Once daily amlodipine in the treatment of mild to moderate hypertension

A Retrospective Cohort Study of the Association of Inpatient Amlodipine Dose With Renal Complication Rates and Hospital Length of Stay

Background Correct hospital medication reconciliation is important for continuity of care, but optimal home antihypertensive medication ordering has not been adequately studied. Since excessive hospital blood pressure control is associated with adverse renal and cardiovascular outcomes, we assessed the association of inpatient doses of amlodipine (10mg vs. 5mg) with length of stay and renal failure and fluid and electrolyte disorders (RF/FED). Methods In this retrospective cohort study, clinical and demographic data on patients not initially admitted to the ICU between 2008 and 2019 were extracted from the Medical Information Mart for Intensive Care (MIMIC-IV). Multivariable logistic regression was used to assess the association between amlodipine dose during the first 24 hours of admission and RF/FED. Multivariable linear regression was used to assess the association between amlodipine dose and length of stay when controlling for RF/FED or maximum blood urea nitrogen (BUN) concentration and other confounders. Results There were 5,932 patients included in this study, and 3,038 of whom received 10mg of amlodipine. A 10mg dose of amlodipine was associated with an increased likelihood of RF/FED (OR: 1.248, 95% CI (1.104, 1.412), p<0.001). It was also associated with a longer length of stay (coef.: 0.338, 95% CI (0.067, 0.609), p=0.015). This was not significant when controlling for RF/FED (dose coef.: 0.197, 95% CI (-0.070, 0.464), p=0.147) or maximum BUN (dose coef.: 0.082, 95% CI (-0.147, 0.312), p=0.482). Interpretation Higher amlodipine dose was associated with longer length of stay, and this is likely mediated by RF/FED. Randomized trials are needed to determine which home blood pressure medications should be ordered in the hospital.

Plasma Trough Concentrations of Antihypertensive Drugs for the Assessment of Treatment Adherence: A Meta-Analysis

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Biochemical drug screening by liquid chromatography-tandem mass spectrometry in plasma is an accurate method for the quantification of plasma concentrations of antihypertensive medications in patients with hypertension. Trough concentrations could possibly be used as drug-specific cutoff values in the biochemical assessment of (non-)adherence. We performed a literature review and meta-analysis of pharmacokinetic studies to determine plasma trough concentrations of amlodipine, hydrochlorothiazide, and valsartan. PubMed was searched for pharmacokinetic studies up to September 2020. Eligible studies reported steady-state mean trough concentration and their variance. Pooled trough concentrations were estimated using a three-level random effects meta-analytic model. Moderator analyses were performed to explore sources of heterogeneity. One thousand three hundred eighteen potentially relevant articles were identified of which 45 were eligible for inclusion. The pooled mean trough concentration was 9.2 ng/mL (95% CI, 7.5–10.8) for amlodipine, 41.0 ng/mL (95% CI, 17.4–64.7) for hydrochlorothiazide, and 352.9 ng/mL (95% CI, 243.5–462.3) for valsartan. Substantial heterogeneity was present for all 3 pooled estimates. Moderator analyses identified dosage as a significant moderator for the pooled trough concentration of amlodipine (β₁=0.9; P<0.05), mean age, and mean body weight for the mean trough concentration of hydrochlorothiazide (β₁=2.2, P<0.05, respectively, β₁=−4.0, P<0.05) and no significant moderators for valsartan. Plasma trough concentrations of amlodipine, hydrochlorothiazide, and valsartan, measured with liquid chromatography-tandem mass spectrometry, are highly heterogeneous over the different studies. Use of the pooled trough concentration as a cutoff in the biochemical assessment of adherence can result in inaccurate diagnosis of (non-)adherence, which may seriously harm the patient-physician relationship, and is therefore not recommended.

Low Levels of Amlodipine in Breast Milk and Plasma

OBJECTIVE

Few clinical reports have addressed the use of the antihypertensive drug amlodipine during breastfeeding. The objective of this study is to characterize concentration-time profiles of amlodipine in maternal and infant plasma, and milk.

MATERIALS AND METHODS

Plasma and breast milk samples were obtained from eight nursing mothers and their nine newborn nursing infants (median postnatal age: 6.5 days, range 5-7 days). Participants were recruited from February 2009 to June 2009. Multiple blood and milk samples were obtained from the mothers over a 24 hours dosing interval. The blood of infants was also obtained at before and 8 hours after nursing. Amlodipine concentrations were determined by high-performance liquid chromatography. Relative infant dose (RID) was calculated by dividing the infant's dose via milk in mg/kg/day by the maternal dose in mg/kg/day, assuming that a daily intake of milk is 150 mL/kg/day in the infants.

