J. vet. Pharmacol. Therap. 38, 513--517. doi: 10.1111/jvp.12216.
SHORT COMMUNICATION
The effect of enalapril on furosemide-activated renin–angiotensin– aldosterone system in healthy dogs A. C. LANTIS* M. K. AMES*
,†,1
S. WERRE* & C. E. ATKINS † *Department of Small Animal Clinical Sciences, Virginia-Maryland Regional College of Veterinary Medicine, Blacksburg, VA, USA; † Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA
Lantis A. C., Ames M. K., Werre S., Atkins C. E. The effect of enalapril on furosemide-activated renin–angiotensin–aldosterone system in healthy dogs. J. vet. Pharmacol. Therap. 38, 513–517. Studies in our laboratory have revealed that furosemide-induced RAAS activation, evaluated via the urine aldosterone-to-creatinine ratio (UAldo:C), was not attenuated by the coadministration of benazepril, while enalapril successfully suppressed amlodipine-induced urinary aldosterone excretion. This study was designed to evaluate the efficacy of enalapril in suppressing ACE activity and furosemide-induced circulating RAAS activation. Failure to do so would suggest that this failure may be a drug class effect. We hypothesized that enalapril would suppress ACE activity and furosemide-induced circulating RAAS activation. Sixteen healthy hound dogs. The effect of furosemide (2 mg/kg PO, q12 h; Group F) and furosemide plus enalapril (0.5 mg/kg PO, q12 h; Group FE) on circulating RAAS was determined by plasma ACE activity, 4–6 h post-treatment, and urinary A:C on days 1, 2, 1, 4, and 7. There was a significant increase in the average urine aldosterone-to-creatinine ratio (UAldo:C) after administration of furosemide (P < 0.05). Enalapril inhibited ACE activity (P < 0.0001) but did not significantly reduce aldosterone excretion. A significant (P < 0.05) increase in the UAldo:C was maintained for the 7 days of the study in both groups. Enalapril decreased plasma ACE activity; however, it did not suppress furosemide-induced RAAS activation, as determined by the UAldo:C. While enalapril blunts ACE activity, the absence of circulating RAAS suppression may be due to angiotensin II reactivation, alternative RAAS pathways, and furosemide overriding concurrent ACE inhibition, all indicating the existence of aldosterone breakthrough (ABT). Along with similar findings with benazepril, it appears that failure to suppress aldosterone suppression with furosemide stimulation may be a drug class effect. The discrepancy between the current data and the documented benefits of enalapril likely reflects the efficacy of this ACE inhibitor in suppressing tissue RAAS, variable population responsiveness to ACE-inhibition, and/or providing additional survival benefits, possibly through as yet unknown mechanisms. (Paper received 27 October 2014; accepted for publication 29 January 2015) Dr. Andrea C. Lantis, Veterinary Emergency and Referral Group, Brooklyn, NY 11201, USA. E-mail: [email protected] 1 Present address: Department of Clinical Sciences, College of Veterinary Medicine, Colorado State University, Fort Collins, CO 80526, USA This study was performed at the Virginia-Maryland Regional College of Veterinary Medicine, Blacksburg, Virginia 24060
Angiotensin-converting enzyme inhibitors (ACE-I) reduce plasma ACE activity (ACE) by greater than 50%, with benefit demonstrated in dogs with heart failure (CHF) (The COVE Study Group, 1995; Kitagawa et al., 1997; Ettinger et al.,
© 2015 John Wiley & Sons Ltd
1998; Hamlin & Nakayama, 1998; The BENCH Study Group, 1999; Amberger et al., 2004; O’Grady et al., 2009). While ACE-I have been shown to be beneficial in this setting, aldosterone secretion is not sufficiently suppressed in all dogs
513
514 A. C. Lantis et al.
(aldosterone breakthrough [ABT]) (Bomback & Klemmer, 2007; Lantis et al., 2014). Theoretically, a decrease in the formation of ATII, a major secretogogue of aldosterone, should lead to a significant decrease in aldosterone secretion. However, effective RAAS blockade with ACE-I is lost (ABT) in 40– 50% of human CHF patients after 1 year of therapy (Bomback & Klemmer, 2007). Knowledge of ABT has led to the successful use of mineralocorticoid- and angiotensin II-receptor blockers (ARB) in the management of CHF (Pitt et al., 1999; Bomback & Klemmer, 2007; Bernay et al., 2010). We have demonstrated circulating renin–angiotensin–aldosterone system (RAAS) activation, characterized by a two- to threefold increase in the urine aldosterone:creatinine (UAldo: C), with the administration of both amlodipine and furosemide (Atkins et al., 2007; Sayer et al., 2009). While benazepril successfully suppresses ACE, it does not significantly reduce average furosemide-induced urinary aldosterone excretion, indicating ABT (Lantis et al., 2014). The presence of ABT, despite suppression of ACE, has led to numerous hypotheses about the mechanism of ABT – including non-ACE-mediated generation of ATII and the extra-adrenal formation of aldosterone. The documented population benefit of benazepril in CHF, in the presumed presence of ABT, likely reflects the efficacy of benazepril in temporarily suppressing circulatory RAAS and tissue RAAS activity, the latter of which cannot be readily measured in living animals. Approximately 50% of human heart failure patients do not experience ABT and thereby contribute to the overall population effect of benazepril in heart failure. The observed efficacy of enalapril in suppression of amlodipine-induced circulating RAAS activation (Atkins et al., 2007), in contrast with benazepril’s inability to suppress furosemideinduced circulating RAAS activation (FI-RAAS) (Lantis et al., 2014), may represent another significant difference between these two ACE-I. This experimental study in healthy dogs intended to prove or disprove the existence of enalapril ABT. Using a model of
