Hypotensive effects of diltiazem to normals and essential hypertensives

Retrospective analysis of risk factors of hypotensive bradycardic events during shoulder arthroscopic surgery under interscalene blockade in the sitting position

Background

Hypotensive bradycardic events (HBEs) are a frequent adverse event in patients who underwent shoulder arthroscopic surgery under interscalene block (ISB) in the sitting position. This retrospective study was conducted to investigate the independent risk factors of HBEs in shoulder arthroscopic surgery under ISB in the sitting position.

Methods

A total of 2549 patients who underwent shoulder arthroscopic surgery under ISB and had complete clinical data were included in the study. The 357 patients who developed HBEs were included in the HBEs group, and the remaining 2192 in the non-HBEs group. The potential risk factors for HBEs, such as age, sex, past medical history, anesthetic characteristics, and intraoperative medications were collected and compared between the groups. Statistically significant variables were included in a logistic regression model to further evaluate the independent risk factors for HBEs in shoulder arthroscopic surgery under ISB.

Results

The incidence of HBEs was 14.0% (357/2549). Logistic regression analysis revealed that the intraoperative use of hydralazine (odds ratio [OR] 4.2; 95% confidence interval [CI] 2.9–6.3), propofol (OR 2.1; 95% CI 1.3–3.6), and dexmedetomidine (OR 3.9; 95% CI 1.9–7.8) before HBEs were independent risk factors for HBEs in patients who received shoulder arthroscopic surgery under ISB.

Conclusions

The intraoperative use of antihypertensives such as hydralazine and sedatives such as propofol or dexmedetomidine leads to increased risk of HBEs during shoulder arthroscopic surgery under ISB in the sitting position.

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.

The intrarenal renin-angiotensin system: from physiology to the pathobiology of hypertension and kidney disease

In recent years, the focus of interest on the role of the renin-angiotensin system (RAS) in the pathophysiology of hypertension and organ injury has changed to a major emphasis on the role of the local RAS in specific tissues. In the kidney, all of the RAS components are present and intrarenal angiotensin II (Ang II) is formed by independent multiple mechanisms. Proximal tubular angiotensinogen, collecting duct renin, and tubular angiotensin II type 1 (AT1) receptors are positively augmented by intrarenal Ang II. In addition to the classic RAS pathways, prorenin receptors and chymase are also involved in local Ang II formation in the kidney. Moreover, circulating Ang II is actively internalized into proximal tubular cells by AT1 receptor-dependent mechanisms. Consequently, Ang II is compartmentalized in the renal interstitial fluid and the proximal tubular compartments with much higher concentrations than those existing in the circulation. Recent evidence has also revealed that inappropriate activation of the intrarenal RAS is an important contributor to the pathogenesis of hypertension and renal injury. Thus, it is necessary to understand the mechanisms responsible for independent regulation of the intrarenal RAS. In this review, we will briefly summarize our current understanding of independent regulation of the intrarenal RAS and discuss how inappropriate activation of this system contributes to the development and maintenance of hypertension and renal injury. We will also discuss the impact of antihypertensive agents in preventing the progressive increases in the intrarenal RAS during the development of hypertension and renal injury.

Syntheses and Biological Activities of Chalcone and 1,5-Benzothiazepine Derivatives: Promising New Free-Radical Scavengers, and Esterase, Urease, and?-Glucosidase Inhibitors

A series of 2,4-diaryl-2,3,4,5-tetrahydro- (36-40) and 2,4-diaryl-2,3-dihydro-1,5-benzothiazepines (25-35) have been synthesized from the corresponding chalcones 1-24. Both the benzothiazepines and chalcones were evaluated as DPPH free-radical scavengers and as inhibitors of cholinesterases, urease, and alpha-glucosidase. Compounds 2, 5, 6, 7, 10, 13, 18, 21, 36a, 37a, 37b, and 39a showed significant cholinesterase inhibiting activities. Among the 15 dihydro-1,5-benzothiazepines, 26, 32, and 35 exhibited significant radical-scavenging activities; and six tetrahydro-1,5-benzothiazepines (35, 36a, 36b, 37a, 37b, and 39a) were found to be inhibitors of AChE and BChE. Compounds 22, 25, 26, 33, 35, 36a, 37b, and 39a inhibited urease, and 25 and 27-31 were found to be potent inhibitors of alpha-glucosidase.

