Richard A Preston

Jackson Memorial Hospital, Miami, Florida, United States

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Publications (85)431.25 Total impact

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    ABSTRACT: Two open-label, parallel-group studies evaluated the influence of renal and hepatic insufficiency on the pharmacokinetics of a single-dose anacetrapib 100 mg. Eligible participants included adult men and women with moderate hepatic impairment (assessed by Child-Pugh criteria) or severe renal impairment (CrCl <30 mL/min/1.73 m(2) ). In both studies, patients were matched (race, age, sex, BMI) with healthy control subjects. Twenty-four subjects were randomized in each study (12 with either moderate hepatic or severe renal impairment and 12 matched healthy controls). In the hepatic insufficiency study, the geometric mean ratio (GMR; mean value for the group with moderate hepatic insufficiency/mean value for the healthy controls) and 90% CIs for the area under the concentration-time curve from time zero to infinity (AUC0-∞ ) and the maximum concentration of drug in plasma (Cmax ) were 1.16 (0.84, 1.60) and 1.02 (0.71, 1.49), respectively. In the renal insufficiency study, the GMRs (mean value for the group with severe renal insufficiency/mean value for the healthy controls) and 90% CIs for AUC0-∞ and Cmax were 1.14 (0.80, 1.63) and 1.31 (0.93, 1.83), respectively. Anacetrapib was generally well tolerated and there was no clinically meaningful effect of moderate hepatic or severe renal insufficiency on the pharmacokinetics of anacetrapib.
    The Journal of Clinical Pharmacology 11/2014; 54(11). DOI:10.1002/jcph.320 · 2.47 Impact Factor
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    ABSTRACT: Several consistent lines of evidence indicate an association between sodium sensitivity and impaired nitric oxide bioactivity. Nevertheless, whether restoring nitric oxide in humans by pharmacological means can ameliorate sodium sensitivity has not been investigated. Because nebivolol has been demonstrated to increase nitric oxide bioactivity in both laboratory and clinical investigations, we hypothesized that nebivolol might ameliorate sodium sensitivity and improve renal sodium handling in comparison to metoprolol. We therefore conducted a randomized, 2-treatment-period crossover trial in 19 Hispanic postmenopausal women with hypertension to determine the comparative effects of nebivolol versus metoprolol on (1) 24-hour ambulatory blood pressure response to an increase in dietary sodium from 5 days of low sodium to 5 days of high sodium, (2) renal natriuretic response to a 1-L saline challenge, and (3) asymmetrical dimethylarginine. Clinic blood pressure and heart rate were significantly reduced after 4 weeks of treatment with both nebivolol and metoprolol. Twenty-four-hour mean systolic blood pressure increased sharply from low sodium to high sodium for both nebivolol and metoprolol. Nevertheless, the increases in blood pressure did not differ between the 2 drugs: 7.7 (3.1, 12.3) mm Hg with metoprolol and 9.3 (4.6, 13.9) mm Hg with nebivolol (P=0.63). Furthermore, we observed no differences between the drugs in natriuretic response to saline challenge or asymmetrical dimethylarginine. In a sodium-sensitive population, at doses sufficient to produce reductions in blood pressure and heart rate, nebivolol did not demonstrate a significant effect on sodium sensitivity or sodium handling compared with metoprolol.
    Hypertension 05/2014; 64(2). DOI:10.1161/HYPERTENSIONAHA.114.03476 · 7.63 Impact Factor
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    ABSTRACT: Podocytes are highly differentiated cells and critical elements for the filtration barrier of the kidney. Loss of their foot process (FP) architecture (FP effacement) results in urinary protein loss. Here we show a novel role for the neutral amino acid glutamine in structural and functional regulation of the kidney filtration barrier. Metabolic flux analysis of cultured podocytes using genetic, toxic and immunologic injury models identified increased glutamine utilization pathways. We show that glutamine uptake is increased in diseased podocytes to couple nutrient support to increased demand during the disease state of FP effacement. This feature can be utilized to transport increased amounts of glutamine into damaged podocytes. The availability of glutamine determines the regulation of podocyte intracellular pH (pHi). Podocyte alkalinization reduces cytosolic cathepsin L (cCatL) protease activity and protects the podocyte cytoskeleton. Podocyte glutamine supplementation reduces proteinuria in LPS treated mice whereas acidification increases glomerular injury. In summary, our data provides a metabolic opportunity to combat urinary protein loss through modulation of podocyte amino acid utilization and pHi.
