Kinetics and dynamics of calcium entry antagonists in systemic hypertension

Verapamil-loaded supramolecular hydrogel patch attenuates metabolic dysfunction-associated fatty liver disease via restoration of autophagic clearance of aggregated proteins and inhibition of NLRP3

BACKGROUND

Obesity, a serious threat to public health, is linked to chronic metabolic complications including insulin resistance, type-2 diabetes, and metabolic dysfunction-associated fatty liver disease (MAFLD). Current obesity medications are challenged by poor effectiveness, poor patient compliance, and potential side effects. Verapamil is an inhibitor of L-type calcium channels, FDA-approved for the treatment of hypertension. We previously investigated the effect of verapamil on modulating autophagy to treat obesity-associated lipotoxicity. This study aims to develop a verapamil transdermal patch and to evaluate its anti-obesity effects.

METHODS

Verapamil is loaded in biomimetic vascular bundle-like carboxymethyl pullulan-based supramolecular hydrogel patches cross-linked with citric acid and glycerol linkages (CLCMP). The investigation was then carried out to determine the therapeutic effect of verapamil-loaded CLCMP (Vera@CLCMP) on diet-induced obese mice.

RESULTS

Vera@CLCMP hydrogel patches with hierarchically organized and anisotropic pore structures not only improved verapamil bioavailability without modifying its chemical structure but also enhanced verapamil release through the stratum corneum barrier. Vera@CLCMP patches exhibit low toxicity and high effectiveness at delivering verapamil into the systemic circulation through the dermis in a sustained manner. Specifically, transdermal administration of this patch into diet-induced obese mice drastically improved glucose tolerance and insulin sensitivity and alleviated metabolic derangements associated with MAFLD. Furthermore, we uncovered a distinct molecular mechanism underlying the anti-obesity effects associated with the hepatic NLR family pyrin domain-containing 3 (NLRP3) inflammasome and autophagic clearance by the vera@CLCMP hydrogel patches.

CONCLUSION

The current study provides promising drug delivery platforms for long-term family treatment of chronic diseases, including obesity and metabolic dysfunctions.

Antifertility effect of calcium channel blockers on male rats: association with oxidative stress

PURPOSE

Calcium ions are vital in many biologic processes including a variety of enzymatic reactions, activation of excitable cells, coupling of electrical activation to cellular secretion, haemostasis, bone metabolism and sperm functions. Calcium channel blockers (CCB) appear to have a reversible anti-fertility effect on male rats which does not occur through inhibition of the pituitary-gonadal axis. While the effects of CCB on male reproductive function have been investigated, less information is available regarding other reproductive indices and the underlying mechanism in the pathogenesis of male reproductive dysfunction. Therefore, the involvement of oxidative mechanisms in the adverse manifestation induced by CCB on male reproductive functions is investigated in this study.

METHODS

For this purpose, lipid peroxidation; enzymatic antioxidants such as superoxide dismutase, catalase and glutathione reduced; epididymal sperm count, motility; histopathology of the testes, epididymis, seminal vesicle, prostate glands; and reproductive performance were determined.

RESULTS

CCB administration in rats causes significant oxidative stress in the male reproductive milieu in term of increase in malondialdehyde (MDA) level and a concomitant decrease in catalase, superoxide dismutase and reduced glutathione enzyme activities in the testes. In addition, CCB treatment significantly decreased the sperm count, sperm motility, fertility index, implantation count, and litter size in this study.

CONCLUSION

There is substantial evidence that CCB induces significant oxidative stress in the testes, which appears to be responsible for the adverse effects of decreased sperm count and motility ultimately leading to reduced fertility in rats.

Increased sensitivity to diltiazem hypotensive effect in an experimental model of high-renin hypertension

Objectives

The aim of this work was to evaluate the pharmacokinetic–pharmacodynamic properties of diltiazem in an experimental model of high-renin hypertension, such as the aortic coarctated (ACo) rat, to further characterize the responsiveness of this model to calcium channel blockers.