RAAS activation, it was designed to examine the time course and magnitude of the RAAS response to the administration of furosemide (Salix, Intervet Canada, Whitby, ON, Canada) alone (2 mg/kg p.o. [SD = 0.1], BID) as group F and with co-administration of furosemide (2 mg/kg p.o. [SD = 0.12], BID) and enalapril (0.5 mg/kg p.o. [SD = 0.04] BID; Vasotec (Enalapril) 10 mg, 2.5 mg; Valeant Pharmaceuticals LLC, Bridgewater, NJ, USA) as group FE. The co-administration of furosemide (with enalapril) was utilized as a RAAS activator to mimic neurohormonal activity in CHF, without harming or sacrificing research dogs. Sixteen mature, normal hound dogs weighing 21.2 (SD 8.94; range 7.5–34) kg were enrolled in the study. To measure the time course and magnitude of the RAAS activation, as well as other physiological changes in response to treatment, body weight, systolic blood pressure, a serum chemistry panel, ACE, and UAldo:C, samples were obtained on days 1, 2, 1, 4, and 7. Study design and statistical analysis were as previously described (Lantis et al., 2014). There were no significant abnormalities detected on baseline physical examination, complete blood counts, serum chemistry analyses, urinalyses, or blood pressure evaluations (Tables 1 & 2). Mild, sporadic differences between groups and within groups over time were observed. These were expected with furosemide administration and are not discussed further. Plasma ACE [U/L] was significantly reduced with the administration of furosemide and enalapril (group FE baseline ACE = 15.68, SD = 1.77; day 1 ACE = 4.05, SD = 0.84; day 4 ACE = 3.19, SD = 0.48; day 7 ACE = 4.57, SD = 0.83; P < 0.0001; Fig. 1). With the exception of day 1, ACE during the administration of furosemide alone was not significantly different than that observed at baseline (group F baseline ACE = 14.30; SD = 2.24; day 1 ACE = 11.92; SD = 1.83; day 4 ACE = 15.38; SD = 2.96; day 7 ACE = 15.11; SD = 1.47). On day 1, compared to baseline, there was a 16% reduction in ACE in group F, as compared to 74% suppression from baseline in group FE (Fig. 1a,b). Furthermore, mean ACE for the 3 treatment time points in the F group was significantly
Table 1. Mean (SD) values for packed cell volume (PCV), body weight, systolic blood pressure, and heart rate are displayed for all treatment situations for dogs receiving furosemide (2 mg/kg q12h) and the combination of enalapril (0.5 mg/kg q12h) and furosemide (2 mg/kg q12h) Day 0 (baseline) PCV (%) Reference interval: 43–62% Group F 49 Group FE 49 BW (kg) Group F 11 Group FE 10 SBP (mmHg) Reference interval: 120–160 mmHg Group F 147 Group FE 139 Heart rate (BPM) Group F 109 Group FE 111 *
Day 1
Day 4
Day 7
(3)† (6)
48 (4) 52 (5)*
52 (3)* 54 (5)*
50 (3) 52 (4)
(1)† (0.8)
11.6 (1)* 10 (0.7)*
11.4 (1)* 10 (0.6)*
11.6 (1)* 10 (0.6)*
(10) (13)
145 (13) 147 (21)
153 (16) 138 (16)
145 (13) 138 (18)
(15) (17)
123 (18) 116 (20)
113 (13) 114 (17)
111 (16) 119 (14)
P < 0.05 within group compared to baseline; †P < 0.05 between treatment groups. © 2015 John Wiley & Sons Ltd
Aldosterone breakthrough 515 Table 2. Mean (SD) values for serum chemistry parameters are displayed for all treatment situations for dogs receiving furosemide (2 mg/kg q12h) and the combination of enalapril (0.5 mg/kg q12h) and furosemide (2 mg/kg q12h) Day 0 (baseline) Albumin (g/dL) Reference interval: 2.8–3.7 Group F 3.2 (0.3) Group FE 3.1 (0.4) Phosphorus (mg/dL) Reference interval: 2–6.7 Group F 3.4 (0.5) Group FE 3.9 (0.5) Sodium (mEq/L) Reference interval: 147–154 Group F 144.4 (0.9)† Group FE 146 (1.1) Chloride (mEq/L) Reference interval: 104–117 Group F 115 (1.5) Group FE 114 (1.3) Calcium (mg/dL) Reference interval: 9.4–10.7 Group F 9.7 (0.4) Group FE 10 (0.4) Potassium (mEq/L) Reference interval: 3.9–5.2 Group F 3.9 (0.3) Group FE 3.8 (0.2) Bicarbonate (mEg/L) Reference interval: 18–25.8 Group F 18.4 (2.1) Group FE 20.1 (1.2) SUN (mg/dL) Reference interval: 9–30 Group F 11.9 (1.8) Group FE 12.8 (2.4) Creatinine (mg/dL) Reference interval: 0.7–1.3 Group F 0.69 (0.08) Group FE 0.73 (0.09)
Day 1
Day 4
Day 7
3.4 (0.3) 3.4 (0.4)*
3.3 (0.3) 3.4 (0.4)
3.2 (0.2) 3.3 (0.3)
3.8 (0.7) 4.2 (0.3)
3.8 (0.5) 4.1 (0.3)
3.7 (0.5) 3.8 (0.2)
143.1 (1.0) 143 (1.6)*
143 (2.0) 144 (1.4)*
142 (1.0)* 143.4 (1.8)*
110.1 (2.8)* 109 (1.8)*
109 (4.1)* 107 (3.7)*
109.3 (2.3)* 108 (3.0)*
10 (0.7)* 10.2 (0.4)
10 (0.6)* 10.1 (0.4)
10 (0.5)* 10 (0.3)
3.6 (0.4)* 3.7 (0.2)
3.5 (0.3)* 3.4 (0.2)*
3.5 (0.2)* 3.6 (0.3)
20.4 (2.6)* 21.1 (1.5)
21 (2.4)* 22 (1.4)*
21 (2.6)* 23 (2.1)*
12.9 (1.8) 14 (2.4)
14.3 (1.8)* 15 (1.9)*
14.1 (1.6)* 15.4 (2.3)*
0.76 (0.07)* 0.71 (0.08)
0.79 (0.08)* 0.75 (0.05)
0.74 (0.11)* 0.74 (0.05)
SUN, serum urea nitroten. P < 0.05 within group compared to baseline; †P < 0.05 between treatment groups.
