Clinical applications of slow channel blocking compounds

Efficacy of Diltiazem for the Control of Blood Pressure in Puerperal Patients with Severe Preeclampsia: A Randomized, Single-Blind, Controlled Trial

BACKGROUND

Postpartum preeclampsia is a serious disease related to high blood pressure that occurs commonly within the first six days after delivery.

OBJECTIVE

To evaluate if diltiazem improves blood pressure parameters in early puerperium patients with severe preeclampsia. Methodology. A randomized, single-blind longitudinal clinical trial of 42 puerperal patients with severe preeclampsia was carried out. Patients were randomized into two groups: the experimental group (n = 21) received diltiazem (60 mg) and the control group (n = 21) received nifedipine (10 mg). Both drugs were orally administered every 8 hours. Systolic, diastolic, and mean blood pressures as well as the heart rate were recorded and analyzed (two-way repeated measures ANOVA) at baseline and after 6, 12, 18, 24, 30, 36, 42, and 48 hours. Primary outcome measures were all the aforementioned blood pressure parameters. Secondary outcome measures included the number of hypertension and hypotension episodes along with the length of stay in the intensive care unit.

RESULTS

No statistical differences were found between groups (diltiazem vs. nifedipine) regarding basal blood pressure parameters. Interarm differences in blood pressure (systolic, diastolic, and mean) and heart rate were statistically significant between treatment groups from 6 to 48 hours. Patients in the diltiazem group had lower blood pressure levels than patients in the nifedipine group. Significantly, patients who received diltiazem had fewer hypertension and hypotension episodes and stayed fewer days in the intensive care unit than those treated with nifedipine.

CONCLUSIONS

Diltiazem controlled arterial hypertension in a more effective and uniform manner in patients under study than nifedipine. Patients treated with diltiazem had fewer collateral effects and spent less time in the hospital. This trial is registered with NCT04222855.

Regulation of peripheral blood flow in complex regional pain syndrome: clinical implication for symptomatic relief and pain management

BACKGROUND

During the chronic stage of Complex Regional Pain Syndrome (CRPS), impaired microcirculation is related to increased vasoconstriction, tissue hypoxia, and metabolic tissue acidosis in the affected limb. Several mechanisms may be responsible for the ischemia and pain in chronic cold CPRS.

DISCUSSION

The diminished blood flow may be caused by either sympathetic dysfunction, hypersensitivity to circulating catecholamines, or endothelial dysfunction. The pain may be of neuropathic, inflammatory, nociceptive, or functional nature, or of mixed origin.

SUMMARY

The origin of the pain should be the basis of the symptomatic therapy. Since the difference in temperature between both hands fluctuates over time in cold CRPS, when in doubt, the clinician should prioritize the patient's report of a persistent cold extremity over clinical tests that show no difference. Future research should focus on developing easily applied methods for clinical use to differentiate between central and peripheral blood flow regulation disorders in individual patients.

Some extracardiac effects of diltiazem and other calcium entry blockers

Calcium entry blockers have a well documented relaxing effect of smooth muscle, vascular as well as non-vascular. Mainly as a consequence of this action, the drugs have been used for treatment of several non-cardiac disorders where hyperactivity of smooth muscle is considered to have an important role in the pathogenesis. In this short review some of these extracardiac effects of calcium entry blockers are discussed and also their clinical application.

Calcium antagonists

Calcium antagonists were introduced for the treatment of hypertension in the 1980s. Their use was subsequently expanded to additional disorders, such as angina pectoris, paroxysmal supraventricular tachycardias, hypertrophic cardiomyopathy, Raynaud phenomenon, pulmonary hypertension, diffuse esophageal spasms, and migraine. Calcium antagonists as a group are heterogeneous and include 3 main classes--phenylalkylamines, benzothiazepines, and dihydropyridines--that differ in their molecular structure, sites and modes of action, and effects on various other cardiovascular functions. Calcium antagonists lower blood pressure mainly through vasodilation and reduction of peripheral resistance. They maintain blood flow to vital organs, and are safe in patients with renal impairment. Unlike diuretics and beta-blockers, calcium antagonists do not impair glucose metabolism or lipid profile and may even attenuate the development of arteriosclerotic lesions. In long-term follow-up, patients treated with calcium antagonists had development of less overt diabetes mellitus than those who were treated with diuretics and beta-blockers. Moreover, calcium antagonists are able to reduce left ventricular mass and are effective in improving anginal pain. Recent prospective randomized studies attested to the beneficial effects of calcium antagonists in hypertensive patients. In comparison with placebo, calcium antagonist-based therapy reduced major cardiovascular events and cardiovascular death significantly in elderly hypertensive patients and in diabetic patients. In several comparative studies in hypertensive patients, treatment with calcium antagonists was equally effective as treatment with diuretics, beta-blockers, or angiotensin-converting enzyme inhibitors. From these studies, it seems that a calcium antagonist-based regimen is superior to other regimens in preventing stroke, equivalent in preventing ischemic heart disease, and inferior in preventing congestive heart failure. Calcium antagonists are also safe and effective as first-line or add-on therapy in diabetic hypertensive patients. Heart rate-lowering calcium antagonists (verapamil, diltiazem) may have an edge over the dihydropyridines in post-myocardial infarction patients and in diabetic nephropathy. Thus, calcium antagonists may be safely used in the management of hypertension and angina pectoris.