RESULTS

Maximal amlodipine concentrations in mothers ranged from 4.4 to 14.7 ng/mL in plasma, and 6.5 to 19.7 ng/mL in milk (Average milk/plasma ratio: 1.4). RID was 3.4% of the maternal weight-adjusted dose. All plasma concentrations in infants were under the quantitation limit (0.4 ng/mL).

CONCLUSION

Infant exposure to amlodipine in breast milk appears very small, suggesting that amlodipine can be used with little influence on infants during breastfeeding.

Combination With Low-dose Dextromethorphan Improves the Effect of Amlodipine Monotherapy in Clinical Hypertension: A First-in-human, Concept-proven, Prospective, Dose-escalation, Multicenter Study

The combination of low rather than high dose of dextromethorphan (DXM) with amlodipine (AM) could improve blood pressure (BP) reduction in hypertensive animals. The study aimed to evaluate the feasibility of different doses of DXM combined with standard AM treatment in clinical hypertension.This was a prospective, 14-week, dose-escalation, multicenter study. After 2-week run-in period with AM 5 mg/day, hypertensive patients who got the BP goal of 140/90 mmHg kept receiving AM monotherapy for another 12 weeks. The nonresponders, while kept on AM 5 mg/day, received additional DXM treatment for 3 sequential dose-titrated periods with initially 2.5 mg/day, followed by 7.5 mg/day, and finally 30 mg/day. Each period was for 4 weeks. The patients at BP goal after each treatment period were defined as the responders and kept on the same combination till the end of the study. The responder rate of each treatment period was recorded. The changes of BP and serum antioxidant/endothelial markers between week 14 and week 2 were evaluated.Of the 103 patients initially enrolled, 89 entered the treatment period. In the 78 patients completing the study, 31 (40%) at BP goal after 2-week AM run-in kept on AM monotherapy (DXM0). The addition of 2.5 (DXM2.5) and 7.5 mg/day (DXM7.5) of DXM enabled BP goal achievement in 22 (47%) nonresponders to AM monotherapy including 16 (29%) with DXM2.5 and 6 (18%) with DXM7.5. Only 4 patients (16%) reached BP goal with the combination of DXM 30 mg/day (DXM30). Overall, 73% of the 78 patients reached BP goal at the end of the 14-week study. Mean systolic BP was reduced by 7.9% ± 7.0% with DXM2.5 (P < 0.001) and by 5.4% ± 2.4% with DXM7.5 (P = 0.003) respectively at week 14 from that at week 2, which was unchanged in either DXM0 or DXM30 group. Besides, the effects of combination treatment were particularly significant in the patients with impaired endothelial function suggested by reduced serum NOx level at baseline.Accordingly, the combination with low dose of DXM was feasible to improve BP control in patients who failed to achieve the BP goal by standard AM monotherapy. The benefit effects might be significant especially in patients with impaired endothelial function.

Amlodipine seems to be superior to valsartan in decreasing microalbuminuria in newly diagnosed hypertensive patients: a novel effect to be explained with hyperfiltration?

BACKGROUND

Microalbuminuria (MA) is common in hypertensive population and is a marker for endothelial dysfunction and a predictor of increased cardiovascular risk. A great body of data shows the importance of MA as a strong predictor of renal and cardiovascular disease (CVD) risk in hypertensive population.

AIM

In this study, we aimed to compare the anti-albuminuric effects of an angiotensin II receptor antagonist, valsartan, with a calcium channel blocker, amlodipine, in newly diagnosed hypertensive patients.

MATERIAL AND METHODS

Totally, 20 patients were recruited into the study. Patients were randomized to one of the following intervention protocols: An (a) angiotensin II receptor blocker (valsartan, 80-320 mg/day) or (b) calcium channel blocker (amlodipine, 5-10 mg/day), for 12 weeks immediately after baseline measurements. Ten patients were randomized into valsartan group and 10 patients into the amlodipine group. Twenty-four-hour urinary albumin excretion (UAE) levels of the patient groups were measured before treatment and on the 12th week.

RESULTS

Patients of the two groups were matched for age and body mass index. In the amlodipine group, baseline urine microalbumin levels were higher compared to valsartan group, although the difference was not statistically significant (p = 0.082). At the 12th week, there was a significant decrease in urine microalbumin levels in the amlodipine group, but no significant change was observed in the valsartan group.

