Canine Medicine

Key Canine-Specific Considerations

• Breed diversity creates enormous clinical variation. A 2 kg Chihuahua and a 70 kg Great Dane are the same species but have dramatically different disease profiles, drug dosing, anesthetic risk, and life expectancy (5-7 years for giant breeds vs. 14-16 years for small breeds).
• Sighthound normals differ: Greyhounds and related breeds have lower WBC, platelet counts, and T4, higher PCV (55-65%), and higher creatinine (up to 2.2 mg/dL). These are physiologic, not pathologic.
• MDR1 mutation: Primarily affects herding breeds (Collie, Australian Shepherd, Shetland Sheepdog, Old English Sheepdog, and crosses). Causes sensitivity to ivermectin (high dose), loperamide, acepromazine, and some chemotherapy agents. Test before prescribing P-glycoprotein substrates.
• Brachycephalic breeds (Bulldogs, Pugs, French Bulldogs): Brachycephalic obstructive airway syndrome (BOAS), higher anesthesia risk, corneal ulceration, spinal malformations, heat stroke susceptibility.
• Large/Giant breeds: Higher incidence of orthopedic disease (hip/elbow dysplasia, OCD), osteosarcoma, DCM, GDV. Shorter life expectancy. Prophylactic gastropexy may be recommended for GDV-prone breeds.

Common Canine Diseases (No Feline Equivalent)

• GDV (gastric dilatation-volvulus): Surgical emergency. Deep-chested breeds (Great Dane, German Shepherd, Standard Poodle, Weimaraner). Mortality 10-45% even with treatment.
• CCL rupture (cranial cruciate ligament): Most common orthopedic surgery in dogs. Breeds: Labrador, Rottweiler, Newfoundland. TPLO is gold standard surgical correction.
• Canine cognitive dysfunction (CCD): Age-related dementia. Prevalence >50% in dogs over 11 years. Disorientation, altered sleep cycles, loss of housetraining.
• Idiopathic epilepsy: Breed-dependent prevalence (Border Collie, Belgian Tervuren, Labrador, Golden Retriever). Onset typically 1-5 years. First-line: phenobarbital or levetiracetam.

Canine-Specific Diagnostics

Drug Safety Notes

• Dogs tolerate acetaminophen (with caution, 10 mg/kg PO q12h) but cats cannot.
• Chocolate (theobromine) toxicity: dogs metabolize theobromine slowly (~17.5 hour half-life). Dose-dependent: mild GI at 20 mg/kg, cardiac at 40 mg/kg, seizures/death at 60+ mg/kg.
• Xylitol: Profoundly hypoglycemic in dogs (0.1 g/kg), hepatotoxic at higher doses.
• Grape/raisin toxicity: Idiosyncratic nephrotoxicity. No established safe dose. Treat all exposures as potentially lethal.
• NSAIDs: Carprofen, meloxicam, deracoxib, firocoxib all FDA-approved for canine use. Always check renal function and avoid concurrent corticosteroid use.

Workflow

1. Identify breed, age, sex, reproductive status, and weight.
2. Apply breed-specific disease predispositions to differential ranking.
3. Use canine-specific reference ranges for lab interpretation. Note sighthound exceptions.
4. Check MDR1 status for herding breeds before prescribing P-glycoprotein substrates.
5. Select canine-approved drugs at species-appropriate doses.
6. Consider size-category differences (toy, small, medium, large, giant) for drug dosing, anesthetic protocols, and disease risk.

Limitations

• Canine medicine is the best-evidenced area of veterinary medicine, but many conditions still lack RCT-level evidence.
• Mixed breed dogs may carry predispositions from any contributing breed. DNA testing (Embark, Wisdom Panel) can help but is not comprehensive.
• Regional disease prevalence varies significantly (heartworm, tick-borne diseases, Valley Fever, blastomycosis, leptospirosis).
• Breed-specific reference ranges are only well-established for sighthounds; other breeds may have uncharacterized normals.