Methods

A ‘shunt’ microdialysis probe was inserted in a carotid artery of anaesthetized ACo and control sham-operated (SO) rats for simultaneous determination of diltiazem plasma concentrations and their effects on mean arterial pressure and heart rate after the intravenous application of 3 and 6 mg/kg of the drug. Correlation between plasma levels and cardiovascular effects was established by fitting the data to a modified Emax model.

Key findings

Volume of distribution was greater in ACo than in SO rats. Diltiazem plasma clearance (Cl) was significantly greater in ACo rats than in normotensive SO rats after administration of diltiazem (6 mg/kg). Moreover, Cl increased with dose in ACo but not in SO rats. No differences were observed in the maximal bradycardic effect comparing both experimental groups, and sensitivity (S0) to diltiazem chronotropic effect was similar comparing SO and ACo rats. Differences were not found in the maximal response of the hypotensive effect comparing SO and ACo rats, but the S0 to diltiazem hypotensive effect was greater in ACo rats than in SO rats.

Conclusions

ACo induced profound changes in diltiazem pharmacokinetic behaviour. In addition, our results suggested an increased sensitivity to diltiazem blood pressure lowering effect in experimental renovascular hypertension with high-renin levels.

Antireproductive effect of calcium channel blockers on male rats

Introduction

Drugs have been shown to adversely affect male fertility and recently anti-hypertensive drugs were added to the list. The anti-fertility effects of nifedipine and similar calcium channel blockers are well-illustrated in in vitro experiments but not in vivo.

Purpose

The present study was designed to experimentally elucidate the sub-chronic effect of nifedipine, verapamil and diltiazem on sperm functions and reproductive hormone levels in vivo.

Methods

Male rats (150-200 g) were divided into four groups of ten rats each. Group 1 (control) received distilled water; Group 2 received nifedipine 0.57 mg/kg BW; Group 3 were given verapamil 3.40 mg/kg BW and Group 4 were given diltiazem 2.57 mg/kg BW. Each drug-treated group had its own recovery group from which treatment was discontinued for 30 days before the animals were sacrificed. Blood samples were collected for hormonal assay of FSH, LH and testosterone. Semen evaluation was done and the testes, seminal vesicle, epididymis and prostate were removed, and weighed immediately.

Results

Nifedipine, verapamil and diltiazem significantly decreased (P < 0.05) sperm count and motility in drug treated groups. The weight of the epididymis was significantly reduced (P < 0.05) in the drug treated rats. Semen parameters and other associated changes were restored after 30 days of drug withdrawal.

Conclusion

Calcium channel blockers appear to have a reversible anti-fertility effect on male rats which does not occur through inhibition of the pituitary-gonadal axis.

Pharmacokinetic–pharmacodynamic modeling of diltiazem in spontaneously hypertensive rats: A microdialysis study

INTRODUCTION

The aim of the present work was to study the applicability of a modified E(max) pharmacodynamic model for the pharmacokinetic-pharmacodynamic (PK-PD) modeling of diltiazem in spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto (WKY) rats.

METHODS

A "shunt" microdialysis probe was inserted in a carotid artery of anaesthetized SHR and WKY rats for simultaneous determination of unbound plasma concentrations of diltiazem and their effects on mean arterial pressure (MAP) and heart rate (HR) after the intravenous application of 1 and 3 mg kg(-1) of the drug. Correlation between diltiazem plasma levels and their cardiovascular effects was established by fitting the data to a conventional and modified E(max) model.

RESULTS

Volume of distribution and clearance of diltiazem was greater in SHR than in WKY animals. A proportional increase of area under curve with dose increment was observed in WKY animals but not in SHR. A good correlation between plasma unbound concentrations of diltiazem and their hypotensive and chronotropic effects was found in both experimental groups using both PK-PD models. The application of the modified E(max) model for PK-PD modeling of diltiazem allowed a more accurate and precise estimation of PK-PD parameters than the E(max) equation do. Chronotropic effect of 3 mg kg(-1) diltiazem was lower in SHR compared to WKY animals. Initial sensitivity (S(0)) to diltiazem chronotropic effect was greater in SHR with regards to WKY animals after administration of 1 mg kg(-1). S(0) to diltiazem hypotensive effect was greater in SHR with regards to WKY animals after administration of both doses of diltiazem.