CONCLUSION

Amlodipine seems to be superior to valsartan in decreasing UAE. To reduce cardiovascular risks, endothelial dysfunction, and microinflammation, these factors are taken into consideration while prescribing antihypertensive drugs in hypertensive patients.

Amlodipine 2.5???mg once daily in older hypertensives: a Brazilian multi-centre study

OBJECTIVES

The use of low-dose amlodipine has not yet been well established in the elderly. This study therefore aimed to evaluate the efficacy and tolerability of low-dose amlodipine in elderly patients with Joint National Committee VI stage I or II hypertension.

PATIENTS AND METHODS

Sixty-five hypertensive individuals (aged 66.3 +/- 5.3 years) received amlodipine 2.5 mg per day for 12 weeks before and after two periods of 4 weeks of placebo. At weeks 0, 12 and 16, patients were submitted to office, 24 h ambulatory blood pressure monitoring and home blood pressure measurement.

RESULTS

Office systolic and diastolic blood pressure showed decreases at weeks 8 (153 +/- 17, 90 +/- 9 mmHg) and 12 (152 +/- 16, 90 +/- 9 mmHg) compared with weeks 0 (164 +/- 16, 99 +/- 6 mmHg) and 16 (162 +/- 19, 95 +/- 9 mmHg). During ambulatory monitoring, a decrease was observed in the average 24 h systolic and diastolic pressure at week 12 (143 +/- 13, 86 +/- 7 mmHg) compared with weeks 0 (155 +/- 15, 93 +/- 6 mmHg) and 16 (152 +/- 16, 92 +/- 8 mmHg). A daytime and night-time reduction in systolic and diastolic pressure was observed on home blood pressure monitoring at week 12 (146 +/- 16/88 +/- 8, 144 +/- 16/93 +/- 8 mmHg) compared with weeks 0 (159 +/- 17/94 +/- 8, 161 +/- 19/93 +/- 8 mmHg) and 16 (153 +/- 16/93 +/- 8, 154 +/- 17/92 +/- 8 mmHg). Adverse reactions were infrequent.

CONCLUSIONS

Amlodipine at a dose of 2.5 mg per day showed efficacy and good tolerability in elderly hypertensives.

Effect of amlodipine on systolic blood pressure

BACKGROUND

Systolic hypertension is the most common form of hypertension, particularly in people aged >60 years. Caused by decreased compliance of large arteries, systolic hypertension is an independent risk factor for cardiovascular disease. Recent studies have demonstrated that it is more important to control systolic blood pressure (SBP) than diastolic blood pressure (DBP).

OBJECTIVE

The objective of this study was to perform a systematic literature review to examine the effectiveness of amlodipine in lowering SBP in a variety of patient subgroups and clinical settings.

METHODS

The literature review methodology included identifying, selecting, appraising, extracting, and synthesizing primary research studies. Following an a priori protocol, published literature was searched from 1980 to 2001 using 3 electronic databases. A manual review of the reference lists of recent review articles and all accepted studies was performed. Parallel-group, randomized, controlled trials that included at least 10 adults with baseline hypertension (SBP>or=140 mm Hg, DBP>or=90 mm Hg, or both), included at least 1 arm randomized to initial treatment with amlodipine monotherapy, had a minimum treatment duration of 8 weeks, and reported baseline and end-point blood pressure were included.

RESULTS

Of 696 citations identified, 85 primary studies met all inclusion criteria. Comparable treatment arms were pooled, and weightd mean SBP was calculated. In the amlodipine monotherapy arms, which included >5000 patients, SBP decreased by a mean of 17.5 mm Hg from baseline. The effect of amlodipine in reducing SBP was greater in elderly patients (age>or=60 years) and patients with author-defined isolated systolic hypertension. The dose was titrated to achieve the target blood pressure in 73 of 89 amlodipine treatment arms, whereas 16 treatment arms reported fixed doses. The median daily dose was 5 mg (range, 1.25-15 mg) in both the fixed-dose and dose-titration groups.

CONCLUSIONS

In this review of the published literature, amlodipine monotherapy was effective in reducing SBP. Antihypertensive agents such as amlodipine warrant consideration for the management of patients with inadequately controlled SBP.

