Quantitative susceptibility mapping through model-based deep image prior (MoDIP)

The data-driven approach of supervised learning methods has limited applicability in solving dipole inversion in Quantitative Susceptibility Mapping (QSM) with varying scan parameters across different objects. To address this generalization issue in supervised QSM methods, we propose a novel training-free model-based unsupervised method called MoDIP (Model-based Deep Image Prior). MoDIP comprises a small, untrained network and a Data Fidelity Optimization (DFO) module. The network converges to an interim state, acting as an implicit prior for image regularization, while the optimization process enforces the physical model of QSM dipole inversion. Experimental results demonstrate MoDIP's excellent generalizability in solving QSM dipole inversion across different scan parameters. It exhibits robustness against pathological brain QSM, achieving over 32 % accuracy improvement than supervised deep learning methods. It is also 33 % more computationally efficient and runs 4 times faster than conventional DIP-based approaches, enabling 3D high-resolution image reconstruction in under 4.5 min.

Drug-Polymer Miscibility and the Overlap Concentration (C*) as Measured by Rheology: Variation of Polymer Structure

OBJECTIVES

Amorphous solid dispersions (ASDs), wherein a drug is molecularly dispersed in a polymer, can improve physical stability and oral bioavailability of poorly soluble drugs. Risk of drug crystallization is usually averted using high polymer concentrations. However, we demonstrated recently that the overlap concentration, C*, of polymer in drug melt is the minimum polymer concentration required to maintain drug in the amorphous state following rapid quench. This conclusion was confirmed for several drugs mixed with poly(vinylpyrrolidone) (PVP). Here we assess the solid-state stability of ASDs formulated with a variety of polymers and drugs and at various polymer concentrations (C) and molecular weights (MWs). We further test the hypothesis that degree of drug crystallization decreases with increasing C/C* and vanishes when C>C*, where C* depends on polymer MW and strength of drug-polymer interaction.

METHODS

We test our hypothesis with ASDs consisting of ketoconazole admixed with polyacrylic acid, polymethacrylic acid and poly (methacrylic acid-co-ethyl acrylate); and felodipine admixed with PVP and poly (vinylpyrrolidone-co-vinyl acetate). Values of C* for polymers in molten drug are rheologically determined. Crystallization behavior is assessed by measuring enthalpy of fusion, ΔHf  and by X-ray diffraction.

RESULTS

We confirm that ΔHf/ΔHf, C = 0 = f(C/C∗), and essentially no crystallization occurs when C>C*.

CONCLUSIONS

Our findings will aid researchers in designing or selecting appropriate polymers to inhibit crystallization of poorly soluble drugs. This research also suggests that C* as determined by rheology can be used to compare drug-polymer interactions for similar molecular weight polymers.

A SARS-CoV-2-specific CAR-T-cell model identifies felodipine, fasudil, imatinib, and caspofungin as potential treatments for lethal COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-induced cytokine storm is closely associated with coronavirus disease 2019 (COVID-19) severity and lethality. However, drugs that are effective against inflammation to treat lethal COVID-19 are still urgently needed. Here, we constructed a SARS-CoV-2 spike protein-specific CAR, and human T cells infected with this CAR (SARS-CoV-2-S CAR-T) and stimulated with spike protein mimicked the T-cell responses seen in COVID-19 patients, causing cytokine storm and displaying a distinct memory, exhausted, and regulatory T-cell phenotype. THP1 remarkably augmented cytokine release in SARS-CoV-2-S CAR-T cells when they were in coculture. Based on this "two-cell" (CAR-T and THP1 cells) model, we screened an FDA-approved drug library and found that felodipine, fasudil, imatinib, and caspofungin were effective in suppressing the release of cytokines, which was likely due to their ability to suppress the NF-κB pathway in vitro. Felodipine, fasudil, imatinib, and caspofungin were further demonstrated, although to different extents, to attenuate lethal inflammation, ameliorate severe pneumonia, and prevent mortality in a SARS-CoV-2-infected Syrian hamster model, which were also linked to their suppressive role in inflammation. In summary, we established a SARS-CoV-2-specific CAR-T-cell model that can be utilized as a tool for anti-inflammatory drug screening in a fast and high-throughput manner. The drugs identified herein have great potential for early treatment to prevent COVID-19 patients from cytokine storm-induced lethality in the clinic because they are safe, inexpensive, and easily accessible for immediate use in most countries.

Transfer of trace organic compounds in an operational soil-aquifer treatment system assessed through an intrinsic tracer test and transport modelling

Soil Aquifer Treatment (SAT) can provide supplementary treatment of trace organic compounds (TrOCs) such as pharmaceutical and industrial compounds present in Secondary Treated Wastewater (STWW). Concern on presence of unregulated TrOCs in natural systems has raised recently as well as the interest in SAT systems for remediation. The present study quantifies, at the field scale over35 m of lateral groundwater flow, the effectiveness of the Agon-Coutainville SAT system (Manche, Normandy, France) for TrOCs removal by sorption and biodegradation through monitoring of seven TrOCs (oxazepam, carbamazepine, benzotriazole, tolyltriazole, caffein, paracetamol, ibuprofen) and major inorganic compounds as intrinsic tracers in STWW and groundwater during a 34-day STWW infiltration experiment during operational use of the SAT. Cationic exchanges and mixing between groundwater and STWW during the experiment were highlighted by major ions and geochemical simulations. Due to the low thickness of the unsaturated zone, a 1D analytical solution of the advection-dispersion equation (ADE) was applied on chloride data. Chloride was used as conservative intrinsic tracer to calibrate the horizontal flow and transport parameters such as the aquifer dispersion coefficient (D) and the average pore water velocity (ν) allowing estimation of the groundwater residence time. Transport and attenuation of the TrOCs were simulated assuming first-order degradation constant (μ) and linear retardation coefficient (R), calibrated to simulate the observed temporal changes in the breakthrough of TrOCs. Sorption was found to play a role in the transport of TrOCs, notably for oxazepam with a higher linear retardation coefficient value of 2.2, whereas no significant differences of retardation were observed for carbamazepine, tolyltriazole, benzotriazole (1.37, 1.35, 1.36 respectively). Estimated first order degradation rate constants, between 0.03d^-1 for carbamazepine and 0.09d^-1 for tolyltriazole, were generally high compared to the literature, possibly due to favourable redox conditions and important microbial activities within the system. This study provides evidence of the efficiency of the Agon-Coutainville SAT system for the removal of TrOCs.

