Pharmacokinetics of dilevalol in normotensive and hypertensive volunteers

The National COVID Cohort Collaborative (N3C): Rationale, design, infrastructure, and deployment

Objective

Coronavirus disease 2019 (COVID-19) poses societal challenges that require expeditious data and knowledge sharing. Though organizational clinical data are abundant, these are largely inaccessible to outside researchers. Statistical, machine learning, and causal analyses are most successful with large-scale data beyond what is available in any given organization. Here, we introduce the National COVID Cohort Collaborative (N3C), an open science community focused on analyzing patient-level data from many centers.

Materials and Methods

The Clinical and Translational Science Award Program and scientific community created N3C to overcome technical, regulatory, policy, and governance barriers to sharing and harmonizing individual-level clinical data. We developed solutions to extract, aggregate, and harmonize data across organizations and data models, and created a secure data enclave to enable efficient, transparent, and reproducible collaborative analytics.

Results

Organized in inclusive workstreams, we created legal agreements and governance for organizations and researchers; data extraction scripts to identify and ingest positive, negative, and possible COVID-19 cases; a data quality assurance and harmonization pipeline to create a single harmonized dataset; population of the secure data enclave with data, machine learning, and statistical analytics tools; dissemination mechanisms; and a synthetic data pilot to democratize data access.

Conclusions

The N3C has demonstrated that a multisite collaborative learning health network can overcome barriers to rapidly build a scalable infrastructure incorporating multiorganizational clinical data for COVID-19 analytics. We expect this effort to save lives by enabling rapid collaboration among clinicians, researchers, and data scientists to identify treatments and specialized care and thereby reduce the immediate and long-term impacts of COVID-19.

Labetalol absorption kinetics: Rat small intestine and colon studies

Labetalol is a widely used drug for the management of hypertension, which is preferably administered by the oral route despite its low bioavailability. The objective of this study is to ascertain the mechanisms underlying its absorption as an approach to help in predicting the influence of dosage changes, possible drug-drug and drug-fruit juice interactions. Perfusion experiments have been performed in rats in two sites of absorption: the intestine and the colon. The nonlinearity of the process has been established by means of the assay of a wide range of concentrations (2-2000 microM). Fitting of the concentration versus time data allows the estimation of passive diffusion constant in the intestine (1.42 +/- 0.05/h) and the colon (1.13 +/- 0.06/h), V(m) and K(m) of the input process (9.85 +/- 4.98 microM/h, and 10.44 +/- 26.16 microM, respectively) and K(m) of an efflux system (0.53 +/- 1.16 microM) and V(m) in both intestinal segments (2.60 +/- 11.37 microM . /h in the intestine and 0.66 +/- 1.38 microM . /h in the colon). The efflux carrier implicated is identified by means of several inhibition experiments, whose inhibition ability is mathematically estimated. Results suggest the p-glycoprotein as responsible for the efflux of labetalol.

The effects of age on the pharmacokinetics, antihypertensive efficacy and general tolerability of dilevalol

1. This study investigated the influence of age on the pharmacokinetics, pharmacodynamics, general tolerability and concentration-effect relationships in 18 patients with essential hypertension (age range 23-73 years) during treatment with dilevalol, a non selective beta-adrenoceptor antagonist with vasodilator properties. 2. There were no significant age-related changes in pharmacokinetics for either acute or chronic treatment with dilevalol, although there were significant changes in elimination half-life from 7.8 to 11.7 h (P less than 0.05) and in AUC from 261 to 352 ng ml-1 h (P less than 0.005) following translation from acute to chronic dosing. 3. In absolute terms, dilevalol treatment (as compared with placebo) produced numerically larger falls in average blood pressure in the six oldest as compared with the six youngest patients: for example, supine blood pressure fell by, respectively, 29/15 and 10/7 mm Hg during chronic treatment. 4. Using an integrated kinetic-dynamic model, blood pressure responsiveness was characterised by relating the fall in blood pressure (mmHg) to the plasma drug concentrations in each individual patient. No independent age-related effect was demonstrated. There was a significant relationship between response and the height of initial blood pressure which tended to be higher in the elderly patients. 5. Patient tolerability was generally satisfactory and there was no differential age-related effect. 6. This study has shown that the antihypertensive efficacy of dilevalol is not attenuated in the elderly and that there are no significant age-related differences in pharmacokinetics or pharmacodynamics.

Clinical pharmacokinetics and kinetic-dynamic relationships of dilevalol and labetalol