Sex- and age-related antihypertensive effects of amlodipine. The Amlodipine Cardiovascular Community Trial Study Group

This community-based study assessed whether there were age, sex, or racial differences in response to amlodipine 5 to 10 mg once daily in patients with mild to moderate essential hypertension. This prospective, open-label trial had a 2-week placebo period, a 4-week upward drug titration/efficacy period, and a 12-week drug maintenance period. There were 1,084 evaluable patients (mean age 55.5 years; 65% men and 35% women; 79% white and 21% black; 75% <65 and 25% > or = 65 years old). At the end of the titration/efficacy phase, the mean +/- SD blood pressure (BP) decreased by -16.3 +/- 12.3/-12.5 +/- 5.9 mm Hg, (p < or = 0.0001). Amlodipine produced a goal BP response (sitting diastolic BP < or = 90 mm Hg, or a 10 mm Hg decrease) in 86.0% of patients overall. The BP response was greater in women (91.4%) than in men (83.0%, p < or = 0.001), and greater in those > or = 65 years old (91.5%) than in those < 65 years old (84.1%, p < or = 0.01); however, it was similar between whites and blacks (86.0% vs 85.9%, respectively, p = NS). The sex difference in BP response could not be fully explained by differences in age, weight, dose (mg/kg), race, baseline BP, or compliance, and there were no differences among women based on use of hormone replacement therapy. Amlodipine was well tolerated; mild to moderate edema was the most common adverse effect. Thus, amlodipine was effective and safe as once-a-day monotherapy in the treatment of mild to moderate hypertension in a community-based population. Women had a greater BP response to amlodipine.

Amlodipine induces a flow and pressure-independent vasoactive effect on the brachial artery in hypertension

1. The objectives of this study were to study the flow-dependent arterial reactivity and pressure-independent arterial compliance of the calcium antagonist amlodipine in hypertensive men. 2. Twenty-one hypertensive patients were randomized to receive 2 months treatment with placebo (n = 10) or 5-10 mg amlodipine (n = 11) once a day. Non-invasive measurement of brachial artery mean blood pressure, diameter and flow (pulsed Doppler) and compliance (arterial mechanography and logarithmic elastic model) were obtained before and after drug administration. Vasoreactivity was studied by means of response of the brachial artery during exclusion of the hand and hyperaemia post-ischaemia. 3. Compared with placebo, amlodipine reduced mean blood pressure (% change +/- s.e. mean 11 +/- 1% vs 4 +/- 3%, P < 0.05), and increased arterial compliance at prevailing pressure (44 +/- 13%, vs 1 +/- 8%, P < 0.05) and at isobaric pressure (26 +/- 10% vs -3 +/- 6%, P < 0.05). A significant % change increase from baseline in brachial artery diameter between placebo and amlodipine was observed at rest (-2 +/- 3 vs 8 +/- 3%; P < 0.05), after wrist occlusion (-3 +/- 3 vs 6 +/- 2%; P < 0.05) and during reactive hyperaemia (-5 +/- 3 vs 18 +/- 5%; P < 0.05). No significant differences between amlodipine and placebo groups were observed in blood velocity after forearm manoeuvres before and after treatment. 4. No differences were observed between groups in brachial flow-dependent vasodilation.(ABSTRACT TRUNCATED AT 250 WORDS)

Morning versus evening administration of nifedipine gastrointestinal therapeutic system in the management of essential hypertension

The nifedipine gastrointestinal therapeutic system (GITS) is a recently developed controlled-release formulation for once-a-day dosing. We evaluated the influence of morning versus evening administration of the drug in a randomized double-blind cross-over study including 15 essential hypertensives. Five patients had to be excluded from blood pressure analysis because of noncompliance (three cases) or intolerable side effects (two cases). To assess the exact duration of the antihypertensive efficacy noninvasive automatic ambulatory blood pressure monitoring was performed. After a placebo period patients were given 30 mg nifedipine GITS either at 1000 or 2200 hours. Twenty-four-hours systolic and diastolic blood pressure profiles documented a sustained antihypertensive effect of both nifedipine regimens throughout the whole period without affecting the circadian rhythm. Statistical analysis revealed no significant difference between morning and evening administration. Two patients stopped their medication because of intolerable side effects (fatigue and muscle cramps, respectively). Two more cases suffered from mild reversible headache which provoked no discontinuation of the drug. In conclusion our results document a sustained antihypertensive efficacy of 30 mg nifedipine GITS in patients with moderate essential hypertension. Time of administration has no impact on day- and nighttime blood pressure control.

