Effect of Dupilumab on Type 2 Biomarkers in Chronic Rhinosinusitis With Nasal Polyps: SINUS-52 Study Results

OBJECTIVES

Chronic rhinosinusitis with nasal polyps (CRSwNP), asthma, and non-steroidal anti-inflammatory drug-exacerbated respiratory disease (NSAID-ERD) are frequent coexisting conditions and share type 2 inflammatory pathophysiology, with interleukin (IL)-4 and IL-13 as key cytokines. Dupilumab is a monoclonal antibody that blocks the shared receptor for IL-4 and IL-13. The objective of this analysis was to evaluate dupilumab's effect on type 2 inflammation biomarkers in patients with CRSwNP with/without coexisting asthma or NSAID-ERD from the SINUS-52 (NCT02898454) study.

METHODS

Patients received treatment with dupilumab or placebo for 52 weeks. Blood and urinary biomarkers were evaluated through 52 weeks, and nasal secretions and mucosa brushings through 24 weeks.

RESULTS

Of 447 patients, 60% had coexisting asthma and 27% had coexisting NSAID-ERD. At baseline, blood eotaxin-3, eosinophils, and periostin, nasal secretion eotaxin-3, and urinary leukotriene E4 were significantly higher in patients with coexisting NSAID-ERD than without. Dupilumab reduced eotaxin-3, thymus and activation-regulated chemokine, periostin, and total immunoglobulin E in blood, eotaxin-3, periostin, IL-5, and eosinophil cationic protein in nasal secretions, and leukotriene E4 in urine. Reductions were generally similar or greater in the subgroups with asthma and NSAID-ERD than without. Dupilumab also reduced MUC5AC and mast cell counts in nasal mucosa brushings.

CONCLUSION

Dupilumab reduced local and systemic type 2 inflammatory biomarkers in patients with CRSwNP, including mast cells in nasal mucosa and cysteinyl leukotrienes in urine. These findings provide insight into the processes driving CRSwNP and the mechanisms of dupilumab's therapeutic effects.

CLINICAL TRIAL REGISTRY NAME

SINUS-52 https://www.clinicaltrials.gov/ct2/show/NCT02898454.

CLINICALTRIALS.GOV IDENTIFIER

NCT02898454.

Dupilumab suppresses type 2 inflammatory biomarkers across multiple atopic, allergic diseases

BACKGROUND

Type 2 inflammation is common in numerous atopic/allergic diseases and can be identified by elevated biomarker levels. Dupilumab, a fully human monoclonal antibody, blocks the shared receptor component for interleukin-4 and interleukin-13, key and central drivers of type 2 inflammation.

OBJECTIVE

Assessment of dupilumab effect on type 2 inflammatory biomarkers in atopic dermatitis (AD), asthma, chronic rhinosinusitis with nasal polyps (CRSwNP) and eosinophilic esophagitis (EoE).

METHODS

Data were extracted from three randomized placebo-controlled trials of dupilumab in AD (NCT02277743, N = 671; NCT02277769, N = 708; NCT02260986, N = 740); and one each in asthma (NCT02414854, N = 1902); CRSwNP (NCT02898454, N = 448); and EoE (NCT02379052, N = 47). Biomarkers assessed were serum thymus and activation-regulated chemokine (TARC), plasma eotaxin-3, serum total immunoglobulin E (IgE), serum periostin and blood eosinophil count.

RESULTS

Dupilumab versus placebo significantly suppressed most type 2 inflammatory biomarker levels across all studies/indications where data were assessed. Reductions in serum TARC, plasma eotaxin-3 and serum periostin occurred rapidly, whereas reductions in serum total IgE were more gradual. Across diseases, at the end of treatment, median percentage change from baseline in TARC levels ranged from -24.8% to -88.6% (placebo +2.6% to -53.6%); -38.2% to -51.5% (placebo +8.3% to -0.16%) in eotaxin-3; -24.8% to -76.7% (placebo +8.3% to -4.4%) in total IgE; and -13.6% to -41.1% (placebo +10.1% to -6.94%) in periostin levels. Blood eosinophil responses to dupilumab varied by disease, with minimal changes in AD in the SOLO studies (median percentage change from baseline to end of treatment: 0% [95% CI: -15.8, 0]); transient increases followed by decreases to below-baseline levels in asthma (-14.6% [-20.0, -7.7]) and CRSwNP (-29.4% [-40.0, -16.3]); and significant decreases in EoE (-50.0% [-50.0, -33.3]).

CONCLUSION AND CLINICAL RELEVANCE

Dupilumab reduced levels of type 2 biomarkers across clinical studies in patients with AD, asthma, CRSwNP and EoE.

Pharmacokinetics, Pharmacodynamics, Safety, and Tolerability of Dupilumab in Healthy Adult Subjects

Dupilumab is a fully human monoclonal antibody directed against the interleukin (IL)‐4 receptor α subunit (IL‐4Rα) of IL‐4 heterodimeric type I and type II receptors that mediate IL‐4/IL‐13 signaling through this pathway. Blockade of these receptors broadly suppresses type 2 inflammation associated with atopic/allergic diseases, including atopic dermatitis and asthma. Six phase 1 studies investigated the pharmacokinetics, pharmacodynamics, safety, and tolerability of dupilumab in healthy subjects. Two randomized, double‐blind, placebo‐controlled, sequential studies assessed safety and tolerability of single escalating dupilumab doses administered intravenously or subcutaneously (one included various racial groups, and one included exclusively Japanese subjects); 3 randomized, parallel‐group, single‐dose studies compared the pharmacokinetic profiles of different dupilumab products and formulations after single subcutaneous doses; and one study assessed dupilumab administered as fast versus slow subcutaneous injections. Dupilumab concentrations in serum were measured in all studies, and total immunoglobulin E (IgE) and thymus‐ and activation‐regulated chemokine (TARC) concentrations were measured in 2 studies as pharmacodynamic markers. Across the phase 1 studies, dupilumab exhibited target‐mediated pharmacokinetics consisting of parallel linear and nonlinear elimination, with the target‐mediated phase highly dominated by nonlinearity at lower drug concentrations. Systemic exposure and tolerability of dupilumab were consistent irrespective of differences in product, formulation, or racial background. Dupilumab reduced circulating concentrations of total IgE and TARC, indicating blockade of IL‐4Rα–mediated signaling. Dupilumab had a favorable safety profile across the wide range of doses administered. Together, these findings support the continued development and use of dupilumab in treatment of type 2 diseases.

Efficacy of Dupilumab in a Phase 2 Randomized Trial of Adults With Active Eosinophilic Esophagitis

BACKGROUND & AIMS

Eosinophilic esophagitis (EoE) is an allergen-mediated inflammatory disease with no approved treatment in the United States. Dupilumab, a VelocImmune-derived human monoclonal antibody against the interleukin (IL) 4 receptor, inhibits IL4 and IL13 signaling. Dupilumab is effective in the treatment of allergic, atopic, and type 2 diseases, so we assessed its efficacy and safety in patients with EoE.