Dose-ranging study of a new, once-daily diltiazem formulation for patients with stable angina

A double-blind safety and efficacy dose-ranging study was conducted with a new, once-daily, extended-release (XR) diltiazem hydrochloride formulation (Dilacor XR, Rhône-Poulenc Rorer, Collegeville, PA) in 189 patients with chronic stable angina pectoris. After a 2-week placebo lead-in phase, the patients were randomly assigned to 1 of 4 once-daily, fixed-dose treatment groups: placebo, XR diltiazem 120 mg, 240 mg, or 480 mg. Extended-release diltiazem, at 240-mg and 480-mg once-daily doses, significantly improved (P < .05) total exercise time during treadmill exercise tolerance testing after 2 weeks of treatment when assessed 24 hours after the previous dose. These increasing doses of XR diltiazem were associated with incremental improvements in exercise tolerance. Outpatient function, as assessed by frequency of anginal attacks, nitroglycerin use, and ambulatory electrocardiogram (Holter, Scole Engineering Culver City, CA) monitoring of ischemic events, was also improved by XR diltiazem. This extended-release diltiazem formulation can be clinically titrated within the 120- to 480-mg dosing range, permitting effective once-daily administration for treating chronic stable angina.

Verapamil administration to patients with contraindications: is it associated with adverse outcomes?

STUDY OBJECTIVES

To determine if the use of verapamil in patients with contraindications is associated with adverse sequelae, thereby assessing whether process measures of the quality of care are correlated with patient outcomes.

DESIGN

Retrospective chart review comparing the incidence of adverse outcomes and drug failure in patients with and without contraindications to verapamil administration.

SETTING

University hospital emergency department.

PARTICIPANTS

All patients more than 12 years old who received IV verapamil during the study period.

MEASUREMENTS

The presence or absence of contraindications to verapamil, the occurrence of complications, and the frequency of drug failure were determined by chart review.

MAIN RESULTS

Patients with contraindications to verapamil experienced a significantly higher incidence of adverse outcomes and drug failures than those without contraindications. The presence of contraindicated rhythms, low pretreatment blood pressure, and signs of congestive heart failure were each specifically associated with an increased risk of adverse sequelae.

CONCLUSION

Verapamil should not be administered to patients with contraindications to its use. In this instance, quality assurance process measures correlate with patient outcomes.

Comparative efficacy and safety of bepridil and diltiazem in chronic stable angina pectoris refractory to diltiazem. The Bepridil Collaborative Study Group

The efficacy and safety of bepridil hydrochloride (200 to 400 mg/day) were evaluated in patients with chronic stable angina refractory to maximal tolerated doses of diltiazem (median 360 mg/day) in a randomized, multicenter, double-blind, parallel study. Baseline diltiazem data were obtained during a 2-week period, after which 86 patients were randomized to bepridil (n = 46) or diltiazem (n = 40). Angina frequency, nitroglycerin consumption and ischemic manifestations induced by exercise treadmill testing were evaluated over 8 weeks. Bepridil significantly (p less than 0.05) increased time to angina onset, time to 1 and 2 mm of ST-segment depression, total exercise time and total work over baseline values. Changes in time to angina onset and time to 1 mm of ST-segment depression were significantly (p less than 0.05) greater for bepridil than for diltiazem. Angina frequency and nitroglycerin consumption did not differ significantly between groups. Compared with baseline, bepridil significantly (p less than 0.001) decreased heart rate (mean 4 beats/min) and prolonged QTc (mean 35 ms). The most frequent adverse effects in both groups were nausea, asthenia, dizziness, headache and diarrhea. Four patients taking bepridil and 1 taking diltiazem withdrew from the study because of adverse reactions. No sudden deaths, myocardial infarctions or instances of sustained ventricular tachycardia or torsades de pointes occurred in either group. The data indicate that bepridil provided safe and effective antianginal and antiischemic therapy in patients with chronic stable angina who exhibited less than optimal response to maximal tolerated doses of diltiazem.

