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Biomedical subjects

G G Belz

Publications and source records attributed to G G Belz.

At least 19 recordsLinked to original sources
PubMed2002

Camphor-Crataegus berry extract combination dose-dependently reduces tilt induced fall in blood pressure in orthostatic hypotension.

In order to test the efficacy of a combination of natural D-camphor and an extract of fresh crataegus berries (Korodin Herz-Kreislauf-Tropfen) on orthostatic hypotension, two similar, controlled, randomized studies were carried out in a balanced crossover design in 24 patients each with orthostatic dysregulation. The camphor-crataegus berry combination (CCC) was orally administered as a single regimen in 3 different dosages of 5 drops, 20 drops and 80 drops; a placebo with 20 drops of a 60% alcoholic solution served as control. Orthostatic hypotension was assessed with the tilt table test before and after medication. Source data of both studies were pooled and meta-analytically evaluated for all 48 patients. CCC drops decreased the orthostatic fall in blood pressure versus placebo, as almost uniformly established at all times by mean arterial pressure and diastolic blood pressure. Mean arterial pressure demonstrated the very fast onset of action by a clearly dose-dependent statistically significant effect even after 1-minute orthostasis. Increase of mean arterial pressure as compared to the orthostasis test before medication was on average 4.5 mmHg. CCC affected diastolic blood pressure after 1 minute of orthostasis in all dosages as compared to placebo. A statistically significant effect of the highest dose of 80 drops on diastolic blood pressure could be demonstrated after 1-, 3-, and 5-minute orthostasis. The hemodynamic findings of a stabilizing effect on arterial pressure in orthostasis corroborate the long-term medical experience with CCC and justify the indication orthostatic hypotension.

Adult↗
PubMed2001

Pharmacokinetic and dynamic interactions of the angiotensin-converting enzyme inhibitor imidapril with hydrochlorothiazide, bisoprolol and nilvadipine.

OBJECTIVE: The pharmacokinetic and dynamic interactions of the angiotensin-converting enzyme (ACE) inhibitor imidapril with other therapeutic principles used in hypertension and heart failure were evaluated. METHODS: In three separate, double-blind, placebo-controlled, four-way cross-over studies in healthy volunteers (n = 16 each), single oral doses of imidapril 10 mg (I), hydrochlorothiazide 12.5 mg (H), bisoprolol 5 mg (B) and nilvadipine 8 mg (N) were administered as monotherapies, and in IH, IB and IN combinations. Plasma concentrations of imidaprilat and H were followed up to 48 h, those of B and N up to 24 h and area under the concentration time curve (AUC), maximum plasma concentration (Cmax) and time to Cmax (tmax) were determined. Blood pressure (BP), heart rate (HR) and non-invasive haemodynamics [total peripheral resistance (TPR, N and H), systolic time intervals (STI, N and H), and plasma renin activity (PRA)] were assessed up to 24 h. RESULTS: There were no pharmacokinetic interactions between I plus H, B or N. Bioequivalence between single and combined administrations was verified for all investigational compounds [AUC point estimates (90% confidence interval CI): imidaprilat IH 109% (97.8, 122.8); IB 99.6% (91.2, 109.4); IN 105.7% (92.1, 121.3); H 96.6% (92.5, 100.8); B 103% (100.2, 105.8); N 98% (89, 108)]. The haemodynamic effects were mostly additive and without relevant pharmacodynamic interactions. I significantly reduced the BP by 5-8 mmHg, B by 4-8 mmHg and N by 4-6 mmHg. In addition, H induced a significant reduction of the preload as seen from STI, and B significantly reduced HR (-5 bpm). N induced a significant decrease in TPR (about 15% of baseline values) and showed corresponding changes in STI. PRA increased significantly following I alone (1.5-2.0 ng/ml/h), as well as combined with N (2.5 ng/ ml/h) or H (3.1 ng/ml/h). This increase was clearly blunted by the co-administration of B (0.6 ng/ml/h). CONCLUSIONS: The combination of imidapril with a diuretic, beta-adrenoceptor antagonist or calcium-channel blocker seems a reasonable and safe treatment option when striving for additive pharmacodynamic effects not accompanied by relevant pharmacokinetic interactions.

Adrenergic beta-Antagonists↗
PubMed2001

Treatment of congestive heart failure--current status of use of digitoxin.