Dilevalol and labetalol are examples of a growing number of new beta-blockers which combine nonselective beta-adrenoceptor antagonism with vasodilator activity. Dilevalol is one of the 4 stereoisomers of labetalol, and is estimated to form approximately 25% of the racemic drug. Labetalol itself is an alpha 1-antagonist but dilevalol, which has negligible affinity for alpha-receptors, exerts its vasodilator effect via beta 2-agonism. Both drugs are rapidly and completely absorbed in 60 to 90 min and subject to extensive first-pass hepatic metabolism; the average bioavailability after oral administration is around 20 to 35%, and there is wide interindividual variability in plasma drug concentrations and dosage requirements. The volume of distribution of dilevalol (17 to 25 L/kg) is higher than that reported for labetalol (3 to 16 L/kg), although both drugs are concentrated in the extravascular compartment. Correspondingly, the elimination half-life of dilevalol at steady-state is around 15h compared with 8h for labetalol. There is evidence that the pharmacokinetics of dilevalol change (a reduction in clearance) in translation from single-dose to long term therapy. There is no clinically significant effect of age on the steady-state disposition of either drug and the pharmacokinetics of labetalol appear to be unchanged during pregnancy. Although there is a linear relationship between dose and area under the concentration-time curve, early studies found no evidence of a simple relationship between dose or plasma drug concentration and the fall in blood pressure. However, an integrated pharmacokinetic-pharmacodynamic model has been used to correlate concentrations of both drugs with reductions in systolic and diastolic blood pressure in individuals. This approach derives a mathematical description of antihypertensive response which integrates pharmacokinetic and pharmacodynamic information and also takes account of placebo effects and changes in drug concentration and blood pressure during the dosage interval. The pharmacokinetic-pharmacodynamic relationships of labetalol are characterised by a linear model. For example, in a group of healthy volunteers, the 'responsiveness' to labetalol was -0.19mm Hg/micrograms/L. In contrast, the relationships of dilevalol are best described by a Langmuir maximum effect model, and so individual responses to short and long term treatment have been quantified by the concentration-effect parameters of maximum effect and drug concentration required to produce 50% of this.(ABSTRACT TRUNCATED AT 400 WORDS)

Dilevalol: a selective beta-2 adrenergic agonist vasodilator with beta adrenergic blocking activity

Dilevalol is the R-R' optical isomer of labetalol and differs pharmacologically from the racemic mixture in the following ways: it is seven-fold more potent as a selective beta-2 agonist; it is four times more potent as a nonselective beta antagonist; it has no clinically significant alpha antagonist property. Dilevalol is a vasodilator and reduces blood pressure by reducing systemic vascular resistance. It has a half-life of 15-18 hours, and is demonstrated to be effective as an antihypertensive agent for 24-30 hours. Hemodynamic studies in humans show that following administration of dilevalol either orally or intravenously, blood pressure falls as a consequence of a decrease in systemic vascular resistance. Cardiac index is unchanged and heart rate decreases slightly. Dilevalol is shown to cause regression of left ventricular hypertrophy in younger individuals, to improve left ventricular performance and to have no effect on parameters of renal function. Prospective double-blinded clinical trials in comparison with placebo, propranolol, metoprolol and atenolol were conducted and demonstrate dilevalol to be an effective antihypertensive agent with a favorable side effect profile with a particularly low incidence of central nervous system side effects.

The efficacy and safety of dilevalol in patients with chronic stable angina pectoris

This is the first reported large clinical trial of the antianginal and acute ischemic effectiveness and safety of dilevalol (the R, R-isomer of labetalol) in patients with chronic stable angina pectoris. This was a multicenter double blind fixed-dose parallel group placebo controlled trial. Patients with chronic stable angina and positive and reproducible exercise tests (+/- 20%) were included. If randomized, patients entered one of four fixed dose groups (twice a day placebo, 100 mgm, 200 mgm and 400 mgm bid for 2 weeks). Exercise testing was performed at 2 hours (peak) and 12 hours (trough) postdosing. This was followed by a 2-week once-a-day dosing regimen in which patients received the same total daily dose as the prior 2 weeks, with the full dose in the morning and a matched placebo in the evening. Exercise testing was performed at 2 hours (peak) and 24 hours (trough) postdosing. Anginal frequency and NTG consumption were significantly reduced, and equally so, by qd and bid regimens. The time of exercise to the onset of angina increased and the proportion of patients terminating exercise because of moderate angina decreased in a dose response fashion for both peak and trough tests and for both qd and bid regimens. There was also a dose related decrease in exercise induced ST segment depression and an increase in time to 1 mm ST depression. In 15 patients, 24-hour ambulatory monitoring also revealed a decrease in episodes of silent ischemia. No significant side effects related to the study drug occurred.(ABSTRACT TRUNCATED AT 250 WORDS)

Antihypertensive effect of dilevalol is directly related to dose and plasma concentrations

Dilevalol is a novel antihypertensive agent combining vasodilation due to selective beta 2-adrenergic receptor agonism with nonspecific beta antagonism. To determine the relation of dilevalol dose and plasma concentration to antihypertensive effect, dilevalol (n = 15) or placebo (n = 3) was administered to 18 hypertensive subjects. The study was performed under blinded conditions during a 21-day hospitalization after a 3-week drug-free outpatient phase. In the 15 hypertensive patients receiving dilevalol orally in single morning doses of 200, 400 and 800 mg each for 5 days, the drug was shown to reduce blood pressure effectively for 24 hours at all doses. The antihypertensive effect was significantly related to dose administered and to the concentration of unchanged dilevalol measured in plasma. Dilevalol did not cause excessive changes in heart rate at rest and did not produce postural hypotension. The antihypertensive effectiveness of dilevalol was essentially the same after the first and fifth (steady state) doses at each dose level. Finally, no tendency toward rebound hypertension or tachycardia was observed after the abrupt discontinuation of dilevalol in these patients.