Effects of atrial natriuretic peptide on systemic and renal hemodynamics and renal excretory function in patients with chronic renal failure

Predicting drug-drug interactions with physiologically based pharmacokinetic/pharmacodynamic modelling and optimal dosing of apixaban and rivaroxaban with dronedarone co-administration

BACKGROUND

The concurrent administration of dronedarone and oral anti-coagulants is common because both are used in managing atrial fibrillation (AF). Dronedarone is a moderate inhibitor of the cytochrome P450 3A4 (CYP3A4) enzyme and P-glycoprotein (P-gp). Apixaban and rivaroxaban are P-gp and CYP3A4 substrates. This study aims to investigate the impact of exposure and bleeding risk of apixaban or rivaroxaban when co-administered with dronedarone using physiologically based pharmacokinetic/pharmacodynamic analysis.

METHODS

Modeling and simulation were conducted using Simcyp® Simulator. The parameters required for dronedarone modeling were collected from the literature. The developed dronedarone physiologically based pharmacokinetic (PBPK) model was verified using reported drug-drug interactions (DDIs) between dronedarone and CYP3A4 and P-gp substrates. The model was applied to evaluate the DDI potential of dronedarone on the exposure of apixaban 5 mg every 12 h or rivaroxaban 20 mg every 24 h in geriatric and renally impaired populations. DDIs precipitating major bleeding risks were assessed using exposure-response analyses derived from literature.

RESULTS

The model accurately described the pharmacokinetics of orally administered dronedarone in healthy subjects and accurately predicted DDIs between dronedarone and four CYP3A4 and P-gp substrates with fold errors <1.5. Dronedarone co-administration led to a 1.29 (90 % confidence interval (CI): 1.14-1.50) to 1.31 (90 % CI: 1.12-1.46)-fold increase in the area under concentration-time curve for rivaroxaban and 1.33 (90 % CI: 1.15-1.68) to 1.46 (90 % CI: 1.24-1.92)-fold increase for apixaban. The PD model indicated that dronedarone co-administration might potentiate the mean major bleeding risk of apixaban with a 1.45 to 1.95-fold increase. However, the mean major bleeding risk of rivaroxaban was increased by <1.5-fold in patients with normal or impaired renal function.

CONCLUSIONS

Dronedarone co-administration increased the exposure of rivaroxaban and apixaban and might potentiate major bleeding risks. Reduced apixaban and rivaroxaban dosing regimens are recommended when dronedarone is co-administered to patients with AF.

Protection of kidney function and tissue integrity by pharmacologic use of natriuretic peptides and neprilysin inhibitors

With variable potencies atrial-, brain-type and c-type natriuretic peptides (NP)s, best documented for ANP and its analogues, promote sodium and water excretion, renal blood flow, lipolysis, lower blood pressure, and suppress renin and aldosterone secretion through interaction predominantly with cGMP-coupled NPR-A receptor. Infusion of especially ANP and its analogues up to 50 ng/kg/min in patients with high risk of acute kidney injury (cardiac vascular bypass surgery, intraabdominal surgery, direct kidney surgery) protects kidney function (GFR, plasma flow, medullary flow, albuminuria, renal replacement therapy, tissue injury) at short term and also long term and likely additively with the diuretic furosemide. This documents a pharmacologic potential for the pathway. Neprilysin (NEP, neutral endopeptidase) degrades NPs, in particular ANP, and angiotensin II. The drug LCZ696, a mixture of the neprilysin inhibitor sacubitril and the ANGII-AT1 receptor blocker valsartan, was FDA approved in 2015 and marketed as Entresto®. In preclinical studies of kidney injury, LCZ696 and NPs lowered plasma creatinine, countered hypoxia and oxidative stress, suppressed proinflammatory cytokines, and inhibited fibrosis. Few randomized clinical studies exist and were designed with primary cardiac outcomes. The studies showed that LCZ696/entresto stabilized and improved glomerular filtration rate in patients with chronic kidney disease. LCZ696 is safe to use concerning kidney function and stabilizes or increases GFR. In perspective, combined AT1 and neprilysin inhibition is a promising approach for long-term renal protection in addition to AT1 receptor blockers in acute kidney injury and chronic kidney disease.