Digitalis glycosides exert a positive inotropic effect, i.e. an increase in myocardial contractility associated with a prolongation of relaxation period, and glycosides lower the heart rate (negative chronotropic), impede stimulus conduction (negative dromotropic) and promote myocardial excitability (positive bathmotropic). They seem to influence the activities of both the vagal and the sympathetic systems. Digitalis glycosides that belong to different substance classes are closely comparable concerning pharmacodynamics but differ substantially in regard to pharmacokinetics. Digoxin and its derivatives are less lipophilic, show lower protein binding and shorter half-life, are mainly eliminated via the kidney and accumulate rather rapidly in cases of insufficient kidney function. Digitoxin is highly lipophilic and extensively bound to plasma proteins, has a longer half-life, is mainly eliminated in the metabolized state via urine and faeces and does not accumulate in kidney dysfunction. As a result of a more stable pharmacokinetic profile, the incidence of toxic side effects seems to be lower with digitoxin than with digoxin. Since the beginning of the 1990s, the antagonists of the RAAS qualified as the standard treatment for congestive heart failure, often in combination with diuretics, vasodilators or beta-antagonists. However, the important role of digitalis glycosides as therapeutic comedication or alternative was never denied, especially in atrial fibrillation with tachycardia. The PROVED and RADIANCE trials proved a detrimental effect of the withdrawal of digoxin therapy on exercise capacity, left-ventricular ejection fraction and clinical symptoms. The DIG trial revealed that digoxin comedication in sinus rhythm patients with congestive heart failure was associated with a lower morbidity (as taken from death or hospitalization because of worsening heart failure) and an unchanged overall mortality--being a unique feature among the available inotropic drugs. Comparable studies for digitoxin have not yet been performed but, because of its higher pharmacological stability, it might well be associated with even more advantages in this regard than digoxin.

Cardiotonic Agents↗
PubMed2001

Prophylaxis of radiogenic sialadenitis and mucositis by coumarin/troxerutine in patients with head and neck cancer--a prospective,randomized, placebo-controlled, double-blind study.

OBJECTIVE: To study the efficacy of coumarin/troxerutine for the protection of salivary glands and mucosa during irradiation. DESIGN: Prospective, randomized, placebo-controlled, double-blind trial. SETTING: University hospital, Germany. PATIENTS: 48 patients who had radiotherapy to the head and neck. MAIN OUTCOME MEASURES: Salivary gland scintigraphy and acute side-effects of radiotherapy (Radiation Therapy Oncology Group (RTOG) score). RESULTS: 23 patients (11 experimental, 12 placebo) completed the study. The global efficacy measure combining scintigraphy and RTOG score favoured the experimental arm (P=0.07). The RTOG score showed significantly fewer acute side-effects of radiation in the experimental arm (P<0.05). CONCLUSION: The results suggest that coumarin/troxerutine have a favourable effect in the treatment of radiogenic sialadenitis and mucositis.

Adult↗
PubMed2001

Pharmacological differences among angiotensin II receptor antagonists.

Angiotensin II AT1 receptor antagonists (AIIRAs) have demonstrated efficacy similar to other classes of antihypertensive agents as well as "placebo-level" tolerability at all doses. Pharmacokinetic and pharmacodynamic studies provide a framework for understanding important intra-class dissimilarities. Disparity in antagonistic effects may be determined by in vivo responses to challenges of exogenous angiotensin II (Ang II) and by ex vivo/in vitro responses to a drug's biological activity by radioligand receptor assay (RRA). Two independent studies have been conducted in which irbesartan exhibited a more pronounced and longer-lasting antagonism to the effects of exogenous Ang II than losartan and valsartan. Comparative trials have indicated that both irbesartan and candesartan show greater clinical efficacy in lowering blood pressure than losartan. Recently, we have compared the Ang II antagonistic properties of irbesartan 150 mg/day and candesartan 8 mg/day. Both drugs block AT1 receptors with "insurmountable" antagonism and demonstrate a long duration of action. While both irbesartan and candesartan showed a similar degree of antagonistic activity in vivo, distinctly higher antagonistic activity in plasma was found for irbesartan by RRA at all time-points. Furthermore, plasma renin activity during periods with high antagonistic activity was significantly higher, and aldosterone levels following Ang II stimulation were blunted to a greater extent, following administration of irbesartan. In summary, in the doses tested, irbesartan exhibits the strongest antagonism when compared with losartan, valsartan and candesartan. This finding may have clinical implications.

