Veterinarians prescribe Enalapril to treat several forms of heart disease, high blood pressure and hypertension, some forms of chronic kidney failure and protein loss through the urine in canines. Dogs usually need to stay on it for the long term and must be monitored frequently for adverse reactions. There are a variety of side effects, but most often lead to kidney failure.
Heart Stress Reduction
Enalapril is an angiotensin-converting enzyme inhibitor, or ACEI. It keeps the liver-produced hormone angiotensinogen from turning into a hormone called angiotensin 2. Angiotensin 2 constricts peripheral blood flow when blood pressure drops -- it's good in times of blood loss from injury, but really bad in heart disease because constricted blood flow means more stress on the heart. Enalapril also helps the kidneys remove fluid while retaining solids, so it's used to treat pets who are losing protein through their urine.
Kidney Stress Increase
Side effects can start off small, but lead to the No. 1 long-term risk for dogs, renal, or kidney failure. Refusal of food and water, nausea and vomiting, increased urination and diarrhea can cause dehydration. Lowered blood pressure can cause hypotension -- weakness and low muscle tone -- and lethargy. Enalapril can also raise blood potassium levels, called hyperkalemia, which further contributes to hypotension. Taken together, these initial side effects can cause progressive kidney failure, which is often reversible if caught early.