Angiotensin-neprilysin inhibition confers renoprotection in rats with diabetes and hypertension by limiting podocyte injury

OBJECTIVES

Combined angiotensin receptor--neprilysin inhibition (ARNI) reduces glomerulosclerosis better than single angiotensin receptor blockade (ARB) in diabetic, hypertensive rats. The renoprotective mechanism remains unknown, but may depend on superior blood pressure control, improved renal hemodynamics, suppressed renal inflammation or prevention of podocyte loss.

METHODS

To address this, TGR(mREN2)27 rats (a model of angiotensin II-dependent hypertension) were made diabetic for 12 weeks and treated with vehicle (n = 10), valsartan (ARB; n = 7) or sacubitril/valsartan (ARNI; n = 8) for the final 3 weeks. Arterial pressure was measured via radiotelemetry.

RESULTS

Sacubitril/valsartan lowered mean arterial pressure by -50 ± 4 mmHg and valsartan by -43 ± 4 mmHg (P = 0.3). Both treatments lowered albuminuria, but only sacubitril/valsartan maintained high urinary atrial natriuretic peptide, improved glycemic control and protected podocyte integrity, reflected by increased nephrin expression and suppression of transient receptor potential canonical 6 and regulator of calcineurin 1. This resulted in markedly reduced glomerulosclerosis (P < 0.05 vs. control and valsartan). Despite higher effective renal plasma flow and glomerular filtration rates, sacubitril/valsartan did neither improve filtration fraction nor renal immune cell infiltration.

CONCLUSION

Sacubitril/valsartan offers drug-class-specific renoprotection in a preclinical model of diabetes and hypertension. Renoprotection is unrelated to antihypertensive efficacy, renal hemodynamics or inflammation, but may be related to protective effects of natriuretic peptides on podocyte integrity.

Applications of Physiologically Based Pharmacokinetic Modeling of Rivaroxaban-Renal and Hepatic Impairment and Drug-Drug Interaction Potential

The non–vitamin K antagonist oral anticoagulant rivaroxaban is used in several thromboembolic disorders. Rivaroxaban is eliminated via both metabolic degradation and renal elimination as unchanged drug. Therefore, renal and hepatic impairment may reduce rivaroxaban clearance, and medications inhibiting these clearance pathways could lead to drug‐drug interactions. This physiologically based pharmacokinetic (PBPK) study investigated the pharmacokinetic behavior of rivaroxaban in clinical situations where drug clearance is impaired. A PBPK model was developed using mass balance and bioavailability data from adults and qualified using clinically observed data. Renal and hepatic impairment were simulated by adjusting disease‐specific parameters, and concomitant drug use was simulated by varying enzyme activity in virtual populations (n = 1000) and compared with pharmacokinetic predictions in virtual healthy populations and clinical observations. Rivaroxaban doses of 10 mg or 20 mg were used. Mild to moderate renal impairment had a minor effect on area under the concentration‐time curve and maximum plasma concentration of rivaroxaban, whereas severe renal impairment caused a more pronounced increase in these parameters vs normal renal function. Area under the concentration‐time curve and maximum plasma concentration increased with severity of hepatic impairment. These effects were smaller in the simulations compared with clinical observations. AUC and C_max increased with the strength of cytochrome P450 3A4 and P‐glycoprotein inhibitors in simulations and clinical observations. This PBPK model can be useful for estimating the effects of impaired drug clearance on rivaroxaban pharmacokinetics. Identifying other factors that affect the pharmacokinetics of rivaroxaban could facilitate the development of models that approximate real‐world pharmacokinetics more accurately.