    Journal of Biological Chemistry 05/2014; 289(25). DOI:10.1074/jbc.M114.568998 · 4.60 Impact Factor
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    ABSTRACT: Ospemifene is a nonestrogen tissue-selective estrogen agonist/antagonist approved to treat moderate to severe dyspareunia due to vulvar and vaginal atrophy in postmenopausal women. Three single-dose, open-label, parallel-group pharmacokinetic studies examined the pharmacokinetics of ospemifene in postmenopausal women with (1) mild hepatic impairment (n = 7), (2) moderate hepatic impairment (n = 8), and (3) severe renal impairment (n = 8) compared with a similar number of matched healthy controls. The study durations ranged from 8 to 12 days. Study participants received a single oral dose of ospemifene 60 mg on day 1 and blood samples were collected serially. The geometric mean ratios (hepatic or renal impairment/healthy) and 90% confidence intervals (CIs) for area under the concentration-time curve from time 0 extrapolated to infinity (AUC0-∞) and maximum concentration (Cmax), respectively, of ospemifene were 90.86% (90% CI, 65.95%-125.19%) and 79.48% (90% CI, 65.95%-95.79%) in the mild hepatic impairment study; 128.62% (90% CI, 87.13%-189.88%) and 101.12% (90% CI, 66.17%-154.52%) in the moderate hepatic impairment study, and 119.63% (90% CI, 81.37%-175.88%) and 79.30% (90% CI, 52.85%-118.99%) in the severe renal impairment study. Overall, there was no clinically important effect of hepatic or renal impairment on the pharmacokinetics of ospemifene, indicating that dosing does not need to be adjusted in postmenopausal women with mild or moderate hepatic impairment or in subjects with severe renal impairment.
    American journal of therapeutics 01/2014; 22(3). DOI:10.1097/01.mjt.0000434044.39502.64 · 1.13 Impact Factor
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    ABSTRACT: Apremilast (CC-10004), a PDE4 enzyme inhibitor, is under clinical development for the treatment of inflammatory immune-mediated disorders. Since apremilast is extensively metabolised via multiple routes, impact of hepatic impairment on the pharmacokinetics (PK) of apremilast and M12 metabolite was evaluated. Thirty-two subjects were enrolled in a two-centre, open-label, and single-dose study. Subjects with moderate hepatic impairment and their healthy matches received a single 30-mg dose and subjects with severe hepatic impairment and their healthy matches received a single 20-mg dose of apremilast. Plasma concentrations of apremilast and M12 were measured, PK parameters calculated, and statistically compared. During the study, single doses of apremilast were well tolerated, with no clinically meaningful safety findings observed. PK parameters were comparable between hepatic impaired and healthy subjects, and there was no evidence to suggest that the PK of apremilast is affected by moderate and severe hepatic impairment. Therefore, no dose adjustment is required.
