Dosing and safety
Dual elimination
Benazepril hydrochloride is removed from the body via both the kidneys and the liver; in other words, it has dual elimination:
Dog: liver 50%/ kidneys 50%
Cat: liver 85%/ kidneys 15%
This is in contrast to some other ACE inhibitors, which are excreted almost entirely through the kidneys.
Patients with reduced glomerular filtration rate cannot eliminate waste products efficiently, including any medications that are excreted through the kidneys. Dogs with heart failure often have compromised renal function: over half of dogs with congestive heart failure are azotaemic1.
In animals with compromised renal function, there is a risk that drugs which are excreted mainly through the kidneys could accumulate, i.e. an overdose. Therefore, drugs excreted through the kidneys may require dose adjustment in patients with poor kidney function.
Studies have shown that, in both cats2 and dogs3,4 with renal compromise, there is no increased exposure to benazeprilat, therefore no dose adjustment of Fortekor is required. This is in contrast to enalapril maleate in dogs3, where exposure to enalaprilat is increased in dogs with renal impairment.
Changes in creatinine
In patients with kidney disease, a small rise in creatinine is sometimes seen when treatment is first started, due to the therapeutic effect of Fortekor in reducing glomerular pressure. In humans, it has been shown5 that an acute increase in creatinine of up to 30% that stabilises within the first 2 months of therapy is associated with long-term preservation of renal function. A greater rise in creatinine should be investigated, as it could indicate deterioration in the underlying kidney disease, or an episode of decompensation or dehydration.
References: 1. A.P. Nicolle et al. (2007). JVIM, 21, 943-949. 2. J.N. King et al. (2002). J Vet Pharm Ther, 25, 371-378. 3. H.P. Lefebvre et al. (1999). JVIM, 13, 21-27. 4. P.L. Toutain et al. (2002). JPET, 292(3), 1094-1103. 5. G.L. Bakris and M.R. Weir (2000). Arch Intern Med, 160, 685-693.