METHODS

We performed a phase 2 study of adults with active EoE (2 episodes of dysphagia/week with peak esophageal eosinophil density of 15 or more eosinophils per high-power field), from May 12, 2015, through November 9, 2016, at 14 sites. Participants were randomly assigned to groups that received weekly subcutaneous injections of dupilumab (300 mg, n = 23) or placebo (n = 24) for 12 weeks. The primary endpoint was change from baseline to week 10 in Straumann Dysphagia Instrument (SDI) patient-reported outcome (PRO) score. We also assessed histologic features of EoE (peak esophageal intraepithelial eosinophil count and EoE histologic scores), endoscopically visualized features (endoscopic reference score), esophageal distensibility, and safety.

RESULTS

The mean SDI PRO score was 6.4 when the study began. In the dupilumab group, SDI PRO scores were reduced by a mean value of 3.0 at week 10 compared with a mean reduction of 1.3 in the placebo group (P = .0304). At week 12, dupilumab reduced the peak esophageal intraepithelial eosinophil count by a mean 86.8 eosinophils per high-power field (reduction of 107.1%; P < .0001 vs placebo), the EoE-histologic scoring system (HSS) severity score by 68.3% (P < .0001 vs placebo), and the endoscopic reference score by 1.6 (P = .0006 vs placebo). Dupilumab increased esophageal distensibility by 18% vs placebo (P < .0001). Higher proportions of patients in the dupilumab group developed injection-site erythema (35% vs 8% in the placebo group) and nasopharyngitis (17% vs 4% in the placebo group).

CONCLUSIONS

In a phase 2 trial of patients with active EoE, dupilumab reduced dysphagia, histologic features of disease (including eosinophilic infiltration and a marker of type 2 inflammation), and abnormal endoscopic features compared with placebo. Dupilumab increased esophageal distensibility and was generally well tolerated. ClinicalTrials.gov, Number: NCT02379052.

Dupilumab reduces local type 2 pro-inflammatory biomarkers in chronic rhinosinusitis with nasal polyposis

Background

Chronic rhinosinusitis with nasal polyposis (CRSwNP) is a type 2‐mediated inflammatory disease associated with significant clinical, social, and economic burdens and high unmet therapeutic need. Dupilumab, a fully human monoclonal antibody targeting the interleukin‐4 receptor α (IL‐4Rα) subunit, demonstrated efficacy and acceptable safety in CRSwNP and other type 2 diseases (eg, atopic dermatitis and asthma). We now report the local effects of dupilumab on type 2 inflammatory biomarkers in nasal secretions and nasal polyp tissues of patients with CRSwNP in a randomized, placebo‐controlled, phase 2 trial (NCT01920893).

Methods

Cytokines, chemokines, and total immunoglobulin E (IgE) levels were measured using immunoassay techniques in nasal secretions and nasal polyp tissue homogenates of CRSwNP patients receiving dupilumab 300 mg or placebo weekly for 16 weeks.

Results

With dupilumab, type 2 biomarker concentrations decreased in nasal secretions (least squares mean area under the curve from 0 to 16 weeks for the change from baseline) vs placebo for eotaxin‐3 (−30.06 vs −0.86 pg/mL; P = 0.0008) and total IgE (−7.90 vs −1.86 IU/mL; P = 0.022). Dupilumab treatment also decreased type 2 biomarker levels in nasal polyp tissues at Week 16 vs baseline for eosinophilic cationic protein (P = 0.008), eotaxin‐2 (P = 0.008), eotaxin‐3 (P = 0.031), pulmonary and activation‐regulated chemokine (P = 0.016), IgE (P = 0.023), and IL‐13 (P = 0.031).

Conclusions

Dupilumab treatment reduced multiple biomarkers of type 2 inflammation in nasal secretions and polyp tissues of patients with CRSwNP, demonstrating that antagonism of IL‐4Rα signaling suppresses IL‐4‐/IL‐13‐dependent processes, such as mucosal IgE formation, as well as the expression of chemokines attracting inflammatory cells to the nasal mucosa.

Efficacy and Safety of Dupilumab in Glucocorticoid-Dependent Severe Asthma

BACKGROUND

Dupilumab is a fully human anti-interleukin-4 receptor α monoclonal antibody that blocks both interleukin-4 and interleukin-13 signaling. Its effectiveness in reducing oral glucocorticoid use in patients with severe asthma while maintaining asthma control is unknown.

METHODS

We randomly assigned 210 patients with oral glucocorticoid-treated asthma to receive add-on dupilumab (at a dose of 300 mg) or placebo every 2 weeks for 24 weeks. After a glucocorticoid dose-adjustment period before randomization, glucocorticoid doses were adjusted in a downward trend from week 4 to week 20 and then maintained at a stable dose for 4 weeks. The primary end point was the percentage reduction in the glucocorticoid dose at week 24. Key secondary end points were the proportion of patients at week 24 with a reduction of at least 50% in the glucocorticoid dose and the proportion of patients with a reduction to a glucocorticoid dose of less than 5 mg per day. Severe exacerbation rates and the forced expiratory volume in 1 second (FEV₁) before bronchodilator use were also assessed.

RESULTS

The percentage change in the glucocorticoid dose was -70.1% in the dupilumab group, as compared with -41.9% in the placebo group (P<0.001); 80% versus 50% of the patients had a dose reduction of at least 50%, 69% versus 33% had a dose reduction to less than 5 mg per day, and 48% versus 25% completely discontinued oral glucocorticoid use. Despite reductions in the glucocorticoid dose, in the overall population, dupilumab treatment resulted in a severe exacerbation rate that was 59% (95% confidence interval [CI], 37 to 74) lower than that in the placebo group and resulted in an FEV₁ that was 0.22 liters (95% CI, 0.09 to 0.34) higher. Injection-site reactions were more common with dupilumab than with placebo (9% vs. 4%). Transient blood eosinophilia was observed in more patients in the dupilumab group than in the placebo group (14% vs. 1%).

CONCLUSIONS

In patients with glucocorticoid-dependent severe asthma, dupilumab treatment reduced oral glucocorticoid use while decreasing the rate of severe exacerbations and increasing the FEV₁. Transient eosinophilia was observed in approximately 1 in 7 dupilumab-treated patients. (Funded by Sanofi and Regeneron Pharmaceuticals; LIBERTY ASTHMA VENTURE ClinicalTrials.gov number, NCT02528214 .).

Dupilumab Efficacy and Safety in Moderate-to-Severe Uncontrolled Asthma

BACKGROUND

Dupilumab is a fully human anti-interleukin-4 receptor α monoclonal antibody that blocks both interleukin-4 and interleukin-13 signaling. We assessed its efficacy and safety in patients with uncontrolled asthma.