    International Journal of Medical Engineering and Informatics 01/2014; 6(2):100 - 114. DOI:10.1504/IJMEI.2014.060246
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    ABSTRACT: BACKGROUND AND OBJECTIVE: Azilsartan medoxomil (AZL-M) is a potent angiotensin II receptor blocker that decreases blood pressure in a dose-dependent manner. It is a pro-drug and not detected in blood after oral administration because of rapid hydrolysis to the active moiety, azilsartan (AZL). AZL undergoes further metabolism to the major metabolite M-II and minor metabolites. The objective of this study was to determine the effect of renal impairment on the pharmacokinetics of AZL and its major metabolite. METHODS: This was a single-center, open-label, phase I parallel-group study which examined the single-dose (40-mg) pharmacokinetics of AZL and M-II in 24 subjects with mild, moderate, or severe renal impairment or end-stage renal disease requiring hemodialysis (n = 6 per group), respectively, and healthy matched subjects (n = 24). RESULTS: Renal impairment/disease did not cause clinically meaningful increases in exposure to AZL. M-II exposure was higher in all renally impaired subjects and highest in those with severe impairment (approx fivefold higher vs. control). M-II is pharmacologically inactive; increased exposure was not considered important in dose selection for AZL-M in subjects with renal impairment. Hemodialysis did not significantly remove AZL or M-II. Renal impairment had no clinically meaningful effect on the plasma protein binding of AZL or M-II. Single doses of AZL-M 40 mg were well tolerated in all subject groups. CONCLUSIONS: Based on the pharmacokinetic and tolerability findings, no dose adjustment of AZL-M is required for subjects with any degree of renal impairment, including end-stage renal disease.
    Clinical Pharmacokinetics 04/2013; 52(5). DOI:10.1007/s40262-013-0044-y · 5.49 Impact Factor
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    ABSTRACT: The debate over whether certain antihypertensive medications have benefits beyond what would be expected from their blood pressure lowering spurred the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial, which randomized 42,418 participants to chlorthalidone (15,255), amlodipine (9048), lisinopril (9054), or doxazosin (9061). We compared chlorthalidone, the active control, with each of the other three agents with respect to the primary outcome, fatal coronary heart disease or nonfatal myocardial infarction, and several other clinical endpoints. The arms were similar with respect to the primary endpoint, although some differences were found for other endpoints, most notably heart failure. Although the desire was to achieve similar blood pressure reductions in the four arms, we found some systolic blood pressure and diastolic blood pressure differences. A natural question is to what degree can observed treatment group differences in cardiovascular outcomes be attributed to these blood pressure differences. The purpose of this paper was to delineate the problems inherent in attempting to answer this question, and to present analyses intended to overcome these problems. Copyright © 2012 John Wiley & Sons, Ltd.
    Statistics in Medicine 02/2013; 32(5). DOI:10.1002/sim.5580 · 2.04 Impact Factor
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    ABSTRACT: A gastrointestinal-renal natriuretic signaling axis has been proposed to regulate sodium excretion in response to acute sodium ingestion. Such an axis is thought to be regulated by a gastrointestinal sodium sensor coupled to the activation/release of a natriuretic signal and could have important clinical and scientific implications. Here we systematically tested for this putative axis and the potential involvement of the gastrointestinal-derived natriuretic prohormones prouroguanylin and proguanylin in 15 healthy volunteers. There was no difference in sodium excretion following equivalent oral or intravenous sodium loads during either high- or low-sodium diets. Furthermore, serum concentrations of prouroguanylin and proguanylin did not increase, did not differ following oral or intravenous sodium, and did not correlate with sodium excretion. Thus, our results do not support an acute gastrointestinal-renal natriuretic axis or a central role for prouroguanylin or proguanylin in humans. If such an axis does exist, it is not characterized by a significant difference in the pattern of sodium excretion following either an oral or intravenous sodium load.Kidney International advance online publication, 8 August 2012; doi:10.1038/ki.2012.269.
