Calcium channel blockers. Potential medical benefits and side effects

Gingival Enlargement Caused by Calcium Channel Blockers

Calcium channel blockers, a group of drugs widely used in the treatment of cardiovascular patients, although effective, often cause gingival enlargement, a side effect that is rarely recognized in clinical practice and is not given sufficient importance. Gingival enlargement caused by calcium channel blockers can be localized or generalized, mild or severe. It can negatively affect patients’ appearance, mastication, and speech, thus considerably reducing the quality of life of patients. Risk factors and pathogenesis of this side effect have been the subject of many studies but are still unknown, making this condition a major therapeutic challenge, especially if the cessation of the offending drug is not possible. This study aimed to review the etiology, potential risk factors, pathogenesis, clinical features, and therapy possibilities for gingival enlargement caused by calcium channel blockers.

Altered Extracellular Matrix as an Alternative Risk Factor for Epileptogenicity in Brain Tumors

Seizures are one of the most common symptoms of brain tumors. The incidence of seizures differs among brain tumor type, grade, location and size, but paediatric-type diffuse low-grade gliomas/glioneuronal tumors are often highly epileptogenic. The extracellular matrix (ECM) is known to play a role in epileptogenesis and tumorigenesis because it is involved in the (re)modelling of neuronal connections and cell-cell signaling. In this review, we discuss the epileptogenicity of brain tumors with a focus on tumor type, location, genetics and the role of the extracellular matrix. In addition to functional problems, epileptogenic tumors can lead to increased morbidity and mortality, stigmatization and life-long care. The health advantages can be major if the epileptogenic properties of brain tumors are better understood. Surgical resection is the most common treatment of epilepsy-associated tumors, but post-surgery seizure-freedom is not always achieved. Therefore, we also discuss potential novel therapies aiming to restore ECM function.

3-Aryl-4-nitrobenzothiochromans S,S-dioxide: From Calcium-Channel Modulators Properties to Multidrug-Resistance Reverting Activity

Our research groups have been involved for many years in studies aimed at identifying new active organic compounds endowed with pharmacological properties. In this work, we focused our attention on the evaluation of cardiovascular and molecular drug resistance (MDR) reverting activities of some nitrosubstituted sulphur-containing heterocycles. Firstly, we have examined the effects of 4-nitro-3-(4-methylphenyl)-3,6-dihydro-2H-thiopyran S,S-dioxide 5, and have observed no activity. Then we have extended our investigation to the 3-aryl-4-nitrobenzothiochromans S,S-dioxide 6 and 7, and have observed an interesting biological profile. Cardiovascular activities were assessed for all compounds using ex vivo studies, while the MDR reverting effect was evaluated only for selected compounds using tumor cell lines. All compounds were shown to affect cardiovascular parameters. Compound 7i exerted the most effect on negative inotropic activity, while 6d and 6f could be interesting molecules for the development of more active ABCB1 inhibitors. Both 6 and 7 represent structures of large possible biological interest, providing a scaffold for the identification of new ABCB1 inhibitors.

Evaluation of the effectiveness of sugammadex for verapamil intoxication

Previous studies have shown that medications from the cyclodextrin family bind to verapamil. The aim of our study was to determine whether sugammadex could bind to verapamil and prevent the cardiovascular toxicity of that drug. Twenty-eight sedated Wistar rats were infused with verapamil at 37.5 mg/kg/h. Five minutes after the start of infusion, the animals were treated with a bolus of either 16 mg/kg, 100 mg/kg or 1000 mg/kg sugammadex. The control group was treated with an infusion without sugammadex. The heart rate and respiratory rate were monitored, and an electrocardiogram was recorded. The primary end-point was the time to asystole. The verapamil infusion continued until the animals arrested. The asystole time for the S16 group was significantly longer compared to those for the control and S1000 groups (p < 0.05). The asystole time for the S1000 group was significantly shorter than those for all of the other groups (p < 0.05). Reflecting these data, there was a near doubling of the mean lethal dose of verapamil from 13.57 mg/kg (S.D. ±8.1) in the saline-treated rats to 22.42 mg/kg (S.D. ±9.9) in the sugammadex 16 group (p < 0.05). However, for the sugammadex 1000 group, the mean lethal dose was found to be 6.28 ± 1.11 mg/kg. This dose is significantly lower than those for all of the other groups (p < 0.05). We found that treatment with 16 mg/kg sugammadex delayed verapamil cardiotoxicity in rats. However, 1000 mg/kg sugammadex accelerated verapamil cardiotoxicity in rats. Further studies must be conducted to investigate the interaction between verapamil and sugammadex.