Double-blind comparison of amlodipine and hydrochlorothiazide in patients with mild to moderate hypertension

In the final analysis of this study at Week 26, 26% of the patients randomized to receive amlodipine attained blood pressure control with amlodipine alone compared with 33% of the patients allocated to hydrochlorothiazide (HCTZ). Neither amlodipine nor HCTZ produced clinically significant changes in pulse rate or in the electrocardiogram. Amlodipine treatment did not appear to produce clinically significant changes in blood lipids; HCTZ, however, produced an increase in total plasma cholesterol (delta 22.9 +/- 8.6 mg/dl). The incidence of side effects and the rate of patient withdrawal in the amlodipine and HCTZ groups were comparable. As expected, HCTZ therapy caused well-recognized biochemical alterations in cholesterol and potassium levels, whereas amlodipine was metabolically neutral.

An overview of the pharmacokinetics and pharmacodynamics of amlodipine in elderly persons with systemic hypertension

Pharmacokinetic and pharmacodynamic data were compared between elderly and young patients with hypertension who received single intravenous doses of amlodipine, a dihydropyridine calcium antagonist, followed by oral administration of amlodipine up to 10 mg once daily for 12 weeks. After intravenous administration, elderly patients had prolonged elimination half-life values (58 +/- 11 vs 42 +/- 8 hr; p < 0.05) caused by decreased clearance (19 +/- 5 vs 7 liters/hr; p < 0.05). Systolic and diastolic blood pressures were significantly decreased from baseline throughout the 3-month treatment period in both groups. After long-term oral administration, elderly and young patients had comparable decreases in mean blood pressure at a given drug plasma concentration. The antihypertensive effect of amlodipine is well correlated with plasma concentration and, at a given concentration, is similar in both elderly and young patients.

Combination therapy with amlodipine and captopril for resistant systemic hypertension

This study was conducted to assess the therapeutic utility of combining amlodipine with captopril in patients with moderate-to-severe hypertension. Patients had hypertension of WHO grades I-III, with initial mean sitting and standing diastolic blood pressure of 100-119 mm Hg (phase V) after 2-4 weeks on placebo, and had remained uncontrolled (diastolic blood pressure > 95 mm Hg) despite a further 4 weeks on low-dose captopril. Twenty-nine patients entered the computer-randomized, double-blind, placebo-controlled, 2-way crossover comparison of either amlodipine 10 mg once daily or matching placebo added to continued therapy with captopril 25 mg twice daily for 4 weeks. Patients then acted as their own control and received the alternative amlodipine/placebo treatment plus their continued captopril therapy for another 4 weeks. Once-daily amlodipine was shown to be effective when combined with captopril. Mean baseline supine systolic blood pressure decreased from 167 to 149 mm Hg and standing systolic blood pressure from 167 to 144 mm Hg. Mean supine diastolic blood pressure decreased from 105 to 92 mm Hg, and standing diastolic blood pressure decreased from 110 to 96 mm Hg. The placebo-corrected amlodipine differences in mean changes from captopril baseline were -18/-12.2 mm Hg for supine and -20.1/-11.9 mm Hg for standing systolic and diastolic blood pressures, respectively (p < 0.001 for all 4 measurements). The most common side effects encountered with amlodipine were flushing and pedal edema. The combination of amlodipine and captopril was well tolerated, and no patient discontinued therapy. No significant treatment-related effects on biochemical and hematologic parameters were noted.

A comparison of amlodipine with enalapril in the treatment of moderate/severe hypertension

1. The safety and efficacy of amlodipine vs enalapril as monotherapy was evaluated in patients with moderate/severe hypertension (supine DBP 105-125 mm Hg, SBP 140-220 mm Hg). 2. After 2 weeks placebo treatment 31 patients were randomised by the technique of minimisation in an observer-blind study to receive once daily treatment with either amlodipine (15 patients) 5-10 mg, or enalapril (16 patients) 5-20 mg for 8 weeks. The study design concluded with 2 weeks placebo treatment. In addition to clinic measurements, home blood pressure monitoring (Copal UA-251) was performed during the study. 3. Clinic supine systolic blood pressure was reduced from 177 to 152 mm Hg (amlodipine) and 183 to 169 mm Hg (enalapril) (95% CI for the intergroup difference -22.1, 0.3, P = 0.06) after 8 weeks treatment. 4. Clinic supine diastolic blood pressure was reduced from 110 to 93 mm Hg (amlodipine) and 109-102 mm Hg (enalapril) (95% CI for the intergroup difference -17.7, -2.7, P < 0.01) after 8 weeks treatment. 5. Home blood pressure recordings confirmed these reductions in blood pressure. Although the reduction in blood pressure was greater for the amlodipine treated group, the differences between treatments were not statistically significant. 6. Both drugs were reasonably well tolerated. The adverse events occurring most frequently in the amlodipine group were headache (5), peripheral oedema (3), upper respiratory infection (3) and anxiety (2). The adverse events occurring most frequently in the enalapril treated patients were headache (6), dizziness (3) and upper respiratory infection (2).

