Page 729 - Small Animal Internal Medicine, 6th Edition

CHAPTER 41 Acute Kidney Injury and Chronic Kidney Disease 701

and cats. The use of sevelamer may be associated with adverse Angiotensin-converting enzyme inhibitors
GI effects, including constipation, and at extremely high Angiotensin-converting enzyme (ACE) inhibitors (e.g.,
VetBooks.ir dosages may impair the absorption of folic acid and vitamins enalapril, benazepril) are renoprotective and may slow the
progression of CKD. Angiotensin II increases efferent arte-
K, D, and E. Lanthanum carbonate is not absorbed from the
GI tract and should not be retained in patients with CKD. It
lar hypertension and proteinuria. Increased protein traffic in
has no known toxicity and may be used as a phosphorus riolar vasoconstriction, which contributes to intraglomeru-
binder beginning at a dosage of 30 mg/kg/day. It has been the mesangium promotes glomerular sclerosis. ACE inhibi-
shown to be safe and well tolerated in cats up to a dosage of tors decrease the filtration of protein into Bowman’s space
1 g/kg/day. Lanthanum carbonate decreased digestibility of and the mesangium by lowering intraglomerular hydrostatic
phosphorus and shifted phosphorus excretion from the pressure. Enalapril can be used at a dosage of 0.5 mg/kg PO,
urine to the feces of treated cats. Epakitin decreases the q24h or q12h, or benazepril can be used at a dosage of 0.25
absorption of dietary phosphorus and may have additional to 0.5 mg/kg PO, q24h or q12h. Benazepril is well tolerated
beneficial effects as an oral adsorbent for urea and ammonia. by cats with CKD and decreases proteinuria.
Used at a dosage of 1 g/5 kg body weight q12h, it provides Angiotensin receptor blockers
20 mg/kg calcium carbonate q12h. There is limited informa- The angiotensin receptor blockers also may be used alone
tion about its effectiveness in dogs and cats with CKD. or in conjunction with ACE inhibitors to decrease protein-
If the patient is not hyperphosphatemic at the time of uria. Losartan may be used at a dosage of 0.5 mg/kg/day in
initial evaluation, phosphorus restriction still may be ben- nonazotemic patients or at a dosage of 0.125 mg/kg/day in
eficial in reversing existing renal secondary hyperpara- azotemic patients. Telmisartan may be used at a dosage of
thyroidism. The patient must be monitored carefully for 1.0 mg/kg/day and has been shown to be similar to benaz-
hypophosphatemia. All measurements should be made epril in its effectiveness at decreasing the UPC ratio in cats
in the fasting state to avoid the effect of feeding on the with CKD.
serum phosphorus concentration, and an attempt should Endocrine replacement therapy
be made to maintain the serum phosphorus concentration Erythropoietin. Recombinant human erythropoietin
in the 2.5- to 5.0-mg/dL range. Serial PTH determinations or EPO (epoetin alfa [Epogen], darbepoetin alfa [Aranesp])
are an ideal way to monitor treatment of renal hyperpara- has been used to correct the nonregenerative anemia in dogs
thyroidism, but validated assays for dogs and cats are not and cats with CKD. Dogs and cats treated with EPO experi-
widely available. ence resolution of anemia, weight gain, improved appetite,
Therapy for gastrointestinal signs improved hair coat, and improved sociability with their
Hypergastrinemia in uremic patients can result in owners. The use of epoetin alfa in dogs and cats carries a 20%
increased gastric acidity. H 2 receptor antagonists block to 40% risk of anti-EPO antibody formation within 30 to 90
gastrin–mediated increases in gastric acid secretion and may days of initiating therapy, and antibody development may
be helpful in the treatment of gastrointestinal signs such as result in severe anemia and subsequent transfusion depen-
decreased appetite, nausea, vomiting, and gastrointestinal dence. The starting dosage of epoetin alfa is 100 U/kg SQ,
hemorrhage. Famotidine (1 mg/kg PO, q24h) is commonly three times/wk. The hematocrit must be monitored closely
used. Failure to observe gastric ulceration in cats with during therapy and the dosage adjusted to achieve and main-
CKD and absence of differences in stomach pH and serum tain a target hematocrit of 30% to 40%. The frequency of
gastrin concentrations between normal cats and cats with administration is decreased to twice a week as soon as the
CKD are recent observations that cast doubt on the clini- animal’s hematocrit enters the target range. Small sequential
cal value of using famotidine or other H 2 blockers in cats decreases in the hematocrit value while an animal is being
with CKD. treated with epoetin alfa are presumptive evidence of anti-
Antiemetics also may be used to manage vomiting. Drugs EPO antibody formation. Other observed adverse effects
used include metoclopramide (0.1-0.4 mg/kg PO or SQ, include vomiting, seizures, hypertension, uveitis, and muco-
q8-12h), 5-HT3 (serotonin type 3) receptor antagonists such cutaneous hypersensitivity-like reactions. Because of the
as ondansetron (0.6-1.0 mg/kg PO, q12h), and the NK1 potential for adverse effects and expense, epoetin alfa is
(neurokinin) receptor antagonist maropitant citrate (1 mg/ reserved for animals with severe and symptomatic anemia
kg SQ or 2 mg/kg PO, q24h). The 5-HT3 receptor antagonist (e.g., hematocrit < 12%-15%). Iron supplementation should
mirtazapine (1.88 mg PO q48h) increased appetite, activity be provided during (and ideally before) EPO treatment to
and body weight and decreased vomiting compared with ensure that the animal is iron replete.
placebo in a randomized crossover study of 11 CKD cats, Darbepoetin alfa has two additional glycosylation sites
indicating that it may be helpful in the management of GI that extend its biologic half-life 3-fold. It can be given at a
complications in cats with CKD. Gastroprotectants such as low dosage (0.25-0.5 µg/kg SQ once weekly) and then once
sucralfate (0.5-1.0 g/dog PO, q8-12h) can be used in dogs if every 2 weeks when the lower end of the target range of the
GI ulceration and hemorrhage are suspected, but sucralfate hematocrit (30%) is achieved. When the upper end of the
has been associated with adverse effects in CKD cats (e.g., target range of the hematocrit (40%) is reached, it can be
anorexia, vomiting, constipation, worsening azotemia) and given every 3 weeks. In one study, 14 of 25 anemic CKD cats
therefore is not recommended for cats with CKD. responded to darbopoietin at a dosage of 0.45 to 1.0 µg/kg/