Influence of Polymers on the Crystal Growth Rate of Felodipine: Correlating Adsorbed Polymer Surface Coverage to Solution Crystal Growth Inhibition

The bioavailability of orally administered drugs that exhibit poor aqueous solubility can be enhanced with the use of supersaturating dosage forms. Stabilization of these forms by preventing or inhibiting crystallization in solution is an important area of study. Polymers can be used to stabilize supersaturated systems; however, the properties that impact their effectiveness as crystal growth rate inhibitors are not yet fully understood. In this study, the impact of various polymers on the crystal growth rate of felodipine and the conformation of these polymers adsorbed to crystalline felodipine was investigated in order to gain a mechanistic understanding of crystal growth inhibition. It was determined that polymer hydrophobicity impacted polymer adsorption as well as adsorbed polymer conformation. Polymer conformation impacts its surface coverage, which was shown to directly correlate to the polymer's effectiveness as a growth rate inhibitor. By modeling this correlation, it is possible to predict polymer effectiveness given the surface coverage of the polymer.

Effects of the calcium antagonist felodipine on the sympathetic and renin-angiotensin-aldosterone systems in essential hypertension

Studies were performed in 10 male patients with untreated essential hypertension, WHO grade I-II, aged 25-62 years, to explore the acute (single dose) and long-term (8 weeks) effects of felodipine on sympathetic activity--evaluated by plasma and urinary catecholamines--as related to blood pressure, heart rate and the activity in the renin-angiotensin-aldosterone system. The patients were hospitalized for 8 (acute) and 6 (long-term) days and were maintained on a standardized daily intake of sodium (150 mmol), potassium (75 mmol) and water (2,500 ml). Acute felodipine administration (10 mg) significantly reduced blood pressure and increased heart rate. Plasma and urinary noradrenaline, plasma renin activity and angiotensin II increased, whereas plasma and urinary adrenaline, dopamine, aldosterone and plasma vasopressin were unaltered. Long-term felodipine treatment, 10 mg twice daily, reduced blood pressure to a similar extent as acute felodipine administration, but heart rate was not significantly changed. Plasma noradrenaline 3 and 12 hours after the last dose and urinary noradrenaline were increased, whereas plasma and urinary adrenaline and dopamine were unchanged. Plasma renin activity and angiotensin II were increased 3 hours, but unchanged 12 hours after the last dose. Plasma aldosterone was unchanged but urinary aldosterone increased. Plasma vasopressin was unchanged. The changes in plasma noradrenaline as related to blood pressure, heart rate, plasma renin activity and angiotensin II during long-term felodipine treatment may reflect decreased cardiac and renal beta-adrenoceptor-mediated responses. Increased renal clearance of aldosterone could partly explain the unaltered plasma aldosterone level in spite of increased plasma angiotensin II following long-term felodipine treatment.

Report of two cases

Two women with primary pulmonary hypertension were treated with felodipine, a vasodilating agent. A marked reduction in pulmonary artery pressure was noted in one, whereas the other showed no reduction in pressure but an increase in blood flow and a decrease in pulmonary vascular resistance.

Characteristics of felodipine-located poly(ε-caprolactone) microspheres

Felodipine-loaded poly (epsilon-caprolactone) (PCL) microspheres were prepared by two methods, the conventional emulsion solvent evapouration method and the quenching method. The aim of this work was to investigate the effects of process parameters such as emulsion type, drug loading, molecular-weight of the polymer, types of emulsion stabilizer and dispersed phase solvents, as well as preparation methods. The results show that, when conventional emulsion solvent evapouration method was used, the o/w-method produced smaller mean size and higher encapsulation efficiency compared with the o/o-method. The encapsulation efficiencies increased with an increase in the molecular weight and a decrease in crystallinity of PCL. The size of microspheres varied with the type of emulsion stabilizer used, smaller microspheres with PVA and narrow size distribution with Pol 237. The water solubility of the dispersed phase solvent was one of the critical factors in controlling the encapsulation efficiency and microsphere mean size. When water-soluble solvents such as acetonitrile and ethyl formate were used, the encapsulation efficiencies decreased due to higher evapouration rate. When quenching methods were used, in contrast to the conventional emulsion solvent evapouration method, very narrowly size-distributed but bigger microspheres were obtained.

Oxidation of Hantzsch 1,4-Dihydropyridines of Pharmacological Significance by Electrogenerated Superoxide

PURPOSE

To study the reaction of a series of Hantzsch dihydropyridines with pharmacological significance such as, nifedipine, nitrendipine, nisoldipine, nimodipine, isradipine and felodipine, with electrogenerated superoxide in order to identify products and postulate a mechanism.

METHODS

The final pyridine derivatives were separated and identified by gas chromatography/mass spectrometry (GC-MS). The intermediates, anion dihydropyridine and the HO2*/HO2- species, were observed from voltammetric studies and controlled potential electrolysis was used to electrogenerate O2*-.

RESULTS

The current work reveals that electrogenerated superoxide can quantitatively oxidize Hantzsch dihydropyridines to produce the corresponding aromatized pyridine derivatives.

CONCLUSIONS

Our results indicate that the aromatization of Hantzsch dihydropyridines by superoxide is initiated by proton transfer from the N1-position on the 1,4-dihydropyridine ring to give the corresponding anion dihydropyridine, which readily undergoes further homogeneous oxidations to provide the final aromatized products. The oxidation of the anionic species of the dihydropyridine is more easily oxidized than the parent compound.

Cardiovascular-risk reduction: initial diuretic therapy compared with calcium-antagonist (felodipine) therapy for primary hypertension

Drug therapy for hypertension has failed to demonstrate a significant reduction in coronary mortality. We compared a calcium-antagonist agent, felodipine, with diuretic therapy as a first-line antihypertensive treatment in a randomized study, to assess the effects of six months of each regimen on over-all cardiovascular risk. Both regimens lowered blood pressure to less than 85 mmHg by one month. Felodipine alone was sufficient to control blood pressure in 90% of patients, while 50% of patients who were receiving diuretic therapy required a second agent for control. Diuretic therapy produced a 10% fall in serum potassium levels (P less than 0.001) and a three-fold increase in plasma renin activity (P less than 0.005) by one month; and a 6% rise in serum cholesterol levels (P less than 0.05) and a 38% rise in serum triglyceride levels (P less than 0.05) by three months. Felodipine did not influence these measurements, but caused a 43% increase in plasma noradrenaline levels by one month of therapy (P less than 0.025). In both groups, a significant fall occurred in the risk percentile score at six months, as calculated from the Multiple Risk Factor Intervention Trial data. However, the decrease was significantly greater in the felodipine group at six months (45% compared with 29%; P less than 0.05). Thus, when doses were titrated to achieve equivalent effects on blood pressure, felodipine had the advantages over diuretic treatment of being effective as monotherapy, of having fewer metabolic effects, and of reducing cardiovascular risk to a greater degree.

