Paradoxical release of nitric oxide by an L-type calcium channel antagonist, the R+ enantiomer of amlodipine

Lipid Emulsion Inhibits Amlodipine-Induced Nitric Oxide-Mediated Vasodilation in Isolated Rat Aorta

This study aimed to examine the effect of lipid emulsion on the vasodilation induced by a toxic dose of amlodipine in isolated rat aorta and elucidate its mechanism, with a particular focus on nitric oxide. The effects of endothelial denudation, NW-nitro-L-arginvine methyl ester (L-NAME), methylene blue, lipid emulsion, and linolenic acid on the amlodipine-induced vasodilation and amlodipine-induced cyclic guanosine monophosphate (cGMP) production were examined. Furthermore, the effects of lipid emulsion, amlodipine, and PP2, either alone or combined, on endothelial nitric oxide synthase (eNOS), caveolin-1, and Src-kinase phosphorylation were examined. Amlodipine-induced vasodilation was higher in endothelium-intact aorta than in endothelium-denuded aorta. L-NAME, methylene blue, lipid emulsion, and linolenic acid inhibited amlodipine-induced vasodilation and amlodipine-induced cGMP production in the endothelium-intact aorta. Lipid emulsion reversed the increased stimulatory eNOS (Ser1177) phosphorylation and decreased inhibitory eNOS (Thr495) phosphorylation induced via amlodipine. PP2 inhibited stimulatory eNOS, caveolin-1, and Src-kinase phosphorylation induced via amlodipine. Lipid emulsion inhibited amlodipine-induced endothelial intracellular calcium increase. These results suggest that lipid emulsion attenuated the vasodilation induced via amlodipine through inhibiting nitric oxide release in isolated rat aorta, which seems to be mediated via reversal of stimulatory eNOS (Ser1177) phosphorylation and inhibitory eNOS (Thr495) dephosphorylation, which are also induced via amlodipine.

Effect of a fixed-dose combination of Telmisartan/S-amlodipine on circadian blood pressure compared with Telmisartan monotherapy: TENUVA-BP study

Background

This study evaluated the circadian efficacy of a telmisartan 40 mg/S-amlodipine 2.5 mg fixed-dose combination (Telmisartan40/S-Amlodipine2.5) compared to telmisartan 80 mg (Telmisartan80) in patients with essential hypertension who did not respond to 2–4 weeks’ treatment with telmisartan 40 mg.

Methods

Eligible patients with essential hypertension (clinic mean sitting systolic blood pressure [MSSBP] ≥140 mmHg, or ≥ 130 mmHg in those with diabetes mellitus or chronic kidney disease) were randomly assigned to Telmisartan40/S-Amlodipine2.5 or Telmisartan80 for 8 weeks. All patients underwent ambulatory BP monitoring (ABPM) at baseline and 8 weeks later. Primary endpoints were changes in mean 24-h SBP and DBP on 24-h ABPM from baseline after 8 weeks. Secondary endpoints were changes in daytime, nighttime, and morning SBP and DBP, and clinic MSSBP and MSDBP.

Results

A total of 316 Korean patients were enrolled, 217 patients were randomized to treatment, and 192 patients completed the study. Compared to Telmisartan80, Telmisartan40/S-Amlodipine2.5 showed significantly better reductions in 24-h mean SBP and DBP after 8 weeks. Telmisartan40/S-Amlodipine2.5 also significantly reduced secondary endpoints compared to Telmisartan80. Among 15 adverse events (7 [Telmisartan40/S-Amlodipine2.5] and 8 [Telmisartan80]), there were five adverse drug reactions; 14 events were mild, and none were identified with significant between-group differences.

Conclusions

Telmisartan40/S-Amlodipine2.5 was tolerable and more effective than Telmisartan80 in lowering 24-h mean ambulatory BP in patients with essential hypertension not responding adequately to Telmisartan40. Our findings support the fact that the combination of S-amlodipine with telmisartan is more appropriate than increasing the dose of telmisartan monotherapy.

Trial registration

ClinicalTrials.gov, NCT02231788. Registered 4 September 2014.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40885-021-00184-0.

Effects of different enantiomers of amlodipine on lipid profiles and vasomotor factors in atherosclerotic rabbits

This research aimed to describe the functions of vascular endothelial cells (VECs) in protecting target organs and the anti-atherosclerotic effects of different enantiomers of amlodipine on a rabbit model of atherosclerosis. Thirty male New Zealand white rabbits were randomly allocated to four groups (nA = 9, nB = 7, nC = 7, and nD = 7 rabbits): rabbits in group-A (control group) were fed a high-fat diet, group-B rabbits were fed a high-fat diet plus 2.5 mg/kg/day S-amlodipine, group-C rabbits were fed a high-fat diet plus 2.5 mg/kg/day R-amlodipine, and group-D rabbits were fed a high-fat diet plus 5 mg/kg/day racemic amlodipine. Different enantiomers of amlodipine did not influence lipid profiles and serum level of eNOS in the rabbit atherosclerosis model but decreased ET-1 expression to some extent. The serum NO and iNOS levels in the drug intervention groups were significantly reduced. No significant differences in the rabbits' body weights were observed. At the 4th and 8th weeks, the serum lipid profiles significantly increased in high cholesterol diet groups. The serum ET-1 level was significantly increased in each group of rabbits at the 8th week. Both S-amlodipine and R-amlodipine may protect the endothelium by reducing the serum ET-1 level, downregulating iNOS expression.

Angiotensin axis antagonists increase the incidence of haemodynamic instability in dihydropyridine calcium channel blocker poisoning

CONTEXT

Amlodipine, a dihydropyridine calcium channel blocker (CCB), is the leading cause of cardiovascular drug-related overdose deaths in the USA. In contrast, angiotensin-II receptor blockers (ARBs) and angiotensin converting enzyme inhibitors (ACEIs) cause minimal toxicity in overdose. ACEIs/ARBs are often combined with dihydropyridines in hypertension treatment. Co-ingested ARBs/ACEIs may significantly contribute to the toxicity of dihydropyridine, but this has not been investigated.

OBJECTIVE

To investigate the clinical outcomes from dihydropyridine overdoses with ARBs/ACEIs versus dihydropyridine overdoses alone.

METHODS

This was a retrospective study of patients reported to the New South Wales Poisons Information Centre (NSW PIC) and 3 toxicology units (Jan 2016 to Jun 2019) in Australia. Patients >14 years who took an overdose of dihydropyridines (amlodipine, felodipine, lercanidipine, nifedipine) were included. Concurrent overdoses with non-dihydropyridine CCBs, alpha-blockers and beta-blockers were excluded. Patient demographics, drugs exposure details, serial vital signs, treatments and outcome were collected.