DISCUSSION

Microdialysis sampling is a useful technique for the pharmacokinetic study and pharmacokinetic-pharmacodynamic (PK-PD) modeling of diltiazem. The modified E(max) model allows an accurate estimation of drug sensitivity in conditions when maximal pharmacological response can not be attained. Genetic hypertension induced changes in the pharmacokinetic and PK-PD behavior of diltiazem suggesting that SHR is an interesting animal model for pre-clinical evaluation of calcium channel blockers.

Verapamil: metabolism in cultures of primary human coronary arterial endothelial cells

Endothelium is a metabolically active secretory tissue and an important barrier for metabolic products. Little is known about its contribution to drug oxidation. We investigated the gene and protein expression and enzyme activity of major cytochrome P450 monooxygenases in cultures of primary human coronary endothelial cells and studied its ability to metabolize verapamil, a commonly and widely prescribed calcium antagonist. Of the total 18 P450 monooxygenases investigated, transcripts for CYP1A1, CYP2A6/7, CYP2A13, CYP2B6/7, CYP2C8, CYP2E1, and CYP2J2 were expressed, albeit at different levels. Furthermore, metabolism of verapamil proceeded predominantly via N-desmethylation and/or N-desalkylation, i.e., production of D-617 [2-(3,4-dimethoxyphenyl)-5-amino-2-isopropylvaleronitrile], D-620 [2-(3,4-dimethoxyphenyl)-5-methylamino-2-isopropylvaleronitrile], and norverapamil; but additional metabolites are the O-demethylated products, D-702 [2-(3,4-dimethoxyphenyl)-8-(4-hydroxy-3-methoxyphenyl)-6-methyl-2-isopropyl-6-azaoctanitrile] and D-703 [O-demethylverapamil; 5-N-(3,4-dimethoxyphenethyl)methylamino-2-(3'-methoxy-4'-hydroxyphenyl)-2-isopropylvaleronitrile]. We show endothelium to express an array of monooxygenases, and in view of its large body distribution, endothelium should be considered in the biotransformation of drugs, particularly when tissue-specific metabolism and/or metabolic inactivation are being investigated.

Verapamil: new insight into the molecular mechanism of drug oxidation in the human heart

Verapamil is a commonly prescribed cardiovascular drug, but surprisingly its metabolism in the target tissue of pharmacotherapy is basically unknown. We therefore investigated its biotransformation in human heart tissue and correlate the production of metabolites with the gene expression of major drug metabolising enzymes. Using electrospray LC-MS-MS and LC-MS3 experiments, a total of nine metabolites were observed in incubation experiments with verapamil and microsomes isolated from the human heart tissue, and this included a carbinolamine-, N-formyl-, ahemiacetale-, and formate-intermediate of N-demethyl- and O-demethylverapamil. We also observed a hydroxylation product at the benzylic position of atom C-7 (M9). Metabolites M5-M9 are novel and were not observed in previous studies with liver or other human tissues. A fine example of the considerable metabolic competence of human heart is the formation of M1-M4, e.g. dealkylverapamil, norverapamil and isomers of O-demethylverapamil, which were believed to be exclusively produced by the liver.