How to reduce the incidence of contrast induced acute kidney injury after cardiac invasive procedures, a review and practical recommendations

BACKGROUND

Contrast induced acute kidney injury is an important complication after cardiac (invasive) procedures and is associated with substantial morbidity and mortality. The aim of the current article is to provide a comprehensive overview of the current knowledge regarding contrast induced acute kidney injury.

METHODS

Current literature was reviewed and relevant articles were selected. Articles were identified through MEDLINE and Pubmed selecting articles, limited between 1980 and 2010.

RESULTS

The pathophysiological process resulting in contrast induced acute kidney injury is not completely understood, nevertheless several mechanisms involved have been proposed. However, the risk factors for contrast induced acute kidney injury and its timing are well known, making it amenable for preventive strategies. In the past decade various preventive strategies have been investigated with different results.

CONCLUSIONS

Currently, only adequate hydration, with saline, is uniformly accepted as a beneficial prophylactic strategy. Furthermore promising results have also been reported for several other prophylactic strategies. These results, however, need to be confirmed in future trials.

Renal protective effects and the prevention of contrast-induced nephropathy by atrial natriuretic peptide

OBJECTIVES

This study was designed to examine the protective effects of atrial natriuretic peptide (ANP) on contrast-induced nephropathy (CIN) after coronary angiography.

BACKGROUND

Contrast-induced nephropathy is a common complication after angiography. Some studies have shown that ANP has renal protective effects, but the beneficial effects for CIN prevention remain to be clearly shown.

METHODS

In a prospective, controlled, randomized trial in 254 consecutive patients with serum creatinine concentrations of > or =1.3 mg/dl, patients received either ANP (0.042 microg/kg/min; ANP group, n = 126) or Ringer solution alone (control group, n = 128). Treatment of either type was initiated 4 to 6 h before angiography and continued for 48 h.

RESULTS

There were no significant differences in age, sex, diabetes mellitus, or baseline serum creatinine level between the 2 groups. The prevalence of CIN, defined as a 25% increase in creatinine or an increase in creatinine of > or =0.5 mg/dl from baseline within 48 h, was significantly lower in the ANP group than in the control group (3.2% vs. 11.7%, respectively; p = 0.015). Multivariate analysis revealed that the use of >155 ml of contrast medium (odds ratio: 6.89; p < 0.001) and ANP treatment (odds ratio: 0.24; p = 0.016) were significant predictors of developing CIN. The incidence of an increase in creatinine of > or =25% or of > or =0.5 mg/dl from baseline at 1 month was also significantly lower in the ANP group than in the control group (p = 0.006).

CONCLUSIONS

In addition to hydration, ANP administration is effective in the prevention of CIN in patients with chronic renal failure, and the effect was maintained for 1 month.

Association between atrial natriuretic peptide and cyclic GMP in hypertension and in chronic renal failure

This study has examined the association between circulating atrial natriuretic peptide (ANP), plasma cyclic GMP and urinary cyclic GMP in relation to hypertension and reduced renal function in 30 normotensives, in 30 patients with essential hypertension and in 22 patients with stable dialysis-independent chronic renal failure (CRF). Plasma ANP was significantly raised (about two-three-fold) in the CRF group compared with the hypertensive and normal groups; plasma cyclic GMP was also significantly raised in the CRF group (median group values: 4.6, 5.8 and 11.0 pmol/ml, respectively, for the normal, hypertensive and CRF groups). There were no significant differences in urinary cyclic GMP between the normotensives and hypertensives but urinary cyclic GMP was significantly reduced in the patients with CRF (median group values: 407.1, 450.9 and 247.8 pmol/min for the normal, hypertensive and CRF groups, respectively, P < 0.001). In the subjects with CRF, the clearance of cyclic GMP was reduced in proportion to the clearance of creatinine, but there was no significant difference in the fractional excretion of cyclic GMP (median group values: 78.1% in the normal group, 78.9% in the hypertensive group and 70.2% in the CRF group). In all groups, there was no association between circulating ANP and urinary cyclic GMP: By contrast, there was a positive association between plasma ANP and plasma cyclic GMP (r = 0.39 P < 0.001) that was independent of blood pressure or renal function. These results demonstrate that while a substantial amount of urinary cyclic GMP originates from the glomerular filtrate, to some extent, raised plasma ANP also contributes to the circulating levels of cyclic GMP. However, plasma cyclic GMP cannot be taken as a direct substitute for plasma ANP.