    Kidney International 08/2012; 82(12). DOI:10.1038/ki.2012.269 · 8.52 Impact Factor
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    ABSTRACT: Boceprevir is a novel inhibitor of the hepatitis C virus NS3 protease and was recently approved for the treatment of patients with chronic hepatitis C infection. The objective of this study was to evaluate the impact of impaired hepatic or renal function on boceprevir pharmacokinetics and safety/tolerability. We conducted two open-label, single-dose, parallel-group studies comparing the safety and pharmacokinetics of boceprevir in patients with varying degrees of hepatic impairment compared with healthy controls in one study and patients with end-stage renal disease (ESRD) on haemodialysis with healthy controls in the other. Patients with hepatic impairment (mild [n = 6], moderate [n = 6], severe [n = 6] and healthy controls [n = 6]) received a single dose of boceprevir (400 mg) on day 1, and whole blood was collected at selected timepoints up to 72 hours postdose to measure plasma drug concentrations. Patients with ESRD and healthy subjects received a single dose of boceprevir 800 mg orally on days 1 and 4, with samples for pharmacokinetic analyses collected at selected timepoints up to 48 hours postdose on both days. In addition, 4 hours after dosing on day 4, patients with ESRD underwent haemodialysis with arterial and venous blood samples collected up to 8 hours postdose. In the hepatic impairment study, there was a trend toward increased mean maximum (peak) plasma concentration (C(max)) and area under the plasma concentration-time curve (AUC) of boceprevir with increasing severity of liver impairment. Point estimates for the geometric mean ratio for C(max) ranged from 100% in patients with mild hepatic impairment to 161% in patients with severe hepatic impairment, with the geometric mean ratio for AUC ranging from 91% in patients with mild hepatic impairment to 149% for patients with severe hepatic impairment, relative to healthy subjects. The mean elimination half-life (t(1/2;)) and median time to C(max) (t(max)) values of boceprevir were similar in healthy subjects and patients with hepatic impairment. In the renal impairment study, mean boceprevir C(max) and AUC values were comparable in patients with ESRD and in healthy subjects, with point estimates for the geometric mean ratio of 81% and 90%, respectively, compared with healthy subjects. Mean t(1/2;), median t(max) and mean apparent oral total clearance (CL/F) values were similar in healthy subjects and patients with ESRD. Boceprevir exposure was also similar in patients with ESRD on day 1 (no dialysis) and day 4 (dialysis beginning 4 hours postdose), with point estimates for the geometric mean ratio of C(max) and AUC to the last measurable sampling time (AUC(last)) on day 1 compared with day 4 of 88% and 98%, respectively. Treatment-emergent adverse events were reported in one patient with severe hepatic impairment (mild vomiting) and two patients with ESRD (moderate ventricular extrasystoles, flatulence and catheter thrombosis). In the present studies, the pharmacokinetic properties of boceprevir were not altered to a clinically meaningful extent in patients with impaired liver or renal function. These data indicate that boceprevir dose adjustment is not warranted in patients with impaired hepatic function or ESRD, including those receiving dialysis. Boceprevir is not removed by haemodialysis.
    Clinical Pharmacokinetics 07/2012; 51(9):619-28. DOI:10.2165/11633440-000000000-00000 · 5.49 Impact Factor
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    ABSTRACT: To determine whether hepatic impairment has an effect on the pharmacokinetics (PK) of vorapaxar or M20, its main pharmacologically active metabolite. This was an open-label study in which a single 40-mg oral dose of vorapaxar was administered to patients with mild (n = 6), moderate (n = 6), and severe (n = 4) hepatic impairment and healthy controls (n = 16) matched for age, gender, weight, and height. Blood samples for vorapaxar and M20 assay were collected predose and at frequent intervals up to 8 weeks postdose. Plasma vorapaxar and M20 PK profiles were similar between patients with impaired liver function and healthy controls. Group mean values for vorapaxar C(max) and AUC(tf) were 206-279 ng/mL and 14,200-18,200 ng·h/mL, respectively, with the lowest values observed in patients with severe impairment. Vorapaxar median T(max) and mean t(1/2) values were 1.00-1.75 h and 298-366 h, respectively. There was no apparent correlation between vorapaxar or M20 exposure or t(1/2) values and disease severity. Vorapaxar was generally well tolerated; one serious adverse event (gastrointestinal bleeding secondary to ruptured esophageal varices) was reported in a patient with severe hepatic impairment. Hepatic impairment had no clinically relevant effect on the PK of vorapaxar and M20. No dose or dosage adjustment of vorapaxar will be required in patients with mild to moderate hepatic impairment. Although systemic exposure to vorapaxar does not appear to increase in patients with severe hepatic impairment, administration of vorapaxar to such patients is not recommended given their bleeding diathesis.