RESULTS

There were 100 patients. 68 took mixed overdoses of dihydropyridines with ARBs/ACEIs and 32 took single overdoses of dihydropyridines without ARBs/ACEIs. The mixed group had lower median nadir mean arterial pressures (62 vs 75 mmHg, p < 0.001), more frequently had hypotension (OR 4.5, 95%CI: 1.7-11.9) or bradycardia (OR 8.8, 95%CI: 1.1-70). Multivariable analysis indicated the mixed overdoses had an 11.5 mmHg (95%CI: 4.9-18.1) lower minimum systolic blood pressure (SBP) compared with the single group; other factors associated with a lower minimum SBP were higher doses [2.3 mmHg (95%CI: 1.1-3.5) lower per 10 defined daily doses] and younger age [2.2 mmHg (95%CI: 0.3-4.2) higher per decade]. A larger proportion of the mixed ingestion group received intravenous fluids (OR 5.7, 95%CI: 1.8-18.6) and antidotes and/or vasopressors (OR 2.9, 95%CI: 1.004-8.6).

CONCLUSION

Combined overdoses of dihydropyridines with ARBs/ACEIs caused more significant hypotension and required more haemodynamic support than overdoses of dihydropyridines alone.

Amlodipine Improves Vessel Function and Remodeling in the Lewis Polycystic Kidney Rat Mesenteric Artery

BACKGROUND

Hypertension is a common comorbidity associated with chronic kidney disease (CKD). Treatment in these patients often involves L-type Ca2+ channel (LTCC) blockers. The effect of chronic LTCC-blockade treatment on resistance vasculature was investigated in a genetic hypertensive rat model of CKD, the Lewis Polycystic Kidney (LPK) rat.

METHODS

Mixed-sex LPK and Lewis control rats (total n = 38) were allocated to treated (amlodipine 20 mg/kg/day p.o. from 4 to 18 weeks) and vehicle groups. Following systolic blood pressure and renal function assessment, animals were euthanized and mesenteric vasculature was collected for functional and structural assessment using pressure myography and histology.

RESULTS

Amlodipine treatment reduced LPK rat blood pressure (untreated vs. treated: 185 ± 5 vs. 165 ± 9 mm Hg; P = 0.019), reduced plasma creatinine (untreated vs. treated: 197 ± 17 vs. 140 ± 16 µmol/l; P = 0.002), and improved some vascular structural parameters (internal and external diameters and wall-lumen ratios); however wall thickness was still increased in LPK relative to Lewis despite treatment (Lewis vs. LPK: 31 ± 2 vs. 41 ± 2 µm, P = 0.047). Treatment improved LPK rats' endothelium dysfunction, and nitric oxide-dependent and endothelium-derived hyperpolarization vasorelaxation components, and downregulated prostanoid contributions. LTCC blockade had no effect on biomechanical properties of compliance and intrinsic stiffness, nor artery wall composition.

CONCLUSIONS

Our results indicate that blockade of LTCCs with amlodipine is effective in improving, to a certain extent, detrimental structural and functional vascular features of resistance arteries in CKD.

Enantioseparation of racemic amlodipine using immobilized ionic liquid by solid-phase extraction

In this paper, a novel l-glutamate based immobilized chiral ionic liquid (SBA-IL (Glu)) was prepared by chemical bonding method and applied as a solid sorbent for chiral separation of amlodipine. The performance of SBA-IL (Glu) was investigated for the absorption of (S)-amlodipine and separation of amlodipine enantiomer. The static experiment showed that equilibrium adsorption was achieved within 80 minutes, and the saturation adsorptions capacity was 12 mg/g. The complex was then packed in a glass chromatographic column for the separation of amlodipine and the enantiomeric excess (%ee) of (S)-amlodipine reached 24.67%. The immobilized ionic liquids exhibit good reusability, and the separation efficiency remains 18.24% after reused five times, which allows potential scale-up for the chiral separation of amlodipine.

S-amlodipine-bisoprolol combination therapy caused elevated transaminases and triglyceride levels in healthy Chinese subjects: a randomized controlled, open-label, multiple-dose pharmacokinetic interaction study

Introduction: S-amlodipine is main anti-hypertensive active enantiomer of amlodipine. Bisoprolol is a β-blocker particularly suitable for hypertensive patients with sinus tachycardia. We evaluated the pharmacokinetic interaction between S-amlodipine and bisoprolol in healthy Chinese subjects. Areas covered: Thirty-two subjects were randomly divided into two equal groups. Subjects in group A were administered S-amlodipine 5 mg for 10 days followed by S-amlodipine 5 mg plus bisoprolol 5 mg for 7 days. Subjects in group B were administered bisoprolol 5 mg for 7 days, followed by S-amlodipine 5 mg plus bisoprolol 5 mg for 10 days. Blood samples were collected for evaluation of pharmacokinetic interaction. Tolerability was evaluated by interview, vital signs, 12-lead ECGs, physical examination, and clinical laboratory tests. Expert opinion: The geometric mean ratio (90% CI) for amlodipine AUC_τ,ss and C_ss-max during the monotherapy and combination therapy periods were 1.0389 (0.9879, 1.0926) and 1.0213 (0.9556, 1.0915). For bisoprolol, it was 1.0193 (0.9834, 1.0566) and 0.9989 (0.9133, 1.0925). Most adverse events were mild-moderate. There was high incidence of elevated alanine aminotransferase, aspartate aminotransferase, and triglyceride.This study found no pharmacokinetic interaction between S-amlodipine and bisoprolol. Alanine aminotransferase, aspartate aminotransferase, and triglycerides should be closely monitored.

Comparative effectiveness of methylene blue versus intravenous lipid emulsion in a rodent model of amlodipine toxicity

Context: Calcium channel blocker (CCB) poisonings are the leading cause of death from cardiovascular medication-related overdoses. Current treatments (calcium salts, vasopressors, inotropes) are often insufficient. Intravenous lipid emulsion (ILE) and methylene blue (MB) show promise in treating CCB overdoses unresponsive to conventional therapy. Objective: To compare the effectiveness of MB versus ILE in a rodent model of amlodipine (AML) poisoning with survival as the primary outcome and hemodynamic parameters as secondary outcomes. Materials and methods: Sixty-four adult male albino rats were anesthetized and cannulated for non-invasive hemodynamic measurement. Rats received amlodipine intraperitoneally (42 mg/kg). We then divided the rats into four groups: AML only without antidote, AML followed by ILE (24.8 mL/kg over 10 min), AML followed by normal saline (an equivalent volume of ILE), and AML followed by IV MB (2 mg/kg over 5 min). They received study treatments at 5, 30, and 60 minutes from the start of the protocol and with observation for 2 hours. Results: Survival time in ILE group was greater than in the control and NS groups. Differences between ILE and MB and between MB and NS were not significant. Hemodynamic parameters significantly increased in ILE group compared to the MB group at the 30, 60 and 120 min assessments but not after induction of AML poisoning and at 5 min assessment. Conclusions: Survival was greatest in rats treated with ILE. Both MB and NS had little effect on survival when compared to control animals. Both ILE and MB improved hemodynamics.