A comparison of amlodipine with enalapril in the treatment of isolated systolic hypertension

1. The safety and efficacy of amlodipine and enalapril were compared in patients with isolated systolic hypertension (supine DBP < 95 mm Hg and supine SBP 160-200 mm Hg). 2. After 2 weeks treatment with placebo 31 patients were randomised by the technique of minimisation in an observer-blind study to receive once daily treatment with either amlodipine (16 patients) or enalapril (15 patients) for 8 weeks. The study design concluded with 2 weeks placebo treatment. In addition to clinic measurements, home blood pressure monitoring (Copal UA-251) was performed during the study. 3. Mean supine systolic blood pressure was reduced from 185 to 164 mm Hg (amlodipine) and 183 to 159 mm Hg (enalapril) (95% CI for the difference between the drugs -10.5, 15.3) after 8 weeks treatment. 4. Mean supine diastolic blood pressure was reduced from 86 to 80 mm Hg (amlodipine) and 88 to 80 mm Hg (enalapril) (95% CI for the difference between the drugs -4.9, 7.6) after 8 weeks treatment. 5. Home blood pressure recordings confirmed these reductions in blood pressure, although there was no significant difference between treatments for the reductions in blood pressure. 6. Both drugs were reasonably well tolerated. The adverse events occurring most frequently in the amlodipine group were headache (2), peripheral oedema (5) and palpitations (2). The adverse events occurring most frequently in the enalapril group were headache (2), peripheral oedema (2), palpitations (2) and dizziness (3).

Amlodipine combined with beta blockade for chronic angina: Results of a multicenter, placebo-controlled, randomized double-blind study

Amlodipine, a potent long-acting dihydropyridine calcium antagonist, was compared with placebo in a parallel, randomized, double-blind study in 134 patients with chronic stable angina pectoris maintained on beta-adrenergic blocking agents. After a single-blind, two-week placebo period, patients were randomized to receive either amlodipine (2.5, 5, and 10 mg) or placebo once daily for four weeks. The effects of amlodipine on maximal exercise time, work, time to angina onset, and subjective indices including angina frequency, nitroglycerin tablet consumption, and patient and investigator ratings were assessed. Each dose of amlodipine produced increases in exercise time and calculated total work accomplished compared to baseline. Improvements at 5 and 10 mg were significantly greater than placebo which produced no significant change (p less than 0.05). Qualitative improvements in the severity of angina were produced by amlodipine at 5 and 10 mg daily assessed by patient-rating questionnaires (p less than 0.05). Reductions in angina frequency attacks per week and weekly nitroglycerin tablet consumption occurred but were not statistically significant when compared with placebo. Adverse effects observed during amlodipine treatment prompted discontinuation of treatment in only 2 out of 100 patients. Three patients discontinued treatment for reported lack of efficacy. No laboratory abnormalities prompted treatment discontinuation and minor side effects of dizziness, nausea, headache, and fatigue were observed infrequently. The results of this controlled, large-scale multicenter trial suggest that amlodipine significantly increased exercise capacity and was well tolerated when added to the antianginal regimen of patients remaining symptomatic while receiving beta-blocking agents.

Clinical pharmacokinetics of amlodipine

Amlodipine is a dihydropyridine calcium antagonist drug with distinctive pharmacokinetic characteristics which appear to be attributable to a high degree of ionisation. Following oral administration, bioavailability is 60 to 65% and plasma concentrations rise gradually to peak 6 to 8h after administration. Amlodipine is extensively metabolised in the liver (but there is no significant presystemic or first-pass metabolism) and is slowly cleared with a terminal elimination half-life of 40 to 50h. Volume of distribution is large (21 L/kg) and there is a high degree of protein binding (98%). There is some evidence that age, severe hepatic impairment and severe renal impairment influence the pharmacokinetic profile leading to higher plasma concentrations and longer half-lives. There is no evidence of pharmacokinetic drug interactions. Amlodipine shows linear dose-related pharmacokinetic characteristics and, at steady-state, there are relatively small fluctuations in plasma concentrations across a dosage interval. Thus, although structurally related to other dihydropyridine derivatives, amlodipine displays significantly different pharmacokinetic characteristics and is suitable for administration in a single daily dose.