2D Autocorrelation modeling of the negative inotropic activity of calcium entry blockers using Bayesian-regularized genetic neural networks

Negative inotropic potency of 60 benzothiazepine-like calcium entry blockers (CEBs), Diltiazem analogs, was successfully modeled using Bayesian-regularized genetic neural networks (BRGNNs) and 2D autocorrelation vectors. This approach yielded reliable and robust models whilst by means of a linear genetic algorithm (GA) search routine no multilinear regression model was found describing more than 50% of the training set. On the contrary, the optimum neural network predictor with five inputs described about 84% and 65% variances of 50 randomly selected training and test sets. Autocorrelation vectors in the nonlinear model contained information regarding 2D spatial distributions on the CEB structure of van der Waals volumes, electronegativities, and polarizabilities. However, a sensitivity analysis of the network inputs pointed out to the electronegativity and polarizability 2D topological distributions at substructural fragments of sizes 3 and 4 as the most relevant features governing the nonlinear modeling of the negative inotropic potency.

Lacidipine and blood pressure variability in diabetic hypertensive patients

The aim of our study was to assess the effects of lacidipine, a long-acting calcium antagonist, on 24-hour average blood pressure, blood pressure variability, and baroreflex sensitivity. In 10 mildly to moderately hypertensive patients with type II diabetes mellitus (aged 18 to 65 years), 24-hour ambulatory blood pressure was continuously monitored noninvasively (Portapres device) after a 3-week pretreatment with placebo and a subsequent 4-week once daily lacidipine (4 mg) or placebo treatment (double-blind crossover design). Systolic blood pressure, diastolic blood pressure, and heart rate means were computed each hour for 24 hours (day and night) at the end of each treatment period. Similar assessments were also made for blood pressure and heart rate variability (standard deviation and variation coefficient) and for 24-hour baroreflex sensitivity, which was quantified (1) in the time domain by the slope of the spontaneous sequences characterized by progressive increases or reductions of systolic blood pressure and RR interval and (2) in the frequency domain by the squared ratio of RR interval and systolic blood pressure spectral power approximately 0.1 and 0.3 Hz over the 24 hours. Compared with placebo, lacidipine reduced the 24-hour, daytime, and nighttime systolic and diastolic blood pressure (P<0.05) with no significant change in heart rate. It also reduced 24-hour, daytime, and nighttime standard deviation (-19.6%, -14.4%, and -24.0%, respectively; P<0.05) and their variation coefficient. The 24-hour average slope of all sequences (7.7+/-1.7 ms/mm Hg) seen during placebo was significantly increased by lacidipine (8.7+/-1.8 ms/mm Hg, P<0.01), with a significant increase being obtained also for the 24-hour average alpha coefficient at 0.1 Hz (from 5.7+/-1.5 to 6.4+/-1.3 ms/mm Hg, P<0.01). Thus, in diabetic hypertensive patients, lacidipine reduced not only 24-hour blood pressure means but also blood pressure variability. This reduction was accompanied by an improvement of baroreflex sensitivity. Computer analysis of beat-to-beat 24-hour noninvasive blood pressure monitoring may offer valuable information about the effects of antihypertensive drugs on hemodynamic and autonomic parameters in daily life.