Validated LC-MS/MS method for the determination of amlodipine enantiomers in rat plasma and its application to a stereoselective pharmacokinetic study

A rapid and sensitive method was established to determine amlodipine enantiomers using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Stereoselective separation was performed on CHIRALCEL OZ-RH column (150 mm × 4.6 mm i.d., 5 μm) with acetonitrile-water (10 mM ammonium acetate, 0.5% ammonia solution) (95:5, v/v) at a flow rate of 0.5 mL/min. The substances were detected by mass spectrometer equipped with an electrospray ionization source interface in positive ion mode. Multiple reaction monitoring was selected with the transition of the m/z 409.1 → 238.0 for amlodipine enantiomers and m/z 237.0 → 194.1 for carbamazepine (IS) respectively. Calibration curves were linear at the range of 0.9375-120 ng/mL for both isomers with r > 0.99, while using a lower sample volume (50 μL) compared with previously reported enantiospecific methods The accuracy was at the range of 84.1-119.0% for R-amlodipine, and 87.4-118.2% for S-amlodipine, respectively. The within- and between-run precision (CV%) was within 10% in all cases for both enantiomers. Enantiomers were stable under different conditions, e.g. processed sample, short-term, residue, long-term and freeze/thaw. The LC-MS/MS method was successfully applied in pharmacokinetic study of amlodipine enantiomers in rats. It was observed the concentration of the S- amlodipine was significantly higher than that of the R-amlodipine in racemate-treated group. And there was no significant difference in the pharmacokinetic profiles of the S-amlodipine between the 10 mg/kg racemate- and 5 mg/kg S-amlodipine-treated groups. In addition, it was the first time to find that the main pharmacokinetic parameters (AUC_(0-t), AUC_(0-∞) and C_max) of R-amlodipine were significantly lower in the 5 mg/kg R-amlodipine-treated group compared with the racemate-treated group.

S-Amlodipine: An Isomer with Difference-Time to Shift from Racemic Amlodipine

Calcium channel blockers are among the first-line drugs for treatment of hypertension (HTN). S-amlodipine (S-AM), an S-enantiomer of amlodipine, is available in India and in other countries like China, Korea, Russia, Ukraine, and Nepal. Being clinically researched for nearly two decades, we performed in-depth review of S-AM. This review discusses clinical evidence from total 42 studies (26 randomized controlled trials, 14 observational studies, and 2 meta-analyses) corroborating over 7400 patients treated with S-AM. Efficacy and safety of S-AM in HTN in comparison to racemic amlodipine, used as monotherapy and in combination with other antihypertensives, efficacy in angina, and pleiotropic benefits with S-AM, are discussed in this review.

Comparative pharmacokinetics of a fixed-dose combination vs concomitant administration of telmisartan and S-amlodipine in healthy adult volunteers

Objective

This study compared the pharmacokinetic (PK) and safety profiles of a fixed-dose combination (FDC) formulation of telmisartan and S-amlodipine with those of concomitant administration of the two drugs.

Materials and methods

This was an open-label, randomized, crossover study in healthy male Koreans. All subjects were administered an FDC tablet containing 40 mg telmisartan and 5 mg S-amlodipine and were also coadministered the same dose of both drugs given separately. The crossover study design included a 14-day washout period between the two treatments. Blood samples were collected up to 168 h following drug administration. The plasma concentrations of telmisartan and S-amlodipine were determined by liquid chromatography tandem mass spectrometry. PK parameters and plasma concentration–time curves were compared. Safety was assessed by measuring vital signs, clinical laboratory tests, physical examinations, and patient interviews.

Results

The geometric mean ratios and 90% CIs for the maximum plasma concentration (C_max) and area under the curve from time zero to the last sampling time (AUC_t) were 0.8782 (0.8167–0.9444) and 0.9662 (0.9210–1.0136) for telmisartan and 1.0069 (0.9723–1.0427) and 1.0324 (0.9969–1.0690) for S-amlodipine, respectively. A total of 36 adverse events (AEs) were reported by 23 subjects, but no statistical differences were observed between the two treatments. The most frequently reported AE was a mild-to-moderate headache that was generally self-limiting.

Conclusion

For both telmisartan and S-amlodipine, the C_max and AUC_t 90% CIs were between ln (0.8) and ln (1.25). These results suggest that the FDC formulation is pharmacokinetically bioequivalent and has a similar safety profile to the coadministration of these drugs.

Lipid emulsion alleviates the vasodilation and mean blood pressure decrease induced by a toxic dose of verapamil in isolated rat aortae and an in vivo rat model

This study aimed to examine the effects of lipid emulsion on the vasodilation and cardiovascular depression induced by toxic doses of calcium channel blockers. The effects of lipid emulsion on the vasodilation induced by bepridil, verapamil, nifedipine, and diltiazem were investigated in isolated endothelium-denuded rat aortae. The effect of lipid emulsion on the comparable hemodynamic depression induced by the continuous infusion of a toxic dose of either verapamil or diltiazem was examined in an in vivo rat model. The results showed the following decreasing order for the magnitude of lipid emulsion-mediated inhibition of vasodilation: bepridil, verapamil, nifedipine, and diltiazem. Lipid emulsion (0.5–2%) reversed the vasodilation induced by a toxic dose of verapamil, whereas only a higher concentration (2%) reversed the vasodilation induced by a toxic dose of diltiazem. Pretreatment with lipid emulsion alleviated the systolic and mean blood pressure decreases induced by a toxic dose of verapamil, whereas it had no effect on the decrease induced by diltiazem. Taken together, these results suggest that lipid emulsion alleviates the severe vasodilation and systolic blood pressure decrease induced by a toxic dose of verapamil, and this alleviation appears to be associated with the relatively high lipid solubility of verapamil.

Bioequivalence Study of a New Fixed-dose Combination Tablet Containing S-Amlodipine Nicotinate and Olmesartan Medoxomil in Healthy Korean Male Subjects

PURPOSE

A fixed-dose combination (FDC) pill of amlodipine (relatively old calcium channel blocker as dihydropyridine) and olmesartan (relatively new angiotensin II receptor blocker) is used for hypertension that is not adequately controlled with a single-formulation drug. Because the FDC is a one-pill formulation, and amlodipine and olmesartan have different mechanisms of action, it is expected to improve patients' medication compliance and have an increased blood pressure-lowering efficacy. The purpose of this study was to assess the safety profile and the bioequivalence of two different FDC formulations [amlodipine besylate/olmesartan medoxomil 10/40 mg (reference product) and S-amlodipine nicotinate/olmesartan medoxomil 5/40 mg (test product)].

METHODS

A randomized, open-label, single-dose, 2-treatment, 2-way, and 2-period crossover study, including a 3-week washout period, was performed in 32 healthy Korean male volunteers. To analyze the concentration of S-amlodipine or olmesartan, plasma samples were collected up to 144 hours after the dose for S-amlodipine and 48 hours after the dose for olmesartan. Pharmacokinetic parameters, including the C_max and the area under the curve from time 0 to the last measurable concentration (AUC_0-last) for the time versus concentration plot, were calculated. Analysis of variance for bioequivalence was conducted using C_max and AUC_0-last converted to log scale, and the mean ratios and 90% CIs were determined. Safety data included analysis of adverse events (AEs), vital signs, physical examinations, clinical laboratory test, and 12-lead ECGs.