Plasma concentration-effect relationship of felodipine intravenously in patients with congestive heart failure

The pharmacodynamics of felodipine were analyzed in patients with congestive heart failure in a randomized, double-blind, placebo-controlled study. Felodipine at a dose of 1 mg (n = 11) or placebo (n = 12) was given intravenously during a 60-min period. Hemodynamic measurements and plasma samples were obtained every 15 min during a 2-hour period. An increase in heart rate (HR, +8%, p less than 0.01) and cardiac output (CO, +36%, p less than 0.001), and a decrease in mean arterial pressure (MAP, -24%, p less than 0.001) and systemic vascular resistance (SVR, -46%, p less than 0.001), were found. Pulmonary artery, right atrial, wedge pressure, and stroke-work index did not change. Linear regression analysis showed a significant correlation between felodipine plasma levels and changes in HR (r = 0.71, p less than 0.05), MAP (r = 0.94, p less than 0.01), CO (r = 0.73, p less than 0.05), and SVR (r = 0.88, p less than 0.01). A strong hyperbolic correlation was demonstrated between individual plasma levels and changes in MAP (r = 0.97, p less than 0.001). Hysteresis analysis showed that plasma levels are directly related to the concentration at the receptor site. A clockwise hysteresis was found in HR, CO, and SVR, but not in MAP. It is concluded that changes in flow and resistance are based on a physiological adjustment, a baroreflex-mediated response to vasodilation induced by felodipine, resulting in MAPs that remain closely related to felodipine plasma levels over a wide range.

Contribution of the intestine to the first-pass metabolism of felodipine in the rat

The systemic availability of intraduodenally (i.d.) administered felodipine in the rat is about 10%. The purpose of this study was to determine to what extent intestinal metabolism contributes to the first-pass elimination of felodipine in the rat. Four different types of experiments were performed. 1) [3H]Felodipine was given i.v. and i.p.; 2) the uptake of i.p. administered [3H]felodipine by the lymph was studied for 3 hr after dosing; 3) portal blood was collected quantitatively for 40 min after i.d. administration of [3H]felodipine; and 4) the in vitro metabolism of felodipine was studied in intestinal cell suspensions. The mean bioavailability of the i.p. dose was approximately 48%. The uptake via the lymph was negligible as an insignificant amount of the radioactive i.p. dose was recovered in lymph from a main lymph vessel in the peritoneal cavity. An average of 21 +/- 12% of given radioactive dose was recovered in portal blood during the first 40 min after i.d. dosing. The recovered radioactivity was to 40 to 70% due to felodipine and 9 to 16% was due to dehydro-felodipine. These results indicate that substantial first-pass elimination occurs in the intestine of the rat. Further support for gastrointestinal metabolism of felodipine in the rat was obtained from incubations with intestinal cells.

Pharmacokinetics of felodipine after intravenous and chronic oral administration in patients with congestive heart failure

1. In a randomized, parallel, double-blind study felodipine was administered to 11 and placebo to 12 patients with congestive heart failure. The kinetics of felodipine were studied after acute intravenous administration and after chronic oral treatment for 8 weeks. The relationship between cardiac output and pharmacokinetics was analyzed. The pharmacokinetic data were compared with data from young healthy individuals and hypertensive patients. 2. After oral therapy, significant correlations were found between cardiac output and AUC and systemic bioavailability (F). Furthermore, cardiac output before therapy was also significantly correlated with absorption characteristics. No relationship could be demonstrated between cardiac output and i.v. pharmacokinetics. A comparison of patients with heart failure and young healthy individuals revealed that the AUC was three times higher in heart failure patient, while Vss and the ratio of the AUC of the pyridine metabolite to that of felodipine were similar. Oral clearance was reduced by 50% and the terminal half-life was concomitantly increased. Pharmacokinetic data for felodipine are similar in patients with heart failure to published data from elderly hypertensive patients. 3. An increase in liver blood flow during chronic oral therapy, induced by felodipine itself, appears to explain an increase in bioavailability and thus to higher plasma drug concentrations. Thus, it is advisable to start felodipine treatment at a low dosage in patients with congestive heart failure.

A placebo-controlled dose-response study of felodipine extended release in hypertensive patients

This placebo-controlled study assessed antihypertensive effect and tolerability of two dose levels of an extended release (ER) formulation of felodipine (Plendil), given once daily to patients in primary health care. The patients had mild to moderate hypertension and were randomized to receive felodipine ER (FER) 20 mg (n = 50), FER 10 mg (n = 50), or placebo (n = 51) in a 4-week, double-blind, parallel-group multicenter study. After 4 weeks, the 24-h reduction in supine diastolic BP (DBP) was greater (p less than 0.01) in both FER groups (7 +/- 6 and 8 +/- 5 mm Hg) than in the placebo group (4 +/- 6 mm Hg). The 24-h reduction in supine systolic BP (SBP) was greater (p less than 0.01) in the FER 20-mg group (14 +/- 11 mm Hg), but not in the FER 10-mg group, than in the placebo group (8 +/- 11 mm Hg). No significant difference in blood pressure (BP) was found between FER 10 and 20 mg. Heart rate (HR) did not differ between any of the groups, nor did body weight or routine laboratory parameters. During felodipine treatment, 17 patients (12 receiving FER 20 mg) were withdrawn mostly because of vasodilatory side effects such as headache and ankle edema. We conclude that FER 10 mg and 20 mg once daily had an antihypertensive 24-h effect and that FER 10 mg may be more suitable as initial dose.

Oral pharmacokinetics of felodipine in patients with congestive heart failure: variable prediction using intravenous data

Peak and trough concentrations after 8 weeks oral therapy with felodipine, a vasodilating calcium antagonist of the dihydropyridine group, were predicted from intravenous pharmacokinetic data before therapy in 11 patients, randomly allocated to felodipine treatment 10 mg b.i.d., during a placebo controlled study in patients with congestive heart failure. Peak concentrations were well predictable, but trough levels varied between a good agreement in some patients to a large underestimation in others. Predictability was significantly correlated with half life, plasma clearance and distribution volume of the intravenous pharmacokinetic study. After 8 weeks chronic oral therapy no significant differences could be detected between the oral pharmacokinetics of predictable (n = 6) and unpredictable (n = 5) patients. This demonstrates that felodipine kinetics change during felodipine treatment. Differences in the distribution of blood flow before therapy combined with an interindividual variability in blood flow response during therapy is probably responsible for the observed impossibility to calculate trough levels, and thus oral dosage schedules, from intravenous pharmacokinetic data in patients with congestive heart failure.