The Diltiazem Different Doses Study--a dose-response study of once-daily diltiazem therapy for hypertension

The objective was to evaluate the dose-related efficacy/tolerance profile of 240, 300, 360, and 420 mg diltiazem slow-release, once-daily (OD) doses, with emphasis on the 300 mg dose. The study was randomized and double-blinded with a 36-week parallel, two-branched, cross-over design after a single-blind, run-in period of 4 weeks on placebo and 6 weeks on 300 mg diltiazem OD. Each branch included six 6-week active treatment periods with 180, 240, and 300 mg tablets, one or two tablets OD. Participants were men and postmenopausal women, aged 40-70 years, with uncomplicated primary hypertension (WHO stages I and II) and a supine diastolic blood pressure of 95-115 mm Hg in the absence of antihypertensive medication. A total of 138 patients from various clinics participated in the study. All were included in the intention to treat analysis, and 117 patients were included in the per protocol analysis. Criteria for evaluation were blood pressure, heart rate, and response rate, as well as plasma diltiazem and metabolite M1 concentration before morning dose. Well-being of the patients and adverse events were recorded. Electrocardiogram and standard laboratory tests were obtained. Analysis of variance was used for statistical calculations. Supine blood pressures and response rates in the per protocol analysis were 161.2/97.0 for placebo (29.1%), 155.2/ 92.8 for 240 mg (54.7%), 153.8/91.6 for 300 mg (55.6%), 155.5/92.0 for 360 mg (59.0%), and 152.0/90.5 for 420 mg (63.2%) of diltiazem OD. The intention to treat analysis was very similar to the per protocol analysis. There was a small but statistically significant decrease in heart rate for all doses of diltiazem OD compared to placebo. A linear relationship existed between the dose and the plasma concentration of both diltiazem and metabolite M1, as well as a dose-response relationship. Diltiazem OD in the dose range 240-420 mg was generally well tolerated and not differently perceived from the placebo treatment except for ankle edema (2-6%). The study shows that OD diltiazem is significantly superior to placebo for mild to moderate hypertension and that the effect is large enough to be clinically valuable. It also shows that there is a linear dose-response relationship for diltiazem between 240 and 420 mg.

Gender differences in exercise and recovery blood pressure responses in normal volunteers given diltiazem

This preliminary phase I study was conducted in healthy volunteers to determine whether gender differences exist in the hemodynamic effects of diltiazem at rest, during exercise, and after exercise. At comparable serum concentrations of the drug, women demonstrated lower systolic and diastolic pressure during exercise and after exercise. ST slope after diltiazem administration in women became less positive during exercise and was gender specific. Heart rate and P-R interval changes were not gender dependent. Results of this study demonstrate that some hemodynamic responses to diltiazem are gender specific while others are not. It indicates that direct comparison studies may be required to detect such differences. In healthy women, hypotension after exercise and the effects of diltiazem are more synergistic than in men. Such a gender difference in response may be an important consideration in determining the correct dosages of this drug for treatment of hypertension.

Pharmacokinetics and pharmacodynamics of a slow-release formulation of diltiazem after the administration of a single and repeated doses to healthy volunteers

Diltiazem is a calcium antagonist used in angina pectoris and hypertension. There is little information concerning the slow-release (SR) formulation in the literature. The pharmacokinetics of diltiazem SR (120 mg) have been assessed over a 36h period in healthy volunteers after single- (SD) and multiple-dose (MD) administrations. Cmax, AUC0-36, and AUC0-infinity were significantly increased at steady state compared to the extrapolated SD values, suggesting accumulation of the drug. Renal and cardiovascular parameters have also been assessed at intervals of 3-6h during baseline (B) and following single and multiple doses of diltiazem SR. Diuresis over a 24 h period was increased, but not significantly, by the administration of diltiazem SR i.e. 1782 ml (MD) and 1915 ml (SD), versus 1626 ml (B). Natriuresis and creatinine clearance were slightly decreased by diltiazem SR, compared to B values; this might be due to the relatively short period over which steady state was maintained (five days) and the effects of norepinephrine and angiotensine II on renal vasculature and the pharmacokinetics of diltiazem SR. No increase in the systolic blood pressure occurred after the administration of diltiazem SR; diastolic blood pressure and PR interval were decreased and increased respectively by diltiazem SR. These results do not appear to be clinically significant. Finally, no relation was found between the pharmacokinetics and pharmacodynamics of diltiazem. This may be attributed to the absence of clinically significant effects in healthy volunteers, the presence of active metabolites, the pharmacokinetics of the SR formulation and/or the accumulation of the drug at steady state.

