Vetdrugs 2.0Losartan is an angiotensin II type-1 receptor blocker used extensively in human medicine. Veterinary applications are extra-label and include selected attempts to reduce proteinuria or other effects of renin–angiotensin signaling. Species-specific metabolism influences activity. A separate investigational oncology application involves modulation of monocyte recruitment in dogs with metastatic osteosarcoma.
Group
Angiotensin II receptor blocker
Mechanism of Action
Losartan and its active metabolite antagonize AT1 receptors, reducing angiotensin-II-mediated vasoconstriction and aldosterone signaling. Reduced intraglomerular pressure provides a rationale for antiproteinuric use, although canine formation of the potent metabolite is limited. At substantially different investigational exposures, losartan has also inhibited CCL2–CCR2-associated monocyte migration in canine osteosarcoma studies; that mechanism is distinct from conventional cardiovascular use.
Dose Rates
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Historical renin-angiotensin blockade | 0.125 mg/kg | PO | Every 24 h | Azotaemic patients; reported regimen has limited established efficacy. |
| Historical renin-angiotensin blockade | 0.5 mg/kg | PO | Every 24 h | Nonazotaemic patients; reported regimen has limited established efficacy. |
Indications
- Empirical adjunctive management of selected proteinuric renal disease or systemic hypertension in dogs, with limited and variable clinical evidence.
- Investigational combination treatment with toceranib in dogs with pulmonary metastatic osteosarcoma, supported by an early clinical study rather than established standard-care efficacy.
Contraindications
- Pregnancy
Interactions
- Combined use with ACE inhibitors may increase renal injury.
Adverse effects
- Hypotension and possible renal or electrolyte effects
Toxicity
Stop excess exposure and monitor blood pressure, renal function and electrolytes.
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Losartan 25 mg tablet | Tablet | 25 mg / tablet | PO |
| Losartan 50 mg tablet | Tablet | 50 mg / tablet | PO |
| Losartan 100 mg tablet | Tablet | 100 mg / tablet | PO |
Monitoring and Administration
Monitor blood pressure, renal parameters and potassium.
Consider considering telmisartan or irbesartan instead because losartan has limited canine activity and was not effective in cats.