Double-blind comparison with atenolol]

Felodipine is a new dihydropyridine calcium antagonist which selectively relaxes vascular smooth muscle. It lovers dose-dependently blood pressure in hypertensives patients. In this multicentre double-blind study, 113 patients (mean age 50 +/- 14 years) whose diastolic blood pressure was higher than 95 mmHg after withdrawal of an eventual antihypertensive therapy and a week of placebo administration. The patients received randomly either felodipine (5 mg x 2/j during two weeks and then 10 mg x 2/day) either atenolol (100 mg/day) during two months. Antihypertensive effects of these two drug regimens were not significantly different. Supine blood pressure decreased from 177 +/- 22/107 +/- 8 mmHg to 152 +/- 27/91 +/- 13 mmHg with felodipine and from 176 +/- 19/107 +/- 8 to 152 +/- 24/91 +/- 12 with atenolol. Side effects recorded by means of active questioning were ankle oedemas and headache with felodipine and fatigue and headache with atenolol.

Activation of protein kinase C by the dihydropyridine calcium channel blocker, felodipine

Felodipine, a dihydropyridine Ca2+ channel blocker, appears to have intracellular sites of action in addition to its ability to attenuate voltage-dependent Ca2+ channels in smooth muscle cells. In vitro, felodipine inhibits several calmodulin-dependent enzymes such as myosin light chain kinase, cyclic nucleotide phosphodiesterase and caldesmon kinase [Walsh MP, Sutherland C and Scott-Woo GC, Biochem Pharmacol 37: 1569-1580, 1988]. Such effects may partially explain the relaxant effects of felodipine and related dihydropyridines on vascular smooth muscle. We have examined the effects of felodipine on the activity of another important enzyme which has been implicated in the regulation of the contractile state of smooth muscle, protein kinase C. We chose to use a physiologically relevant substrate of protein kinase C for these studies, viz. platelet P47 protein, rather than the more commonly used lysine-rich histone which is probably not a physiologically important substrate. Protein kinase C and P47 were purified from human platelets and their important structural and functional properties were characterized. Felodipine and the p-chloro analogue of felodipine enhanced both the rate and extent of P47 phosphorylation by protein kinase C. Half-maximal activation was observed at 9.5 microM felodipine and 8.5 microM p-chloro analogue. Activation by felodipine was dependent upon the presence of phospholipid but did not require diacylglycerol. These observations suggest that the pharmacological actions of felodipine and related dihydropyridines may involve activation of protein kinase C in addition to their known effects on voltage-dependent Ca2+ channels and calmodulin-dependent enzymes.

Effects of felodipine on plasma digoxin levels and haemodynamics in patients with heart failure

The interaction between felodipine and digoxin was studied after a single oral dose and at steady state in 14 patients with congestive heart failure. Felodipine (10 mg) was randomly given as an extended release (FER) tablet in a double-blind, placebo-controlled, cross-over fashion. In addition, felodipine (10 mg) was given openly as a plain tablet, following the double-blind period. Each period lasted for 7 d. Felodipine ER did not alter the pharmacokinetics of digoxin when given as a single dose or at steady state compared with placebo. At steady state the felodipine plain tablet resulted in an 11% increase (P less than 0.05) in peak plasma concentrations of digoxin. Systolic time intervals as noninvasively measured haemodynamic parameters were not significantly altered following the felodipine ER period, while the felodipine plain tablet significantly decreased the pre-ejection/left ventricular ejection time ratio compared to placebo.

Efficacy of felodipine in congestive heart failure

The efficacy of felodipine, a vasodilating calcium antagonist, was analysed in 23 patients with congestive heart failure, New York Heart Association class III, during an 8-week, double-blind, randomized, placebo-controlled, parallel study. After felodipine, exercise duration increased significantly without changes in oxygen consumption. Heart rate, arterial pressures and rate pressure product decreased at similar submaximal exercise levels. Invasive haemodynamics before and after 8 weeks of therapy revealed arterial vasodilation without reflex tachycardia and no significant reduction in right atrial, pulmonary and capillary wedge pressures. Subjective symptom scores improved and side-effects were minor. Fluid retention, as assessed by body weight and ankle circumference did not occur. Felodipine has a beneficial effect in patients with moderately severe heart failure. Further research is necessary to demonstrate its long-term efficacy and safety.

The effects of treatment with felodipine as a single agent in coronary artery disease

In an earlier study one dose of the vasodilator felodipine improved haemodynamic function in patients with angina without having a negative inotropic effect. The haemodynamic response of sustained treatment with felodipine as a single agent in stable angina was investigated in a double blind crossover study of 25 patients. The dosage of felodipine was increased from 5 mg twice daily to 10 mg twice daily after two weeks. Twenty one patients completed the study, two were withdrawn because of acute myocardial infarction, and a further two because of symptoms of vasodilatation. Felodipine reduced both supine and erect blood pressure and increased the resting heart rate. Median exercise time was increased by 10% at two weeks and 7% at four weeks. There was a sustained reduction in the number of angina attacks and use of sublingual nitrate on active treatment. Felodipine has antianginal effects but these are limited and seem less than those of other related compounds. This finding is unexpected and possibly related to increased heart rate.

A comparison of felodipine and nifedipine as monotherapies for the treatment of mild to moderate hypertension

We conducted a randomised double-blind crossover comparison of felodipine, 10 mg once daily, nifedipine 20 mg twice daily, each treatment being given as a monotherapy for four weeks. Active treatment was preceded by a two-week placebo run-in. Both systolic (SBP) and diastolic (DBP) blood pressures (supine and erect) fell significantly (all P less than 0.001) following both drug treatments. Nifedipine produced a greater orthostatic effect, and hence a significantly greater fall in erect SBP than felodipine (P less than 0.05). There was no significant difference between the effects of the drugs on DBP. Achieved DBP was 90 mmHg or less in 18/22 patients on felodipine and 18/22 patients on nifedipine. Both drugs were well-tolerated. Felodipine given once daily was effective as a monotherapy for the control of mild to moderate hypertension and compared favourably with twice daily nifedipine.

Comparative double-blind randomized study]

This study involved 113 patients (mean age 50 +/- 14 years) with diastolic blood pressure above 95 mmHg. The patients abstained from taking any antihypertensive drug and received a placebo for one week before entering felodipine, a new calcium antagonist (5 mg x2/day for 2 weeks, then 10 mg x2/day) or atenolol (100 mg/day). There was no significant difference between the two treatment groups. Atenolol tended to be more effective in young subjects and felodipine in subjects aged 60 years or more. Heart rate was more reduced by atenolol than by felodipine (P less than 0.01). Undesirable side-effects were recorded by means of an open questionnaire. Their incidence was 23 per cent during the week under placebo and 84 per cent and 80 per cent respectively during treatment with felodipine or atenolol. The most frequent side-effects were oedema of the ankles and headache under felodipine, fatigue and headache under atenolol. Alkaline phosphatase levels were higher in the felodipine group (P less than 0.05), and a slight rise in blood potassium level (0.2 mmol/l) was noted in the atenolol group (P = 0.001), but these values remained within normal limits.