    European Journal of Clinical Pharmacology 04/2012; 68(11):1501-8. DOI:10.1007/s00228-012-1269-7 · 2.70 Impact Factor
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    ABSTRACT: CKD is common among older patients. This article assesses long-term renal and cardiovascular outcomes in older high-risk hypertensive patients, stratified by baseline estimated GFR (eGFR), and long-term outcome efficacy of 5-year first-step treatment with amlodipine or lisinopril, each compared with chlorthalidone. This was a long-term post-trial follow-up of hypertensive participants (n=31,350), aged ≥55 years, randomized to receive chlorthalidone, amlodipine, or lisinopril for 4-8 years at 593 centers. Participants were stratified by baseline eGFR (ml/min per 1.73 m(2)) as follows: normal/increased (≥90; n=8027), mild reduction (60-89; n=17,778), and moderate/severe reduction (<60; n=5545). Outcomes were cardiovascular mortality (primary outcome), total mortality, coronary heart disease, cardiovascular disease, stroke, heart failure, and ESRD. After an average 8.8-year follow-up, total mortality was significantly higher in participants with moderate/severe eGFR reduction compared with those with normal and mildly reduced eGFR (P<0.001). In participants with an eGFR <60, there was no significant difference in cardiovascular mortality between chlorthalidone and amlodipine (P=0.64), or chlorthalidone and lisinopril (P=0.56). Likewise, no significant differences were observed for total mortality, coronary heart disease, cardiovascular disease, stroke, or ESRD. CKD is associated with significantly higher long-term risk of cardiovascular events and mortality in older hypertensive patients. By eGFR stratum, 5-year treatment with amlodipine or lisinopril was not superior to chlorthalidone in preventing cardiovascular events, mortality, or ESRD during 9-year follow-up. Because data on proteinuria were not available, these findings may not be extrapolated to proteinuric CKD.
    Clinical Journal of the American Society of Nephrology 04/2012; 7(6):989-1002. DOI:10.2215/CJN.07800811 · 5.25 Impact Factor
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    Clinical Journal of the American Society of Nephrology 04/2012; · 5.25 Impact Factor
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    ABSTRACT: The primary purpose of the study was to explore the safety and tolerability of telcagepant in patients with stable coronary artery disease. Triptans are effective acute anti-migraine drugs whose vasoconstrictive effects limit their use in patients at risk for adverse cardiovascular events. Telcagepant, a calcitonin gene-related peptide receptor antagonist, is being developed for the acute treatment of migraine. Antagonism of calcitonin gene-related peptide, which does not appear to cause vasoconstriction, may allow for treatment of migraine in patients with coronary artery disease. In this randomized, double-blind, placebo-controlled, crossover study, patients with documented stable coronary artery disease were assigned to 1 of 2 treatment sequences: telcagepant then placebo, or placebo then telcagepant. In each treatment period, patients received 2 doses of telcagepant 300-mg or placebo 2 hours apart. They remained in the research center for 24 hours after receiving the first dose of each period, during which time continuous 12-lead ambulatory electrocardiographic (Holter) monitoring was performed. Twenty-eight patients were enrolled; all patients completed the study and were included in all analyses. Telcagepant was generally well tolerated. No laboratory or serious adverse experiences were reported, and no patient discontinued due to an adverse experience. There were no consistent treatment-related changes in laboratory, vital signs or electrocardiogram safety parameters. Three patients (2 after receiving placebo and 1 after receiving telcagepant) experienced ST segment depression during the study; none of these patients reported chest pain. Two doses of 300-mg telcagepant, administered 2 hours apart, did not appear to exacerbate spontaneous ischemia and were generally well tolerated in a small cohort of patients with stable coronary artery disease. Results of this study support further evaluation of telcagepant in patients with stable coronary artery disease.