Insulin-like growth factor-I treatment to enhance renal function in advanced chronic renal failure

Because of the potential for IGF-I to enhance renal function in advanced chronic renal failure (CRF) we set out to determine whether IGF-I can induce a sustained increase in renal function in patients with near end-stage renal failure. To this end we first examined the impact of CRF on the pharmacokinetics of IGF-I and then we examined the effect of prolonged IGF-I treatment on the renal function of patients with an average GFR of 17 mL/min/1.73 m2. Interestingly the metabolic clearance rate of IGF-I in CRF subjects was similar to that in normal subjects even though the total serum IGF-I levels rose to higher maximum levels. This increase was due to a reduced volume of IGF-I distribution, a consequence of the elevated serum IGF binding proteins in CRF subjects. Treatment with IGF-I (60 mg/kg twice daily sc) for 31 days resulted in a 14% and 18% increase in the inulin and PAH clearances respectively (n = 6 patients). These parameters returned to basal levels on stopping treatment. Serum immunoreactive IGFBP-3 levels fell and IGFBP-2 and -3 levels rose during IGF-I therapy. Adverse effects were mild, of short duration and easily manageable. Thus IGF-I pharmacokinetics are largely unchanged in CRF and the administration of IGF-I produces a modest improvement in the GFR. These results appear to justify more extensive examination of the therapeutic role of IGF-I in the treatment of CRF.

Early experience with extended use of insulin-like growth factor-1 in advanced chronic renal failure

Short-term high-dose insulin-like growth factor-1 (IGF-1) therapy has been shown to enhance glomerular filtration rate (GFR) in end-stage chronic renal failure (CRF), but the efficacy and safety of prolonged therapy is unproven. To determine if prolonged therapy with IGF-1 can enhance renal function in advanced CRF, eight patients were entered into a study to receive one month of IGF-1 treatment, 60 micrograms/kg subcutaneously b.i.d. Six patients completed the study and two dropped out for reasons considered to be unrelated to the IGF-I treatment. Baseline inulin and PAH clearances averaged 17 +/- 3 and 66 +/- 14 ml/min/1.73 m2, respectively, in the subjects who completed the study. With treatment there was a modest 14% increase in the average GFR which approached statistical significance (P = 0.051). After stopping treatment the clearance values returned to basal values. The PAH clearance showed a similar trend. There were no significant changes in BUN, serum creatinine or electrolyte levels. On the other hand there were marked changes in the serum IGF binding protein (IGFBP) profile. Serum IGFBP-3 levels fell while IGFBP-1 and -2 levels rose during treatment, changes that likely affect the bioavailability of IGF-I. Thus, in this small series of patients IGF-1 treatment produced significant changes in the serum IGFBP profile and a modest upward trend in the GFR.

The pathophysiology of ureteral obstruction

Ureteral obstruction can have a variety of causes intrinsic or extrinsic to the kidney. The effects of obstruction are examined from the perspectives of duration, severity, totality, and the presence of complicating factors. There is a difference in the postobstructive pathophysiology depending on whether one or both ureters were obstructed. Atrial natriuretic peptide may be important in postobstructive diuresis, and preliminary evidence suggests a role for it as protection against nephron ischemia in acute obstruction. The potential for recovery of renal function after relief of obstruction depends on the duration and degree of obstruction, the condition of the contralateral kidney, and the presence or absence of infection. Ability to acidify the urine to pH < 6.0 preoperatively may be a good predictor of the recovery potential of an obstructed kidney. Urine concentrations of lysosomal enzymes such as N-acetylglucosaminidase also may be useful for this purpose, as may measurement of creatinine clearance in urine obtained from a nephrostomy tube.