METHODS

We randomly assigned 1902 patients 12 years of age or older with uncontrolled asthma in a 2:2:1:1 ratio to receive add-on subcutaneous dupilumab at a dose of 200 or 300 mg every 2 weeks or matched-volume placebos for 52 weeks. The primary end points were the annualized rate of severe asthma exacerbations and the absolute change from baseline to week 12 in the forced expiratory volume in 1 second (FEV₁) before bronchodilator use in the overall trial population. Secondary end points included the exacerbation rate and FEV₁ in patients with a blood eosinophil count of 300 or more per cubic millimeter. Asthma control and dupilumab safety were also assessed.

RESULTS

The annualized rate of severe asthma exacerbations was 0.46 (95% confidence interval [CI], 0.39 to 0.53) among patients assigned to 200 mg of dupilumab every 2 weeks and 0.87 (95% CI, 0.72 to 1.05) among those assigned to a matched placebo, for a 47.7% lower rate with dupilumab than with placebo (P<0.001); similar results were seen with the dupilumab dose of 300 mg every 2 weeks. At week 12, the FEV₁ had increased by 0.32 liters in patients assigned to the lower dose of dupilumab (difference vs. matched placebo, 0.14 liters; P<0.001); similar results were seen with the higher dose. Among patients with a blood eosinophil count of 300 or more per cubic millimeter, the annualized rate of severe asthma exacerbations was 0.37 (95% CI, 0.29 to 0.48) among those receiving lower-dose dupilumab and 1.08 (95% CI, 0.85 to 1.38) among those receiving a matched placebo (65.8% lower rate with dupilumab than with placebo; 95% CI, 52.0 to 75.6); similar results were observed with the higher dose. Blood eosinophilia occurred after the start of the intervention in 52 patients (4.1%) who received dupilumab as compared with 4 patients (0.6%) who received placebo.

CONCLUSIONS

In this trial, patients who received dupilumab had significantly lower rates of severe asthma exacerbation than those who received placebo, as well as better lung function and asthma control. Greater benefits were seen in patients with higher baseline levels of eosinophils. Hypereosinophilia was observed in some patients. (Funded by Sanofi and Regeneron Pharmaceuticals; LIBERTY ASTHMA QUEST ClinicalTrials.gov number, NCT02414854 .).

Delivery of high-quality biomarker assays

Biomarker measurements now support key decisions throughout the drug development process, from lead optimization to regulatory approvals. They are essential for documenting exposure-response relationships, specificity and potency toward the molecular target, untoward effects, and therapeutic applications. In a broader sense, biomarkers constitute the basis of clinical pathology and laboratory medicine. The utility of biomarkers is limited by their specificity and sensitivity toward the drug or disease process and by their overall variability. Understanding and controlling sources of variability is not only imperative for delivering high-quality assay results, but ultimately for controlling the size and expense of research studies. Variability in biomarker measurements is affected by: biological and environmental factors (e.g., gender, age, posture, diet and biorhythms), sample collection factors (e.g., preservatives, transport and storage conditions, and collection technique), and analytical factors (e.g., purity of reference material, pipetting precision, and antibody specificity). The quality standards for biomarker assays used in support of nonclinical safety studies fall under GLP (FDA) regulations, whereas, those assays used to support human diagnostics and healthcare are established by CLIA (CMS) regulations and accrediting organizations such as the College of American Pathologists. While most research applications of biomarkers are not regulated, biomarker laboratories in all settings are adopting similar laboratory practices in order to deliver high-quality data. Because of the escalation in demand for biomarker measurements, the highly-parallel (multi-plexed) assay platforms that have fueled the rise of genomics will likely evolve into the analytical engines that drive the biomarker laboratories of tomorrow.

Steady state serum concentrations of pravastatin and digoxin when given in combination

Pravastatin is an HMG CoA reductase inhibitor used in the treatment of hypercholesterolaemia. The steady state pharmacokinetics of pravastatin (20 mg) and digoxin (0.2 mg) were evaluated in 18 healthy male subjects following the administration of each drug alone or in combination for 9 days. Serum and urine were collected for up to 48 h after the ninth dose in this open, randomized 3-way crossover study. Digoxin concentrations were measured by radioimmunoassay, and pravastatin and its metabolites. SQ 31,906 and SQ 31,945 were measured by GC-MS. Digoxin and pravastatin pharmacokinetics were unchanged following combined administration. Combination therapy with pravastatin and digoxin is unlikely to expose patients to additional risk compared with pravastatin alone.

Pharmacokinetic interaction between propranolol and the HMG-CoA reductase inhibitors pravastatin and lovastatin

1. Single oral 20 mg doses of the HMG-CoA reductase inhibitors pravastatin and lovastatin, with and without concomitant propranolol (40 mg twice daily), were administered to 16 healthy male subjects participating in a randomized, four-way crossover study. 2. Serum concentrations of total and active inhibitors were measured by bioassay and concentrations of pravastatin, two pravastatin metabolites and lovastatin acid were measured by gas chromatography/mass spectrometry. 3. Coadministration of propranolol with pravastatin reduced the mean area under the serum concentration-time curve (AUC) of total inhibitors by 23%, of active inhibitors by 20% and of pravastatin by 16%. 4. Coadministration of propranolol with lovastatin also resulted in decreases in the mean serum AUC of total inhibitors by 18%, of active inhibitors by 12% and of lovastatin acid by 13%. 5. These decreases in systemic drug concentrations may reflect enhanced drug first-pass hepatic clearance in the presence of propranolol. 6. The clinical significance of these changes is likely to be small.

Dihydropyrimidine calcium channel blockers. 3. 3-Carbamoyl-4-aryl-1,2,3,4-tetrahydro-6-methyl-5-pyrimidinecarboxylic acid esters as orally effective antihypertensive agents

In order to explain the potent antihypertensive activity of the modestly active (IC50 = 3.2 microM) dihydropyrimidine calcium channel blocker 5, we carried out drug metabolism studies in the rat and found 5 is metabolized to compounds 6-10. Two of the metabolites, 6 (IC50 = 16 nM) and 7 (IC50 = 12 nM), were found to be responsible for the antihypertensive activity of compound 5. Potential metabolism of 6 into 7 in vivo precluded our interest in pursuing compounds related to 6. Structure-activity studies aimed at identifying additional aryl-substituted analogues of 7 led to 17g,j,p with comparable potential in vivo, though these compounds were less potent than 7 in vitro. To investigate the effects of absolute stereochemistry on potency, we resolved 7 via diastereomeric ureas 19a,b, prepared from 18 by treatment with (R)-alpha-methylbenzylamine. Our results demonstrate that the active R-(-)-enantiomer 20a of 7 is both more potent and longer acting than nifedipine (1) as an antihypertensive agent in the SHR. The in vivo potency and duration of 20a is comparable to the long-acting dihydropyridine amlodipine. The superior oral antihypertensive activity of 20a compared to that of previously described carbamates 2 (R2 = COOEt) could be explained by its improved oral bioavailability, possibly resulting from increased stability of the urea functionality.