Aldosterone↗
PubMed2000

Blocking the tissue renin-angiotensin system: the future cornerstone of therapy.

The development of angiotensin-converting enzyme inhibitors and selective angiotensin type 1 (AT1)-receptor antagonists has provided new insights into understanding the mechanism of the renin-angiotensin system (RAS) in the pathophysiology of cardiovascular disease. There is good evidence from meta-analyses that shows that inhibition of the RAS achieves organ protection features that go beyond blood pressure control. Candesartan cilexetil, a new angiotensin II receptor antagonist, is characterised by its tight binding to and slow dissociation from the AT1 receptor, and high antagonistic potency, resulting in long-lasting antagonistic effects. It is anticipated that these pharmacological characteristics may bring additional benefits to patients, not only for the management of essential hypertension but also for the management of end-organ damage.

Angiotensin II↗
PubMed2000

Comparative pharmacodynamics and pharmacokinetics of candesartan and losartan in man.

The angiotensin II antagonistic effects of candesartan and losartan were compared in-vivo after single and repeated doses. Effects were related to antagonistic activity in plasma. In this double-blind, crossover study, 12 healthy male volunteers received, in random order, daily oral doses of 8 mg candesartan cilexetil or 50 mg losartan for seven days. On day 1 and day 8, dynamics and kinetics were assessed up to 48 h after dosing. Antagonistic effect was determined from the antagonist-induced rightward shifts of the diastolic blood pressure response curves to exogenously administered angiotensin II measured as the dose ratio (DR). The antagonistic activity in plasma was measured using an ex-vivo/in-vitro radioreceptor assay. Specific high-performance liquid chromatography assays determined plasma concentrations of candesartan, losartan and its active metabolite EXP-3174. The pharmacokinetic properties of candesartan and losartan were comparable and antagonistic activity in plasma almost identical (ratio candesartan: losartan = 0.97 and 1-2 after single and multiple doses, respectively). However, the antagonistic effects of candesartan and losartan in-vivo were quite different. Twenty-four hours after single dosing with candesartan a clinically relevant rightward shift in the angiotensin II dose-response curve (DR= 3.2) occurred that was more pronounced than that following losartan administration (DR=2.1, ratio candesartan: losartan= 1.65). Twenty-four hours after multiple doses of candesartan or losartan, the values of the DR were 4.8 and 2.3, respectively (ratio candesartan: losartan = 1.94). The values of DR for candesartan were significantly higher compared with losartan between 6 and 36h after a single dose and between 3 and 24 h post-dose following multiple dose administration. A counter-clockwise hysteresis was apparent between antagonistic activity in plasma and antagonistic effect. Despite equivalent angiotensin II antagonistic activity in plasma, the pharmacodynamic effect of candesartan cilexetil was greater than that of losartan. Candesartan appeared to have a slower off-rate from the angiotensin AT1-receptor compared with losartan, nevertheless differences in distributional phenomena or the extent of insurmountable antagonistic activity cannot be ruled out.

Adult↗
PubMed2000

The pharmacological potency of various AT(1) antagonists assessed by Schild regression technique in man.

RATIONALE: A quantitative technique was used to compare the pharmacological potency in healthy volunteers of angiotensin II receptor antagonists (AIIA): candesartan cilexetil, losartan, irbesartan, valsartan, and telmisartan. METHODS: In a randomised, double-blind, parallel-group (4x12 subjects) study, single oral doses of candesartan cilexetil 4, 8 and 16 mg, losartan potassium 25, 50 and 100 mg, valsartan 40, 80 and 160 mg, and irbesartan 75, 150 and 300 mg were administered on three consecutive days. Telmisartan 20, 40 and 80 mg was similarly evaluated in 12 volunteers in an open amendment. Angiotensin II (Ang II) antagonistic effects were determined in vivo from rightward shifts in Ang II dose-response curves for diastolic blood pressure (BP) and dose ratios were calculated. Apparent K(i)-doses, i.e. doses (in mg) required to induce a two-fold shift in Ang II dose-response curves (equivalent to approx. 50% blockade of receptors) were determined, using Schild regression analysis. RESULTS: All treatments dose-dependently attenuated increases in diastolic BP induced by infusion of exogenous Ang II. Candesartan cilexetil appeared to have a more pronounced increase in effect following cumulative dosing. At 24 hours, apparent K(i)-doses were: candesartan cilexetil 6 mg, irbesartan 123 mg, valsartan 93.5 mg, and telmisartan 54 mg. It was not possible to determine an apparent K(i)-dose for losartan at 24 hours. CONCLUSION: Consistent with results from experimental pharmacology, candesartan cilexetil displayed the highest pharmacological potency (i.e. antagonistic activity per mg substance) of the AIIAs tested. Apparent K(i)-doses at 24 hours were within the dose range recommended for clinical use in patients with hypertension.