Verapamil drug metabolism studies by automated in-tube solid phase microextraction

Verapamil is a common calcium antagonist described with antianginal, antihypertensive and antiarrythmic properties. The metabolites of verapamil have also shown pharmacological properties and therefore sample preparation and analysis techniques capable of metabolic screening for verapamil are important. In-tube SPME is a relatively new method integrating sample extraction, concentration and introduction into one single step without the use of organic solvents. The capability of in-tube SPME in bioanalysis has been reviewed but there has been no application described in the field of drug metabolism. Since automation and interfacing of in-tube SPME coupled to liquid chromatography-mass spectrometry (LC-MS) is possible, we confirm in this study that it is a powerful method to monitor the main metabolites of verapamil in various biological matrices like plasma, urine and cell culture media. Further, we show that it could also be used in routine pharmacokinetics measurements. An in-tube SPME LC-MS method was developed to extract and analyze the metabolic profile of verapamil from biological matrices. The detection limit for verapamil, gallopamil, norverapamil and PR22 were 52, 53, 65 and 83 ng/ml (UV detection) and 5, 6, 6 and 8 ng/ml (MS detection), respectively. The precision of the method was calculated in various biological matrices and the average % R.S.D. (N=5) for verapamil, gallopamil, norverapamil and PR22 was 3.9, 3.7, 3.8 and 4.3% (MS detection), respectively. The linear dynamic range was determined to be 100-800 ng/ml (UV detection) with a total sample preparation and analysis time of 34 min.

Determination of nifedipine in human serum by gas chromatography-mass spectrometry: validation of the method and its use in bioavailability studies

A procedure for the determination of nifedipine in human serum is described. The light-sensitive substance is isolated from serum by liquid-liquid extraction and analyzed using capillary gas chromatography with a mass-selective detector. The validation of the method shows that the extraction recovery is ca. 85%, the limit of detection is 2 ng/ml and the standard deviations of the intra-day precision test range from 5.8 to 7.4% with respect to the concentration. The procedure is highly selective and sensitive. It is especially suited for bioavailability studies because of its stability and high sampling rate.

Comparative efficacy, safety and pharmacokinetics of verapamil SR vs verapamil IR in hypertensive patients

The antihypertensive effects of the regular immediate release formulation of verapamil (verapamil IR) and the newer sustained release formulation of verapamil (verapamil SR) were compared in Hispanic patients with untreated essential hypertension. Verapamil IR was given in 3 divided doses (80 or 160mg 3 times daily) and verapamil SR was given either as a single daily dose of 240mg or as 240mg every 12 hours. With both formulations there was a significant reduction in systolic (SBP) and diastolic blood pressure (DBP); a greater lowering of BP was observed with verapamil 480 mg/day than with 240 mg/day. With verapamil SR 480 mg/day, 91% of patients had reductions in SBP and DBP greater than 20 and 15mm Hg, respectively. In addition, 83% of patients reached normotension. With the lower dose (240mg once daily), 83% of patients had decreases in DBP greater than 10mm Hg and 73% of patients achieved normotension. Comparable effects were achieved with verapamil IR. With verapamil IR there was a more rapid fall in BP which peaked 3 to 4 hours postdose, whereas with verapamil SR a more gradual and sustained BP reduction was observed. Only small changes in heart rate (HR) were observed with verapamil IR and verapamil SR. For verapamil SR, the mean increase in HR was 5 beats/min (to 80 beats/min) and the mean decrease in HR was 13 beats/min (to 62 beats/min). Both verapamil SR and verapamil IR prolonged the PR interval of the ECG. An equal degree of PR prolongation was observed with 240 and 480 mg/day. The incidence of side effects (headache, palpitations, dizziness and flushing) was dose dependent, decreased with continuous treatment and was much higher with verapamil IR than with verapamil SR. Steady-state plasma verapamil concentrations were monitored. Compared with verapamil IR, verapamil SR produced a more gradual rise and a more sustained elevation of plasma verapamil and norverapamil concentrations. Comparable trough verapamil concentrations (Cmin) were observed with verapamil IR (98 micrograms/L) and SR (81 micrograms/L); morning Cmin verapamil concentrations were higher than daytime Cmin values. The normalised area under the plasma concentration-time curve (AUC) and maximum concentration (Cmax) were 10 to 20% greater for verapamil IR than SR. The 2-fold increase in oral dose produced a 2.2- and 2.4-fold increase in AUC for verapamil IR and SR, respectively, associated with a 20% reduction in metabolism to norverapamil. Fasting increased the rate and extent of absorption of verapamil.(ABSTRACT TRUNCATED AT 400 WORDS)