FINDINGS

Of the 32 enrolled participants, 29 healthy volunteers completed the study. For both S-amlodipine and olmesartan, the main pharmacokinetic parameters were all within the acceptable range for regulatory bioequivalence. The 90% CIs for the geometric mean ratios of C_max and AUC_0-last were 0.8766 to 0.9760 and 0.8288 to 0.9224, respectively, for S-amlodipine and 0.9097 to 1.1229 and 0.8904 to 1.0407, respectively, for olmesartan. Hypotension was the most frequent AE, and it was observed in 4 volunteers with the test product and 7 volunteers with the reference product. Both the test and reference formulations were well tolerated.

IMPLICATIONS

The present study demonstrates that the newly developed FDC product (test drug) and the conventional FDC product (reference drug) have comparable pharmacokinetic characteristics in healthy adult male volunteers. Both the test and reference products indicated good tolerance in this population, and no serious AEs were observed.

Perspectives and challenges of antioxidant therapy for atrial fibrillation

Atrial fibrillation (AF) is the most common sustained arrhythmia associated with significant morbidity and mortality. The mechanisms underlying the pathogenesis of AF are poorly understood, although electrophysiological remodeling has been described as an important initiating step. There is growing evidence that oxidative stress is involved in the pathogenesis of AF. Many known triggers of oxidative stress, such as age, diabetes, smoking, and inflammation, are linked with an increased risk of arrhythmia. Numerous preclinical studies and clinical trials reported the importance of antioxidant therapy in the prevention of AF, using vitamins C and E, polyunsaturated fatty acids, statins, or nitric oxide donors. The aim of our work is to give a current overview and analysis of opportunities, challenges, and benefits of antioxidant therapy in AF.

Formulations of Amlodipine: A Review

Amlodipine (AD) is a calcium channel blocker that is mainly used in the treatment of hypertension and angina. However, latest findings have revealed that its efficacy is not only limited to the treatment of cardiovascular diseases as it has shown to possess antioxidant activity and plays an important role in apoptosis. Therefore, it is also employed in the treatment of cerebrovascular stroke, neurodegenerative diseases, leukemia, breast cancer, and so forth either alone or in combination with other drugs. AD is a photosensitive drug and requires protection from light. A number of workers have tried to formulate various conventional and nonconventional dosage forms of AD. This review highlights all the formulations that have been developed to achieve maximum stability with the desired therapeutic action for the delivery of AD such as fast dissolving tablets, floating tablets, layered tablets, single-pill combinations, capsules, oral and transdermal films, suspensions, emulsions, mucoadhesive microspheres, gels, transdermal patches, and liposomal formulations.

Host-Guest Inclusion Complexes between Amlodipine Enantiomers in the Biphasic Recognition Chiral Extraction System using Tartaric Acid and β-Cyclodextrin Derivatives as Positive Confirmation by using their Enantioselective Extraction

The current work reports an extended theoretical study from our previous experimental work for the enantioselective extraction of amlodipine enantiomers in a biphasic recognition chiral extraction system (BRCES) consisting of hydrophobic D-diisopropyl tartrate dissolved in organic phase (n-decanol) and hydrophilic hydroxypropyl-β-cyclodextrin (HP-β-CD) in aqueous phase (acetate buffer) which preferentially recognize the R-enantiomer and S-enantiomer, respectively. The calculations were simulated using a semi-empirical PM3 method as a part of the Gaussian09 software package and were used to optimize the structures of the hosts, guests, and host-guest complexes in the gas phase without any restrictions. It was found that HP-β-CD has the strongest recognition ability among the three β-CD derivatives studied, namely HP-β-CD, hydroxyethyl-β-cyclodextrin (HE-β-CD), and methylated-β-cyclodextrin (Me-β-CD), due to the large interaction energies (E_comp = −14.3025 kcal/ mol), while D-diisopropyl tartrate has the strongest ability among the four tartaric acid derivatives studied namely; L-diisopropyl tartrate, D-diisopropyl tartrate, L-diethyl tartrate, and D-diethyl tartrate (E_comp = −5.9964 kcal/ mol). The computational calculations for the enantioselective partitioning of amlodipine enantiomers rationalized the reasons for the different behaviors for this extraction. The present theoretical results may be informative to scientists who are devoting themselves to developing models for their experimental parts or for enhancing the hydrophobic drug solubility in drug delivery systems.

1,4-Dihydropyridine Derivatives: Dihydronicotinamide Analogues-Model Compounds Targeting Oxidative Stress

Many 1,4-dihydropyridines (DHPs) possess redox properties. In this review DHPs are surveyed as protectors against oxidative stress (OS) and related disorders, considering the DHPs as specific group of potential antioxidants with bioprotective capacities. They have several peculiarities related to antioxidant activity (AOA). Several commercially available calcium antagonist, 1,4-DHP drugs, their metabolites, and calcium agonists were shown to express AOA. Synthesis, hydrogen donor properties, AOA, and methods and approaches used to reveal biological activities of various groups of 1,4-DHPs are presented. Examples of DHPs antioxidant activities and protective effects of DHPs against OS induced damage in low density lipoproteins (LDL), mitochondria, microsomes, isolated cells, and cell cultures are highlighted. Comparison of the AOA of different DHPs and other antioxidants is also given. According to the data presented, the DHPs might be considered as bellwether among synthetic compounds targeting OS and potential pharmacological model compounds targeting oxidative stress important for medicinal chemistry.

Cyclodextrine screening for the chiral separation of amlodipine enantiomers by capillary electrophoresis

PURPOSE

Amlodipine is a long acting, dihydropyridine type calcium channel blocker frequently used in the treatment of hypertension and coronary insufficiency. The calcium channel blocking activity resides primarily in the S-amlodipine enantiomer, while R-amlodipine is a potent inhibitor of smooth muscle cell migration.

METHODS

In this study capillary electrophoresis was applied for the enantiomeric separation of amlodipine using different native and derivatized; neutral and charged cyclodextrines as chiral selectors. The effects of pH and composition of the background electrolyte, concentration and type of chiral selector, capillary temperature, running voltage and injection parameters have been investigated.

RESULTS

Stereoselective interactions were observed when using α-CD, β-CD, HP-β-CD, RAMEB, CM-β-CD and SBE-β-CD. Optimized separation conditions consisted on a 50 mM phosphate buffer, pH - 3.0, 20 mM RAMEB as chiral selector, + 25 kV applied voltage, 15°C temperature and UV detection at 238 nm. Using the optimized electrophoretic conditions we succeeded the chiral separation of amlodipine enantiomers in approximately 6 minute, the order of migration being R-amlodipine followed by S-amlodipine. The method was successfully applied for the determination of amlodipine enantiomers from commercially available pharmaceuticals. The linearity range, limits of detection and quantification, precision and accuracy were determined and the results obtained confirmed that the method was suitable for this purpose.

CONCLUSION

It can be concluded that the proposed capillary electrophoresis methods can be useful for routine pharmaceutical applications with benefits of its effectivity, simplicity, short analysis time and low consumption of analytes, solvents and chiral selectors.

