The angiotensin II AT1 receptor antagonist candesartan at antihypertensive plasma concentrations reduces damage induced by ischemia-reperfusion

Enhancing the Oral Bioavailability of Candesartan Cilexetil Loaded Nanostructured Lipid Carriers: In Vitro Characterization and Absorption in Rats after Oral Administration

Candesartan Cilexetil (CC) is a prodrug widely used in the treatment of hypertension and heart failure, but it has some limitations, such as very poor aqueous solubility, high affinity to P-glycoprotein efflux mechanism, and hepatic first-pass metabolism. Therefore, it has very low oral bioavailability. In this study, glyceryl monostearate (GMS) and Capryol™ 90 were selected as solid and liquid lipids, respectively, to develop CC-NLC (nanostructured lipid carrier). CC was successfully encapsulated into NLP (CC-NLC) to enhance its oral bioavailability. CC-NLC was formulated using a hot homogenization-ultrasonication technique, and the physicochemical properties were characterized. The developed CC-NLC formulation was showed in nanometric size (121.6 ± 6.2 nm) with high encapsulation efficiency (96.23 ± 3.14%). Furthermore, it appeared almost spherical in morphology under a transmission electron microscope. The surgical experiment of the designed CC-NLC for absorption from the gastrointestinal tract revealed that CC-NLC absorption in the stomach was only 15.26% of that in the intestine. Otherwise, cellular uptake study exhibit that CC-NLCs should be internalized through the enterocytes after that transported through the systemic circulation. The pharmacokinetic results indicated that the oral bioavailability of CC was remarkably improved above 2-fold after encapsulation into nanostructured lipid carriers. These results ensured that nanostructured lipid carriers have a highly beneficial effect on improving the oral bioavailability of poorly water-soluble drugs, such as CC.

AT2 receptor and apoptosis during AT1 receptor blockade in reperfused myocardial infarction in the rat

We assessed whether upregulation of the angiotensin II (AngII) type 2 receptor (AT2R) during AngII type 1 receptor (AT1R) blockade might induce apoptosis in the in vivo rat model of reperfused myocardial infarction (RMI) and whether addition of an AT2R blocker abolishes that effect. We measured in vivo hemodynamics and left ventricular (LV) systolic and diastolic function (echocardiograms/Doppler), and ex vivo infarct size (triphenyl tetrazolium chloride), regional AT1R and AT2R proteins (immunoblots), and apoptosis (TUNEL assay and DNA ladder) after regional anterior RMI (60 min ischemia, 90 min reperfusion) in Sprague-Dawley rats randomized to intravenous AT1R blockade with candesartan (1 mg/kg, n = 9) or saline (controls, n = 14) over 30 min before RMI, and sham (n = 8). We also assessed the effect of AT2R blockade (PD123319, 10 mg/kg i.v.) plus candesartan on infarct size and apoptosis. Compared to controls, candesartan significantly (p < 0.001) limited increases in left atrial pressure, improved positive LV dP/dtmax and negative dP/dtmin, normalized LV ejection fraction, improved LV diastolic function, limited infarct expansion, decreased infarct size and apoptosis, and increased AT2R protein (not AT1R) in the reperfused ischemic zone. There were no changes in sham hearts. PD123319 abolished the candesartan-induced decrease in infarct size and LV dysfunction but not the decrease in apoptosis. Thus, during AT1R blockade in the in vivo rat model of RMI, regional AT2R upregulation contributes to the beneficial effect on infarct size and LV dysfunction but not on apoptosis, suggesting that the apoptosis is AT1R not AT2R-mediated.

Candesartan cilexetil plus hydrochlorothiazide combination: a review of its use in hypertension

The combination of candesartan cilexetil [an angiotensin II type 1 (AT(1)) receptor antagonist] plus hydrochlorothiazide (a thiazide diuretic), has been used in the treatment of patients with hypertension. The blood pressure (BP) lowering effect of various doses of this combination, administered orally once a day for 4 to 52 weeks, has been demonstrated in clinical trials. These studies showed that combinations of candesartan cilexetil 4 to 16 mg with hydrochlorothiazide 12.5 or 25 mg induced significant reductions reductions in systolic (S) BP and diastolic (D) BP from baseline in patients with mild to severe hypertension. Data from clinical trials indicated that reductions in BP induced by candesartan cilexetil 4 to 32 mg/hydrochlorothiazide 12.5 mg combinations were significantly greater than those observed after monotherapy with either drug. Treatment for 8 weeks with candesartan cilexetil 16 mg/hydrochlorothiazide 12.5 mg or candesartan cilexetil 16 mg induced SBP/DBP reductions of 12.0/7.5 mm Hg and 7.5/5.5mm Hg, respectively (p < 0.05 both comparisons). Moreover, data from a randomised, double-blind, placebo-controlled, dose-finding study in 1038 patients with mild to moderate hypertension showed that the greatest reductions in SBP/DBP were achieved by candesartan cilexetil 16 mg/hydrochlorothiazide 12.5 mg. Significant differences in BP reduction in favour of the combination were observed when hypertensive patients were given candesartan cilexetil 4 or 8 mg/hydrochlorothiazide 12.5 mg or hydrochlorothiazide monotherapy for 8 weeks. Additionally, greater efficacy of the combination compared to monotherapy with either drug was demonstrated by response rates to treatment. Moreover, a fixed combination of candesartan cilexetil 16 mg/hydrochlorothiazide 12.5 mg demonstrated a greater antihypertensive effect than losartan 50 mg/hydrochlorothiazide 12.5 mg in two clinical trials. Candesartan cilexetil 8 mg/hydrochlorothiazide 12.5 mg showed a similar antihypertensive effect compared with that of combined lisinopril 10 mg/hydrochlorothiazide 12.5 mg. Candesartan cilexetil/hydrochlorothiazide combination was well tolerated in patients with hypertension. Combined data from placebo-controlled trials showed that most adverse events were uncommon and not serious. Patients receiving combination therapy exhibited, among other adverse events, headache (3.2 vs 5.5% for candesartan cilexetil/hydrochlorothiazide and placebo, respectively), back pain (3.0 vs 2.4%), dizziness (2.6 vs 1.2%) and respiratory infection (2.5 vs 1.4%). Moreover, 3.3 and 2.7% of patients receiving candesartan cilexetil/hydrochlorothiazide or placebo, respectively, discontinued treatment because of adverse events.