*
(P < 0.0001) greater than in the FE group (11.92 U/L vs. 4.05 U/L) and there was no significant difference between baseline ACE and that found on days 4 and 7 in the FB group. There was a statistically significant difference in the ACE at days 1, 4, and 7 between groups F and FE (P < 0.0001; Fig. 1). Furosemide administration produced an approximately threefold increase in UAldo:C (group F baseline UAldo:C = 1.19, SD = 0.57; day 1 UAldo:C = 2.79, SD = 1.61, P < 0.001; day 4 UAldo:C = 2.76, SD = 1.91, P < 0.01; day 7 UAldo: C = 3.13, SD = 1.59, P < 0.01; Fig. 2). Furosemide and enalapril administration was associated with a similar significant increase in UAldo:C (group FE baseline UAldo:C = 0.79, SD = 0.50; day 1 UAldo:C = 0.1.64, SD = 0.62, P = 0.07; day 4 UAldo:C = 2.80, SD = 1.38, P < 0.001; day 7 UAldo: C = 2.51, SD = 1.48, P < 0.01; Fig. 2). There was no significant difference in UAldo:C between groups F and FE on days 1, 4, and 7 (Fig. 2). © 2015 John Wiley & Sons Ltd
The results of this study revealed an expected two- to threefold increase in RAAS activation in normal dogs, receiving furosemide monotherapy, as demonstrated by a significant increase in urinary aldosterone excretion (Fig. 1). Group FE experienced a similar increase in aldosterone excretion, despite the fact that ACE, 4–6 h postenalapril, was reduced by at least 55% (range 55–85%). Maximum RAAS suppression is known to occur 1–3 h post-ACE-I (Hamlin & Nakayama, 1998). These data answer questions raised by two separate studies in our laboratory, in which FI-RAAS was not ameliorated by benazepril (Lantis et al., 2014), yet in a previous investigation, amlodipine-induced RAAS activation was at least partly attenuated by enalapril (Atkins et al., 2007; Fig. 3). This raises the possibility that enalapril suppresses ACE to a greater degree in this model. However, the more likely explanation for this discrepancy is the greater power of furosemide (vs. amlodipine) as an aldosterone secretagogue, rather than a difference between
516 A. C. Lantis et al.
UAldo:C (µg·g—1)
(a)
UAldo:C Group F 4
*
*
*
3
2
1
ACE activity (U·L—1)
(a)
ACE activity group F
20
†
15
10
5
*
3
7 F
F
D
D
ay
ay
ay D F
da
*
*
2
1
ACE activity (U·L—1)
UAldo:C (µg·g—1)
UAldo:C Group FE
4
4
F Pr e-
y
7
4
F
F
F
D ay
D ay
1
F Pr e
(b) (b)
1
0 0
ACE activity group FE
20
15
* **
10
5
* **
* **
ACE-I. This is because current and past (Lantis et al., 2014) data demonstrate that ABT in this model is not due to failure of the ACE-I to suppress ACE. Secondly, as both benazepril and enalapril are apparently affected, ABT may be a drug class phenomenon. Persistent aldosterone secretion with ACE-I or ARB therapy, even with significant reduction in plasma ACE and presumed reduced genesis of angiotensin II, is termed ‘aldosterone escape’ or ‘aldosterone breakthrough’ (MacFadyen et al., 1999). Aldosterone breakthrough has been defined in the human literature as an increase in serum aldosterone concentration that exceeds a baseline value after initiation of RAAS-blocking therapy (Bomback & Klemmer, 2007). There is no consensus within the human literature regarding the time course of ABT, as some authors have described it as the condition in which serum aldosterone
D FE
ay D FE
ay
4
1 ay D FE
Pr
e-
FE FE
da
y
7
4 ay D FE
FE
D
ay
1
FE e Pr
Fig. 1. (a) The urinary UAldo:C (lg/g) before (pre-F) and after the administration of furosemide (2 mg/kg q 12 h) at days 1, 4, and 7. (b) The urinary UAldo:C (lg/g) before (pre-FE) and after the administration of furosemide and enalapril (0.5 mg/kg q 12 h) at days 1, 4, and 7. The figure demonstrates the mean (box) and the standard error of the mean (bars). Compared to baseline values (pre-F and pre-FB), there is activation of circulating renin–angiotensin–aldosterone system with furosemide administration alone (*P < 0.05) and with the combination of furosemide and enalapril (*P < 0.05). There is no difference between the two groups at any sampling date (P > 0.05). F, furosemide; FE, furosemide and enalapril; UAldo:C, urinary aldosterone:creatinine.