Efficacy of methylene blue in an experimental model of calcium channel blocker-induced shock

STUDY OBJECTIVE

Calcium channel blocker poisonings account for a substantial number of reported deaths from cardiovascular drugs. Although supportive care is the mainstay of treatment, experimental therapies such as high-dose insulin-euglycemia and lipid emulsion have been studied in animal models and used in humans. In the most severe cases, even aggressive care is inadequate and deaths occur. In both experimental models and clinical cases of vasodilatory shock, methylene blue improves hemodynamic measures. It acts as a nitric oxide scavenger and inhibits guanylate cyclase that is responsible for the production of cyclic guanosine monophosphate (cGMP). Excessive cGMP production is associated with refractory vasodilatory shock in sepsis and anaphylaxis. The aim of this study is to determine the efficacy of methylene blue in an animal model of amlodipine-induced shock.

METHODS

Sprague-Dawley rats were anesthetized, ventilated, and instrumented for continuous blood pressure and pulse rate monitoring. The dose of amlodipine that produced death within 60 minutes was 17 mg/kg per hour (LD50). Rats were divided into 2 groups: amlodipine followed by methylene blue or amlodipine followed by normal saline solution, with 15 rats in each group. Rats received methylene blue at 2 mg/kg during 5 minutes or an equivalent amount of normal saline solution in 3 intervals from the start of the protocol: minutes 5, 30, and 60. The animals were observed for a total of 2 hours after the start of the protocol. Mortality risk and survival time were analyzed with Fisher's exact test and Kaplan-Meier survival analysis with the log rank test.

RESULTS

Overall, 1 of 15 rats (7%) in the saline solution-treated group survived to 120 minutes compared with 5 of 15 (33%) in the methylene blue-treated group (difference -26%; 95% confidence interval [CI] -54% to 0.3%). The median survival time for the normal saline solution group was 42 minutes (95% CI 28.1 to 55.9 minutes); for the methylene blue group, 109 minutes (95% CI 93.9 to 124.1 minutes). Pulse rate and mean arterial pressure (MAP) differences between groups were analyzed until 60 minutes. Pulse rate was significantly higher in the methylene blue-treated group beginning 25 minutes after the start of the amlodipine infusion (95% CI 30 to 113 minutes) that was analyzed until 60 minutes. MAP was significantly higher in the methylene blue-treated group starting 25 minutes after the amlodipine infusion (95% CI 2 to 30 minutes) that was analyzed until 60 minutes.

CONCLUSION

Methylene blue did not result in a significant difference in mortality risk. There was an increased pulse rate, MAP, and median survival time in the methylene blue group.

Tolerability and effectiveness of (S)-amlodipine compared with racemic amlodipine in hypertension: a systematic review and meta-analysis

BACKGROUND

Amlodipine is a calcium channel blocker prescribed for the management of angina and hypertension. As a racemic mixture, amlodipine contains (R)- and (S)-amlodipine isomers, but only (S)-amlodipine as the active moiety possesses therapeutic activity. Based on pharmacologic research, it remains uncertain if (S)-amlodipine alone has similar efficacy and fewer associated adverse events (AEs) compared with the racemic mixtures.

OBJECTIVE

The aim of this systematic review and meta-analysis was to determine the effectiveness and tolerability of (S)-amlodipine compared with that of racemic amlodipine.

METHODS

A systematic literature search was performed using MEDLINE (1966-2009), EMBASE (1966-2009), the Cochrane Central Register of Controlled Trials (issue 3, 2009), the Chinese Biomedical Database (1978-2009), and the China National Knowledge Internet (1980-2009). All randomized controlled trials (RCTs) comparing (S)-amlodipine 2.5 mg and racemic amlodipine 5.0 mg in the treatment of hypertension were included in the review. The outcome measures to be collected were cardiovascular events, systolic blood pressure (SBP), diastolic BP (DBP), and AEs. Quality assessments of clinical trials were conducted using a modified Jadad Scale, with trials being rated as low quality (score 0-3) or high quality (score 4-7). Meta-analysis of the included studies was performed using RevMan software.

RESULTS

Of the 229 references identified, 214 were excluded after screening the titles, abstracts, or full texts. Fifteen RCTs were included, of which 13 were in Chinese and 2 in English. Based on the Jadad Scale score, 3 of the RCTs were classified as high quality (score 5 or 6) and the remaining 12 as low quality (score 1-3). None of the trials evaluated cardiovascular events beyond 40 weeks. Meta-analysis of the 15 trials indicated that (S)-amlodipine was not significantly different from racemic amlodipine in the effect on BP. When only high-quality studies were included, after 4 weeks' treatment, the weighted mean difference (WMD) of SBP and DBP decrease (1 study) was -2.84 (95% CI, -6.42 to 0.74) with (S)-amlodipine and -1.71 (95% CI, -3.48 to 0.06) with racemic amlodipine. After 8 weeks' treatment, the WMD of SBP and DBP decrease (2 studies) was -1.13 (95% CI, -5.29 to 3.03) and -1.34 (95% CI, -2.67 to -0.01), respectively. The risk difference (RD) for the number of patients who experienced AEs with (S)-amlodipine and racemic amlodipine was found to be -0.04 (95% CI, -0.06 to -0.02). When all the trials were included, (S)-amlodipine treatment was associated with significantly less edema than racemic amlodipine (RD, -0.02; 95% CI, -0.03 to 0.00); however, when only high-quality studies (2 studies) were included, no difference was found between the 2 groups (RD, 0.01; 95% CI, -0.02 to 0.03). One high-quality study found significant differences in increases in aspartate and alanine aminotransferase activities in the 2 groups (RD, 0.08; 95% CI, 0.01 to 0.05). No significant differences between the 2 groups were found in the incidence of headache (RD, 0.00; 95% CI, -0.02 to 0.01) or flushing (RD, -0.01; 95% CI, -0.02 to 0.00).

CONCLUSIONS

The majority of the clinical trials comparing (S)-amlodipine and racemic amlodipine treatment were low quality (12/15 [80%]). According to the limited evidence, there were no significant differences between (S)-amlodipine 2.5 mg and racemic amlodipine 5.0 mg in controlling BP. When all the trials were considered, (S)-amlodipine treatment was associated with significantly less edema than racemic amlodipine; however, when only high-quality trials were included, no significant difference was found. More long-term, high-quality RCTs with cardiovascular events as the primary outcome are needed to compare the safety and efficacy of (S)-amlodipine and racemic amlodipine.

Methylene blue for distributive shock: a potential new use of an old antidote

Methylene blue is used primarily in the treatment of patients with methemoglobinemia. Most recently, methylene blue has been used as a treatment for refractory distributive shock from a variety of causes such as sepsis and anaphylaxis. Many studies suggest that the nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway plays a significant role in the pathophysiology of distributive shock. There are some experimental and clinical experiences with the use of methylene blue as a selective inhibitor of the NO-cGMP pathway. Methylene blue may play a role in the treatment of distributive shock when standard treatment fails.