Comparative pharmacokinetics and pharmacodynamics of pravastatin and lovastatin

The oral bioavailability of two HMG-CoA reductase inhibitors, pravastatin and lovastatin, was investigated in this randomized, two-way crossover study. Twenty healthy men were randomly assigned to treatment with a 40-mg dose of pravastatin or lovastatin once daily for 1 week; steady state kinetics were assessed after the last dose. After 1 week of washout, each subject received the alternate treatment. Serum specimens were assayed by gas chromatography/mass spectrometry (GC/MS) for intact pravastatin or lovastatin acid and by bioassay for active inhibitor concentration and, after hydrolysis of lactones, for total inhibitor concentration. The systemic bioavailabilities of total (active plus potentially active) inhibitors for the two drugs were different, with the mean AUC value for lovastatin being 50% higher than that of pravastatin (mean +/- SEM AUC0-24 values of 285 +/- 25 and 189 +/- 13 ng-equiv x hr/mL, respectively, P less than .0001). Pravastatin, which is administered as the monosodium salt, is present in the systemic circulation as the open acid; lovastatin, which is administered as the lactone, is present as both open-acid active metabolites (62%) and closed-ring lactone metabolites (38%), which are potentially active. Based on mean AUC values, pravastatin accounted for 75% of the active inhibitors from a pravastatin dose. Lovastatin acid accounted for just 25% of the active inhibitors from a lovastatin dose, with the remainder due to other active metabolites. Significant decreases from baseline in total and low-density lipoprotein (LDL) cholesterol were observed during the first treatment leg for both pravastatin and lovastatin.(ABSTRACT TRUNCATED AT 250 WORDS)

Dihydropyrimidine calcium channel blockers. 2. 3-substituted-4-aryl-1,4-dihydro-6-methyl-5-pyrimidinecarboxylic acid esters as potent mimics of dihydropyridines

To enhance the intrinsic potency of dihydropyrimidine calcium channel blockers, we have modified the structure of previously described 2-heteroalkyl-1,4-dihydropyrimidines 2 to 3-substituted 1,4-dihydropyrimidines 3. Structure-activity studies using potassium-depolarized rabbit aorta show that ortho, meta-disubstituted aryl derivatives are more potent than either ortho- or meta-monosubstituted compounds. While vasorelaxant activity was critically dependent on the size of the C5 ester group, isopropyl ester being the best, a variety of substituents (carbamate, acyl, sulfonyl, alkyl) were tolerated at N3. Our results show dihydropyrimidines 3 are significantly more potent than corresponding 2-heteroalkyl-1,4-dihydropyrimidines 2 and only slightly less potent than similarly substituted 2-heteroalkyl-1,4-dihydropyridines 4 and 5. Whereas dihydropyridine enantiomers usually show 10-15-fold difference in activity, the enantiomers of dihydropyrimidine 3j show more than a 1000-fold difference in activity. These results strengthen the requirement of an enamino ester for binding to the dihydropyridine receptor and indicate a nonspecific role for the N3-substituent.

Effect of repeated doses of L-5-hydroxytryptophan and carbidopa on prolactin and aldosterone secretion in man

To evaluate changes in serum prolactin and plasma and urine aldosterone after a serotonergic challenge, 8 healthy men (19 to 42 yr), taking dexamethasone (0.75 mg qid), received the serotonin precursor L-5-hydroxytryptophan (L5HTP; 100 mg qid) with the peripheral decarboxylase inhibitor carbidopa (C; 50 mq qid) or matching placebos in a randomized, crossover manner. Serum prolactin concentration increased in all subjects after L5HTP/C in comparison to placebo, mean (SD) prolactin (ng/ml) at 8 h after dosing was 19.8 +/- 6.3 after L5HTP/C and 12.0 +/- 3.1 after placebo (p less than 0.05). In contrast, in comparison to values on placebo, L5HTP/C had no apparent effect on mean plasma concentration at all observation times; mean (SD) aldosterone (ng/dl) at 8 h after dosing was 12.0 +/- 5.1 and 12.0 +/- 3.8 after placebo (NS). Mean (SD) urinary aldosterone (micrograms/24 h), Na+(mEq/24 h) and K+(mEq/24 h) excretion were 7.0 +/- 4.4, 49.3 +/- 30.6, 30.1 +/- 11.2, after L5HTP/C and 7.4 +/- 5.8, 59.7 +/- 23.9, 33.3 +/- 7.4 after placebo (NS). Under these study conditions, subacute serotonergic stimulation with oral L5HTP/C resulted in prolactin but not aldosterone release.

Effect of renal failure or biliary stasis on the pharmacokinetics of amiodarone in the rat

The single dose intravenous pharmacokinetics of amiodarone (50 mg/kg) were examined in rats with 72 h of biliary stasis secondary to bile duct ligation compared with paired control animals; and in rats with uranyl nitrate induced acute renal failure compared with paired control animals. Plasma and tissue levels (liver, kidney, heart, and lung) of amiodarone (1) and its N-deethyl metabolite 2 were obtained at 4 and 24 h following drug administration. Pharmacokinetic parameters were derived from plasma samples obtained over a 24-h period. Compared with controls, biliary stasis caused a decrease in the total clearance of 1 (1.74 versus 0.35 L/h/kg) and in the volume of distribution at steady state (21.1 versus 5.0 L/kg); renal failure caused a decrease in total clearance (1.67 versus 0.9 L/h/kg) and an increase in apparent elimination half-life (13.7 versus 10.1 h). Both disease processes produced significantly higher plasma levels of 1 when compared with control animals at 4 and 24 h. However, only the cholestatic animals had consistently higher tissue levels of 1 in the face of elevated plasma levels. In normal rats, no 1 or 2 was detected in the urine after a 50 mg/kg intravenous dose of 1, and less than 0.5% of the total dose of amiodarone (1) was excreted into bile by 12 h.

Steady-state disposition of diflunisal: once- versus twice-daily administration

To evaluate the steady-state bioequivalence of the nonsteroidal antiinflammatory analgesic agent, diflunisal, administered once versus twice daily, 13 healthy volunteers received diflunisal as follows: 1000 mg at 8:00 AM and 500 mg at 8:00 AM and 8:00 PM, each for 14 days in a randomized crossover study. The mean (+/- SD) steady-state peak plasma concentrations were significantly greater after once-daily dosing (186 +/- 25 micrograms/ml vs 150 +/- 37 micrograms/ml; p less than 0.01). The time to peak concentration was also longer after the single-dose regimen (2.5 +/- 0.8 vs 1.9 +/- 0.9 hr; p less than 0.05). The regimens were similar with respect to the mean 24-hour area under the plasma concentration-time curve at steady state (2839 +/- 612 vs 2782 +/- 778 micrograms.hr.ml-1), steady-state plasma concentrations (118 +/- 25 vs 116 +/- 32 micrograms/ml), trough plasma concentration (85 +/- 27 vs 92 +/- 28 micrograms/ml) as well as 24-hour urinary excretion (776 +/- 79 vs 771 +/- 89 mg) of diflunisal. Based on urinary recoveries, the bioequivalence ratio (once vs twice daily) was 1.01 +/- 0.08. These results indicate that diflunisal administered once daily might offer comparable therapeutic effects but be more convenient than a twice-daily regimen.