    Headache The Journal of Head and Face Pain 06/2011; 51(6):954-60. DOI:10.1111/j.1526-4610.2011.01901.x · 3.19 Impact Factor
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    ABSTRACT: Females are more susceptible to drug-induced torsade de pointes (TdP), which is associated with excessive prolongation of the heart rate-corrected QT interval (QTc). Sotalol prolongs the cardiac action potential that can be observed as QT prolongation and can induce TdP. The aim of this study was to assess gender differences in sotalol-induced QTc prolongation. A total of 15 healthy volunteers, 9 female and 6 male (age: 32 ± 8 years) received 75 mg intravenous sotalol over 2.5 hours at a constant infusion rate. A 12-lead electrocardiograph (ECG) was recorded at baseline, 0.5, 1, 2, 3, 4, and 5 hours following the start of the infusion, and blood samples were collected simultaneously. QTc was calculated by the Fridericia and Framingham formulas. The 2 formulas resulted in virtually identical QTc intervals. The data analysis included repeated measures of analysis of variance (ANOVA), univariate analysis, and linear regression analysis. The longest average QTc intervals were observed at 2 hours of sotalol infusion in both genders. Compared to baseline, the increase was very significant in females (411 ± 13 vs 438 ± 13 ms, P < .001), while it was less significant in males (395 ± 23 vs 413 ± 27 ms, P < .05). The magnitude of individual changes from baseline were greater in females than in males (34 ± 8 vs 21 ± 12 ms, P < .05). In each gender, QTc and serum sotalol concentration strongly correlated (r = .93, P < .001). An upward shift of the regression line in females indicates a longer QTc at any concentration level. Males had greater body weight and body surface area than females (P < .05) but neither correlated with QTc or predicted QTc prolongation. The univariate analysis indicated that the single predictor for the greater QTc prolongation was female gender. Females had greater QTc prolongation than males following sotalol administration. This enhanced response to drug action may explain the higher incidence of drug-induced TdP seen in females.
    Journal of Cardiovascular Pharmacology and Therapeutics 04/2011; 17(1):86-92. DOI:10.1177/1074248411406505 · 3.07 Impact Factor
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    David Afshartous, Richard A. Preston
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    ABSTRACT: We revisit the problem of determining confidence interval widths for the comparison of means. For the independent two-sample (two-sided) case, Goldstein and Healy (1995) draw attention to the fact that comparisons based on 95% error bars are not very effective in assessing the statistical significance of the difference in means and derive the correct confidence interval for such a comparison. We provide an extension to Goldstein and Healy (1995) to account for the correlation structure and unequal variances. We use the results to develop rules of thumb for evaluating differences, in an exploratory manner, like Moses (1987) and Cumming (2009), from the independent case. We illustrate the method for the simple comparison of two means in a real data set, provide R code that may be easily implemented in practice, and discuss the extension of the method to other applied problems.
    Computational Statistics & Data Analysis 10/2010; 54(10-54):2296-2305. DOI:10.1016/j.csda.2010.04.011 · 1.15 Impact Factor
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    ABSTRACT: Recently, an intravenous formulation of sotalol has been approved by the food and drug administration for substitution for oral therapy in patients who are unable to take oral sotalol. The purpose of this randomized, 2-treatment, 2-period, crossover study was to develop a safe dosing regimen for intravenous sotalol that provides similar blood levels and therefore similar efficacy and safety to orally administered sotalol. Fifteen healthy subjects received 75 mg intravenous sotalol infusion administered over 2.5 hours and 80 mg oral sotalol. Standard pharmacokinetic methods were used to obtain maximum serum concentrations (Cmax) and areas under the concentration-time curves (AUC). Individual pharmacokinetic parameters were used in simulation studies to determine the optimal intravenous administration regimen. Intravenous sotalol administered over 2.5 hours resulted in a significantly greater Cmax than oral administration (830 +/- 391 vs. 601 +/- 289 ng/mL, P < 0.001). With increasing the length of infusions to 3, 4, and 5 hours, simulation studies showed that the Cmax decreased to 128%, 113%, and 102% of the oral Cmax. The length of infusion did not affect AUC. Based on these studies, a safe intravenous regimen for the replacement of 80-mg oral therapy requires 75 mg intravenous sotalol administered as a 5-hour infusion. Because the pharmacokinetics of sotalol are linear and dose proportional, 150 mg intravenous sotalol administered over 5 hours will provide similar Cmax and AUC as 160 mg oral sotalol. The food and drug administration-approved dosing regimen is 75 mg intravenous sotalol to replace 80 mg oral sotalol and 150 mg intravenous sotalol to replace 160 mg oral sotalol, both administered over 5 hours.