Comparative pharmacokinetics and pharmacodynamics of two marketed bid formulations of diltiazem in healthy volunteers

Cardizem SR and Bi-Tildiem were both approved in their respective countries on the basis of clinical trials demonstrating efficacy and safety in the treatment of angina pectoris. In this cross-over randomized study, we assessed whether these two sustained-release formulations of diltiazem have equivalent pharmacokinetic and pharmacodynamic profiles. Twenty-four young healthy male volunteers were hooked to Holters and ambulatory blood pressure monitors for 24 h to establish baseline systolic blood pressure (SBP), diastolic blood pressure (DBP), sinus rate and PR intervals. They then received a single dose of 120 mg of diltiazem from one formulation. The pharmacodynamic measurements were recorded for a further 24 h and blood samples were collected over 36 h for evaluation of diltiazem in plasma by a high-performance liquid chromatogrpahic (HPLC) method. The procedures were repeated with the alternate formulation after a 7 d wash-out. Pharmacokinetics showed statistically significant (p < 0.01) differences in AUC0-12 with means (+/- SD) of 519.2(+/- 172.8) and 429.6(+/- 147.2) ng h ml-1, AUC0-36 of 835.6(+/- 281.6) and 730.9 (+/- 271.5) ng h ml-1 and Cmax of 89.1(+/- 30.3) and 61.1(+/- 21.2) ng ml-1 for Cardizem SR and Bi-Tildiem, respectively. The only pharmacodynamic parameter showing a statistically significant difference in change from baseline between the two formulations was DBP with mean (+/- SD) change in AUC0-12 of -13.6(+/- 20.8) and +8.4(+/- 31.7) mm Hg h (p = 0.0135) and in AUC0-24 of -33.0(+/- 43.7) and -0.3(+/- 59.2) mm Hg h (p = 0.0463) for Cardizem SR and Bi-Tildiem, respectively. These findings suggest that assessment of efficacy of sustained-release formulations of diltiazem by bioequivalence could be misleading. They also confirm that a single dose of diltiazem does not elicit a significant pharmacodynamic response in healthy volunteers. Equivalence for such formulations should therefore be demonstrated by pharmacodynamic evaluation or clinical studies in a patient population.

Determination of diltiazem hydrochloride in human serum by high-performance liquid chromatography

A simple and sensitive reversed-phase high-performance liquid chromatographic method for the determination of diltiazem in human serum has been developed. The method involves a one-step deproteinization of serum for sample clean-up using acetonitrile. A LiChrosorb RP-8 column (30 cm x 4.1 mm I.D.) was eluted isocratically with acetonitrile-0.01 M dibasic sodium phosphate (40:60, v/v) containing 0.01% triethanolamine. Diltiazem was monitored at 237 nm and 0.1 a.u.f.s. The completion time for assay was less than 15 min, and the lower limit of quantitation was 10 ng/ml for a 100-microliters injection volume. Using this method, the pharmacokinetic parameters were calculated from a serum concentration versus time profile of diltiazem.