Plasmodium falciparum: in vitro drug interaction between chloroquine and enantiomers of amlodipine

Both enantiomers of amlodipine, whose calcium antagonist action resides almost exclusively in the R(-) enantiomer, reversed chloroquine resistance in Plasmodium falciparum in vitro. R(-) enantiomer was slightly more effective than the S(+) enantiomer in potentiating chloroquine action against chloroquine-resistant strains of parasites. No potentiating effect was observed in chloroquine-sensitive parasites. Both enantiomers entered rapidly into parasitized erythrocytes to the same extent. Reversal of chloroquine resistance by the enantiomers of amlodipine was related to dose-dependent increase in the accumulation of chloroquine inside the erythrocytes parasitized by resistant parasites. These results suggest that the potentiating effect on chloroquine is independent of calcium metabolism of malaria parasites.

Amlodipine. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic use in cardiovascular disease

Amlodipine, a basic dihydropyridine derivative, inhibits the calcium influx through 'slow' channels in peripheral vascular and coronary smooth muscle cells, thus producing marked vasodilation in peripheral and coronary vascular beds. Short to medium term clinical trials indicate that amlodipine is effective as both an antianginal agent in patients with stable angina pectoris and an antihypertensive agent in patients with mild to moderate hypertension. In small comparative studies amlodipine was at least as effective as 'standard' agents, including atenolol, verapamil, hydrochlorothiazide or captopril in hypertension, and diltiazem or nadolol in angina pectoris. Amlodipine is well tolerated, and does not appear to cause some of the undesirable effects often associated with other cardiovascular agents (e.g. adverse changes in serum lipid patterns, cardiac conduction disturbances, postural hypotension). The most common adverse effects associated with amlodipine therapy--oedema and flushing--are related to the vasodilatory action of the drug, and are generally mild to moderate in severity. Thus, amlodipine seems to provide a useful alternative to other agents currently available for the treatment of essential hypertension and chronic stable angina pectoris, with certain pharmacodynamic and tolerability properties that should be advantageous in many patients.

Calcium Channel Blockers

Calcium is an integral component in numerous physiological processes and functions. As such, drugs that interfere with the movement of calcium into or out of cells, or the activity of intracellular calcium are useful in treating a variety of disease states. This article will review the calcium channel blockers currently available, along with their approved indications, as well as select dihydropyridine investigational agents and nonapproved indications for their use.

The interactions of 1,4-dihydropyridines bearing a 2-(2-aminoethylthio)methyl substituent at voltage-dependent Ca2+ channels of smooth muscle, cardiac muscle and neuronal tissues

The Ca2+ channel antagonistic potencies of tiamdipine [2-(2-aminoethylthio)methyl-3-carboethoxy-5-carbomethoxy-6-m ethyl-4-(3- nitrophenyl)-1,4-dihydropyridine] and nifedipine [2,6-dimethyl-3,5-dicarbomethoxy-4-(2-nitrophenyl)-1,4-dihydrop yri dine] analogs bearing phenyl ring substituents were studied using pharmacologic and radioligand binding techniques. Additionally, analogs of tiamdipine possessing (2-aminoethylthio)methyl-, (2-acetamidoethylthio)methyl- and (2-pyrrolidinylmethylthio)methyl- groups at the C2 position of the 1,4-dihydropyridine ring have been studied. Tiamdipine and nifedipine analogs inhibited K(+)-induced contractile responses in rat tail artery. IC50 values of 4-phenyl ring substituted 2-(2-aminoethylthio)methyl tiamdipine analogs ranged from 10(-7) mol/l to 10(-8) mol/l. However, the corresponding 4-phenyl ring substituted nifedipine analogs covered a wider range of potency from 10(-6) mol/l to 10(-9) mol/l. KI values of the corresponding tiamdipine analogs for the inhibition of specific [3H]PN 200-110 [(+)-[3H]isopropyl-4-(2,1,3-benzoxadiazol-4-yl)-1,4-dihydro-5- methoxycarbonyl-2,6-dimethyl-3-pyridinecarboxylate] binding ranged from 10(-7) mol/l to 10(-9) mol/l in guinea pig ileal and rat heart membranes and rat brain synaptosomes. The two stereoisomers of tiamdipine and its analog 2-(2-acetamidoethylthio)methyl-3-carboethoxy-5-carbomethoxy- 6-methyl-4-(3- nitrophenyl)-1,4-dihydropyridine, and the four stereoisomers of 2-(2-pyrrolidinylmethylthio)methyl-3-carboethoxy-5-carbom eth oxy-6-methyl-4-(3- nitrophenyl)-1,4-dihydropyridine showed high stereoselectivity ratios of approximately (-)/(+) = 100 and 1000 in pharmacologic and binding experiments, respectively. The inhibitory actions of 2-(2-aminoethylthio)methyltiamdipine analogs against K(+)-induced contractile responses in rat tail artery developed very slowly requiring at least 2 h for maximum effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium channel antagonists: Part VI: Clinical pharmacokinetics of first and second-generation agents