7
0 0
Fig. 2. (a) Group F (n = 8 dogs) – plasma ACE activity (U/L) at baseline (average of days 1 and 2; pre-F) and 4–6 h after administration of furosemide (2 mg/kg q 12 h) on days 1, 4, and 7. (b) Group FE (n = 8 dogs) – plasma ACE activity (U/L) at baseline (average of days 1 and 2; pre-FE) and 4–6 h after administration of the combination of furosemide (2 mg/kg q 12 h) and enalapril (0.5 mg/kg q 12 h) on days 1, 4, and 7. The figure demonstrates the mean and standard error of the mean (bars) for ACE activity. ACE activity is essentially unchanged in the furosemide group (with the exception of a minor, but significant fall of 16% on day 1 vs. 74% on day 1 in the FE group), whereas ACE activity is significantly attenuated by the combination of furosemide and enalapril at every time point. *P < 0.0001 within group compared to baseline; **P < 0.0001 between treatment groups, †P < 0.05 between treatment day and baseline. ACE, angiotensin-converting enzyme; F, furosemide; FE, furosemide and enalapril.
concentration exceeds a baseline (pre-ACE-I and/or ARB therapy) value of 6–12 months after initiation of RAASblocking therapy (Bomback & Klemmer, 2007). However, early failure of ACE-I to reduce aldosterone production, as reported herein using a laboratory model, has also been documented in human patients 4–6 weeks after initiation of an ACE-I (Staessen et al., 1981). A limitation of this study is that our experimental model of RAAS activation does not mimic the typical duration of pharmacotherapy in naturally occurring heart failure. Also, these dogs do not have underlying cardiac dysfunction, although its presence would likely further stimulate RAAS and contribute to ABT. © 2015 John Wiley & Sons Ltd
Aldosterone breakthrough 517 400
24 Hour Aldosterone (ug) Aldosterone: Creatinine (ug/dg)
*
300
*
200
100
0
C
A
A+E
24-Hour Aldosterone
C
A
A+E
Aldosterone: Creatinine
Fig. 3. 24-hour urinary aldosterone and the ratio of urinary aldosterone to creatinine (Aldo:Creat) are displayed for normal beagles at baseline (C), after 5 days of amlodipine administration (A) and after 3 additional days of treatment with amlodipine and enalapril (A+E). Significance assumed at *P = 0.05 vs Control.
FUNDING Funded by Veterinary Memorial Fund.
REFERENCES Amberger, C., Chetboul, V., Bomassi, E., Rougier, S., Woehrle, F., Thoulon, F.; FIRST (First Imidapril Randomized Study) group (2004) Comparison of the effects of imidapril and enalapril in a prospective, multicentric randomized trial in dogs with naturally acquired heart failure. Journal of Veterinary Cardiology, 6, 9–16. Atkins, C.E., Rausch, R.W., Gardner, S.Y., DeFrancesco, T.C., Keene, B.W. & Levine, J.F. (2007) The effect of amlodipine and the combination of amlodipine and enalapril on the renin-angiotensin-aldosterone system in the dog. Journal of Veterinary Pharmacology and Therapeutics, 30, 394–400. Bernay, F., Bland, J.M., H€ aggstr€ om, J., Baduel, L., Combes, B., Lopez, A. & Kaltsatos, V. (2010) Efficacy of spironolactone on survival in dogs with naturally occurring mitral regurgitation caused by myxomatous mitral valve disease. Journal of Veterinary Internal Medicine, 24, 331– 341. Bomback, A.S. & Klemmer, P.J. (2007) The incidence and implications of aldosterone breakthrough. Nature Clinical Practice Nephrology, 3, 486–492.
© 2015 John Wiley & Sons Ltd
Ettinger, S.J., Benitz, A.M., Ericsson, G.F., Cifelli, S., Jernigan, A.D., Longhofer, S.L., Trimboli, W. & Hanson, P.D. (1998) Effects of enalapril maleate on survival of dogs with naturally acquired heart failure. The Long-Term Investigation of Veterinary Enalapril (LIVE) Study Group. Journal of the American Veterinary Medical Association, 11, 1573–1577. Hamlin, R.L. & Nakayama, T. (1998) Comparison of some pharmacokinetic parameters of 5 angiotensin-converting enzyme inhibitors in normal beagles. Journal of Veterinary Internal Medicine, 12, 93–95. Kitagawa, H., Wakamiya, H., Kitoh, K., Kuwahara, Y., Ohba, Y., Isaji, M., Iwasaki, T., Nakano, M. & Sasaki, Y. (1997) Efficacy of monotherapy with benazepril, an angiotensin converting enzyme inhibitor, in dogs with naturally acquired chronic mitral insufficiency. Journal of Veterinary Medical Science, 59, 513–520. Lantis, A., Ames, M., Atkins, C., Keene, B., DeFrancesco, T. & Werre, S. (2014) Aldosterone breakthrough with benazepril in furosemide-activated renin-angiotensin-aldosterone system in normal dogs. Journal of Veterinary Pharmacology and Therapeutics, 38, 65–73. MacFadyen, R.J., Lee, A.F., Morton, J.J., Pringle, S.D. & Struthers, A.D. (1999) How often are angiotensin II and aldosterone concentrations raised during chronic ACE inhibitor treatment in cardiac failure? Heart, 82, 57–61. O’Grady, M.R., O’Sullivan, M.L., Minors, S.L. & Horne, R. (2009) Efficacy of benazepril hydrochloride to delay the progression of occult dilated cardiomyopathy in Doberman pinschers. Journal of Veterinary Internal Medicine, 23, 977–983. Pitt, B., Zannad, F., Remme, W.J., Cody, R., Castaigne, A., Perez, A., Palensky, J. & Wittes, J. (1999) The effect of spironolactone on morbidity and mortality in patients with severe heart failure. Randomized Aldactone Evaluation Study Investigators. New England Journal of Medicine, 341, 709–717. Sayer, M.A., Atkins, C.E., Fujii, Y., Adams, A.K., DeFrancesco, T.C. & Keene, B.W. (2009) Acute effect of pimobendan and furosemide on the circulating renin-angiotensin-aldosterone system in healthy dogs. Journal of Veterinary Internal Medicine, 23, 1003–1006. Staessen, J., Lijnen, P., Fagard, R., Verschueren, L.J. & Amery, A. (1981) Rise in plasma concentration of aldosterone during long-term angiotensin II suppression. Journal of Endocrinology, 91, 457–465. The BENCH Study Group (1999) The effect of Benazepril on survival times and clinical signs of dogs with congestive heart failure: results of a multicenter, prospective, randomised, double-blinded, placebocontrolled, long term clinical trial. Journal of Veterinary Cardiology, 1, 7–18. The COVE Study Group (1995) Controlled clinical evaluation of enalapril in dogs with heart failure: results of the Cooperative Veterinary Enalapril Study Group. Journal of Veterinary Internal Medicine, 9, 243–252.
