Age & Life‑Stage
Puppy, Adult & Senior Considerations
Life‑stage frameworks divide dogs into puppy, young adult, mature adult, senior, and end‑of‑life, with care plans tailored to each stage.
| Life stage | Key pharmacology points |
|---|---|
| Puppy / Juvenile | Immature hepatic and renal clearance; avoid long half‑life or narrow‑index drugs when safer alternatives exist and adjust dose intervals where needed. |
| Adult | Standard mg/kg ranges usually apply, but lifestyle, body condition, and concurrent disease still modify risk. |
| Senior / Geriatric | Reduced cardiac, renal, and hepatic reserve; many references suggest starting at 33–50% of usual dose or extending intervals for narrow‑index or nephrotoxic agents. |
Breed & Size
Breed‑Linked Sensitivities
Certain breeds carry MDR1 or other mutations that increase sensitivity to specific drugs even at routine doses.
| Breed examples | Drug / class to use cautiously | Notes |
|---|---|---|
| Collies, Australian Shepherds, related herding breeds | Ivermectin and selected macrocyclic lactones | Dogs with MDR1 mutation can show neurotoxicity at doses tolerated by other breeds; genetic testing or safer alternatives are recommended for high‑dose uses. |
| Giant breeds | Growth‑plate‑affecting drugs, chronic steroids | Rapid growth and joint loading mean long‑term steroid plans need extra caution and owner counselling around weight and exercise. |
| Toy / small breeds | Concentrated oral liquids, insulin, potent sedatives | Small absolute body weight magnifies dosing errors; use syringes with fine graduations and double check unit conversions. |
Body Condition
Obesity & Under‑Conditioning
Obese dogs often need dosing based on lean or adjusted body weight for some drugs, particularly those with narrow therapeutic indices.
- For lipophilic drugs, total body weight may overestimate the safe dose in very obese animals; check references for adjusted‑weight formulas.
- Under‑conditioned or cachectic dogs can have reduced protein binding and altered distribution, so slow titration and closer monitoring are prudent.
Organ Function
Renal & Hepatic Reserve
Many references recommend reducing dose by about 25–50% or extending intervals when moderate to severe renal or hepatic impairment is present.
- For renally cleared drugs, extending the interval can be safer than full‑dose frequent administration in dogs with CKD.
- In hepatic insufficiency, guidelines frequently suggest starting hepatically cleared drugs at half the usual dose or with longer intervals where no safer option exists.