Action of pinaverium bromide, a calcium-antagonist, on gastrointestinal motility disorders

1. The evidence reviewed here indicates that pinaverium bromide (Dicetel) relaxes gastrointestinal (GI) structures primarily by inhibiting Ca2+ influx through potential-dependent channels of surface membranes of smooth muscle cells. 2. The in vivo selectivity of pinaverium bromide for the GI tract appears to be due mainly to its pharmacokinetic properties. Because of its low absorption (typical for quaternary ammonium compounds) and marked hepatobiliary excretion, most of the orally-administered dose of pinaverium bromide remains in the GI tract. 3. Orally-administered pinaverium bromide does not elicit adverse cardiovascular side-effects at doses that effectively relieve GI spasm, pain, transit disturbances and other symptoms related to motility disorders. 4. Pinaverium bromide is the only Ca2(+)-antagonist with known therapeutic efficacy in the treatment of irritable bowel syndrome and certain other functional intestinal disorders.

Evidence for the existence of a cardiac specific isoform of the alpha 1 subunit of the voltage dependent calcium channel

Biochemical, pharmacological and electrophysiological evidence implies the existence of tissue specific isoforms of the L-type VDCC. The alpha 1 and alpha 2 subunits of the skeletal muscle calcium channel have been previously cloned and their amino acid sequence deduced. Here we report the isolation and sequencing of a partial cDNA that encodes a heart specific isoform of the alpha 1 subunit. The amino acid sequence deduced from this part cDNA clone shows 64.7% similarity with the skeletal muscle alpha 1 subunit. Northern analysis reveals 2 hybridizing bands, 8.5 and 13 kb, in contrast to one 6.5 kb band in the skeletal muscle. Selective inhibition of mRNA expression in Xenopus oocytes by complementary oligodeoxy-nucleotides derived from the heart clone provides further evidence that the cDNA corresponds to an essential component of the VDCC. These data further support the existence of tissue-specific isoforms of the L-type VDCC.

Nimodipine in the treatment of subarachnoid hemorrhage

Nimodipine, a calcium-channel antagonist with a relatively selective vasodilatory effect on cerebral blood vessels, has recently been approved for improvement of neurologic deficits due to spasm following subarachnoid hemorrhage. Nimodipine has low oral bioavailability (2.7-27.9 percent), a short half-life (2 h), is highly protein bound (98-99 percent), and is hepatically metabolized. Clinical studies have evaluated topical, intravenous, and oral administration of nimodipine for the treatment of cerebral artery spasm associated with subarachnoid hemorrhage. These studies document some benefit of the drug in reducing the occurrence of severe neurologic deficit, although this effect is not universal. Few adverse effects have been noted. Further studies are necessary to evaluate the pharmacologic and pharmacokinetic characteristics, the appropriate dose and route of administration, adverse effects, drug interactions, and the therapeutic efficacy of nimodipine before routine use can be recommended.

Receptor pharmacology of calcium entry blocking agents

The mechanism of action of calcium channel modulators, a class of drugs that includes 3 chemical groups--1,4-dihydropyridines, phenylalkylamines and benzothiazepines--has been extensively reviewed. The best known representatives of these 3 groups are nifedipine, verapamil and diltiazem, respectively. These drugs bind reversibly, stereospecifically and with high affinity to both the membrane-bound and the purified receptor complex. Non-dihydropyridines allosterically regulate dihydropyridine binding. This has been shown by using (-) [3H]202-791 and (+) [3H]PN200-110 as labeled ligands. The purified receptor complex that possesses binding sites for all 3 chemical groups is likely to be related to the voltage-dependent calcium channel. As the result of a drug-receptor interaction, voltage-dependent calcium channels are either activated or inactivated. The drugs that activate channels act by promoting long-lasting channel openings. The drugs that inhibit calcium channels, the calcium entry-blocking agents, act by preventing channel openings upon membrane depolarization. A complex pharmacologic, electrophysiologic, biochemical, immunologic and molecular genetic approach is required to determine the molecular mechanism of action of calcium channel modulators. Clinically, calcium entry-blocking agents are recommended for the treatment of angina pectoris, hypertension, posthemorrhagic cerebral vasospasm, supraventricular tachycardia, migraine and asthma and the protection of the ischemic myocardium.