SHORT COMMUNICATION
The effect of enalapril on furosemide-activated renin–angiotensin– aldosterone system in healthy dogs A. C. LANTIS* M. K. AMES*
,†,1
S. WERRE* & C. E. ATKINS † *Department of Small Animal Clinical Sciences, Virginia-Maryland Regional College of Veterinary Medicine, Blacksburg, VA, USA; † Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA
Lantis A. C., Ames M. K., Werre S., Atkins C. E. The effect of enalapril on furosemide-activated renin–angiotensin–aldosterone system in healthy dogs. J. vet. Pharmacol. Therap. 38, 513–517. Studies in our laboratory have revealed that furosemide-induced RAAS activation, evaluated via the urine aldosterone-to-creatinine ratio (UAldo:C), was not attenuated by the coadministration of benazepril, while enalapril successfully suppressed amlodipine-induced urinary aldosterone excretion. This study was designed to evaluate the efficacy of enalapril in suppressing ACE activity and furosemide-induced circulating RAAS activation. Failure to do so would suggest that this failure may be a drug class effect. We hypothesized that enalapril would suppress ACE activity and furosemide-induced circulating RAAS activation. Sixteen healthy hound dogs. The effect of furosemide (2 mg/kg PO, q12 h; Group F) and furosemide plus enalapril (0.5 mg/kg PO, q12 h; Group FE) on circulating RAAS was determined by plasma ACE activity, 4–6 h post-treatment, and urinary A:C on days 1, 2, 1, 4, and 7. There was a significant increase in the average urine aldosterone-to-creatinine ratio (UAldo:C) after administration of furosemide (P < 0.05). Enalapril inhibited ACE activity (P < 0.0001) but did not significantly reduce aldosterone excretion. A significant (P < 0.05) increase in the UAldo:C was maintained for the 7 days of the study in both groups. Enalapril decreased plasma ACE activity; however, it did not suppress furosemide-induced RAAS activation, as determined by the UAldo:C. While enalapril blunts ACE activity, the absence of circulating RAAS suppression may be due to angiotensin II reactivation, alternative RAAS pathways, and furosemide overriding concurrent ACE inhibition, all indicating the existence of aldosterone breakthrough (ABT). Along with similar findings with benazepril, it appears that failure to suppress aldosterone suppression with furosemide stimulation may be a drug class effect. The discrepancy between the current data and the documented benefits of enalapril likely reflects the efficacy of this ACE inhibitor in suppressing tissue RAAS, variable population responsiveness to ACE-inhibition, and/or providing additional survival benefits, possibly through as yet unknown mechanisms. (Paper received 27 October 2014; accepted for publication 29 January 2015) Dr. Andrea C. Lantis, Veterinary Emergency and Referral Group, Brooklyn, NY 11201, USA. E-mail: [email protected] 1 Present address: Department of Clinical Sciences, College of Veterinary Medicine, Colorado State University, Fort Collins, CO 80526, USA This study was performed at the Virginia-Maryland Regional College of Veterinary Medicine, Blacksburg, Virginia 24060
Angiotensin-converting enzyme inhibitors (ACE-I) reduce plasma ACE activity (ACE) by greater than 50%, with benefit demonstrated in dogs with heart failure (CHF) (The COVE Study Group, 1995; Kitagawa et al., 1997; Ettinger et al.,
© 2015 John Wiley & Sons Ltd
1998; Hamlin & Nakayama, 1998; The BENCH Study Group, 1999; Amberger et al., 2004; O’Grady et al., 2009). While ACE-I have been shown to be beneficial in this setting, aldosterone secretion is not sufficiently suppressed in all dogs