Effect of phenobarbitone on the pharmacokinetics and tissue levels of amiodarone in the rat

Phenobarbitone pretreatment has been shown to increase amiodarone total clearance and decrease amiodarone elimination half-life after a single intravenous amiodarone dose in the rat. Coadministration of phenobarbitone with amiodarone for 7 days resulted in decreased tissue amiodarone levels compared to controls. These results may have implications for patients undergoing therapy with amiodarone and concomitant potent enzyme inducing drugs.

Radioenzymatic assay of angiotensin-converting enzyme inhibitors in plasma and urine

A rapid, sensitive assay for angiotensin-converting enzyme (ACE) inhibitors is described. Biological samples were diluted with methanol to precipitate endogenous ACE and centrifuged. Supernatants were further diluted with 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid buffer, pH 8. Diluted samples were incubated at 37 degrees C with the substrate [3H]hippurylglycylglycine and rabbit lung ACE for 45 min. Acid (1.0 N HCl) was then added, and the product, [3H]hippuric acid, was extracted into a water-immiscible scintillation cocktail. Drug standards were prepared in the biological matrix to correct for drug recovery. A computer program was used to convert radioactivity (dpm) to units of enzyme activity and then correlate enzyme activity with drug concentration. The ester prodrugs fosenopril and enalapril could be assayed down to 4 ng/ml in plasma after ester hydrolysis with NaOH. Drug disposition studies in rats, dogs, and monkeys have demonstrated that the method can be readily adapted to any ACE inhibitor and is suitable for determining drug bioavailability and pharmacokinetics.

Medical use of dimethyl sulfoxide (DMSO)

DMSO is a clear odorless liquid, inexpensively produced as a by-product of the paper industry. It is widely available in the USA as a solvent but its medical use is currently restricted by the FDA to the palliative treatment of interstitial cystitis and to certain experimental applications. Cutaneous manifestations of scleroderma appear to resolve (albeit equivocally) following topical applications of high concentrations of DMSO. A limited number of small clinical trials indicate that intravenous DMSO may be of benefit in the treatment of amyloidosis, possibly by mobilizing amyloid deposits out of tissues into urine. Dermal application of DMSO seems to provide rapid, temporary, relief of pain in patients with arthritis and connective tissue injuries. However, claims for antiinflammatory effects or acceleration of healing are currently unwarranted. There is no evidence that DMSO can alter progression of degenerative joint disease, and, for this reason, DMSO may be considered for palliative treatment only and not to the exclusion of standard antiinflammatory agents. The safety of DMSO in combination with other drugs has not been established; neurotoxic interactions with sulindac have been reported. In experimental animals, intravenous DMSO is as effective as mannitol and dexamethasone in reversing cerebral edema and intracranial hypertension. An initial clinical trial in 11 patients tends to support this latter application. DMSO enhances diffusion of other chemicals through the skin, and, for this reason, mixtures of idoxuridine and DMSO are used for topical treatment of herpes zoster in the UK. Adverse reactions to DMSO are common, but are usually minor and related to the concentration of DMSO in the medication solution. Consequently, the most frequent side effects, such as skin rash and pruritus after dermal application, intravascular hemolysis after intravenous infusion and gastrointestinal discomfort after oral administration, can be avoided in large part by employing more dilute solutions. Most clinical trials of DMSO have not incorporated the components of experimental design necessary for objective, statistical evaluation of efficacy. Randomized comparisons between DMSO, placebo and known active treatments were rarely completed. Final approval of topical DMSO for treatment of rheumatic diseases in particular will require a multi-center, randomized comparison between high and low concentrations of DMSO and an orally-active, nonsteroidal antiinflammatory agent.(ABSTRACT TRUNCATED AT 400 WORDS)

Sulindac and ibuprofen inhibit furosemide-stimulated renin release but not natriuresis in men on a normal sodium diet

We compared the effect of two commonly prescribed nonsteroidal anti-inflammatory drugs, ibuprofen and sulindac, and placebo on intravenous furosemide-induced natriuresis and renin stimulation in 11 healthy male volunteers, consuming a 100 mEq sodium, 80 mEq potassium diet. Chronic (6-day) therapy with each agent was followed by a 1-week washout period. There were no significant treatment-related differences in either urine volume or sodium excretion for any of the designated collection periods or for the cumulative value for the 4 h after furosemide administration. Similarly, differences among groups were not observed for creatinine clearance, urinary potassium and urinary chloride excretion. Mean basal plasma renin activity levels prior to furosemide administration on day 6 were significantly lower in the presence of ibuprofen (1.5 +/- 2.0 ng/ml/h;p less than 0.01) and sulindac (2,3 +/- 0.9 ng/ml/h; p less than 0.05), compared with placebo (3.3 +/- 1.1 ng/ml/h); the difference between the two NSAIDs was also significant (p less than 0.05). Mean plasma renin activity levels in the 4 h after furosemide increased significantly at all time points in comparison to basal values, but were significantly less for ibuprofen and sulindac groups in the first hour. Our data suggest that the natriuresis following intravenous furosemide in men consuming a normal sodium intake is not prostaglandin-dependent. Furthermore, the observation that sulindac suppressed basal and stimulated plasma renin activity levels, albeit to a lesser extent than ibuprofen, questions the claim that sulindac "spares' the kidney and compels further evaluation of this issue.

Effect of captopril and hydrochlorothiazide on the response to pressor agents in hypertensives

The effect on arterial pressure of incremental doses of norepinephrine (2 to 10 micrograms/min) and angiotensin II (50 to 800 ng/min) administered over 10 min periods was studied in sodium-replete hypertensive patients after crossover oral treatments with placebo, captopril 50 mg in a single dose, captopril 50 mg three times daily for one week and hydrochlorothiazide 50 mg daily for a week. Neither captopril nor hydrochlorothiazide affected the dose response to infusions of angiotensin II. In comparison to placebo responses, however, both single and multiple-dose captopril therapy, and hydrochlorothiazide attenuated the pressor responses to infusions of norepinephrine. Captopril significantly depressed angiotensin converting enzyme activity from pre-dose levels and angiotensin II infusions significantly elevated plasma aldosterone concentrations. These results confirm findings reported for single dose captopril in normotensive volunteers and indicate that attenuation of the vascular responsiveness to sympathetic stimulation may contribute to the antihypertensive effects of captopril and hydrochlorothiazide therapy.