    American journal of therapeutics 07/2010; 17(4):365-72. DOI:10.1097/MJT.0b013e3181ea3184 · 1.13 Impact Factor
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    ABSTRACT: In this open-label, randomized, multiple-dose, two-treatment crossover study, 24 postmenopausal women with moderate to severe atrophic vaginitis received 0.3 mg conjugated estrogens daily for 14 days: 7 days orally (0.3 mg tablet) and 7 days vaginally (0.5 g cream). Steady-state plasma concentrations of E2 and estrone were one-third lower after vaginal versus oral administration of conjugated estrogens.
    Fertility and sterility 05/2010; 94(6):2365-8. DOI:10.1016/j.fertnstert.2010.03.076 · 4.30 Impact Factor
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    ABSTRACT: The aim of this study was to evaluate the correlation between QT interval (QT) and serum sotalol concentration following a single low dose of oral and intravenous sotalol. Fifteen healthy volunteers received 75 mg intravenous sotalol over 2.5 h and 80 mg oral sotalol in a random order. Serum sotalol concentrations and 12-lead electrocardiograms were obtained simultaneously at baseline and 7 times following dosings. Rate-corrected QT (QTc) was calculated by the Bazett, Fridericia and Framingham formulas. Linear regression analysis was performed between sotalol concentrations and QT measurements. Significant QT prolongation was seen at very low sotalol doses and serum concentrations. QTc intervals calculated by the Framingham and Fridericia formulas showed the strongest and virtually identical correlations with serum sotalol concentration (r >or= 0.97, p < 0.001) following oral and intravenous administrations. The equation QTc = 0.0342 (sotalol concentration) + 398 closely predicted actual QTc at any sotalol concentration. A strong correlation was observed between serum sotalol concentration and QTc prolongation across the entire concentration range. Low-dose sotalol caused significant QT prolongation. At similar concentrations, intravenous and oral sotalol caused similar QT and QTc effects. Knowing the QT effect can be used to guide further dose increase.
    Cardiology 01/2010; 116(3):219-25. DOI:10.1159/000316050 · 2.04 Impact Factor
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    ABSTRACT: To evaluate posaconazole pharmacokinetics in subjects with different degrees of hepatic impairment compared with matched healthy subjects. A total of 37 subjects were enrolled in this open-label, single-dose, parallel-group study; 19 with hepatic impairment and 18 healthy subjects with matching demographics. Each subject received a single 400-mg oral dose of posaconazole after a high-fat meal. Blood samples for analysis were taken up to 648 h ( approximately 4 weeks) postdose. Compared with maximum plasma concentration (C(max)) values in matched subjects with normal hepatic function, values were higher among subjects with moderate hepatic impairment (517 vs. 724 ng/mL) but lower among subjects with severe hepatic impairment (608 vs. 403 ng/mL). No clear trend toward increased or decreased exposure was observed with increasingly severe hepatic impairment, and extensive overlap occurred between normal and hepatically impaired subjects. Therefore, pharmacokinetic variables C(max) and area under the curve from time 0 to the time of final quantifiable sample (AUC(tf)) values were pooled for subjects with hepatic impairment. Pooled C(max) values were similar to the pooled normal groups (607 vs. 605 ng/mL), whereas there was an overall 36% increase in exposure (AUC(tf)) for the pooled hepatic impairment group compared with the pooled normal group. Posaconazole was well-tolerated, with six (33%) healthy subjects and six (32%) hepatically impaired subjects reporting adverse events. The data from this small single-dose study suggest posaconazole is safe. Furthermore, although limited by the small number of subjects enrolled, the authors feel that dose adjustments are probably not necessary in patients with hepatic impairment; however, physicians should continue to monitor posaconazole use in patients with hepatic impairment.