513
514 A. C. Lantis et al.
(aldosterone breakthrough [ABT]) (Bomback & Klemmer, 2007; Lantis et al., 2014). Theoretically, a decrease in the formation of ATII, a major secretogogue of aldosterone, should lead to a significant decrease in aldosterone secretion. However, effective RAAS blockade with ACE-I is lost (ABT) in 40– 50% of human CHF patients after 1 year of therapy (Bomback & Klemmer, 2007). Knowledge of ABT has led to the successful use of mineralocorticoid- and angiotensin II-receptor blockers (ARB) in the management of CHF (Pitt et al., 1999; Bomback & Klemmer, 2007; Bernay et al., 2010). We have demonstrated circulating renin–angiotensin–aldosterone system (RAAS) activation, characterized by a two- to threefold increase in the urine aldosterone:creatinine (UAldo: C), with the administration of both amlodipine and furosemide (Atkins et al., 2007; Sayer et al., 2009). While benazepril successfully suppresses ACE, it does not significantly reduce average furosemide-induced urinary aldosterone excretion, indicating ABT (Lantis et al., 2014). The presence of ABT, despite suppression of ACE, has led to numerous hypotheses about the mechanism of ABT – including non-ACE-mediated generation of ATII and the extra-adrenal formation of aldosterone. The documented population benefit of benazepril in CHF, in the presumed presence of ABT, likely reflects the efficacy of benazepril in temporarily suppressing circulatory RAAS and tissue RAAS activity, the latter of which cannot be readily measured in living animals. Approximately 50% of human heart failure patients do not experience ABT and thereby contribute to the overall population effect of benazepril in heart failure. The observed efficacy of enalapril in suppression of amlodipine-induced circulating RAAS activation (Atkins et al., 2007), in contrast with benazepril’s inability to suppress furosemideinduced circulating RAAS activation (FI-RAAS) (Lantis et al., 2014), may represent another significant difference between these two ACE-I. This experimental study in healthy dogs intended to prove or disprove the existence of enalapril ABT. Using a model of
RAAS activation, it was designed to examine the time course and magnitude of the RAAS response to the administration of furosemide (Salix, Intervet Canada, Whitby, ON, Canada) alone (2 mg/kg p.o. [SD = 0.1], BID) as group F and with co-administration of furosemide (2 mg/kg p.o. [SD = 0.12], BID) and enalapril (0.5 mg/kg p.o. [SD = 0.04] BID; Vasotec (Enalapril) 10 mg, 2.5 mg; Valeant Pharmaceuticals LLC, Bridgewater, NJ, USA) as group FE. The co-administration of furosemide (with enalapril) was utilized as a RAAS activator to mimic neurohormonal activity in CHF, without harming or sacrificing research dogs. Sixteen mature, normal hound dogs weighing 21.2 (SD 8.94; range 7.5–34) kg were enrolled in the study. To measure the time course and magnitude of the RAAS activation, as well as other physiological changes in response to treatment, body weight, systolic blood pressure, a serum chemistry panel, ACE, and UAldo:C, samples were obtained on days 1, 2, 1, 4, and 7. Study design and statistical analysis were as previously described (Lantis et al., 2014). There were no significant abnormalities detected on baseline physical examination, complete blood counts, serum chemistry analyses, urinalyses, or blood pressure evaluations (Tables 1 & 2). Mild, sporadic differences between groups and within groups over time were observed. These were expected with furosemide administration and are not discussed further. Plasma ACE [U/L] was significantly reduced with the administration of furosemide and enalapril (group FE baseline ACE = 15.68, SD = 1.77; day 1 ACE = 4.05, SD = 0.84; day 4 ACE = 3.19, SD = 0.48; day 7 ACE = 4.57, SD = 0.83; P < 0.0001; Fig. 1). With the exception of day 1, ACE during the administration of furosemide alone was not significantly different than that observed at baseline (group F baseline ACE = 14.30; SD = 2.24; day 1 ACE = 11.92; SD = 1.83; day 4 ACE = 15.38; SD = 2.96; day 7 ACE = 15.11; SD = 1.47). On day 1, compared to baseline, there was a 16% reduction in ACE in group F, as compared to 74% suppression from baseline in group FE (Fig. 1a,b). Furthermore, mean ACE for the 3 treatment time points in the F group was significantly
Table 1. Mean (SD) values for packed cell volume (PCV), body weight, systolic blood pressure, and heart rate are displayed for all treatment situations for dogs receiving furosemide (2 mg/kg q12h) and the combination of enalapril (0.5 mg/kg q12h) and furosemide (2 mg/kg q12h) Day 0 (baseline) PCV (%) Reference interval: 43–62% Group F 49 Group FE 49 BW (kg) Group F 11 Group FE 10 SBP (mmHg) Reference interval: 120–160 mmHg Group F 147 Group FE 139 Heart rate (BPM) Group F 109 Group FE 111 *
Day 1
Day 4
Day 7
(3)† (6)
48 (4) 52 (5)*
52 (3)* 54 (5)*
50 (3) 52 (4)
(1)† (0.8)
11.6 (1)* 10 (0.7)*
11.4 (1)* 10 (0.6)*
11.6 (1)* 10 (0.6)*
(10) (13)
145 (13) 147 (21)
153 (16) 138 (16)
145 (13) 138 (18)
(15) (17)
123 (18) 116 (20)
113 (13) 114 (17)
111 (16) 119 (14)
P < 0.05 within group compared to baseline; †P < 0.05 between treatment groups. © 2015 John Wiley & Sons Ltd
Aldosterone breakthrough 515 Table 2. Mean (SD) values for serum chemistry parameters are displayed for all treatment situations for dogs receiving furosemide (2 mg/kg q12h) and the combination of enalapril (0.5 mg/kg q12h) and furosemide (2 mg/kg q12h) Day 0 (baseline) Albumin (g/dL) Reference interval: 2.8–3.7 Group F 3.2 (0.3) Group FE 3.1 (0.4) Phosphorus (mg/dL) Reference interval: 2–6.7 Group F 3.4 (0.5) Group FE 3.9 (0.5) Sodium (mEq/L) Reference interval: 147–154 Group F 144.4 (0.9)† Group FE 146 (1.1) Chloride (mEq/L) Reference interval: 104–117 Group F 115 (1.5) Group FE 114 (1.3) Calcium (mg/dL) Reference interval: 9.4–10.7 Group F 9.7 (0.4) Group FE 10 (0.4) Potassium (mEq/L) Reference interval: 3.9–5.2 Group F 3.9 (0.3) Group FE 3.8 (0.2) Bicarbonate (mEg/L) Reference interval: 18–25.8 Group F 18.4 (2.1) Group FE 20.1 (1.2) SUN (mg/dL) Reference interval: 9–30 Group F 11.9 (1.8) Group FE 12.8 (2.4) Creatinine (mg/dL) Reference interval: 0.7–1.3 Group F 0.69 (0.08) Group FE 0.73 (0.09)
Day 1
Day 4
Day 7
3.4 (0.3) 3.4 (0.4)*
3.3 (0.3) 3.4 (0.4)
3.2 (0.2) 3.3 (0.3)
3.8 (0.7) 4.2 (0.3)
3.8 (0.5) 4.1 (0.3)
3.7 (0.5) 3.8 (0.2)
143.1 (1.0) 143 (1.6)*
143 (2.0) 144 (1.4)*
142 (1.0)* 143.4 (1.8)*
110.1 (2.8)* 109 (1.8)*
109 (4.1)* 107 (3.7)*
109.3 (2.3)* 108 (3.0)*
10 (0.7)* 10.2 (0.4)
10 (0.6)* 10.1 (0.4)
10 (0.5)* 10 (0.3)
3.6 (0.4)* 3.7 (0.2)
3.5 (0.3)* 3.4 (0.2)*
3.5 (0.2)* 3.6 (0.3)
20.4 (2.6)* 21.1 (1.5)
21 (2.4)* 22 (1.4)*
21 (2.6)* 23 (2.1)*
12.9 (1.8) 14 (2.4)
14.3 (1.8)* 15 (1.9)*
14.1 (1.6)* 15.4 (2.3)*
0.76 (0.07)* 0.71 (0.08)
0.79 (0.08)* 0.75 (0.05)
0.74 (0.11)* 0.74 (0.05)
SUN, serum urea nitroten. P < 0.05 within group compared to baseline; †P < 0.05 between treatment groups.