Twenty-four hour ambulatory blood pressure profile of a new slow-release formulation of diltiazem in mild to moderate hypertension

Twelve patients with a mild to moderate essential hypertension were included in a double-blind, balanced, randomized placebo-controlled cross-over study to assess the efficacy and duration of action of a new slow-release formulation of diltiazem (300 mg) given once daily for 3 weeks. All office blood pressure measurements were done 24 hours after drug intake. In order to improve the accuracy of the trial, 24-hours non-invasive ambulatory blood pressure monitoring (Spacelabs 90207 system) were performed as well. Diltiazem significantly lowered supine and standing systolic and diastolic office blood pressure (by 16.9/12.7 mmHg and by 17.3/13.8 mmHg, respectively), without changing office heart rate. Diltiazem also significantly lowered ambulatory blood pressure measured over 24 hours, as well as ambulatory heart rate. The blood pressure lowering effect was most pronounced during the daytime period and did not reach statistical significance during the sleeping hours. The treatment was well tolerated, and there were no significant side effects. The results confirm the antihypertensive efficacy of diltiazem LP 300 mg once daily during the daytime and during the early morning blood pressure rise, without inducing nocturnal hypotension.

Studies on inhibition of human platelet response by diltiazem

1. Aim of the present investigation was to investigate the effects of calcium blocking agent diltiazem on human platelet response to aggregating agents. 2. Results showed that diltiazem inhibits platelet aggregation induced by ADP, arginine vasopressin, adrenaline, collagen, Na arachidonate, thrombin and phorbol ester PMA in a dose-dependent way. 3. Diltiazem decreased also beta-thromboglobulin release and Thromboxane B2 production from stimulated platelets. 4. Intraplatelet cyclic AMP levels were not modified by the substance. 5. Data provide evidence that the modulation of human platelet function by diltiazem could be also related to inhibition of protein kinase C.

Determinants of antihypertensive response to calcium antagonists in systemic hypertension

Calcium antagonists are an important group of drugs in the treatment of systemic hypertension. Examination of the factors that determine the magnitude of antihypertensive response to calcium antagonists is of interest for clinical and basic pathophysiologic reasons. Possible factors influencing response include drug dose, plasma drug concentration, plasma renin activity, baseline blood pressure, nonionized calcium in blood and inside vascular smooth muscle cells, patient age and patient race. Published studies have examined the determinants of antihypertensive response. The striking fact about many of these studies is that they fail to control for other possible factors that might influence response. This article reviews the methods used and the results of 23 different studies that examined the determinants of response to calcium antagonists. Possible relationships between plasma renin activity, intra- and extracellular calcium levels, and the antihypertensive response, are of interest from a pathophysiologic point of view. From a clinician's standpoint, the only determinants that matter are the dose of the drug and the degree of elevation of the blood pressure. In this regard, calcium channel blocking drugs are no different from other drugs that act by peripheral vasodilation.

Hormonal and metabolic effects of calcium channel antagonists in man

Calcium is a component of many metabolic reactions. By blocking calcium transport across cell membranes, calcium channel antagonists can therefore theoretically affect numerous metabolic and hormonal processes. In vitro studies have often documented just such an effect. Because of the expanding use and prevalence of calcium antagonists in clinical practice, a review of their in vivo effects on hormones and metabolism is warranted. The effect on glucoregulatory hormones, calcium regulatory hormones, anterior and posterior pituitary secretion, the renin-angiotensin axis, plasma catecholamines, and plasma lipids and lipoproteins is herein reviewed. The various calcium antagonists, by virtue of their distinct chemical structures, influence metabolism in their own unique manner. Despite the widespread involvement of calcium in hormone action, however, calcium channel antagonists have little dramatic impact on hormone regulation. This is, in part, due to the drug dosage used in clinical practice and to the inherent compensatory mechanisms built into normal endocrine function. The development of agents with greater and more potent metabolic specificity, however, coupled with the ability to target drug action, holds promise for expanded therapeutic application in the future.