Nifedipine gastrointestinal therapeutic system versus atenolol in stable angina pectoris. The Netherlands Working Group on Cardiovascular Research (WCN)

The gastrointestinal therapeutic system formulation of nifedipine enables a once-daily dosing resulting in predictable, relatively constant plasma concentrations. To evaluate the efficacy and safety of this formulation and to compare this with the beta-blocker atenolol, we conducted a double-blind, randomised, multi-centre study in 129 male patients with documented exercise induced angina pectoris. After 4 weeks' treatment, nifedipine (60 mg), improved time to onset of 0.1 mV ST-segment depression from 536 s by 72 +/- 117s, time to onset of pain from 619 s by 56 +/- 120 s, and total exercise time from 685 s by 40 +/- 88 s. Atenolol 100 mg, had a comparable effect, time to onset of 0.1 mV ST-segment depression improved from 496 s by 53 +/- 129 s, time to onset of pain from 572 s by 57 +/- 118 s, and total exercise time from 653 s by 33 +/- 99 s. Between group analysis revealed no statistically significant differences for these exercise parameters. Atenolol, but not nifedipine, significantly reduced heart rate and systolic blood pressure at rest and during exercise (P < 0.001 between groups), indicating different modes of action of the drugs. With regard to safety, both drugs were generally well tolerated. There were significantly (P = 0.01) more vasodilation related side effects with nifedipine. These data demonstrate that gastrointestinal therapeutic system formulation of nifedipine and atenolol as once-daily monotherapy are equally effective and safe, but with different effects on exercise parameters.

Indapamide regresses, but transdermal clonidine does not regress, left ventricular hypertrophy in hypertensive diabetic patients

This report describes the effects of indapamide versus transdermal clonidine on left ventricular hypertrophy (LVH) in hypertensive diabetic patients. A sample of 24 hypertensive diabetic men, aged 40-68 years, with echocardiographically proven LVH was equally divided in to 2 groups. Group 1 was treated with indapamide 2.5 mg/day, and group C with transdermal clonidine weekly. Left ventricular mass and posterior wall and septal thickness were measured by standard echocardiograms done at baseline and every 6 months. At 24 months, treatment crossover was done. Normotension was maintained throughout the study. With indapamide, LVH regression was measurable at 6 months, and left ventricular mass had returned to normal after 18 months. Transdermal clonidine did not regress LVH, but when the patients were switched to indapamide, LVH did regress. Clonidine maintained normal ventricular dimensions after regression had been induced by indapamide.

Adverse interaction between clonidine and verapamil

OBJECTIVE

To report two cases of a possible adverse interaction between clonidine and verapamil resulting in atrioventricular (AV) block in both patients and severe hypotension in one patient.

CASE SUMMARIES

A 54-year-old woman with hyperaldosteronism was treated with verapamil 480 mg/d and spironolactone 100 mg/d. After the addition of a minimal dose of clonidine (0.15 mg bid), she developed complete AV block and severe hypotension, which resolved upon cessation of all medications. A 65-year-old woman was treated with extended-release verapamil 240 mg/d. After the addition of clonidine 0.15 mg bid she developed complete AV block, which resolved after all therapy was stopped.

DISCUSSION

An adverse interaction between clonidine and verapamil has not been reported previously. We describe two such cases and discuss the various mechanisms that might cause such an interaction. Clinicians should be acquainted with this possibly fatal interaction between two commonly used antihypertensive drugs.

CONCLUSIONS

Caution is recommended in combining clonidine and verapamil therapy, even in patients who do not have sinus or AV node dysfunction. The two drugs may act synergistically on both the AV node and the peripheral circulation.

Calcium antagonists in the elderly

The calcium antagonists are associated with a number of advantages over other antihypertensive agents, such as a lack of metabolic, vascular and respiratory adverse events, yet are effective in reducing blood pressure. The currently available calcium antagonists are widely used, and new members, particularly of the dihydropyridine group, continue to emerge. These agents may well be considered for use in the management of hypertension and angina in elderly people. They undergo significant first-pass metabolism and tend to have high values of hepatic clearance with minimal amounts of unchanged drug in the urine. Plasma concentrations tend to be higher in elderly people and for that reason it may be prudent to initiate therapy with lower dosages. With this caveat, adverse effect profiles seem to be qualitatively and quantitatively similar in younger and older people. At equivalent plasma concentrations, the antihypertensive effect appears similar in young and elderly patients, and clinical studies point to comparable efficacy with other drug classes. Calcium antagonists do not have adverse renal, respiratory, cardiovascular, metabolic or peripheral vascular effects and therefore may be useful in patients with relevant concomitant disease.