Adult↗
PubMed1999

[Prospective double-blind study of prophylaxis of radioxerostomia with Coumarin/Troxerutine in patients with head and neck cancer].

AIM: Prospective, randomized placebo-controlled double-blind study to prove the efficacy of Coumarin/Troxerutine (Venalot Depot) for protection of salivary glands during a head and neck irradiation. PATIENTS AND METHOD: Forty-eight radiotherapy patients (60 Gy) with head and neck cancer were included in this trial. During radiotherapy the salivary glands were located in the core irradiation field. Primary efficacy parameters were sialometry, quantitative salivary gland scintigraphy and clinical evaluation of early effects of radiotherapy (RTOG-score, Table 1). All data were collected at 6 assessments: 1 week pre-radiation (U1), at start (U2), half time (U3) and end (U4) of irradiation, 8 days (U5) and 28 days (U6) after the end of irradiation (Figure 1). RESULTS: Twenty-three patients (11 verum, 12 placebo) completed the study with all assessments. Sialometrically, all patients were severely (half of radiotherapy) or completely (end of radiotherapy) xerostomatic (Figure 2). In a global efficacy measure according to O'Brien combining scintigraphy and RTOG there was a tendency for a higher efficacy of verum compared to placebo (p = 0.068). After start of irradiation therapy, the RTOG-score showed continuously and significantly lower early radiation effects under verum than under placebo (U3 vs U6: p < 0.05, area under curve: p = 0.032; Table 2, Figure 3). The scintigraphically determined excretion fraction was slightly less impaired in the verum group compared to the placebo treatment (p = 0.12. Figure 4). There was no difference in drug safety between placebo and verum for adverse events, changes in the activity of liver enzymes and for global impression of tolerability. CONCLUSIONS: The results give support for an advantageous effect of Venalot Depot in the treatment of radiogenic sialadenitis and mucositis. In even a small number of evaluable patients, early clinical effects of irradiation (RTOG-score) were less pronounced in the active treatment group than in the placebo group, but the sample size was too low to prove statistically also the benefit of coumarin/troxerutine with the scintigraphic method. Sialometry seems not suitable for the assessment of early radiation effects.

Adult↗
PubMed1999

Dose-proportionality of oral thioctic acid--coincidence of assessments via pooled plasma and individual data.

Thioctic acid (TA), a racemate of R-(+)- and S-(-)-enantiomers of alpha-lipoic acid, acts as a powerful lipophilic, free-radical scavenger and is used in the treatment of diabetic neuropathy. This trial investigated the dose-linearity of enantiomer pharmacokinetics following the oral administration of single doses of 50 to 600 mg TA (formulation provided by ASTA (Medica)) in healthy volunteers. TA enantiomer concentrations in individual and pooled plasma samples were determined using enantioselective, high-performance liquid chromatography. TA was rapidly absorbed (tmax, 0.5 to 1 h). Maximum plasma concentrations (Cmax) of the R-(+)-enantiomer were about 40-50% higher than those of the S-(-)-enantiomer (50 mg: 135.45 ng/ml R-(+)-TA, 67.83 ng/ml S-(-)-TA; 600 mg: 1812.32 ng/ml R-(+)-TA, 978.20 ng/ml S-(-)-TA; geometric means). The decline observed in the plasma concentration was steep (t1/2, 0.5 h). The dose-linearity and proportionality of pharmacokinetic parameters could be demonstrated on an intra-individual basis and for the group geometric means. An analysis of pooled plasma samples proved to be a suitable means for deriving reliable first-sight results prior to individual assessments.