Sustained-release diltiazem compared with atenolol monotherapy for mild to moderate systemic hypertension

The daily administration of 240 to 360 mg of diltiazem lowered blood pressure in a dose-related pattern similar to that seen in patients taking a daily dosage of 50 to 100 mg of atenolol. Sustained-release diltiazem was administered twice daily and atenolol once. Goal blood pressure was defined as less than 90 mm Hg or a reduction of greater than or equal to 10 mm Hg for patients with baseline pressures of 95 to 99 mm Hg in the supine position and was achieved in 60% of diltiazem-treated and 63% of atenolol-treated patients. The mean diltiazem dosage at the end of the study was 329 mg daily; for atenolol it was 80 mg daily. Adverse reactions considered possibly or probably drug related were reported by 26% of diltiazem patients and 38% of atenolol patients. Although both drugs were associated with a slower heart rate, atenolol patients showed a significantly greater negative chronotropic effect. Diltiazem, in a sustained-release form taken twice daily, is as effective as atenolol as a sole antihypertensive agent. It has a favorable side-effect profile and may be a useful alternative antihypertensive medication compared with existing beta-blocker therapy with atenolol.

Acute and chronic studies of diltiazem in elderly versus young hypertensive patients

The pharmacodynamics, disposition and hormonal responses to acute intravenous and chronic oral diltiazem treatment were compared in young and elderly hypertensive patients. In elderly patients, supine diastolic blood pressure decreased significantly during the first week of treatment (baseline mean +/- standard error of the mean, 100 +/- 1 to 93 +/- 2 mm Hg) and decreased further during the study to 86 +/- 2 mm Hg at the end of the study. Diastolic blood pressure of the young patients decreased significantly by the third week of treatment (from 104 +/- 2 to 97 +/- 3 mm Hg) and decreased further during the study to 94 +/- 2 mm Hg at the end of the study. Baseline supine systolic blood pressure was greater in elderly than in young patients (167 +/- 5 vs 144 +/- 3 mm Hg; p less than 0.01) and was significantly reduced in the elderly by the fourth week (167 +/- 5 to 154 +/- 3 mm Hg; p less than 0.003), with a significantly reduction sustained throughout the 14-week period. Young patients had little change in systolic blood pressure. Supine heart rate tended to decrease in both groups during the 14-week period. Acute intravenous diltiazem pharmacokinetics determined at the beginning of the study showed that total diltiazem clearance was similar in elderly (13.3 +/- 1.0 ml/min/kg) and young (13.7 +/- 1.9 ml/min/kg) patients as was volume of distribution (4.2 +/- 0.3 vs 4.3 +/- 0.6 liters/kg) and elimination half-life (3.78 +/- 0.19 vs 3.69 +/- 0.23 hours).(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term renal effects of diltiazem in essential hypertension

Eighteen hypertensive patients underwent short-term (8 weeks) and long-term (6 months) assessment of renal function and body fluid composition following diltiazem monotherapy (240 to 480 mg/day). Diltiazem monotherapy effectively lowered blood pressure in 60% of patients at 8 weeks. In 12 of the 18 patients continued on diltiazem monotherapy for 6 months, good control of blood pressure was sustained. Glomerular filtration rate, effective renal plasma flow, filtration fraction, and renal vascular resistance were unchanged throughout the protocol period. In individuals with pretreatment glomerular filtration rates less than or equal to 80 ml/min/1.73m2, diltiazem monotherapy showed both short-term and long-term improvement in glomerular filtration rate (62%) and effective renal plasma flow (34%). Filtration fraction was unchanged, suggesting that the changes in glomerular filtration rate might be related to the attenuated intrarenal effects of angiotensin II and/or norepinephrine. No long-term effect was seen on salt and water excretion or body fluid composition.

Calcium modulators: future agents, future uses

The calcium modulators have been a significant therapeutic advancement for the treatment of angina. Structural analogs of verapamil and nifedipine have been synthesized, as have structurally unique compounds. As the role of calcium in body processes is further elucidated, the efficacy of the calcium modulators is being evaluated for numerous disorders. It is anticipated that the newly synthesized compounds will have specificity toward particular body processes, thus providing efficacy with minimal side effects.