    Current Medical Research and Opinion 11/2009; 26(1):1-7. DOI:10.1185/03007990903364657 · 2.37 Impact Factor
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    ABSTRACT: The combination of an aldosterone receptor antagonist added to an angiotensin-converting enzyme inhibitor has been demonstrated to reduce cardiovascular and renal end points in hypertensive humans but can produce hyperkalemia in the common clinical setting of impaired renal function. We investigated the effects of dual therapy on acute and chronic potassium handling in hypertensive humans with renal impairment by conducting a randomized crossover clinical trial of 4 weeks of 40 mg lisinopril/25 mg spironolactone versus placebo in 18 participants with a glomerular filtration rate of 25 to 65 mL/min. Study end points, following an established protocol, were hourly determinations of dynamic renal potassium excretion (mmol/h) and serum potassium (mmol/L) after 35 mmol oral potassium challenge in addition to ambulatory potassium concentration. After 4 weeks, ambulatory potassium concentration was 4.87 mmol/L with lisinopril/spironolactone versus 4.37 with placebo (P<0.001). Lisinopril/spironolactone produced only a modest 0.44 mmol/h reduction in stimulated potassium excretion (P=0.03) but a substantial 0.67 mmol/L increase in serum potassium (P<0.001) in response to 35 mmol potassium; these findings are consistent with impaired extrarenal/transcellular potassium disposition. We found the increase in serum potassium after an oral potassium challenge to be a strong predictor of the increase in ambulatory potassium with lisinopril/spironolactone. Our study suggests that dual renin-angiotensin-aldosterone blockade may impair extrarenal/transcellular potassium disposition in addition to reducing potassium excretion in humans with renal impairment, and that acute changes in dynamic potassium handling are predictive of chronic changes in ambulatory potassium concentration with dual renin-angiotensin-aldosterone blockade.
    Hypertension 04/2009; 53(5):754-60. DOI:10.1161/HYPERTENSIONAHA.108.125252 · 7.63 Impact Factor

Publication Stats

2k Citations
431.25 Total Impact Points

Institutions

  • 2012–2014
    • Jackson Memorial Hospital
      Miami, Florida, United States
    • Case Western Reserve University
      • Division of Nephrology and Hypertension
      Cleveland, OH, United States
  • 1992–2014
    • University of Miami
      • • Department of Medicine
      • • Miami Veterans Affairs Medical Center
      • • Miller School of Medicine
      كورال غيبلز، فلوريدا, Florida, United States
  • 2004–2011
    • Rush University Medical Center
      • • Division of Pharmacology
      • • Department of Preventive Medicine
      Chicago, IL, United States
    • Florida Clinical Research Center
      Florida, United States
  • 2005
    • University of Connecticut
      Storrs, Connecticut, United States
  • 2001–2005
    • University of Miami Miller School of Medicine
      • • Division of Hospital Medicine
      • • Division of Clinical Pharmacology
      Miami, Florida, United States
  • 2001–2002
    • Clinical pharmacology of Miami
      Miami, Florida, United States
  • 1996
    • James A. Haley Veterans Hospital
      Tampa, Florida, United States
  • 1994
    • U.S. Department of Veterans Affairs
      Washington, Washington, D.C., United States