Influence of food on the bioavailability of enalapril

In a randomized, two-period crossover study in 12 normal volunteers, serum and urine concentrations of the angiotensin-converting enzyme inhibitor enalapril and its active metabolite enalaprilat were determined following administration of a single 40-mg tablet of enalapril maleate administered both in the fasting state and with a standard breakfast. A 7-d interval separated the two treatment periods. Area under the serum concentration-time curves for enalaprilat and urinary recoveries for enalaprilat and total drug did not differ significantly between the fed and fasted conditions. The mean observed maximum serum concentration of enalaprilat was slightly higher for the fasting treatment, but the time to peak concentration was almost identical for the two treatments. Enalapril maleate is unlike the prototype angiotensin-converting enzyme inhibitor captopril in that a standard meal does not appear to influence absorption of this new drug.

Relationship of morphine-induced miosis to plasma concentration in normal subjects

The relationship between morphine plasma concentration and pupil diameter was evaluated 2-10 h following intravenous administration of morphine sulfate (10 mg). Seven healthy male volunteers received 10 mg of morphine intravenously following pretreatment for 4 d with either cimetidine (300 mg po four times a day) or placebo in a single blind, balanced crossover study. Pupil diameters were measured directly from contact prints using calipers and a photographed millimeter scale. Cimetidine pretreatment had no significant effect on pupil size either before or after morphine administration or on morphine pharmacokinetics. The relationship between morphine plasma concentration (2-10 h postdose) and pupil diameter was evaluated from the pooled data from both morphine treatment periods by perpendicular least-square regression. In each individual, a strong relationship existed between morphine plasma concentrations and pupil diameter (r = -0.76 to -0.91; p less than 0.05). Weaker correlations for both pupil diameter (r = -0.65; p less than 0.0001) and the absolute change in pupil diameter from baseline (r = 0.72; p less than 0.0001) for the grouped data probably reflect intersubject variation in morphine sensitivity. Thus, the miotic response to an intravenous dose of morphine varies in proportion to morphine plasma concentration.

Steady-state serum amiodarone concentrations: relationships with antiarrhythmic efficacy and toxicity

The relationship of apparent steady-state serum concentrations of amiodarone and its metabolite, desethylamiodarone, to therapeutic and toxic effects was assessed in 127 patients who had treatment-resistant ventricular or supraventricular arrhythmias or were intolerant to other agents. After at least 2 months (mean, 9.8) of treatment with daily maintenance doses of 200 to 600 mg, arrhythmias were effectively suppressed in 78% of patients. Arrhythmias recurred in 47% of patients with serum amiodarone concentrations of less than 1.0 mg/L, whereas only 14% of patients with higher concentrations had recurrences (p less than 0.005). Side effects, most of them mild, occurred in 57%; only 9 patients required discontinuation of drug therapy. The risk of developing adverse reactions was related to serum amiodarone concentrations (p less than 0.0001). Adverse reactions were common in patients with serum values exceeding 2.5 mg/L, although pulmonary complications did occur at lower concentrations. Monitoring serum amiodarone concentrations may differentiate failure of drug therapy from suboptimal dosing and reduce the incidence of concentration-related side effects.

Indacrinone: natriuretic and uricosuric effects of various ratios of its enantiomers in healthy men

Indacrinone is an investigational loop-acting diuretic. To evaluate the natriuretic and uricosuric effects of varying ratios of its enantiomers, 10 healthy men, on a controlled Na+ (100 mEq) and K+ (80 mEq) diet, participated in a double-blind, randomized, balanced incomplete block, multiple-dose (one week) study of a fixed daily dose (10 mg) of (-) enantiomer combined with increasing doses (40, 90 and 140 mg) of (+) enantiomer versus 50 mg hydrochlorothiazide and placebo. On day 1, mean 24-h urinary Na+ increased (p less than 0.01) comparably (approximately 285 mEq) after each enantiomer combination and hydrochlorothiazide; however, the enantiomer combinations had marked uricosuric and hypouricemic effects that were enhanced with increased (+) enantiomer doses. By day 7, while enantiomer combinations and hydrochlorothiazide demonstrated comparable natriuretic activity, mean serum uric acid levels (mg/dl), in comparison to placebo, were increased (p less than 0.05) with hydrochlorothiazide but progressively decreased with increases in (+) enantiomer. Thus varying the ratio [(+, uricosuric): (-, natriuretic)] of the enantiomers of indacrinone caused natriuresis similar to hydrochlorothiazide, but had an opposite effect on serum uric acid.

Methyldopa does not alter the disposition of digoxin

To investigate whether methyldopa alters digoxin disposition, eight healthy subjects received methyldopa titrated to 250 mg t.i.d. or placebo in a double-blind, cross-over manner for 16 consecutive days, with 0.25 mg intravenous digoxin coadministered on day 5 and 0.25 mg oral digoxin on days 9 to 16. Digoxin concentrations in plasma and urine were measured by RIA. Although assay sensitivity did not allow an adequate assessment of serum AUC(0-infinity) after intravenous administration, mean digoxin AUC(0-24) was 10.2 +/- 3.5 and 10.0 +/- 1.8 ng/ml X hr with placebo and methyldopa, respectively (P greater than 0.05). Mean urinary excretion after digoxin with or without methyldopa treatment was 0.204 +/- 0.34 and 0.197 +/- 0.38 mg, respectively. The mean steady-state serum concentrations of oral digoxin (AUC(0-24)/zeta) with and without methyldopa were 0.65 +/- 0.2 and 0.62 +/- 0.3 ng/ml, respectively. These data revealed no significant differences (P greater than 0.05) for various parameters with power of greater than 0.8 to detect meaningful differences of approximately 30 per cent. Thus, methyldopa did not alter digoxin disposition in healthy subjects, and a pharmacokinetic interaction in patients is unlikely.

Bucindolol, a beta-adrenoceptor blocker with vasodilatory action: its effect in systemic hypertension

Bucindolol is a newly developed, nonselective beta-adrenergic blocking agent with intrinsic sympathomimetic activity and direct vasodilator properties. In 14 patients with mild to moderate essential hypertension, the effects of bucindolol, hydrochlorothiazide and their combination on blood pressure (BP), heart rate (HR) and parameters of the renin-aldosterone system were compared with those after placebo. Bucindolol's antihypertensive effect was evident within the first hour after drug administration, maximal at 2 to 3 hours, and lasted for as long as 12 hours. Compared with placebo values (108 +/- 5 mm Hg), both bucindolol (97 +/- 9 mm Hg) and hydrochlorothiazide (99 +/- 10 mm Hg) alone significantly and comparably reduced the 12-hour averaged standing diastolic BP, with the combination resulting in approximately additive effects (91 +/- 9 mm Hg). Although bucindolol alone did not affect HR, it attenuated the hydrochlorothiazide-induced increase in HR. There was a tendency for bucindolol to decrease plasma renin activity. Except for transient postural hypotension in 2 patients, bucindolol was well tolerated.