Short- and long-term effects of calcium entry blockers on the kidney

The renal effects of the calcium entry-blocking drugs diltiazem, nifedipine, nitrendipine, nicardipine and verapamil are reviewed. Although nifedipine may acutely increase plasma renin activity, most of the calcium entry blockers have no sustained effect on any of the components of the renin-angiotensin-aldosterone system. Although all of the calcium entry blockers effectively lower blood pressure, none adversely affects renal function: Glomerular filtration rate and effective renal plasma flow are maintained. Diltiazem may increase glomerular filtration rate via attenuation of the intrarenal effects of angiotensin II or norepinephrine. Although all of the calcium entry blockers acutely increase salt and water excretion, most of the calcium entry blockers have no clinically sustained effect on salt and water excretion; serum electrolytes, urinary sodium and potassium excretion, body fluid composition and body weight are usually unchanged. Calcium entry blockers can be expected to assume a prominent role in the treatment of hypertension because of their ability to lower blood pressure while preserving renal perfusion and function.

Exercise and antihypertensive therapy

The effects of exercise on central hemodynamic mechanisms and the changes induced by treatment have been studied invasively in approximately 500 men with essential hypertension. In patients with mild hypertension, the increase in blood pressure (BP) during dynamic exercise is similar to that seen in normal subjects, but in patients with severe hypertension it is steeper. During dynamic exercise total peripheral resistance is increased in all categories of hypertensive patients, including young subjects with apparently "normal" resistance at rest. The increase in stroke volume in transition from rest to exercise is subnormal, probably reflecting increased stiffness in the left ventricle. Static exercise causes dramatic increase in systolic as well as diastolic BP. Most antihypertensive agents control BP similarly during exercise and at rest. The hemodynamic mechanisms, however, differ greatly. The beta blockers induce a long-term reduction in cardiac output, muscle blood flow and, frequently, endurance capacity. In contrast, alpha-receptor blockers, calcium antagonists and angiotensin converting enzyme inhibitors all reduce total peripheral resistance and do not decrease blood flow. Increase in endurance time has been reported with long-term calcium antagonist treatment. It would seem logical to select an antihypertensive drug that does not reduce exercise capacity when treating physically active patients with mild and moderate hypertension.

Effect of the calcium antagonist nilvadipine on haemodynamics at rest and during cold stimulation in essential hypertension

The immediate haemodynamic effects of the calcium antagonist nilvadipine have been studied in ten patients with established mild essential hypertension. Nilvadipine 4 mg p.o. reduced both the systolic and diastolic blood pressures within 60 min, associated with a fall in total peripheral resistance and an increase in heart rate and cardiac index. The peak of blood pressure and total peripheral resistance reached during a cold pressor test were reduced by nilvadipine, but it did not affect the haemodynamic responsiveness to cold stimulation. Plasma renin activity was unaltered and the plasma noradrenaline concentration was increased only slightly. Thus, nilvadipine lowered blood pressure at rest and during cold stimulation as a result of arteriolar dilatation. The hypotensive effect at rest was associated with a reflex increase in heart rate and cardiac index.

Effects of diltiazem hydrochloride on cardiovascular response, platelet aggregation and coagulating activity during exercise testing in systemic hypertension

The effects of diltiazem hydrochloride on exercise-induced changes in cardiovascular response, plasma renin activity, platelet function and blood coagulability were evaluated with multistage treadmill exercise in 20 patients who had systemic hypertension of stage 1 to 2 (World Health Organization classification). Heart rates, blood pressure, and pressure-rate product at rest, at peak exercise and in the recovery period were significantly reduced after 4 weeks of diltiazem administration, 180 mg/day. Plasma renin activity tended to increase after the medication. However, platelet adenosine diphosphate-induced aggregation sensitivity, prothrombin time, activated partial thromboplastin time, plasma fibrinogen concentration and antithrombin III activity did not change significantly. It is concluded that diltiazem could ameliorate the hyperresponsiveness of heart rate and BP to exercise in hypertensive patients without affecting blood coagulability.

Calcium channel blockers and treatment of hypertension

Over the past years, research efforts have been focused on the pathophysiologic role of calcium ions, and the implication for the potential role of calcium channel blockers in the management of essential hypertension. Numerous studies have shown that nifedipine and verapamil are effective antihypertensive agents, initial experience with diltiazem is also encouraging. The magnitude of blood pressure reduction with these drugs is related to the pre-treatment blood pressure. In refractory hypertension, combination with other antihypertensive agents provide additive effect. In the elderly population and in patients with ischemic heart disease, supraventricular arrhythmia, bronchospastic disease, peripheral vascular disease or diabetes mellitus, the calcium channel blockers offer potential advantages over other antihypertensive agents. Experimental studies also suggest that these drugs may reverse ventricular hypertrophy. When long-term safety with these drugs is documented from well-controlled clinical trials, the calcium channel blockers may be our first line of therapy for the management of hypertension.