Interaction of calcium antagonists with beta-adrenoceptor blocking agents

Responsiveness to verapamil, the best studied calcium antagonist, was examined in cardiac preparations of rabbits pretreated with beta-adrenoceptor blockers (propranolol 2 mg/kg or oxprenolol 4 mg/kg s.c.) twice daily for either one or six weeks. Using this dose-regimen, the degree of cardiac beta-adrenoceptor blockade in conscious rabbits was substantial and similar for propranolol and oxprenolol. When administered for one week, neither propranolol nor oxprenolol affected to any marked extent the electrical and mechanical response to verapamil, diltiazem or fendiline in tissues isolated from various parts of the heart. In contrast, pretreatment with propranolol for six weeks resulted in a significant aggravation of the negative inotropic effect of verapamil in both atrial and ventricular muscle, and the verapamil-induced delay in atrio-ventricular and intra-ventricular conduction also became more pronounced. The same long-term administration of oxprenolol, one of the beta-blockers with "intrinsic" sympathomimetic activity, did not alter the atrial or ventricular contractile response to verapamil and did not significantly increase the lengthening of atrio-ventricular conduction time occurring in the presence of verapamil. It is concluded that from the point of view of adverse direct cardiac interactions with verapamil prolonged administration of oxprenolol appears to be less dangerous than chronic treatment with propranolol. It is also assumed that in those cases in which acute administration of verapamil may be necessary, concomitant chronic blockade of cardiac beta-adrenoceptors is less dangerous if drugs known to possess not only beta-adrenoceptor blocking properties, but also some "intrinsic" sympathomimetic activity are applied.

Efficacy and safety of sublingual nifedipine in hypertensive emergencies

Hypertensive emergencies are a diverse group of disorders characterized by a marked elevation of systemic arterial pressure that is associated with acute end-organ dysfunction. The efficacy and safety of sublingual nifedipine were evaluated in 16 men and 14 women (mean age 65 +/- 14 years) who had hypertensive emergencies. Before treatment, mean systolic blood pressure was 224 +/- 23 mm Hg, mean diastolic blood pressure was 125 +/- 18 mm Hg, and the average mean arterial pressure was 158 +/- 16 mm Hg. Administration of 10 or 20 mg of sublingual nifedipine initiated a smooth and predictable decline in blood pressure values within five minutes and produced a peak effect between 30 and 60 minutes. At 30 minutes, the decreases in the systolic blood pressure, diastolic blood pressure, and mean arterial pressure for the group were 49 +/- 24 mm Hg, 31 +/- 17 mm Hg, and 39 +/- 20 mm Hg, respectively, all of which were highly significant (p less than 0.001). By 60 minutes, nifedipine had decreased the diastolic blood pressure to less than 120 mm Hg in 97 percent of patients, less than 110 mm Hg in 93 percent, and less than 100 mm Hg in 67 percent. Fourteen patients required other antihypertensive medications within the first 12 hours for the antihypertensive effect to be maintained. In this group, the systolic, diastolic, and mean arterial pressures were significantly lower than baseline values (p less than 0.001) at the time that the other drugs were started (which occurred at a mean of 4.3 +/- 3.2 hours after entry into the study). The response to nifedipine correlated with the blood pressure value prior to treatment, but did not correlate with age, gender, value prior to treatment, but did not correlate with age, gender, or the type of hypertensive emergency. Twenty mg of nifedipine produced a significantly greater antihypertensive effect than did 10 mg during the first 20 minutes (176 +/- 15 mm Hg versus 201 +/- 18 mm Hg systolic; p = 0.009) and appeared to be more efficacious clinically. In only two of 30 patients (7 percent) was the blood pressure response considered inadequate, and all 10 patients with pulmonary edema or myocardial ischemia showed clinical improvement within 60 minutes of treatment. In one patient, flushing and another symptom suggestive of transient symptomatic hypotension developed after treatment with nifedipine. These results suggest that sublingual nifedipine is a safe, effective, and practical agent for treating patients with hypertensive emergencies.