Adult↗
PubMed1999

Time course and extent of angiotensin II antagonism after irbesartan, losartan, and valsartan in humans assessed by angiotensin II dose response and radioligand receptor assay.

OBJECTIVES: To compare the angiotensin II antagonistic properties of the usual recommended oral starting doses of various angiotensin II receptor antagonists-150 mg irbesartan, 80 mg valsartan, and 50 mg losartan-in humans. SUBJECTS AND METHODS: Eighteen healthy men were enrolled in a double-blind, randomized crossover study. Angiotensin II dose-effect curves of diastolic blood pressure and radioreceptor assay were performed before and up to 47 hours after single and multiple doses of the antagonists. The rightward shift of the angiotensin II dose-effect curves (dose ratio-1) assessed the antagonistic effects in vivo. The degree of receptor occupancy in plasma was detected by a rat lung radioreceptor assay ex vivo in vitro. RESULTS: All of the drugs clearly showed antagonistic effects to angiotensin II in vivo (dose ratio-1) and in vitro (radioreceptor assay). Within the given doses the dose ratio-1 for irbesartan was greater than for valsartan and losartan after single and repetitive dosing, reaching statistical significance at various time points up to 36 hours versus valsartan and up to 47 hours versus losartan. The apparent half-lives of the decay of the effects were approximately 8 hours for valsartan and losartan, whereas 15 to 18 hours were obtained with irbesartan. These findings were supported by the radioreceptor assay data: the percentage of receptor occupancy for irbesartan was significantly greater than for valsartan and losartan up to 47 hours. CONCLUSION: Angiotensin II antagonistic effects of irbesartan, valsartan, and losartan were compared. Irbesartan showed the slowest decay and longest duration of its antagonistic effects. With the recommended initial doses used in this study, the following rank order of antagonistic intensity was obtained: irbesartan > valsartan > losartan. The findings of this study, specifically the longer-lasting effects of irbesartan, may have clinical implications.

Adult↗
PubMed1999

Epidemiology of the arterial stiffness.

Aortic stiffening is as much an important risk factor in cardiovascular morbidity and mortality, as it serves as reliable surrogate marker for clinical endpoints like myocardial and cerebrovascular incidents. Elevated aortic stiffness induces high systolic blood pressure, augmented pulse pressure with increased ventricular afterload, reduced subendocardial blood flow and augmented pulsatile stress in the peripheral arteries. Factors with relevant impact on the epidemiology of arterial stiffness are widely spread. 3 major groups of parameters influencing the stiffness of the aorta and the large arteries have been studied and described up to now: (i) physiological properties like age, gender, body height, pressure, hormonal state, genetic factors; (ii) environmental factors like nutrition (fish-, salt-, garlic consumption), smoking, performance of sports and aerobic capacity; (iii) diseases like hypertension, hypercholesterolemia, diabetes, coronary heart disease, cerebrovascular disease, renal failure, Marfan-syndrome, growth hormone deficiency. Close association between several of these factors impedes analyzing them independently from each other. Age and blood pressure were found to be the most prominent predictors of arterial stiffness in normal as well as in disease populations. Physiological and environmental factors can modulate these effects of aging, diseases generally seem to amplify them.

Aging↗
PubMed1998

Angiotensin II antagonism and plasma radioreceptor-kinetics of candesartan in man.

AIMS: The pharmacodynamic properties of the angiotensin II antagonist candesartan in humans were assessed from the rightward shifts of angiotensin II dose-effect curves (Schild regression technique). The pharmacokinetic characteristics were determined by radioreceptor assay (r.r.a.) and h.p.l.c. METHODS: Twelve healthy male volunteers received single oral doses of 4, 8 and 16 mg candesartan cilexetil and placebo. Plasma was obtained for h.p.l.c. and r.r.a. (receptors: rat lung; radioligand: [125I-Sar1Ile8]-angiotensin II). Before and up to 24 h post dosing angiotensin II was infused in ascending dose steps until blood pressure (systolic and/or diastolic) increased by +25 mmHg. Individual angiotensin II dose-effect curves were fitted according to an Emax model and dose ratios (DR) calculated from the antagonist induced rightward shifts. RESULTS: Candesartan, the active metabolite of candesartan cilexetil, declined from peak concentrations at about 4 h with a t1/2 of about 6 h. A linear relation (slope 1) between h.p.l.c. and r.r.a. data revealed that there is no other active metabolite. DR at 6-9 h post dosing reached a maximum of about 30 and at 24 h still amounted to 4-7, indicating the persistence of a relevant antagonistic effect in vivo. The apparent Ki-doses (derived from Schild regression plots) indicated a high potency (1.9 mg at 24 h) and slow decline of effect. Between plasma concentrations and antagonistic effect a counterclockwise hysteresis was visible. CONCLUSIONS: A longer persistence of the antagonistic effect at the receptor site than expected by the presence in plasma indicates a slow off-rate of candesartan cilexetil from in vivo receptors. This provides an additional rationale for the observed 24 h therapeutic activity of candesartan cilexetil.