Renal effects of diltiazem in primary hypertension

Although the calcium channel blocker diltiazem has been shown to be an effective antihypertensive agent, its effect on renal function, salt and water excretion, and body fluid composition has not been well characterized in patients with primary hypertension. Therefore, these parameters were prospectively studied in 18 subjects with primary hypertension after placebo and 8 weeks of diltiazem monotherapy. Diltiazem monotherapy was confirmed to be an effective antihypertensive agent. Although mean arterial pressure was reduced from 121 to 108 mm Hg, diltiazem had no overall effect on glomerular filtration rate, renal plasma blood flow, salt and water excretion, or body fluid composition. Renal vascular resistance, however, was decreased. In subjects with pretreatment glomerular filtration rates of 80 ml/min/1.73 m2 or less, diltiazem therapy was associated with marked improvement in glomerular filtration rate (48%) and effective renal plasma flow (36%). Since the filtration fraction was unchanged, changes in glomerular filtration rate may have been related to the attenuated intrarenal effects of angiotensin II or norepinephrine, or both.

Pharmacodynamic aspects of intravenous diltiazem administration

The diltiazem serum concentration and the magnitude and time course of systemic and coronary hemodynamic and ECG responses to intravenous diltiazem (250 micrograms/kg intravenous bolus plus 1.4 micrograms/kg/min infusion) were investigated in 14 patients with chronic stable angina pectoris. After 3, 8, and 15 minutes this dosing schedule produced serum concentrations of 570 +/- 259, 199 +/- 62, and 136 +/- 30 ng/ml, respectively (mean +/- SD). These drug levels were associated with a small, transient increase in heart rate (6 bpm, mean) at 3 minutes, which occurred during the nadir of the blood pressure response. But at 8 and 15 minutes, heart rate was unchanged compared to control rates, although blood pressure remained decreased (19%, p less than 0.01 at 15 minutes). Pressure-rate product was significantly reduced as left ventricular end-diastolic pressure and dP/dT remained unchanged. Systemic resistance decreased 17% (p less than 0.05) and stroke index increased 10% (p less than 0.01). Coronary flow was maintained as coronary resistance declined (14%, p less than 0.01). PR interval prolongation (14%, p less than 0.01) occurred at 15 minutes. Correlations between changes in systolic, diastolic, and mean pressures and drug concentration were significant (r = -0.59, -0.80, and -0.78, respectively, all p less than 0.05). The intercept for each regression line was approximately 96 ng/ml diltiazem concentration, suggesting that this represents the minimum effective diltiazem serum concentration. These results indicate that intravenous diltiazem is well tolerated and promptly reduces blood pressure and both systemic and coronary resistances without oxygen-wasting effects of an increase in heart rate.

Pharmacokinetics of slow-release diltiazem and its effect on atrioventricular conduction in healthy volunteers

The pharmacokinetics and effect of a slow-release and a conventional diltiazem tablet on atrioventricular conduction were compared in a randomized cross-over study after a single dose and at steady state in 12 healthy volunteers. The time to peak concentration was significantly delayed after the slow-release as compared to the conventional tablet, both after a single dose (2.7 vs. 0.9 h) and at steady-state (1.9 vs. 0.9 h). The peak concentration was also significantly reduced. There was no marked loss in bioavailability with the slow-release formulation. The maximal fluctuations in serum diltiazem at steady-state for the slow-release tablet were markedly less than after the conventional tablet (62 vs 87%). The PQ-interval was longer after the conventional tablet as compared to the slow-release tablet (both in doses of 120 mg) after a single dose (187 vs 163 ms) and at steady-state (197 vs 174 ms). The maximal prolongation was seen 1 h after intake of the drug. Heart rate was decreased only by 6-9 beats/min, irrespective of the dose. Slow-release diltiazem appears to have many advantages over a conventional tablet.