*
(P < 0.0001) greater than in the FE group (11.92 U/L vs. 4.05 U/L) and there was no significant difference between baseline ACE and that found on days 4 and 7 in the FB group. There was a statistically significant difference in the ACE at days 1, 4, and 7 between groups F and FE (P < 0.0001; Fig. 1). Furosemide administration produced an approximately threefold increase in UAldo:C (group F baseline UAldo:C = 1.19, SD = 0.57; day 1 UAldo:C = 2.79, SD = 1.61, P < 0.001; day 4 UAldo:C = 2.76, SD = 1.91, P < 0.01; day 7 UAldo: C = 3.13, SD = 1.59, P < 0.01; Fig. 2). Furosemide and enalapril administration was associated with a similar significant increase in UAldo:C (group FE baseline UAldo:C = 0.79, SD = 0.50; day 1 UAldo:C = 0.1.64, SD = 0.62, P = 0.07; day 4 UAldo:C = 2.80, SD = 1.38, P < 0.001; day 7 UAldo: C = 2.51, SD = 1.48, P < 0.01; Fig. 2). There was no significant difference in UAldo:C between groups F and FE on days 1, 4, and 7 (Fig. 2). © 2015 John Wiley & Sons Ltd
The results of this study revealed an expected two- to threefold increase in RAAS activation in normal dogs, receiving furosemide monotherapy, as demonstrated by a significant increase in urinary aldosterone excretion (Fig. 1). Group FE experienced a similar increase in aldosterone excretion, despite the fact that ACE, 4–6 h postenalapril, was reduced by at least 55% (range 55–85%). Maximum RAAS suppression is known to occur 1–3 h post-ACE-I (Hamlin & Nakayama, 1998). These data answer questions raised by two separate studies in our laboratory, in which FI-RAAS was not ameliorated by benazepril (Lantis et al., 2014), yet in a previous investigation, amlodipine-induced RAAS activation was at least partly attenuated by enalapril (Atkins et al., 2007; Fig. 3). This raises the possibility that enalapril suppresses ACE to a greater degree in this model. However, the more likely explanation for this discrepancy is the greater power of furosemide (vs. amlodipine) as an aldosterone secretagogue, rather than a difference between
516 A. C. Lantis et al.
UAldo:C (µg·g—1)
(a)
UAldo:C Group F 4
*
*
*
3
2
1
ACE activity (U·L—1)
(a)
ACE activity group F
20
†
15
10
5
*
3
7 F
F
D
D
ay
ay
ay D F
da
*
*
2
1
ACE activity (U·L—1)
UAldo:C (µg·g—1)
UAldo:C Group FE
4
4
F Pr e-
y
7
4
F
F
F
D ay
D ay
1
F Pr e
(b) (b)
1
0 0
ACE activity group FE
20
15
* **
10
5
* **
* **
ACE-I. This is because current and past (Lantis et al., 2014) data demonstrate that ABT in this model is not due to failure of the ACE-I to suppress ACE. Secondly, as both benazepril and enalapril are apparently affected, ABT may be a drug class phenomenon. Persistent aldosterone secretion with ACE-I or ARB therapy, even with significant reduction in plasma ACE and presumed reduced genesis of angiotensin II, is termed ‘aldosterone escape’ or ‘aldosterone breakthrough’ (MacFadyen et al., 1999). Aldosterone breakthrough has been defined in the human literature as an increase in serum aldosterone concentration that exceeds a baseline value after initiation of RAAS-blocking therapy (Bomback & Klemmer, 2007). There is no consensus within the human literature regarding the time course of ABT, as some authors have described it as the condition in which serum aldosterone
D FE
ay D FE
ay
4
1 ay D FE
Pr
e-
FE FE
da
y
7
4 ay D FE
FE
D
ay
1
FE e Pr
Fig. 1. (a) The urinary UAldo:C (lg/g) before (pre-F) and after the administration of furosemide (2 mg/kg q 12 h) at days 1, 4, and 7. (b) The urinary UAldo:C (lg/g) before (pre-FE) and after the administration of furosemide and enalapril (0.5 mg/kg q 12 h) at days 1, 4, and 7. The figure demonstrates the mean (box) and the standard error of the mean (bars). Compared to baseline values (pre-F and pre-FB), there is activation of circulating renin–angiotensin–aldosterone system with furosemide administration alone (*P < 0.05) and with the combination of furosemide and enalapril (*P < 0.05). There is no difference between the two groups at any sampling date (P > 0.05). F, furosemide; FE, furosemide and enalapril; UAldo:C, urinary aldosterone:creatinine.