Administration, Oral↗
PubMed1998

Blood pressure and aortic elastic properties--verapamil SR/trandolapril compared to a metoprolol/hydrochlorothiazide combination therapy.

The effects of 2 fixed antihypertensive combination drugs on blood pressure and aortic elastic properties were compared in 2 parallel groups. Twenty-six patients for 6 months received a calcium antagonist plus ACE inhibitor (verapamil SR 180 mg/trandolapril 1 mg (Vera/Tran)) and 25 patients a beta-adrenoceptor antagonist plus diuretic (metoprolol 100 mg/hydrochlorothiazide 12.5 mg (Meto/HCTZ)). In addition to blood pressure (SBP, DBP), carotidofemoral pulse wave velocity (PWV) was assessed non-invasively. Total peripheral resistance (TPR) was determined from cardiac output derived by electrical impedance cardiography. Sitting DBP decreased for -14.4 mmHg following Vera/Tran compared with -9.2 mmHg following Meto/HCTZ (p = 0.02 for difference between treatments). Blood pressure was normalized (i.e. DBP < 90 mmHg) in 69% of patients with Vera/Tran and in 52% with Meto/HCTZ. PWV was lowered with Vera/Tran to a higher extent than with Meto/HCTZ (differences between group means -0.46 to -0.98 m/sec, statistically not significant). Vera/Tran induced a decrease in TPR of about 15% of baseline values, whereas Meto/HCTZ showed no influence. Treatment-related adverse events following Meto/HCTZ were bradycardia and associated symptoms; following Vera/Tran these were cough and edema in 1 case each. In the Meto/HCTZ group, there were more withdrawals/drop-outs (9/25) than in the Vera/Tran group (2/26). The somewhat more intense reduction in PWV with Vera/Tran is indicative of an increase in aortic elastic properties associated with the more potent decrease in BP. In the present study, the combination of calcium antagonist plus ACE inhibitor was found to be an effective and well tolerated antihypertensive regimen and in these respects appears to have some advantages compared with a combination of beta-blocker plus diuretic.

Adrenergic beta-Antagonists↗
PubMed1997

Protective effect of chronic garlic intake on elastic properties of aorta in the elderly.

BACKGROUND: Epidemiological studies have suggested that garlic may have protective effects against cardiovascular diseases. We undertook this cross-sectional observational study to test the hypothesis that regular garlic intake would delay the stiffening of the aorta relating to aging. METHODS AND RESULTS: We studied healthy adults (n=101; age, 50 to 80 years) who were taking > or = 300 mg/d of standardized garlic powder for > or = 2 years and 101 age- and sex-matched control subjects. Pulse wave velocity (PWV) and pressure-standardized elastic vascular resistance (EVR) were used to measure the elastic properties of the aorta. Blood pressures, heart rate, and plasma lipid levels were similar in the two groups. PWV (8.3+/-1.46 versus 9.8+/-2.45 m/s; P<.0001) and EVR (0.63+/-0.21 versus 0.9+/-0.44 m2 x s(-2) x mm Hg(-1); P<.0001) were lower in the garlic group than in the control group. PWV showed significant positive correlation with age (garlic group, r=.44; control group, r=.52) and systolic blood pressure (SBP) (garlic group, r=.48; control group, r=.54). With any degree of increase in age or SBP, PWV increased less in the garlic group than in the control group (P<.0001). ANCOVA and multiple regression analyses demonstrated that age and SBP were the most important determinants of PWV and that the effect of garlic on PWV was independent of confounding factors. CONCLUSIONS: Chronic garlic powder intake attenuated age-related increases in aortic stiffness. These data strongly support the hypothesis that garlic intake had a protective effect on the elastic properties of the aorta related to aging in humans.