Sustained release nifedipine formulations. An appraisal of their current uses and prospective roles in the treatment of hypertension, ischaemic heart disease and peripheral vascular disorders

Nifedipine antagonises influx of calcium through cell membrane slow channels, and sustained release formulations of the calcium channel blocker have been shown to be effective in the treatment of mild to moderate hypertension and both stable and variant angina pectoris. Preliminary findings also indicate that these formulations are effective in the treatment of Raynaud's phenomenon and hypertension in pregnancy, and that they reduce the frequency of ischaemic episodes in some patients with silent myocardial ischaemia. The exact mechanism of action of nifedipine in all of these disorders has not been defined. However, its potent peripheral and coronary arterial dilator properties, together with improvements in oxygen supply/demand, are of particular importance. A major goal of sustained release therapy is to permit reductions in the frequency of nifedipine administration, preferably to once daily, and thus improve patient compliance. Two new once-daily formulations--the nifedipine gastrointestinal therapeutic system (GITS) and a fixed combination capsule comprising sustained release nifedipine 20 mg and atenolol 50 mg--have exhibited marked antihypertensive efficacy. The GITS preparation has also been used effectively in the treatment of stable angina pectoris, and both formulations appear to be well tolerated. Sustained release nifedipine formulations are generally better tolerated than their conventionally formulated counterparts, particularly with regard to reflex tachycardia. Adverse effects seem to be dose related, are mainly associated with the drug's potent vasodilatory action, and include headache, flushing and dizziness. Generally, these effects are mild to moderate in severity and transient, usually diminishing with continued treatment. Thus, sustained release nifedipine formulations are useful and established cardiovascular therapeutic agents which have demonstrable efficacy in various forms of angina, mild to moderate hypertension and Raynaud's phenomenon. Further, promising results shown by the nifedipine GITS formulation, with its advantage of once daily administration suggest that it is likely to become one of the preferred nifedipine formulations for the treatment of hypertension and the various forms of angina.

Metabolic considerations in the choice of therapy for the patient with hypertension

The objective of treating patients with hypertension is not simply to reduce blood pressure but rather to prevent the associated morbidity and mortality. Recent assessments of clinical trials have shown that while the risk of stroke is consistently lower with antihypertensive therapy, the same degree of success has not been demonstrated for coronary artery disease (CAD). Although there are many explanations of why we have not done as well in preventing CAD, one possibility is that the therapy used in clinical trials, primarily thiazide diuretics and beta-adrenoreceptor blockers, has increased the patient's risk of developing coronary atherosclerosis or lethal arrhythmias. Four classes of antihypertensive agents are recommended for initial therapy--thiazide diuretics, beta-adrenoreceptor blockers, angiotensin-converting enzyme (ACE) inhibitors, and calcium entry blockers. The metabolic effects of thiazide diuretics include electrolyte disturbances (hypokalemia, hypomagnesemia, and hyponatremia), dyslipidemia (increased triglycerides), abnormalities of glucose metabolism (hyperglycemia, hyperinsulinemia, and peripheral insulin resistance), and hyperuricemia. beta-Adrenoreceptor blockers have many of the same metabolic adverse reactions. beta-Adrenoreceptor blockers without intrinsic sympathomimetic activity (ISA) also cause dyslipidemias (lowered high-density lipoprotein cholesterol and increased triglycerides) and abnormalities of glucose metabolism (hyperglycemia, hyperinsulinemia, and peripheral insulin resistance). beta-Adrenoreceptor blockers with ISA and third-generation beta-blockers with selective partial agonist activity (celiprolol and dilevalol) do not cause dyslipidemia and to date do not appear to induce abnormalities in glucose metabolism. ACE inhibitors may decrease triglycerides and increase high-density lipoprotein cholesterol, and captopril may improve insulin sensitivity. Calcium entry blockers are metabolically neutral.(ABSTRACT TRUNCATED AT 250 WORDS)