Initial evaluation of the non-sulfhydryl-containing converting enzyme inhibitor MK-521 in hypertensive humans

MK-521 is a new orally active, nonsulfhydryl angiotensin-converting enzyme (ACE) inhibitor. Single doses of 2.5, 5.0, 10.0, and 20.0 mg were administered to nine hypertensive patients alternating with placebo. All doses of MK-521 caused profound suppression of ACE activity for more than 24 h and decreased standing diastolic blood pressure for more than 12 h without changes in pulse rate. Although there was no further reduction in blood pressure with doses above 5.0 mg, the duration of action was prolonged for more than 24 h with the higher doses. Serum MK-521 concentrations increased with dosage, and ACE was inhibited maximally at concentrations above 10 ng/ml. In this initial study, MK-521 was well tolerated and proved to be a potent and long-acting antihypertensive agent.

Enalapril, a new nonsulfhydryl angiotensin converting enzyme inhibitor, does not potentiate morphine analgesia

Sprague-Dawley rats received oral doses of enalapril maleate (5 mg/kg), a potent, nonsulfhydryl, angiotensin converting enzyme inhibitor, or saline. Sixty min later, morphine sulfate, 5 mg/kg, or saline was injected subcutaneously. Response to a thermal stimulus was monitored before and up to 5 h ter morphine injection using the rat tail flick test. Serum ACE activity was greater than 90% inhibited by enalapril throughout the experiment. Enalapril did not exhibit analgesic activity nor did it potentiate morphine analgesia.

Hemodynamic and humoral responses to enalapril and nifedipine in the rat

The hemodynamic and humoral effects of enalapril, an angiotensin converting enzyme (ACE) inhibitor, and nifedipine, a calcium-entry blocker, were evaluated in conscious spontaneously hypertensive rats (SHR). Rats received enalapril (5 mg/kg, po) or vehicle, followed in one hour by nifedipine (2.5 mg/kg, ip) or its vehicle. After treatment with enalapril alone, systolic blood pressure (BP) declined over a 3 hour period from 204 +/- 4 (mean +/- SE) to 168 +/- 6 mm Hg and remained suppressed for an additional 4 hours. Heart rate (HR) did not change. Plasma renin activity (PRA) increased approximately 9-fold and serum ACE was maximally inhibited. BP response to nifedipine was more rapid, greater in magnitude (-59 +/- 6 mm Hg) and shorter in duration; heart rate increased and remained elevated for 2.5 hours. PRA only rose two-fold. After the drugs in combination, BP declined as rapidly and to the same degree as after nifedipine and remained reduced for a longer duration. Treatment with enalapril attenuated the reflex tachycardia observed after nifedipine. These data suggest that coadministration of an ACE inhibitor and calcium-entry blocker may provide better blood pressure control than either drug class alone and at the same time prevent the reflex tachycardia frequently observed after nifedipine.

Antihypertensive efficacy of once daily MK-521, a new nonsulfhydryl angiotensin-converting enzyme inhibitor

The effects of the new nonsulfhydryl-containing oral converting-enzyme inhibitor MK-521 on blood pressure, heart rate, angiotensin-converting enzyme activity, plasma renin activity and plasma aldosterone concentration were assessed in 10 hypertensive patients. After a 2-week no-treatment period, patients received placebo and then 14 days each: MK-521 20 mg once daily, hydrochlorothiazide 50 mg once daily and the latter 2 in combination. During the last day of each treatment, the mean (+/- standard deviation) time-averaged (1- to 12-hour) standing diastolic blood pressure decreased from 106 +/- 8 (placebo) to 95 +/- 10 mm Hg with MK-521, 95 +/- 13 mm Hg with hydrochlorothiazide (p less than 0.05 vs placebo) and 88 +/- 11 mm Hg with the combination (p less than 0.05 vs all other treatments). The antihypertensive effect of MK-521 was maintained 24 hours after dosing. Heart rate did not change significantly after MK-521 treatment. MK-521 caused a marked suppression of converting enzyme activity for over 24 hours; plasma renin activity increased significantly after each active treatment and MK-521 significantly decreased the hydrochlorothiazide-induced elevation of plasma aldosterone concentration. In this short-term trial, MK-521 was well tolerated.

Amiodarone: individualizing dosage with serum concentrations

The purpose of the present report is to review the available pharmacokinetic information on amiodarone with an emphasis on our own experience in monitoring serum amiodarone concentrations. We have found that 400 mg should be the maximal maintenance dose; if that treatment fails, careful addition of other antiarrhythmic agents is preferable over an increase in amiodarone dosage. Serum concentrations below 2.5 mg/L will significantly improve amiodarone's benefit-to-risk ratio.

Inhibition of sulindac metabolism by dimethyl sulfoxide in the rat

Dimethyl sulfoxide (DMSO) suppresses conversion of the prodrug sulindac to its bioactive sulfide metabolite (SD) by competitively inhibiting sulfoxide reductase. During continuous iv infusions of sulindac (1 mg/kg X h), plasma concentrations of SD at steady-state equilibrium were 80% lower when DMSO was infused concomitantly at 0.34 ml/kg X h, whereas sulindac plasma concentrations were not significantly affected by DMSO. Dermal application and intragastric administration of DMSO also inhibited SD accumulation in plasma. DMSO was only a weak inhibitor of SD oxidation in vitro and did not affect the rate of SD elimination in vivo. In contrast, dimethyl sulfide, a metabolite of DMSO, was a potent inhibitor of SD oxidase in vitro. These data suggest that DMSO can inhibit bioactivation and, hence, the antiinflammatory effects of sulindac.

Plasma platelet products and exercise-induced myocardial ischemia

Peripheral plasma concentrations of PF-4 and TxB2 were measured by RIA in 26 patients who underwent exercise stress testing. In group A (n = 15; age 50 +/- 16, mean +/- S.D.) in whom blood sampling was performed by venipuncture, seven patients had a positive stress test associated with an increase in PF-4 concentrations from 3.3 +/- 1.6 ng/ml to 6.9 +/- 3.6 (mean +/- S.D.); six of them demonstrated a greater than 50% increase in PF-4; and only one of eight with a negative stress test had such an increase. In group B (n = 11; 49 +/- 10 yr), patients also underwent postexercise thallium-201 scanning and blood samples were obtained through an intravenous catheter. These patients consistently demonstrated higher PF-4 values (before exercise 7.5 +/- 3.9 ng/ml; after exercise 11.9 +/- 7.1), regardless of the results of the exercise and thallium studies. TxB2 concentrations were unchanged in both groups. To further evaluate the effect of catheter-collected samples on PF-4, five healthy males had serial concurrent blood sampling in opposite arms via both venipuncture and catheter. Although PF-4 concentrations in venipuncture samples were constant, those collected through the catheter increased as a function of time. On the basis of the findings in group A, enhanced platelet activation appears to be associated with exercise-induced ischemia. The observations in group B and the healthy controls indicated that catheter-collection of samples artifactually increased PF-4 concentrations.