Aged↗
PubMed1997

Beta-adrenergic stimulation enhances left ventricular diastolic performance in normal subjects.

To determine the effects of beta-adrenergic stimulation on transmitral Doppler echocardiography flow characteristics of left ventricular diastolic filling, we studied 10 healthy volunteers aged 23-31 years (mean age, 26.6 years) during intravenous infusion of isoprenaline in consecutive steps of 0.1, 0.2, 0.4, 0.75, and 1.5 micrograms/min (each for 15 min). Saline control infusion was given in the same manner in a crossover and blinded protocol. Compared with the infusion of placebo, stepwise increasing doses of isoprenaline caused a dose-related increase in early and late diastolic filling velocities and velocity-time integrals, a lengthening of the acceleration time, and a shortening of the deceleration and filling time. The chosen method proved highly sensitive, as statistically significant changes were detectable at the lowest dose of 0.1 microgram/min for all variables except velocity-time integral of late filling and deceleration time (> or = 0.2 microgram/min). The effects related to dose in a log-linear fashion except for the lengthening of the acceleration time (early ceiling), the increase of peak early filling velocity (increased steepness at higher doses), and the shortening of the filling time. Inclusion of the associated increases in heart rate and systolic blood pressure and the decrease in diastolic blood pressure blunted all treatment contrasts except for the increase of peak early filling velocity. In addition, the hemodynamics with respect to heart rate and loading conditions were not altered at low dosages of drug (< 0.4 microgram/min). Effects of at least the peak early filling velocity must be interpreted as an active adrenergically mediated myocardial relaxation process. These findings have potentially important clinical implications for this noninvasive, readily available, and convenient technique in clinical pharmacology, stress testing, and possibly therapeutic interventions in diastolic dysfunction in humans.

Adrenergic beta-Agonists↗
PubMed1997

Pharmacodynamic and pharmacokinetic properties of an angiotensin II receptor antagonist--characterization by use of Schild regression technique in man.

OBJECTIVE: The pharmacodynamic properties of a new angiotensin II receptor antagonist (BAY 10-6734) in humans were to be quantitatively characterized from the rightward shifts of the agonist dose-response curves after administration of different doses of the antagonist. METHODS: 24 healthy male volunteers received single oral doses of 20-300 mg BAY 10-6734. Before and up to 23 h post dosing (p.d.) plasma was obtained for HPLC measurement of parent compound and active metabolite BAY 10-6735. Exogenous angiotensin II was infused in increasing dose steps until blood pressure had increased by +25 mmHg. Angiotensin II dose-response curves were fitted individually using the sigmoidal Emax model. From the antagonist-induced rightward shifts, as compared to a premedication curve, dose ratios (DR) were determined and DR-1 plotted versus applied dosages and measured plasma concentrations. From these Schild regression plots the fictive doses and concentration (Ki) inducing a DR-1 = 1, i.e. a 2-fold shift in agonist dose-response curves, were derived. The "doubling (t2.0) time" of the apparent Ki doses was calculated. RESULTS: BAY 10-6734 dose-dependently induced rightward shifts of the angiotensin II blood pressure response curves, mean maximum DR at 2 h p.d. ranged from 42 (80 mg) to 216 (300 mg), and at 23 h p.d. decreased to about 2 (80 mg) to 4 (300 mg). Pharmacodynamic (3.4-4.6 h) and pharmacokinetic half-lives (3.4-4.3 h) were nearly identical. Apparent Ki doses increased from about 1-2 mg at 2 h p.d. to about 80-100 mg at 23 h p.d., their time course revealed a doubling (t2.0) time of 3.5-3.8 h. A Ki concentration of about 10 micrograms/l was obtained for the active metabolite BAY 10-6735. CONCLUSIONS: Oral administration of BAY 10-6734 in man antagonized angiotensin II dose blood pressure response curves in a dose-dependent manner. The time kinetics of the pharmacodynamic effect, derived from the decay of DR-1 values, as well as the doubling time of the apparent Ki values well agreed with the pharmacokinetic half-life. Schild regression revealed competitive angiotensin II antagonistic properties within the dose/concentration range tested. This technique was shown to be an adequate means to evaluate pharmacodynamic potency and kinetic behavior of an angiotensin II receptor antagonist in vivo.

Administration, Oral↗