Caution with other CNS depressants
|
Side effects
|
Likely: Increased appetite, sedation, muscle relaxation Possible: ataxia, aggression, paradoxical excitation
|
Table 11. Telazol® (tiletamine/zolazepam)
Dose
|
5–10 mg/kg IM—dogs* and cats
|
Class
|
Dissociative general anesthetic/benzodiazepine
|
MOA
|
NMDA receptor antagonist/potentiates GABA activity
|
Onset of action
|
3–5 min
|
Duration of action
|
30–60 min
|
Contraindications
|
Pancreatic disease, severe cardiac or respiratory disease
|
Drug interactions
|
Caution with other CNS depressants
|
Side effects
|
Anesthesia, respiratory depression, jerky recovery possible, but less likely than with ketamine
|
How do we get the injection into the dog?
Drive-by sedation (aka “ninja stab”)
Squeeze cage option
Can also use a door and adjacent wall—less for smaller patients
Injection administration for cats
Ideally can keep cat corralled in own carrier
Can give IM injection through soft, mesh carrier
Can lift top off of hard carrier and use towel to restrain for quick IM injection (a bit riskier)
Can use EZ Nabber to restrain and give IM injection through the mesh
Achieving and maintaining adequate sedation
Visual blocking: Avoid lobby time if at all possible; use Calming Cap or carrier cover to reduce visual input before/during/after injection; keep room dark after injection.
Auditory blocking: Play classical music and white noise; minimize talking; use room away from lobby and treatment areas; place cotton balls in ears after injection.
Tactile: No touching after injection; avoid moving patient until fully sedate.
Olfactory: Have pheromones applied to room ahead of time.
Keeping Track
Write down drugs, doses and time each medication given (including oral meds given at home).
References
1. Herron M, Shreyer T. Fear and Aggression in Veterinary Visits. Blackwell’s Five-Minute Veterinary Consult: Canine and Feline. 6th ed. 2015:484–487.
2. Herron M, Shreyer T. Blackwell’s Five-Minute Veterinary Consult Clinical Companion: Canine and Feline Behavior. 2nd ed. In Press.