Rationale for calcium entry-blocking drugs in systemic hypertension complicated by coronary artery disease

There is considerable rationale for the use of the calcium entry-blocking drugs for the treatment of hypertension and prevention of recurrent episodes of angina pectoris in patients with systemic hypertension and significant coronary artery disease--the 2 entities commonly occurring together. Calcium entry-blocking drugs improve myocardial blood flow while decreasing myocardial oxygen demand. These agents can be given to most patients with ischemic heart disease and its complications, and are associated with a relatively low incidence of serious adverse effects and toxicity during long-term therapy. They reduce the frequency of anginal attacks, prolong exercise time to ST-segment depression or angina and improve exercise capacity. With long-term therapy, tolerance does not develop as it does in many patients with the "long-acting" nitrates. Calcium entry-blocking drugs reduce systolic blood pressure in patients with hypertension by a decrease in peripheral vascular resistance and a uniform improvement in blood flow affecting the myocardium, kidney and brain. There are no central nervous system adverse effects and hypokalemia does not occur. Unlike therapy with the beta-blocking drugs, chronic treatment with the calcium entry blockers does not reduce the serum level of high-density lipoprotein cholesterol nor increase serum triglyceride concentration. The calcium blockers decrease the arterial blood pressure without increasing intravascular plasma volume and are associated with only a slight increase in reflex-mediated sympathetic activity and heart rate, the latter occurring predominantly with nifedipine. Calcium entry-blocking drugs provide alternative or preferred therapy to beta-blocking agents in patients with a combination of hypertension and angina pectoris.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of diltiazem on hormonal and hemodynamic responses to lower body negative pressure and tilt in patients with mild to moderate systemic hypertension

Mean arterial blood pressure, forearm vascular resistance, plasma norepinephrine, plasma renin activity and aldosterone responses to graded lower body negative pressure and tilt at 80 degrees were examined in 10 men with mild to moderate essential hypertension before and after 12 weeks of diltiazem (240 to 360 mg/day) therapy. Diltiazem therapy lowered basal supine systolic and diastolic blood pressures without affecting basal heart rate. Mean arterial blood pressure and forearm vascular resistance were decreased from 114 +/- 1.5 to 105 +/- 1 mm Hg, p less than 0.01 and from 29.3 +/- 3.5 to 18.9 +/- 2.1 units, p less than 0.01, respectively. Diltiazem therapy had no effect on basal supine levels of norepinephrine, plasma renin activity or aldosterone, nor on the responses of these hormones to lower body negative pressure. Diltiazem did decrease the forearm vascular resistance responses to lower body negative pressure and tilt. Diltiazem abolished an orthostatic increase (10 +/- 0.3 mm Hg) in mean arterial blood pressure and this was associated with a greater plasma norepinephrine response to tilt. These results suggest that diltiazem decreases vascular resistance through a reduction in the postjunctional effects of norepinephrine on vascular smooth muscle.

Effects of calcium entry blockers on renin-angiotensin-aldosterone system, renal function and hemodynamics, salt and water excretion and body fluid composition

The renal effects of the calcium entry-blocking drugs diltiazem, nifedipine, verapamil and nitrendipine are reviewed. Although nifedipine stimulates plasma renin activity on a short-term basis, none of the calcium entry blockers produces a clinically significant sustained effect on any of the components of the renin-angiotensin-aldosterone system. Although all of the calcium entry blockers effectively lower blood pressure, none adversely affects renal function; glomerular filtration rate and effective renal plasma flow are maintained. Diltiazem may increase glomerular filtration rate via attenuation of the intrarenal effects of angiotensin II or norepinephrine. Although diltiazem and nifedipine increase salt and water excretion on a short-term basis, none of the calcium entry blockers produces a clinically significant sustained effect on salt and water excretion; serum electrolytes, urinary sodium and potassium excretion, body fluid composition and body weight are unchanged. Thus, calcium entry blockers can be expected to assume a prominent role in the treatment of hypertension because of their ability to lower blood pressure while preserving renal perfusion and function.