A survey of the pharmacokinetic properties of the three prototypical calcium antagonist agents shows that they have in common a very high rate of hepatic first-pass metabolism with, in the case of verapamil and diltiazem, the formation of an active metabolite that affects the dose during chronic therapy. Therefore, the major factor altering the pharmacokinetic properties and the dose of the drug required is the capacity of the liver to metabolize the drug, which in turn depends on the hepatic blood flow and the activity of the hepatic metabolizing systems. Hence liver disease, a low cardiac output, and coadministration of certain drugs inducing or inhibiting the hepatic enzymes, all indirectly affect the pharmacokinetic properties of the calcium antagonists. There are also other potential drug interactions of a kinetic or dynamic nature that may arise. In general, renal disease has little effect on the pharmacokinetics of calcium antagonists.

24 h blood pressure control with the once daily calcium antagonist, amlodipine

1. Amlodipine is a novel calcium antagonist which, although pharmacologically similar to other dihydropyridine calcium antagonists, has a long plasma half-life, permitting steady state blood levels to be achieved with a once-daily dose regimen. 2. We have performed a study to examine the effects of this drug on the blood pressure of hypertensive patients over a 24 h period. After a placebo run-in, the drug was administered to 11 patients at a starting dose of 5 mg, and increased to 10 mg after 2 weeks of treatment if the cuff diastolic blood pressure response was unsatisfactory. Cuff measurements were made at entry, after 2 weeks treatment with placebo, after 2 weeks on amlodipine 5 mg once daily, and after a further 4 weeks on amlodipine 5 mg or 10 mg once daily. Intraarterial blood pressure recordings were made at the end of the placebo phase and at completion of the study. 3. Mean supine blood pressure measured sphygmomanometrically was 168/103 (n = 11) mm Hg at entry, 169/104 (n = 11) mm Hg at the end of the placebo phase, 153/95 (n = 11) mm Hg after 2 weeks of treatment and 146/92 (n = 11) mm Hg at the end of the study. Blood pressure curves plotted for each phase of the study revealed an effective 24 h duration of action. Mean daytime blood pressure was reduced from 165/103 to 147/89 mm Hg (P less than 0.05, n = 10), and mean night-time blood pressure was reduced from 137/79 to 121/69 mm Hg (P less than 0.05, n = 10).(ABSTRACT TRUNCATED AT 250 WORDS)

A dose-response study of amlodipine in mild to moderate hypertension

The antihypertensive efficacy and suitability for once daily dosing of amlodipine, a new calcium antagonist, was studied in a series of 205 patients with mild to moderate hypertension. The study was conducted double-blind in 13 centres. The starting doses of amlodipine were 1.25, 2.5 and 5 mg, respectively, which were doubled after 4 weeks if normotension or a preset target blood pressure was not reached. Target blood pressure was reached in 25% of patients with placebo, 41% with 2.5 mg of amlodipine, 56% with 5 mg of amlodipine and 73% with 10 mg of amlodipine once daily. The drug was well tolerated at all dose levels and no changes occurred in heart rate, body weight or electrocardiogram during treatment. Amlodipine is a useful new calcium antagonist for the treatment of hypertension producing smooth, dose-dependent blood pressure reductions with convenient once daily dosing.

Pharmacokinetics of amlodipine in renal impairment

Amlodipine was administered as 14 single 5-mg oral daily doses to 27 male subjects with renal function ranging from normal to haemodialysis-dependent. Blood specimens were obtained for measurement of plasma amlodipine concentrations for 24 h following the first dose, for 168 h following the final dose and during daily administration of amlodipine. Amlodipine was well tolerated. Renal impairment had little effect on the pharmacokinetics of amlodipine. The elimination half-life was of the order of 50 h, similar to previously reported values and did not vary with renal function. Steady-state pre-dose concentrations were observed after the ninth dose. Accumulation of amlodipine was not significantly different from that expected on theoretical grounds and did not significantly change with renal function. These results suggest that once daily administration of amlodipine is suitable for all degrees of renal function and that dosage adjustment is not necessary in renal impairment.