Clinical utility of nifedipine and diltiazem plasma levels in patients with angina pectoris receiving monotherapy and combination treatment

The clinical utility of nifedipine and diltiazem blood levels in patients with angina pectoris receiving monotherapy (N = 14) and combination treatment (N = 9) were assessed in a placebo run-in, double blind, randomized, crossover study. Compared to placebo, diltiazem (mean daily dose 360 mg), nifedipine (mean daily dose 90 mg) and combination diltiazem-nifedipine therapy (mean daily dose 55 mg of nifedipine, 360 mg of diltiazem) were associated with reductions in weekly angina attacks and nitroglycerin consumption. Although both drugs used as monotherapy and in combination were also associated with significant increments in exercise tolerance and other improved angina parameters, these changes were not related to the plasma levels of either drug. Nifedipine plasma levels were measured by gas chromatography and diltiazem plasma levels measured by reverse high-pressure liquid chromatography from specimens obtained 2-5 hours after the last previous dose, after 1, 2 and 3 weeks of treatment, and during baseline placebo and placebo washout periods. With combination therapy, there was no effect on the diltiazem plasma level compared to monotherapy. The significant decrease in the nifedipine dose in patients on combination therapy did not significantly change nifedipine plasma levels. Determinations of plasma levels of diltiazem and nifedipine in the management of patients is of no value in the management of patients with angina pectoris except for monitoring treatment compliance and overdosage.

Verapamil. An updated review of its pharmacodynamic and pharmacokinetic properties, and therapeutic use in hypertension

Although verapamil is a well-established treatment for angina, cardiac arrhythmias and cardiomyopathies, this review reflects current interest in calcium antagonists as anti-hypertensive agents by focusing on the role of verapamil in hypertension. Verapamil is a phenylalkylamine derivative which antagonises calcium influx through the slow channels of vascular smooth muscle and cardiac cell membranes. By reducing intracellular free calcium concentrations, verapamil causes coronary and peripheral vasodilation and depresses myocardial contractility and electrical activity in the atrioventricular and sinoatrial nodes. Verapamil is well suited for the management of essential hypertension since it produces generalised systemic vasodilation resulting in a marked reduction in systemic vascular resistance and, consequently, blood pressure. Evidence from clinical studies supports the role of oral verapamil as an effective and well-tolerated first-line treatment for the management of patients with mild to moderate essential hypertension. Clinical studies have shown that verapamil is more effective the higher the pretreatment blood pressure and some authors have found a more pronounced antihypertensive effect in older patients or in patients with low plasma renin activity. Sustained release verapamil formulations are available for oral administration which, as a single daily dose, are as effective in lowering blood pressure over 24 hours as equivalent doses of conventional verapamil formulations given 3 times daily. As a first-line antihypertensive agent, oral verapamil is equivalent to several other calcium antagonists, beta-blockers, diuretics, angiotensin-converting enzyme (ACE) inhibitors and other vasodilators, and is not associated with many of the common adverse effects of these treatments. Verapamil may be preferred as an alternative first-line antihypertensive treatment to diuretics in elderly patients because it has similar efficacy in these patients without causing the adverse effects commonly linked with diuretic treatment. Furthermore, because verapamil does not cause bronchoconstriction, it may be used in preference to beta-blockers in patients with asthma or chronic obstructive airway disease. Reflex tachycardia, orthostatic hypotension or development of tolerance is not evident following verapamil administration. As a second- or third-line treatment for patients refractory to established antihypertensive regimens, verapamil produces marked blood pressure reductions when combined with diuretics and/or ACE inhibitors, beta-blockers and vasodilators such as prazosin.(ABSTRACT TRUNCATED AT 400 WORDS)