Page 710 - Small Animal Internal Medicine, 6th Edition

682 PART V Urinary Tract Disorders

azotemia (i.e., increase in serum creatinine concentration The ACEi and ARB have modest effects on systemic
> 30% above baseline) is uncommon when ACEi are used blood pressure (i.e., approximately 10%-15% decrease from
VetBooks.ir alone. If the patient fails to respond adequately to an ACEi baseline). Additional antihypertensive treatment is recom-
mended if systolic blood pressure is > 160 mm Hg and
alone, an ARB such as lorsartan or telmisartan can be added
to the treatment regimen (Box 40.3). Finally, spironolactone
merular disease already receiving ACEi and ARB. Typically,
can be added to the treatment regimen if aldosterone escape diastolic pressure is > 100 mm Hg in a patient with glo-
occurs, but any additional improvement must be weighed the calcium channel blocker amlodipine (0.1-0.2 mg/kg/
against the risk of hyperkalemia or worsening azotemia day) is added to the treatment regimen to manage system
when these drugs are used in combination. Loop diuretics blood pressure. In the glomerulus, its effect is primar-
(e.g., furosemide) may be used in animals with ascites, but ily on the afferent arteriole and consequently it has little
caution must be exercised to avoid dehydration and prerenal effect on proteinuria. The goal should be to decrease systolic
azotemia. blood pressure to < 150 mm Hg and diastolic pressure to
< 95 mm Hg.
Platelet inhibition may decrease intraglomerular coagula-
tion and decrease the risk of thromboembolism. In dogs, an
BOX 40.3 aspirin dosage of 1 to 5 mg/kg PO, q24h, may inhibit platelet
cyclooxygenase without preventing the beneficial effects of
Drugs Used in the Management of Glomerular Disease prostacyclin formation (e.g., vasodilatation, inhibition of
platelet aggregation). An aspirin dosage of 5 mg PO, q72h,
Drug Initial Dosage Dose Escalation may be considered in cats.
Ace Inhibitors Immunosuppressive drugs (e.g., corticosteroids, cy-
Enalapril 0.5 mg/kg PO Increase by 0.5 mg/kg/
q24h day to a maximum of closporine, cyclophosphamide, chlorambucil, azathioprine,
2.0 mg/kg/day divided mycophenolate, leflunomide) seem like logical candidates
q12h for treatment of immune-mediated GN, but no studies in
Benazepril 0.5 mg/kg PO Increase by 0.5 mg/kg/ veterinary medicine are available that clearly demonstrate
q24h day to a maximum of their effectiveness. Corticosteroid administration can cause
2.0 mg/kg/day divided proteinuria in dogs, and one retrospective study suggested
q12h
that corticosteroid therapy actually may be detrimental in
Angiotensin Receptor Blockers dogs with idiopathic GN. A controlled trial of cyclosporine
Losartan 0.125 mg/kg/day Up to 0.25 mg/kg/day treatment (15 mg/kg PO, q24h) in dogs with GN failed to
in azotemic dogs; in azotemic dogs; up to show a beneficial effect. Cyclophosphamide and chloram-
0.5 mg/kg/day in 1.0 mg/kg/day in
nonazotemic dogs nonazotemic dogs bucil are alkylating agents that can be considered, but stud-
Telmisartan 1.0 mg/kg/day Increase by 0.5 mg/kg/ ies in dogs with GN are lacking and adverse effects are a
day to a maximum of concern, especially with cyclophosphamide. Azathioprine
2
2.0 mg/kg/day (50 mg/m PO, q24-48h) may be considered for immuno-
Aldosterone Receptor Blockers suppression in dogs with idiopathic GN, but only anecdotal
Spironolactone 1.0-2.0 mg/kg PO evidence of effectiveness is available. Azathioprine is thought
q12h to require 2 to 5 weeks of treatment to be fully effective in
dogs, and consequently it usually is combined initially with
Calcium Channel Blockers a more rapidly acting immunosuppressive drug. Azathio-
Amlodipine 0.1-0.75 mg/kg prine should not be used in cats because they metabolize
q24h
the drug very slowly and develop bone marrow suppression
Loop Diuretics and severe leukopenia when given dosages similar to those
Furosemide 1.0 mg/kg q6h to Incremental increases of used in dogs; chlorambucil can be used as an alternative in
q12h 0.5-1.0 mg/kg q6h to cats. Whether corticosteroids are beneficial for the treat-
q12h up to total of
4.0 mg/kg; or, constant ment of cats with GN is unclear. Mycophenolate inhibits
rate infusion of purine synthesis and is less toxic than alkylating agents. Its
2-15 µg/kg/min after a adverse effects are primarily gastrointestinal and reversible
loading dose of 2 mg/ upon discontinuation of the drug. Leflunomide inhibits py-
kg
rimidine synthesis and can be associated with unexplained
Antithrombotic Therapy hemorrhage and thrombocytopenia at higher dosages. These
Aspirin 1.0-5.0 mg/kg/ newer immunosuppressive drugs have potential in the treat-
day ment of immune-mediated disease but limited information
is available for their use in GN in dogs. The mechanism of
Adapted from: IRIS Canine GN Study Group Standard Therapy
Subgroup, S. Brown, chair, J. Elliott, T. Francey, D. Polzin, S. action, dosage, and adverse effects of immunosuppressive
Vaden: Consensus recommendations for standard therapy of drugs potentially useful in the treatment of GN are presented
glomerular disease in dogs, J Vet Int Med 27:S27, 2013. in Box 40.4.