7
0 0
Fig. 2. (a) Group F (n = 8 dogs) – plasma ACE activity (U/L) at baseline (average of days 1 and 2; pre-F) and 4–6 h after administration of furosemide (2 mg/kg q 12 h) on days 1, 4, and 7. (b) Group FE (n = 8 dogs) – plasma ACE activity (U/L) at baseline (average of days 1 and 2; pre-FE) and 4–6 h after administration of the combination of furosemide (2 mg/kg q 12 h) and enalapril (0.5 mg/kg q 12 h) on days 1, 4, and 7. The figure demonstrates the mean and standard error of the mean (bars) for ACE activity. ACE activity is essentially unchanged in the furosemide group (with the exception of a minor, but significant fall of 16% on day 1 vs. 74% on day 1 in the FE group), whereas ACE activity is significantly attenuated by the combination of furosemide and enalapril at every time point. *P < 0.0001 within group compared to baseline; **P < 0.0001 between treatment groups, †P < 0.05 between treatment day and baseline. ACE, angiotensin-converting enzyme; F, furosemide; FE, furosemide and enalapril.
concentration exceeds a baseline (pre-ACE-I and/or ARB therapy) value of 6–12 months after initiation of RAASblocking therapy (Bomback & Klemmer, 2007). However, early failure of ACE-I to reduce aldosterone production, as reported herein using a laboratory model, has also been documented in human patients 4–6 weeks after initiation of an ACE-I (Staessen et al., 1981). A limitation of this study is that our experimental model of RAAS activation does not mimic the typical duration of pharmacotherapy in naturally occurring heart failure. Also, these dogs do not have underlying cardiac dysfunction, although its presence would likely further stimulate RAAS and contribute to ABT. © 2015 John Wiley & Sons Ltd
Aldosterone breakthrough 517 400
24 Hour Aldosterone (ug) Aldosterone: Creatinine (ug/dg)
*
300
*
200
100
0
C
A
A+E
24-Hour Aldosterone
C
A
A+E
Aldosterone: Creatinine
Fig. 3. 24-hour urinary aldosterone and the ratio of urinary aldosterone to creatinine (Aldo:Creat) are displayed for normal beagles at baseline (C), after 5 days of amlodipine administration (A) and after 3 additional days of treatment with amlodipine and enalapril (A+E). Significance assumed at *P = 0.05 vs Control.
FUNDING Funded by Veterinary Memorial Fund.
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Ettinger, S.J., Benitz, A.M., Ericsson, G.F., Cifelli, S., Jernigan, A.D., Longhofer, S.L., Trimboli, W. & Hanson, P.D. (1998) Effects of enalapril maleate on survival of dogs with naturally acquired heart failure. The Long-Term Investigation of Veterinary Enalapril (LIVE) Study Group. Journal of the American Veterinary Medical Association, 11, 1573–1577. Hamlin, R.L. & Nakayama, T. (1998) Comparison of some pharmacokinetic parameters of 5 angiotensin-converting enzyme inhibitors in normal beagles. Journal of Veterinary Internal Medicine, 12, 93–95. Kitagawa, H., Wakamiya, H., Kitoh, K., Kuwahara, Y., Ohba, Y., Isaji, M., Iwasaki, T., Nakano, M. & Sasaki, Y. (1997) Efficacy of monotherapy with benazepril, an angiotensin converting enzyme inhibitor, in dogs with naturally acquired chronic mitral insufficiency. Journal of Veterinary Medical Science, 59, 513–520. Lantis, A., Ames, M., Atkins, C., Keene, B., DeFrancesco, T. & Werre, S. (2014) Aldosterone breakthrough with benazepril in furosemide-activated renin-angiotensin-aldosterone system in normal dogs. Journal of Veterinary Pharmacology and Therapeutics, 38, 65–73. MacFadyen, R.J., Lee, A.F., Morton, J.J., Pringle, S.D. & Struthers, A.D. (1999) How often are angiotensin II and aldosterone concentrations raised during chronic ACE inhibitor treatment in cardiac failure? Heart, 82, 57–61. O’Grady, M.R., O’Sullivan, M.L., Minors, S.L. & Horne, R. (2009) Efficacy of benazepril hydrochloride to delay the progression of occult dilated cardiomyopathy in Doberman pinschers. Journal of Veterinary Internal Medicine, 23, 977–983. Pitt, B., Zannad, F., Remme, W.J., Cody, R., Castaigne, A., Perez, A., Palensky, J. & Wittes, J. (1999) The effect of spironolactone on morbidity and mortality in patients with severe heart failure. Randomized Aldactone Evaluation Study Investigators. New England Journal of Medicine, 341, 709–717. Sayer, M.A., Atkins, C.E., Fujii, Y., Adams, A.K., DeFrancesco, T.C. & Keene, B.W. (2009) Acute effect of pimobendan and furosemide on the circulating renin-angiotensin-aldosterone system in healthy dogs. Journal of Veterinary Internal Medicine, 23, 1003–1006. Staessen, J., Lijnen, P., Fagard, R., Verschueren, L.J. & Amery, A. (1981) Rise in plasma concentration of aldosterone during long-term angiotensin II suppression. Journal of Endocrinology, 91, 457–465. The BENCH Study Group (1999) The effect of Benazepril on survival times and clinical signs of dogs with congestive heart failure: results of a multicenter, prospective, randomised, double-blinded, placebocontrolled, long term clinical trial. Journal of Veterinary Cardiology, 1, 7–18. The COVE Study Group (1995) Controlled clinical evaluation of enalapril in dogs with heart failure: results of the Cooperative Veterinary Enalapril Study Group. Journal of Veterinary Internal Medicine, 9, 243–252.