Amlodipine increased endothelial nitric oxide and decreased nitroxidative stress disproportionately to blood pressure changes

BACKGROUND

Clinical trials have shown that amlodipine reduces cardiovascular events at a rate that is not predicted by changes in brachial arterial pressure alone. These findings may be explained, in part, by the pleiotropic effects of amlodipine on endothelial cell (EC) function. In this study, we elucidated the effect of amlodipine on nitric oxide (NO) bioavailability and cytotoxic peroxynitrite (ONOO(-)) and blood pressure (BP).

METHODS

Spontaneously hypertensive rats (SHRs) were treated with vehicle or amlodipine (5 mg/kg/day) for 8 weeks and compared with untreated, baseline rats. NO and ONOO(-) release from aortic and glomerular ECs were measured ex vivo using amperometric nanosensors following maximal stimulation with calcium ionophore. BP was measured using the tail-cuff method.

RESULTS

As compared with baseline, vehicle treatment had reduced aortic endothelial NO release from 157 ± 11 nM to 55 ± 6 nM and increased ONOO(-) from 69 ± 7 nM to 156 ± 19 nM. The NO/ONOO(-) ratio, a comprehensive measurement of eNOS function, decreased from 2.3 ± 0.3 to 0.3 ± 0.1. Compared with vehicle, amlodipine treatment restored NO to 101 ± 3 nM, decreased ONOO(-) to 50 ± 4 nM, and increased the NO/ONOO(-) ratio to 2.0 ± 0.2, a level similar to baseline. Similar changes were observed for glomerular ECs. Mean arterial blood pressure increased from 149 ± 3 mm Hg (baseline) to 174 ± 1 mm Hg (vehicle). Amlodipine slightly, but significantly, decreased mean arterial blood pressure to 167 ± 3 mm Hg vs. vehicle treatment.

CONCLUSIONS

Amlodipine increased NO bioavailability and decreased nitroxidative stress in SHRs with EC dysfunction disproportionately to BP changes. These direct, vascular effects of amlodipine on EC function may contribute to reduced risk for atherothrombotic events as observed in clinical trials.

AN ANGIOTENSIN-CONVERTING ENZYME INHIBITOR AND CALCIUM ANTAGONIST COMBINATION IN PHARMACOTHERAPY OF ARTERIAL HYPERTENSION

The paper focuses on the justification for preferential administration of antihypertensive combination therapy. Pharmacotherapeutic features of starting the treatment with a combination of angiotensin-converting enzyme inhibitors (ACEI) and calcium antagonists (AC) are reviewed. The authors also present the latest evidence on the ACEI/AC combination effects on such vascular parameters as microcirculation and endothelial dysfunction.

The effects of amlodipine and S(-)-amlodipine on vascular endothelial function in patients with hypertension

BACKGROUND

Amlodipine has been shown to improve vascular endothelial function in hypertensive patients, but whether S(-)-amlodipine has a similar effect remains controversial. This study compared the effects of amlodipine and S(-)-amlodipine on vascular endothelial function in hypertensive patients and investigated relevant mechanisms of action in cell culture.

METHODS

Twenty-four patients with essential hypertension received amlodipine and S(-)-amlodipine for 6 weeks in a randomized, crossover study. Associated flow-mediated dilation (FMD), nitric oxide (NO), and endothelial nitric oxide synthase (eNOS) levels were determined. NO levels were measured after exposure of human umbilical vein endothelial cells (HUVECs) to amlodipine, S(-)-amlodipine, the eNOS inhibitor N w-nitro-L-arginine (L-NA), and the Protein Kinase C (PKC) inhibitor Ro 31-8220. Phosphorylation levels of Ser(1177) and Thr(495) in eNOS were determined after exposure to amlodipine, S(-)-amlodipine, and Ro 31-8220.

RESULTS

FMD, NO, and eNOS levels significantly improved after treatment with amlodipine and S(-)-amlodipine. The levels were all higher with amlodipine, although the between-treatment difference was not statistically significant. Amlodipine and S(-)-amlodipine significantly increased NO levels in cultured HUVECs, but increases in NO levels were more marked with amlodipine. Western blot assay showed that both amlodipine and Ro31-8220 induced Ser(1177) phosphorylation and weakened Thr(495) phosphorylation in eNOS. S(-)-amlodipine had no similar effects. Amlodipine, but not S(-)-amlodipine, decreased the PKC phosphorylation in a time-dependent manner.

CONCLUSIONS

Amlodipine and S(-)-amlodipine can both improve endothelial function in hypertensive patients. Amlodipine has greater potential for vascular endothelial protection than S(-)-amlodipine. It affects eNOS phosphorylation at Ser(1177) and Thr(495) by the PKC pathway, further enhancing eNOS activation.

Effects of dihydropyridine calcium channel blockers on oxidized low-density lipoprotein induced proliferation and oxidative stress of vascular smooth muscle cells

Background

Dihydropyridine calcium channel blockers (CCBs) are more effective in reducing carotid intima-media thickness (IMT) than other classes of antihypertensive drugs due to their vascular effects. However, the mechanism remains to be elucidated.

Findings

Ox-LDL induced HUVSMCs proliferation in a time- and dose-dependent manner. When pretreated with three CCBs before 50 μg/ml ox-LDL stimulation, 30 μM lacidipine and 3 μM amlodipine exhibited 27% and 18% decrease of pro-proliferative effect induced by ox-LDL, whereas (S-)-amlodipine did not have any anti-proliferative effect. 30 μM lacidipine inhibited about two-thirds of the ox-LDL induced ROS production in HUVSMCs, whereas amlodipine and (S-)-amlodipine did not have influence on ROS production. The MAPKs pathway inhibitors inhibited the ox-LDL induced proliferation of HUVSMCs.

Conclusion

Our study has demonstrated that lipophilic CCBs, such as lacidipine may inhibit ox-LDL induced proliferation and oxidative stress of VSMCs, and that the ROS-MAPKs pathway might be involved in the mechanism.

Pharmacokinetic interaction of telmisartan with s-amlodipine: an open-label, two-period crossover study in healthy Korean male volunteers

BACKGROUND

Telmisartan belongs to a class of orally active angiotensin II receptor blockers (ARBs), and S-amlodipine is an enantiomer of amlodipine. Amlodipine is a racemic mixture and the calcium channel blocking (CCB) effect is confined to S-amlodipine, whereas R-amlodipine has a 1000-fold lower activity and no racemization occurs in vivo in human plasma. Combination therapy of ARBs with CCBs provides advantages for blood pressure control and vascular protection over monotherapy.

OBJECTIVE

To investigate the effects of coadministration of telmisartan and S-amlodipine on the steady-state pharmacokinetic properties of each drug as a drug-drug interaction study required before developing the fixed-dose combination agent.