Influence of age on calcium entry blocking drugs in rat aorta is spasmogen-dependent

On rat aorta, diltiazem (0.2 microM) caused parallel shifts in the Ca2+ concentration-response curves (K+-depolarized preparations). In aged (greater than 19 months) rats, this shift (0.57 log units) was smaller than in young (2 months) rats (1.04 log units) indicating an age-related reduction in the potency of diltiazem. Felodipine (10 nM), like diltiazem (1 microM) in a previous study, depressed the maximum response to noradrenaline more in preparations from aged rats (40% reduction) than from young rats (14% reduction). This increase in the effect of felodipine or diltiazem vs. noradrenaline reflected a reduction in the alpha-adrenoceptor reserve for noradrenaline. Accordingly, the depression in the maximum responses to other spasmogens (5-HT or K+) by 1 microM diltiazem was not increased by age (5-HT, young 59%, aged 49% reduction; K+, young 65%, aged 70% reduction). This aging can have two opposing influences on the effects of Ca2+ entry blocking drugs on rat aorta - a decrease in potency, yet an increase in effectiveness against spasmogens with a reduced receptor reserve.

Felodipine reduces the absorption of theophylline in man

Ten healthy male volunteers (mean age 26 years) received 200 mg theophylline aminopropanol orally 8-hourly for 4 days, followed by 5 mg felodipine 8-hourly for 6 days, and then the combination of oral felodipine and theophylline for a further 4 days. Plasma concentrations of theophylline and felodipine were determined, and theophylline and its metabolites in urine were also measured. Felodipine led to a reduction in the plasma AUC of theophylline of 18.3%. The metabolic and renal clearances of theophylline remained unchanged, but the total recovery of theophylline-derived products was significantly reduced during felodipine treatment. No change in felodipine pharmacokinetics was observed during simultaneous treatment with theophylline. Compared to theophylline treatment alone, the diastolic blood pressure was significantly reduced during felodipine treatment alone and in combination with theophylline. It is concluded that felodipine slightly but significantly lowered the plasma theophylline concentration by interfering with its absorption. The interaction in most instances would probably be of minor clinical consequence.

The influence of antihypertensive treatment on the mesenteric arterial structure in spontaneously hypertensive rats. A morphometric study

Spontaneously hypertensive rats (SHR) and stroke-prone spontaneously hypertensive rats (SHRSP) were treated with a combination of a beta 1-blocker (metoprolol) and a calcium antagonist (felodipine) from 1 to 4 or from 4 to 6 months of age. The main trunk and peripheral branches of the mesenteric arterial tree were fixed by immersion and embedded in plastic. The total length of the internal elastic membrane and the media area were measured in cross-sectioned arteries. The ratio between media thickness (m) and luminal radius (ri) was then determined for a calculated, standardized condition, assuming a smooth and circular internal elastic membrane. The treatment caused a significant decrease in blood pressure and a reduction in m/ri ratios in the mesenteric arterial trunk as well as in mesenteric arterial branches when initiated in young as well as in adult SHR and SHRSP, i.e. the therapy efficiently prevents as well as reverses hypertensive arterial changes. The m/ri ratios in the superior mesenteric arterial trunks were significantly smaller in treated 4-month-old SHR and SHRSP than in WKY, although their blood pressures were not fully normalized. There was a marked increase in luminal radius in the young treated rats, possibly secondary to a therapy-induced increase in splanchnic blood flow.

Calcium and calmodulin antagonism for inhibition of uterine contractions

In search for a new tocolytic agent we investigated felodipine, a calmodulin-antagonizing drug. Felodipine reduced the spontaneous activity of 22 uterine strips taken from the uterus in the course of a cesarean section to 52 +/- 12% (mean +/- SEM) after 10 min, to 20 +/- 7% after 20 min and to 12 +/- 4% after 60 min (P less than 0.001).

Effect of felodipine on blood pressure and vascular reactivity in stroke-prone spontaneously hypertensive rats

Isolated tail arteries from stroke-prone spontaneously hypertensive rats (SHRSP), but not from normotensive Wistar-Kyoto rats (WKY), exhibit oscillatory contractions in response to norepinephrine. Previous studies indicate that the mechanism for these oscillations involves altered membrane calcium and/or potassium handling, and that this vascular change is a genetic defect associated with hypertension in SHRSP. The purpose of this experiment was to determine whether treatment of SHRSP with the calcium entry blocker felodipine would alter oscillatory activity. Adult SHRSP and WKY rats were treated orally with felodipine for 8 weeks. Felodipine treatment produced a significant decrease in blood pressure in SHRSP (control SHRSP: 240 +/- 7 mmHg, n = 6; felodipine-treated SHRSP: 164 +/- 8 mmHg, n = 5, P less than 0.05; tail-cuff method). Helically-cut tail artery strips from all rats were mounted in tissue baths for isometric force recording and exposed to norepinephrine (6 x 10(-9) to 6 x 10(-6) mol/l) for 20 min at each concentration. Oscillatory activity was defined as the sum of the magnitudes of all phasic contractions occurring during the final 10 min of norepinephrine incubation. Oscillatory activity was markedly reduced in tail arteries from felodipine-treated SHRSP when compared with control SHRSP. Felodipine also inhibited oscillatory activity when added directly to the tissue bath. It seems, therefore, that felodipine may lower blood pressure in SHRSP, at least in part, by correcting the genetic defect responsible for oscillatory activity.

Pharmacokinetics of felodipine in patients with liver disease

Nine patients (6 males, 3 females) with biopsy-proven liver cirrhosis participated in an open, cross-over, three centre study of the effect of impaired liver function on the pharmacokinetics of felodipine. Two of the nine patients had undergone porto-caval anastomosis. Each patient was given 0.75 mg i.v. and 10 mg p.o. on separate occasions. The results of this study have been compared with published data from younger subjects and elderly hypertensive patients. The mean peak plasma concentration normalized to a dose of 10 mg (Cmax 46 nmol/l) was twice as high in the cirrhotic patients as in the healthy subjects, but the bioavailability, f, (17.0%) was comparable. Subjects with a porto-caval shunt did not have higher f than the mean for the group. The volume of distribution at steady-state, Vss, was significantly lower than in the healthy subjects. Protein binding was significantly lower in the patients with cirrhosis: 99.46% compared to 99.64% in the healthy subjects. The weight-corrected clearance was 1/3 of the value in healthy subjects. No correlation between systemic availability and oral clearance was found, so it is proposed that felodipine is metabolized both in the liver and also in the gut wall. The results suggest that at least the starting dose should be reduced in patients with severe liver disease.