CONCLUSION

The combination of candesartan cilexetil and hydrochlorothiazide (AT(1)-receptor antagonist and thiazide diuretic, respectively) is an effective treatment for patients with hypertension. Data from randomised, double-blind, placebo-controlled clinical trials showed that this combination is significantly more efficacious than either agent alone. Moreover, the combination of these two agents showed an excellent adverse event profile. Current data support the use of this combination as an alternative when monotherapy with either agent is not effective, and there are no compelling or specific indications for other drugs. However, data from large clinical trials, evaluating morbidity and mortality outcomes, are needed to determine the precise role of candesartan cilexetil/hydrochlorothiazide combination in the treatment of patients with hypertension.

Effects of angiotensin II type 1 receptor antagonist (candesartan) in preventing fatal ventricular arrhythmias in dogs during acute myocardial ischemia and reperfusion

Fatal arrhythmias may be prevented by long-term oral administration of angiotensin-converting enzyme (ACE) inhibitors or angiotensin II type 1 (AT 1 ) receptor antagonists. However, there have been no studies evaluating the electrophysiologic changes that occur with the acute administration of AT 1 receptor antagonists during acute myocardial ischemia and reperfusion. This study aimed to evaluate the ability of candesartan to prevent fatal arrhythmias during acute myocardial ischemia and reperfusion. The left anterior descending (LAD) coronary artery was ligated for 10 min and then reperfused for 10 min in 45 adult mongrel dogs. Candesartan (1 mg/kg) or saline was administered intravenously 10 min before ligation of the LAD coronary artery (candesartan group [n = 20] and control group [n = 25], respectively). Changes in ventricular effective refractory period (ERP) and intramyocardial conduction time (ICT) in the risk area were compared during LAD occlusion and reperfusion. Ischemia-induced shortening of ERP was inhibited in the candesartan group compared with the control. There was a 4.7 +/- 5.8% increase in ERP in the candesartan group, compared with a 11.5 +/- 6.3% shortening in the control group (p < 0.01). Prolongation of ICT was inhibited in the candesartan group compared with the control group during both ischemia and reperfusion (maximal prolongation of ICT: 0.1 +/- 3.0% vs. 37.7 +/- 9.6%, respectively; p < 0.01). Incidence of ventricular fibrillation was lower in the candesartan group than in the control group (25% [5/20] vs. 72% [18/25], respectively; p < 0.01). Candesartan suppresses changes in ERP and ICT during acute myocardial ischemia and reperfusion, suggesting that candesartan can prevent the development of fatal arrhythmias.

Enhanced reduction of myocardial infarct size by combined ACE inhibition and AT(1)-receptor antagonism

The effects of the angiotensin-converting-enzyme inhibitor (ACEI) ramiprilat, the angiotensin II type 1 receptor antagonist (AT(1)A) candesartan, and the combination of both drugs on infarct size (IS) resulting from regional myocardial ischaemia were studied in pigs. Both ACEI and AT(1)A reduce myocardial IS by a bradykinin-mediated process. It is unclear, however, whether the combination of ACEI and AT(1)A produces a more pronounced IS reduction than each of these drugs alone. Forty-six enflurane-anaesthetized pigs underwent 90 min low-flow ischaemia and 120 min reperfusion. Systemic haemodynamics (micromanometer), subendocardial blood flow (ENDO, microspheres) and IS (TTC-staining) were determined. The decreases in left ventricular peak pressure by ACEI (by 9+/-2 (s.e. mean) mmHg), AT(1)A (by 11+/-2 mmHg) or their combination (by 18+/-3 mmHg, P<0.05 vs ACEI and AT(1)A, respectively) were readjusted by aortic constriction prior to ischaemia. With placebo (n=10), IS averaged 20.0+/-3.3% of the area at risk. IS was reduced to 9.8+/-2.6% with ramiprilat (n=10) and 10.6+/-3.1% with candesartan (n=10). Combined ramiprilat and candesartan (n=10) reduced IS to 6.7+/-2.1%. Blockade of the bradykinin-B(2)-receptor with icatibant prior to ACEI and AT(1)A completely abolished the reduction of IS (n=6, 22.8+/-6.1%). The relationship between IS and ischaemic ENDO with placebo was shifted downwards by each ACEI and AT(1)A and further shifted downwards with their combination (P<0.05 vs all groups); icatibant again abolished such downward shift. The combination of ACEI and AT(1)A enhances the reduction of IS following ischaemia/reperfusion compared to a monotherapy by either drug alone; this effect is mediated by bradykinin.