METHODS

This study comprised 2 separate parts, A and B; each was a multiple-dose, open-label, 2-sequence, 2-period, crossover study in healthy male Korean volunteers. In part A, volunteers were administered 80 mg of telmisartan, either alone or with 5 mg of S-amlodipine. In part B, volunteers were administered 5 mg of S-amlodipine, either alone or with 80 mg of telmisartan. Blood samples were taken on days 9 and 37, following the final dose of each treatment, and at 0 (predose), 0.5, 1, 1.5, 2, 3, 4, 5, 6, 8, 10, 12, and 24 hours after administration in part A, and were taken at 0 (predose), 1, 2, 3, 4, 5, 6, 7, 8, 10, 12, 14, and 24 hours after administration in part B. Plasma concentrations were determined using LC-MS/MS. The pharmacokinetic properties of each drug after coadministration of telmisartan and S-amlodipine were compared with those of each drug administered alone. Tolerability was assessed using measurements of vital signs, clinical chemistry tests, and interviews.

RESULTS

Fifty-six volunteers were enrolled (32 in part A and 24 in part B), and all completed except 4 volunteers (3 withdrawn in part A and 1 withdrawn in part B). The geometric mean ratios (GMRs) (90% CI) for the C(max,ss) and AUC(τ,ss) of telmisartan (with or without S-amlodipine) were 1.039 (0.881-1.226) and 1.003 (0.926-1.087), respectively. The GMRs (90% CI) for C(max,ss) and AUC(τ,ss) of S-amlodipine (with or without telmisartan) were 0.973 (0.880-1.076) and 0.987 (0.897-1.085). Total 11 adverse events (AEs) were reported in 7 volunteers (21.9%) in part A. A total of 9 AEs were reported in 6 volunteers (25.0%) in part B. Statistical analysis confirmed that the 90% CIs for these pharmacokinetic parameters were within the commonly accepted bioequivalence range of 0.8 to 1.25, indicating that the extent of bioavailability of S-amlodipine was not affected by telmisartan. The intensity of all AEs was considered to be mild, and there were no significant differences in the prevalences of AEs between the 2 formulations.

CONCLUSIONS

Following multiple-dose coadministration of high doses of telmisartan and S-amlodipine, the steady-state pharmacokinetic properties of telmisartan were not significantly affected, and telmisartan had no significant effect on the pharmacokinetic properties of S-amlodipine at steady state in these selected groups of healthy volunteers. Both formulations were generally well-tolerated.

Modern views on amlodipine and new S-amlodipine medications

The review presents the latest evidence on the calcium antagonist amlodipine, summarizing its mechanisms of action, its pleiotropic, endothelial function-related effects, and its anti-atherogenic activity. Amlodipine suppresses the proliferation of vascular smooth myocytes and extracellular matrix and improves endothelial vasodilatation, despite the absence of L-type calcium channels in these cells. This mechanism is related to an increase in endothelial nitric oxide (NO) release. The results of experimental studies on the role of S and R amlodipine isomers in its hemodynamic and pleiotropic activity are presented. While S-amlodipine is a pharmacologically active blocker of L-type calcium channels, R-amlodipine increases endothelial NO release. New medications have been developed, based on S-amlodipine. It has been shown that S-amlodipine 5 mg/d is bioequivalent to amlodipine 10 mg/d. The pharmacodynamics analysis demonstrated that S-amlodipine 5 mg/d and amlodipine 10 mg/d did not differ significantly in terms of mean levels of systolic and diastolic blood pressure, or mean heart rate. S-amlodipine was better tolerated and characterised by a lower incidence of peripheral edema than amlodipine. However, the effects of S-amlodipine on hard end-points should be investigated in the long-term prospective studies.

Methylene blue in the treatment of refractory shock from an amlodipine overdose

Amlodipine is a potent vasodilator with a long half-life and delayed onset of action that is particularly concerning after an overdose. Vasodilation occurs through stimulation of nitric oxide release with increased cyclic guanosine monophosphate (cGMP) production. Methylene blue inhibits guanylate cyclase. This enzyme is responsible for the production of cGMP. Methylene blue also has the ability to scavenge nitric oxide, as well as inhibit nitric oxide synthase. We report the use of methylene blue for refractory shock in a patient with amlodipine toxicity.

In vivo and in vitro antimalarial properties of azithromycin-chloroquine combinations that include the resistance reversal agent amlodipine

Evidence of emerging Plasmodium falciparum resistance to artemisinin-based combination therapies, documented in western Cambodia, underscores the continuing need to identify new antimalarial combinations. Given recent reports of the resurgence of chloroquine-sensitive P. falciparum parasites in Malawi, after the enforced and prolonged withdrawal of this drug, and indications of a possible synergistic interaction with the macrolide azithromycin, we sought to further characterize chloroquine-azithromycin combinations for their in vitro and in vivo antimalarial properties. In vitro 96-h susceptibility testing of chloroquine-azithromycin combinations showed mostly additive interactions against freshly cultured P. falciparum field isolates obtained from Mali. Some evidence of synergy, however, was apparent at the fractional 90% inhibitory concentration level. Additional in vitro testing highlighted the resistance reversal properties of amlodipine for both chloroquine and quinine. In vivo experiments, using the Peters 4-day suppressive test in a P. yoelii mouse model, revealed up to 99.9% suppression of parasitemia following treatment with chloroquine-azithromycin plus the R enantiomer of amlodipine. This enantiomer was chosen because it does not manifest the cardiac toxicities observed with the racemic mixture. Pharmacokinetic/pharmacodynamic analyses in this rodent model and subsequent extrapolation to a 65-kg adult led to the estimation that 1.8 g daily of R-amlodipine would be required to achieve similar efficacy in humans, for whom this is likely an unsafe dose. While these data discount amlodipine as an additional partner for chloroquine-based combination therapy, our studies continue to support azithromycin as a safe and effective addition to antimalarial combination therapies.

Efficacy and safety profiles of a new S(-)-amlodipine nicotinate formulation versus racemic amlodipine besylate in adult Korean patients with mild to moderate hypertension: an 8-week, multicenter, randomized, double-blind, double-dummy, parallel-group, phase III, noninferiority clinical trial

BACKGROUND

"Chiral switching" from an existing racemate to a pure enantiomeric compound is a popular theme in drug development, especially when the enantiomer is found to have better efficacy and safety profiles. Amlodipine is a racemic mixture, composed of the S(-)-enantiomer, which is the pharmacologically active isomer, and the R(+)-enantiomer, which is 1000-fold less active. S(-)-amlodipine nicotinate, a chirally switched form of amlodipine nicotinate, has been developed and found to be bioequivalent to amlodipine besylate in Phase I clinical trials in Korea.

OBJECTIVE

The aim of this study was to compare the efficacy and safety profiles of S(-)-amlodipine nicotinate with those of amlodipine besylate in adult Korean patients with mild to moderate hypertension (diastolic blood pressure [DBP] >or=90 mm Hg and <or=109 mm Hg).