Increased exercise tolerance and reduced electrocardiographic ischaemia 3 and 12 hours after oral felodipine in effort angina

The antianginal properties and the duration of action of two doses of felodipine, a dihydropyridine calcium antagonist with a vascular:myocardial potency ratio approximating 100:1, were investigated in 15 patients suffering from disabling effort angina pectoris with reproducible exercise tolerance. Felodipine (5 mg, 10 mg) and placebo were administered once in the morning on three different days, with a 24 h interval between them, according to a double-blind 3 x 3 latin square design, 5 times replicated. Symptom-limited cycloergometric exercise tests were performed 3 and 12 h after administration. Duration of exercise to ST segment depression of 1 mm and to peak exercise was increased (all P less than 0.01) by both doses of felodipine in comparison with placebo. Twelve hours after administration, the 10-mg dose induced a significant improvement in the exercise time and a smaller ST segment depression (all P less than 0.01) in comparison with the 5-mg dose. The relationship between ST segment depression and the pressure-rate product during exercise was favourably influenced by the 10-mg dose at 3 and 12 h after intake, and by the 5-mg dose only at 3 h after intake. These findings suggest an increase in coronary blood flow induced by felodipine. Apart from mild headache there were no other unwanted effects. In conclusion, felodipine improves exercise tolerance and reduces electrocardiographic ischaemia for up to 12 h after single oral administration in patients with effort angina. Increasing the dose from 5 mg to 10 mg produces a more prolonged effect, with increased exercise tolerance 12 h after intake.

Pharmacokinetics of felodipine in patients with impaired renal function

1. The pharmacokinetics of felodipine and its effects on blood pressure and heart rate were studied in eight male patients aged between 28 and 57 years with a glomerular filtration rate, GFR, between 8 and 68 ml min-1, following single i.v. and oral administration. 2. Clearance, Cmax, AUC, Vss and V, of felodipine were unaffected by the renal disease. The metabolite excretion (14C-labelled) was slower than in healthy subjects. Initial renal clearance of these metabolites correlated with individual GFR values. The total amount of the dose excreted in the urine was also decreased.

Effects of felodipine on blood pressure and lymphocyte membrane characteristics in spontaneously hypertensive stroke-prone rats

Adult spontaneously hypertensive stroke-prone rats (SHRSP) and age- and sex-matched Wistar-Kyoto rats (WKY) were treated with the calcium-channel antagonist felodipine for 2-4 weeks (1 mg/g in rat chow powder). Control rats of both strains were fed untreated chow. At the end of the treatment period we measured blood pressure, net potassium efflux and intralymphocytic calcium concentration. In the untreated rats the values for these parameters were significantly higher in SHRSP than in WKY. Felodipine treatment caused a reduction in the SHRSP values to WKY levels. We conclude that the high blood pressure of SHRSP results from an increase in membrane permeability to calcium. The resultant increase in intralymphocytic calcium concentration causes an increase in net potassium efflux via calcium-activated potassium channels. By reducing the membrane permeability to calcium with felodipine, these parameters were returned to normal or near-normal levels.

Antihypertensive efficacy of the calcium-antagonist felodipine in patients with persisting hypertension on beta-adrenoceptor blocker therapy. The Canadian Felodipine Study Group

1. The antihypertensive efficacy of two different doses of the calcium antagonist felodipine was evaluated in patients with hypertension persisting despite beta-adrenoceptor blocker therapy. Following a single-blind placebo period of 4 weeks, patients were randomized to placebo (n = 36), felodipine 5 mg twice daily (n = 39) and felodipine 10 mg twice daily (n = 35) for another 4 weeks. beta-adrenoceptor blocker therapy remained unchanged throughout the study. 2. Effects on blood pressure (BP) were evaluated after the first dose and after chronic dosing at 2 h after dosing and the end of the dosing interval (12 h). 3. Felodipine decreased systolic and diastolic BP by 30-35/20-25 mm Hg at 2 h. These decreases were similar after acute and chronic treatment. Twelve hours after dosing, decreases of 15-20/10-15 mm Hg were observed compared to 10/5 mm Hg on placebo, and half of the patients still had a controlled BP (supine diastolic BP less than 90 mm Hg). BP responses were rather similar for both doses of felodipine at 2 and 12 h. 4. Multiple regression analysis showed that both initial BP level and plasma felodipine concentrations were significant predictors of the BP response to felodipine, but age was not. 5. Adverse effects attributed to felodipine were mainly related to vascular symptoms (primarily flushing and ankle swelling); these occurred in about 30% of patients, and were pronounced in three patients (4%). 6. Felodipine is therefore highly effective in lowering BP of hypertensive patients on chronic beta-adrenoceptor blocker therapy, with no evidence for a gradual lowering of the BP or for development of tolerance. Both initial BP level and plasma concentrations are better indicators of antihypertensive efficacy of this calcium antagonist than age.

Effect of indomethacin on the pharmacokinetics and pharmacodynamics of felodipine

1. We studied the effects of pre-treatment with oral indomethacin (25 mg four times daily for 3 days) on the pharmacokinetics, haemodynamics and diuretic properties of oral felodipine (10 mg single dose) in 12 healthy male volunteers using a placebo controlled double-blind four-way crossover protocol. 2. Felodipine with or without indomethacin pretreatment reduced standing diastolic blood pressure (P less than 0.001) at 0.5 to 3.0 h after dosing compared with placebo or indomethacin alone. Systolic blood pressures during indomethacin treatment alone were consistently higher than the other three treatment groups (P less than 0.01), presumably due to sodium and fluid retention. 3. Felodipine and felodipine plus indomethacin produced significantly greater excretion of urine and urinary sodium, but not of urinary potassium or creatinine when compared with placebo (P less than 0.01) over an 8 h period. 4. The pharmacokinetic parameters of felodipine (Cmax, tmax, t1/2 and AUC), the concentration-response curves for blood pressure lowering effects, the reflex tachycardia, diuretic properties and side-effects profile of felodipine were not significantly altered by indomethacin pretreatment in normal volunteers.

Binding of a dihydropyridine felodipine-analogue to calmodulin and related calcium-binding proteins

A dihydropyridine-affinity column was prepared by coupling a physiologically active and vasoselective amino-derivative of felodipine to divinylsulfone-activated Trisacryl GF2000. Calmodulin (CaM) as well as the homologous calcium-binding proteins skeletal and cardiac Troponin C (sTnC and cTnC) and S100b bound to this resin in a calcium-dependent manner. In contrast, other homologous proteins such as parvalbumin and the intestinal calcium-binding protein did not bind. Competition studies showed that CaM had a higher affinity for the felodipine-column than sTnC or cTnC. Through studies with a series of proteolytic fragments of CaM and sTnC, it was found that the felodipine binding site is located in the amino-terminal domain of the protein. These results illustrate the utility of affinity-chromatography for the study of dihydropyridine-binding proteins.