METHODS

This was an 8-week, multicenter, randomized, double-blind, double-dummy, parallel-group, Phase III, noninferiority clinical trial. After an initial 2-week placebo run-in period, patients aged 18 to 75 years with sitting DBP (SiDBP) >or=90 and <or=109 mm Hg at day 0 (baseline) were randomly allocated to receive S(-)-amlodipine nicotinate 2.5 mg QD or amlodipine besylate 5 mg QD for 8 weeks. The dose of study medication was doubled after 4 weeks in patients who had not responded to treatment (SiDBP >or=90 mm Hg). The primary end point was noninferiority of the difference in mean SiDBP from baseline to week 8 for S(-)-amlodipine nicotinate compared with amlodipine besylate. Secondary end points were as follows: (1) noninferiority of the difference in mean sitting systolic blood pressure (SiSBP) from baseline to week 8 between the study groups; and (2) SiDBP response rate (defined as the proportion of patients whose SiDBP was <90 mm Hg or whose SiDBP reduction was >or=10 mm Hg from baseline) after the 8-week treatment. Also, the incidence and severity of adverse events (AEs) and adverse drug reactions (ADRs) were reported. Severe AEs/ADRs were defined as those associated with any of the following: death; an event associated with a high risk of mortality; an event requiring hospitalization; or development of a permanent disability or congenital malformation.

RESULTS

One hundred fifty-seven patients were assessed for inclusion in the study. Of these, 124 patients were randomly allocated to receive S(-)-amlodipine nicotinate (42 men, 21 women; mean [SD] age, 52.4 [10.3] years [range, 23-70 years]; weight, 67.7 [10.8] kg [range, 44-92 kg]) or amlodipine besylate (45 men, 16 women; mean [SD] age, 54.5 [10.0] years [range, 30-73]; weight, 68.9 [9.8] kg [range, 49-95 kg]). One hundred sixteen patients completed the study, but 11 patients (8.9%) were dropped from the per-protocol analysis due to violations; therefore, 105 patients were included in the modified intent-to-treat population analysis (S[-]-amlodipine nicotinate, 55 patients; amlodipine besylate, 50 patients). There were no significant between-group differences in the baseline characteristics. Baseline mean (SD) SiSBP and SiDBP were 142.6 (11.3) and 94.9 (4.8) mm Hg in the S(-)-amlodipine nicotinate group, and 141.8 (8.3) and 96.1 (4.9) mm Hg in the amlodipine besylate group. Mean (SD) changes in SiSBP were 17.6 (11.2) mm Hg in the S(-)-amlodipine nicotinate group and 18.6 (12.3) mm Hg in the amlodipine besylate group. The SiDBP response rates were 92.7% in the S(-)-amlodipine nicotinate group and 88.0% in the amlodipine besylate group. There were no significant between-group differences in the prevalence of AEs and ADRs. In the S(-)-amlodipine nicotinate group, 15 patients (23.8%) reported a total of 28 AEs, and 19 patients (31.1%) reported a total of 27 AEs in the amlodipine besylate group. Six patients (9.5%) in the S(-)-amlodipine nicotinate group and 7 patients (11.4%) in the amlodipine besylate group experienced a total of 19 ADRs (11 and 8, respectively). The most common ADRs were liver enzyme elevation (3/63 [4.8%]) in the S(-)-amlodipine nicotinate group and facial flushing (3/61 [4.9%]) in the amlodipine besylate group. No cases of severe AEs or ADRs were reported in either group.

CONCLUSIONS

The reduction of SiDBP after 8 weeks of treatment with S(-)-amlodipine nicotinate was noninferior compared with that of racemic amlodipine besylate in these adult Korean patients with mild to moderate hypertension. The SiDBP response rate and the reduction of SiSBP after 8 weeks of treatment with S(-)-amlodipine nicotinate were not significantly different from those with racemic amlodipine besylate. Both treatments were generally well tolerated.

Role of nitric oxide in the coupling of myocardial oxygen consumption and coronary vascular dynamics during pregnancy in the dog

We examined the ability of cardiac endothelial nitric oxide synthase (eNOS) to couple myocardial oxygen consumption (MV̇o2) and oxygen delivery during pregnancy. Awake dogs were studied using echocardiography before and at 40 days, 50 days, and 60 days (60D) of pregnancy and at ∼14 days postpartum. Left ventricular eNOS, phosphorylated eNOS, and copper, zinc-superoxide dismutase (CuZnSOD or SOD-1) were determined by immunoblotting. MV̇o2 of left ventricular tissue samples was measured in vitro in response to increasing doses of bradykinin, enalapril maleate, and amlodipine. We examined the changes in passive diameter and flow-dependant arteriolar dilation of coronary arterioles. Echocardiography indicated increases in cardiac output (∼60%) during pregnancy. Myocardial eNOS (21 ± 4%), phosphorylated eNOS (19 ± 3%), and SOD-1 (61 ± 2.7%) protein levels were significantly increased at 60D. Bradykinin, enalapril maleate, and amlodipine (10−4 mol/l) decreased MV̇o2 in a nitric oxide-dependant manner (by 24 ± 1.3% in controls and 34 ± 2.2% at 60D; by 21 ± 1.1% in controls and 29 ± 1.1 at 60D; and by 22 ± 2.5% in controls and 26 ± 1.0% at 60D, respectively). Arterioles from pregnant dogs showed increased flow-dependant dilation in response to increased shear stress and larger passive diameter. Nitrite production was stimulated by bradykinin and carbachol in microvessels in vitro; pregnancy enhanced nitrite release. Myocardial eNOS, phosphorylated eNOS, and SOD-1 protein expression are increased during pregnancy, and this increase is associated with enhanced nitric oxide-dependant control of MV̇o2. Thus increases in eNOS and SOD-1 promote the coupling of oxygen delivery and efficiency in the heart during pregnancy.

Amlodipine prevents monocrotaline-induced pulmonary arterial hypertension and prolongs survival in rats independent of blood pressure lowering

1. The present study was designed to examine the role of amlodipine in preventing and reversing monocrotaline (MCT)-induced pulmonary arterial hypertension (PAH) in rats. 2. Rats were injected with MCT (40 mg/kg, s.c.) and randomly given either 6 mg/kg per day of amlodipine in drinking water or placebo for 3 weeks. Any animals treated with MCT that survived for 3 weeks were given either amlodipine or placebo for the next 3 weeks. 3. Blood pressure was not different between the groups. Amlodipine immediately following MCT markedly inhibited PAH with severe pulmonary vascular remodelling. The survival rate at 3 weeks after treatment was increased significantly in the amlodipine group compared with the placebo group (77%vs 43%; P < 0.01). The placebo group showed markedly diminished expression of endothelial nitric oxide synthase (eNOS) protein and mRNA levels, increased numbers of proliferating cell nuclear antigen-positive cells, enhanced mRNA expression of matrix metalloproteinase-2 and pro-inflammatory cytokines in the lung tissue and upregulation of P-selectin on the endothelium of the pulmonary arteries, whereas these effects were suppressed in the amlodipine-treated group. Furthermore, late treatment with amlodipine did not palliate PAH or improve survival. 4. Amlodipine inhibited the development of PAH and improved survival in rats independent of its effect on lowering blood pressure. These effects were associated with marked inhibition of the downregulation of eNOS and improvement of pulmonary vascular endothelial activation, as well as anti-inflammatory, antiproliferative and antifibrotic effects in the lung tissue. However, amlodipine failed to reverse established PAH. This study may provide an insight into therapeutic strategy of amlodipine in PAH.