A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic use in hypertension

Felodipine is a dihydropyridine calcium antagonist which selectively relaxes vascular smooth muscle. By acting at peripheral arterioles, it lowers systemic vascular resistance and thereby produces substantial decreases in blood pressure and increases in cardiac output. Felodipine is indicated for the management of hypertension, and in patients with mild to moderate disease felodipine monotherapy markedly lowers blood pressure. It proved as effective as atenolol, and equivalent to hydrochlorothiazide, either with or without amiloride, in terms of antihypertensive activity. Comparative studies also demonstrated that once daily administration with an extended-release formulation provides equivalent antihypertensive efficacy to the same amount of drug administered twice daily as the standard tablets. As a second- or third-line treatment for patients with moderate to severe hypertension refractory to standard drug combinations, felodipine produced considerable reductions in blood pressure when added to beta-blockers and diuretics, either alone or in combination, in studies lasting up to 48 weeks. In comparative studies of multiple-drug treatments felodipine was found to have superior efficacy to hydralazine and prazosin, and was at least as effective as nifedipine, minoxidil and propranolol, when used with diuretics and/or beta-blockers. As an alternative to hydrochlorothiazide, in combination with beta-blockers, felodipine consistently controlled blood pressure in a greater percentage of patients and usually provided greater decreases in blood pressure. The main side effects with felodipine are ankle oedema, headache and flushing. Although the overall incidence of effects is quite high, they are usually mild in nature. Nevertheless, withdrawal due to side effects has been necessary in about 7% of patients overall. Thus, the efficacy of felodipine has been demonstrated in mild, moderate and severe hypertension. At the present time it seems particularly suitable as a second- or third-line treatment in refractory hypertension, but it also can be used as monotherapy for mild to moderate disease.

Effects of oxygen free radical scavengers, xanthine oxidase inhibition and calcium entry-blockers on leakage of albumin after ischaemia. An experimental study in rabbit kidneys

The effect of pretreatment with various substances protecting against oxygen free radicals on the leakage of proteins across the vessel walls of rabbit kidneys induced by ischaemia has been studied. The leakage of proteins was estimated from the difference between the 120-min distribution space of [131I]albumin and the 5-min distribution space of [125I]albumin, the latter mainly measuring the intravascular volume. Neither SOD (superoxide dismutase), catalase, allopurinol or two different Ca2+ channel blockers (nifedipine, felodipine) could alone reduce the leakage induced by ischaemia. A combined pretreatment with SOD, catalase and nifedipine reduced the leakage in the cortex, and pretreatment with mannitol alone reduced the leakage in the cortex and outer stripe of the medulla. The results indicate that oxygen free radicals are involved in the leakage of proteins across the vessel walls induced by ischaemia, but that other mechanisms are involved as well.

Reduced felodipine bioavailability in patients taking anticonvulsants

Felodipine is a dihydropyridine calcium antagonist, structurally related to nifedipine, which undergoes extensive first-pass hepatic metabolism and normally has an oral bioavailability of 15%. Felodipine disposition was studied in 10 patients who had microsomal enzyme induction due to chronic anticonvulsant therapy, and in 12 normal volunteers matched for age and sex. Plasma felodipine concentrations after a 5 mg oral dose were grossly reduced in the epileptic patients: the mean peak concentration was 1.6 (vs 8.9) nmol/l, and the area under the curve was only 2.0 (vs 30.0) nmol.h/l. The relative bioavailability of felodipine in the epileptic patients was thus only 6.6% of that in the normal subjects, and less than 1% of the oral dose was systemically available. Patients on anticonvulsant treatment will require substantially higher doses of felodipine to achieve plasma concentrations equivalent to those in non-induced subjects.

Dose-dependent effects of felodipine on diuresis and natriuresis in healthy subjects

We compared the effects of various acute doses of felodipine and placebo on diuresis and natriuresis in healthy men. The subjects were given felodipine, 1 and 3 mg as an intravenous infusion, and 5, 15, and 40 mg as an oral solution on 5 separate days. On each day blood pressure and heart rate were recorded and urine was collected for analysis of volume and sodium for 24 h. Felodipine induced a dose-dependent increase in heart rate and a dose-dependent decrease in diastolic blood pressure. These effects were maximal within 30 min of drug administration. Felodipine induced a maximal increase in diuresis of about 150% compared with placebo and a maximal increase in natriuresis of about 240%. The renal effects were most pronounced during the first 4 h after dose intake. During the 8-24 h interval, diuresis and natriuresis were lower than after placebo, but when the whole 24-h period was considered, no significant differences were found between felodipine and placebo in regard to sodium and water excretion. The most pronounced effects on diuresis and natriuresis were seen after moderate doses (3 mg i.v. and 15 mg orally). The response to the highest dose (40 mg orally) was somewhat less probably due to the excessive drop in diastolic blood pressure.

Antihypertensive effect of felodipine or hydralazine when added to beta-blocker therapy

In a double-blind randomized study, hydralazine (n = 59) or the new dihydropyridine calcium antagonist felodipine (n = 61) was added to previous treatment with beta-adrenoceptor blocking agents in a group of 120 patients with essential hypertension. Active treatment with either hydralazine or felodipine was given for 8 weeks after a 4-week placebo run-in period, at the end of which all patients had supine diastolic blood pressures greater than 95 mm Hg. Assessment of the results according to the intention to treat principle showed that felodipine was significantly more effective than hydralazine at the doses employed, reducing systolic blood pressure 10-19 mm Hg more than hydralazine and reducing diastolic blood pressure 5-11 mm Hg more than hydralazine (95% confidence intervals). The number of patients complaining of side effects, the number of complaints, and the number of patients that had to be withdrawn from treatment were numerically higher during treatment with hydralazine than with felodipine, but these differences were not statistically significant. Against this background it is concluded that felodipine is superior to hydralazine when added to an antihypertensive regimen consisting of beta-adrenoceptor blocking agents.

Felodipine, a new calcium antagonist, modifies exercise-induced asthma

Recently, calcium antagonists have been reported to have a clinically beneficial effect in patients with asthma. Felodipine is a new calcium antagonist of the dihydropyridine group with a high selectivity for arteriolar smooth muscle; it is under clinical investigation for the treatment of hypertension. In this double-blind, randomized crossover trial in 9 patients, the effect of 10 mg felodipine in oral solution on exercise-induced asthma was compared with a placebo on separate days. The FEV1 was at least 80% of the predicted normal value, with variation between study days of less than 10%. Heart rate, blood pressure, and FEV1 were measured before and at 15 and 30 min after each treatment. The exercise test consisted of steady state running at submaximal work loads for 6 to 8 min and started at 30 min after treatments. FEV1 was measured at 1, 2, 5, 10, 15, and 30 min after the end of exercise. The predrug baseline FEV1 values were comparable on the 2 days of the study, and felodipine had no effect on the resting lung function. The mean percentage fall in FEV1 (SEM) after exercise with placebo was 27.0 (4.5)%, and with felodipine it was 13.5 (3.7)%. The difference between felodipine and placebo was statistically significant. While receiving felodipine, the resting heart rate was increased by 15%, with a tendency to lower systolic and diastolic blood pressures. The heart rate after exercise was higher during felodipine treatment than during placebo treatment. One patient receiving placebo and 7 receiving felodipine noted a transient headache. Two patients receiving felodipine also noticed lightheadedness after exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Sustained haemodynamic effects of felodipine in patients with chronic cardiac failure

1. The efficacy of felodipine a new calcium channel blocker with selective vasodilator activity in the management of severe low output cardiac failure, secondary to coronary heart disease, was determined in 10 patients. 2. Haemodynamic measurements were made at rest and during dynamic exercise and left ventricular function was assessed by radionuclide ventriculography. 3. Significant increases in cardiac index, stroke volume index and ejection fraction were found particularly during exercise, both acutely and following 4 weeks administration of felodipine therapy. 4. Felodipine could well have a significant role in the long term management of the patient with chronic cardiac failure.

The contribution of systemic hypertension to progression of chronic renal failure in the rat remnant kidney: effect of treatment with an angiotensin converting enzyme inhibitor or a calcium inhibitor

In order to establish if pharmacological treatment of systemic hypertension modifies the course of progressive renal failure, we studied the effects of an angiotensin converting enzyme inhibitor and a calcium antagonist, on the renal structure and function in the remnant kidney model of chronic renal failure in the rat. Progressive renal failure was induced in adult female Sprague Dawley rats (SDR) by surgical removal of the right kidney, and segmental infarction of seven-eighths of the left kidney. Following subtotal nephrectomy, plasma creatinine rose from 65 +/- 16 mumol/l to 173 +/- 19 mumol/l (P less than 0.001) over a period of 6 weeks, systolic blood pressure (SBP) rose from 121 +/- 2 mmHg to 176 +/- 7 mmHg (P less than 0.001) and urinary protein excretion from 0.6 +/- 0.2 to 84 +/- 22 mg/24 h (P less than 0.001). Glomerular mesangial expansion was present after 2 weeks, then progressed, in association with the development of glomerular sclerosis, which became prominent after 6 weeks. Rats were treated with enalapril (5 mg/kg per day) or felodipine (30 mg/kg per day) from 1 week after subtotal nephrectomy, and their course compared with that of untreated rats. Systemic SBP decreased to a similar degree by both drug treatments. Six weeks after surgery, plasma creatinine concentration was lower in the enalapril-treated group (110 +/- 8 mumol/l, P less than 0.05) than in the felodipine-treated group (153 +/- 23 mumol/l). The latter group showed similar plasma creatinine concentrations to those of the untreated rats (173 +/- 19 mumol/l).(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of combining felodipine and metoprolol in moderate to severe hypertension--a one year study

A dose titration study was performed using felodipine, a new calcium antagonist, in Chinese patients with essential hypertension inadequately controlled by metoprolol alone (DBP greater than 95 mmHg). BP and pulse rate were recorded at rest and during treadmill exercise. Nineteen patients completed the six weeks' dose titration phase (2.5-5-10 mg twice daily) of whom 17 were followed for one year. A single 2.5 mg dose of felodipine produced a rapid and pronounced antihypertensive response with pre-exercise supine BP falling from a mean 168/104 to 146/92 mmHg) (P less than 0.001). The SBP during exercise was reduced from 206 to 185 mmHg (P less than 0.001). After 6 weeks treatment the supine BP had fallen to 132/85 mmHg (P less than 0.001) and the SBP during exercise to 169 mmHg (P less than 0.001). Six patients received 2.5 mg twice daily, eight patients 5 mg twice daily and three patients 10 mg twice daily. The effects, both at rest and during exercise, were maintained for at least 12 hours after dosing. The pulse rate was unaffected by felodipine therapy apart from a small transient increase following the first dose. Sixteen patients achieved the target DBP of 90 mmHg measured 12 hours after dosing and only one patient still had a DBP greater than 95 mmHg. After one year the mean supine BP had fallen slightly further to 128/82 mmHg. One patient was withdrawn due to palpitations. Felodipine was otherwise well tolerated.(ABSTRACT TRUNCATED AT 250 WORDS)

Manganese can inhibit or potentiate contractile responses in mesenteric portal vein

The effects of a number of agents believed to interfere with Ca were examined on contraction induced by noradrenaline (NA) or K in rat mesenteric portal veins. The organic calcium antagonists nifedipine, verapamil, methoxyverapamil, and felodipine slowly produced maximum inhibitory effects, nifedipine being fastest with a T1/2 of 20 min. In contrast, the inhibitory effects of Mn were immediate but disappeared on continued exposure of the tissue to Mn. After removal of Mn from the bath fluid, an above normal contraction was produced by K or NA. Measurement of Mn by atomic absorption spectrometry showed that the concentrations of EDTA-resistant Mn increased in parallel with the loss of inhibitory effects of Mn. This is consistent with an external inhibitory effect of Mn but a potentiating effect of Mn once it reaches an EDTA-inaccessible site. The potentiating effect of Mn was not seen with other ions such as Cd, Ni, Co, Mg, and La, which produced only inhibition of responses to NA or K. Contractile responses to Ba were examined in the absence of external Ca and it was found that the responses decreased with time. The presence of Mn not only prevented the loss of contractility but produced a marked increase in the response to Ba. Relaxation rates were also studied and it was found that Mn speeds the relaxation of contractures produced by NA or Ba as long as Mn is present in the bath fluid, but Mn slows relaxation when it is present (presumably) intracellularly. Mn does not alter relaxation rates of K contractures.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison with young healthy subjects

The pharmacokinetics and antihypertensive effects of felodipine, a new dihydropyridine calcium channel blocker, were studied in elderly hypertensive patients, 67 to 79 years of age and in young healthy subjects, 20 to 34 years of age following oral administration of 5 mg twice daily to steady-state. A single intravenous dose of 3H-felodipine (0.04mg) was given together with the oral dose on the study day. Cmax (17 nmol/L), Cmin (5 nmol/L) and AUC (82 nmol/L.h) were 3 times higher in the elderly than in the young subjects. Systemic availability was about 15% in both groups. Plasma clearance (CL) was reduced from 56.1 L/h in the young to 25.4 L/h in the elderly. There was no effect of age on the volume of distribution at steady-state (Vss). Reduced hepatic blood flow and enzyme activity or increased gut wall metabolism are possible reasons for the altered pharmacokinetics in the elderly. Blood pressure was reduced in the elderly from 190/99 to 177/91 mm Hg 12 hours after 5mg felodipine during twice daily dosage. The effect on blood pressure correlated with plasma concentrations of felodipine.