Dimethyl sulfoxide inhibits bioactivation of sulindac

Sulindac, a nonsteroidal anti-inflammatory agent, is converted to a bioactive sulfide metabolite via reversible reduction of its sulfoxide moiety. To test whether DMSO can inhibit conversion of sulindac to its active form, eight healthy men received, in a randomized, crossover manner, 400 mg of sulindac, orally, either alone or 60 min after an oral dose of DMSO (30 ml, 70% solution). After the drug combination, mean plasma concentrations of the sulfide metabolite were significantly lower than in controls at 1.5, 2, 3, 4, and 8 hr after sulindac administration. The mean area under the plasma sulfide concentration-time curve for 0 to 12 hr was 30% (range 7% to 56%) lower after DMSO treatment. This study suggests that DMSO can inhibit metabolism of other sulfoxides in man and may antagonize the therapeutic efficacy of sulindac.

Urinary excretion of prostacyclin and thromboxane A2 metabolites after angiotensin converting enzyme inhibition in hypertensive patients

The contribution, if any, of various prostaglandins to the antihypertensive effects of angiotensin converting enzyme inhibitors (ACEI) is controversial. We studied the effect of the ACEI captopril (CAP) on the urinary excretion of 6-keto-PGF2 alpha (6-KF), the major metabolite of the vasodilatory prostaglandin, prostacyclin, and thromboxane B2 (TxB2), the stable metabolite of the vasoconstrictor TxA2, in 8 patients with essential hypertension after placebo, two weeks of CAP 25 mg t.i.d. alone, and the same dose of CAP in combination with hydrochlorothiazide (HCTZ) 50 mg/day. Mean 6-KF and TxB2 (nmol/8 hr post-dosing, respectively) did not differ significantly with any treatment; the mean ratio of 6-KF/TxB2 was also unchanged. Likewise, the excretion of these prostaglandins was also evaluated after placebo, the ACEI enalapril (ENA) (5 or 10 mg/day), and the combination of ENA and HCTZ in another group of 8 patients with essential hypertension. Mean 6-KF and TxB2 (nmol/24 hr post-dosing, respectively) showed no significant treatment-related differences; the mean ratio was again unchanged. No correlation existed between the magnitude of blood pressure responses with any treatment and either 6-KF or TxB2 excretion. Thus, the antihypertensive action of ACEI, alone or in combination with HCTZ, does not appear to involve alterations in these vasoactive prostaglandins.

Comparative antihypertensive effects of enalapril maleate and hydrochlorothiazide, alone and in combination

Enalapril maleate is an investigational oral prodrug whose hydrolyzed diacid metabolite is a potent angiotensin-converting enzyme inhibitor. Fourteen patients with mild to moderate hypertension were evaluated after receiving placebo, and two weeks of treatment with each of the following: enalapril maleate (20 mg b.i.d.), hydrochlorothiazide (25 mg b.i.d.), and the two in combination. In comparison to placebo, the magnitudes of the blood pressure reduction after enalapril and hydrochlorothiazide alone were comparable. The reduction in blood pressure following enalapril was evident throughout the 12-hour dosing interval. The combination of enalapril and hydrochlorothiazide resulted in a marked further reduction in blood pressure that was greater than that predicted from the responses to the individual drugs (P less than 0.05). Biochemical parameters confirmed inhibition of angiotensin-converting enzyme during enalapril treatment; serum angiotensin-converting enzyme activity proved an excellent monitor of compliance. Enalapril was generally well tolerated. Adverse effects included symptomatic hypotension in three patients when enalapril was first added to hydrochlorothiazide and hyperesthesia of the oral mucosa without a loss of taste in one patient on enalapril. Enalapril maleate alone and especially in combination with hydrochlorothiazide appears to be an effective, well-tolerated converting enzyme inhibitor with at least a 12-hour duration of action.

Norfloxacin disposition after sequentially increasing oral doses

Single doses of norfloxacin (200, 400, 800, 1,200, and 1,600 mg) or placebo were administered orally at weekly intervals to 14 healthy male volunteers in a double-blind study. Norfloxacin was measured in serum and urine by high-pressure liquid chromatography with UV detection. The concentrations of this drug in serum peaked 1 to 2 h after each dose; the mean peak values for increasing doses were 0.75, 1.58, 2.41, 3.15, and 3.87 micrograms/ml. Mean area under the serum concentration-time curves for the first 12 h after each dose were 3.56, 6.26, 11.4, 16.1, and 19.7 micrograms . h/ml, respectively. The elimination half-life of norfloxacin was about 7 h and was similar for all doses. The concentrations of the drug in urine also peaked 1 to 2 h after dosage; mean peak values for increasing doses were 200, 478, 697, 992, and 1,045 micrograms/ml. Renal clearances approximated 285 ml/min. About 30% of each dose was excreted into urine as unmetabolized norfloxacin. Crystals of the drug were occasionally observed during microscopic examination of freshly voided urine collected after the 1,200- and 1,600-mg doses. Crystalluria was not encountered at lower doses.

Cimetidine does not alter morphine disposition in man

1 The pharmacokinetic parameters of morphine were determined in a crossover fashion following 4 days pretreatment with cimetidine, 300 mg every 6 h, or placebo. 2 Cimetidine had no apparent effect on the mean morphine plasma clearance, volume of distribution, AUC or half-life (P greater than 0.05; power greater than 0.80). 3 Cimetidine had no apparent effect on the magnitude or duration of morphine induced miosis. 4 The absence of a demonstrable effect on the pharmacokinetics of a drug with a high extraction ratio such as morphine suggests that cimetidine did not significantly reduce hepatic blood flow in ambulant normal volunteers.

Elevation in analgetic effect and plasma levels of morphine by desipramine in rats

Pretreatment of rats with desipramine (30 mg/kg, s.c.) enhanced both peak intensity and duration of morphine sulfate (5 mg/kg, s.c.) analgesia as determined by measurement of tail flick latency. Morphine concentrations in plasma were also significantly elevated after desipramine. Increased narcotic analgetic responses following desipramine pretreatment appear related to higher circulating levels of unmetabolized morphine.

Sulindac disposition when given once and twice daily

To investigate whether sulindac once daily in the evening might be equivalent to the currently recommended twice-daily dose schedule in sustaining plasma concentrations of bioactive sulfide metabolite, 12 healthy subjects received, in a randomized crossover study, sulindac, 200 mg b.i.d. (at 9:00 A.M. and 9:00 P.M.) and 400 mg once daily (at 9:00 P.M.), each for 7 days. At steady state the area under the plasma concentration-time curve (AUC) over 24 hr for sulfide metabolite was greater after once-daily dosing (112 and 84 micrograms . hr . ml-1, P less than 0.05), while mean trough concentrations did not differ. The greater AUC seemed to be related to diurnal variation in metabolite cumulation. A circadian rhythm was apparent at steady state during twice-daily dosing; the mean AUC and peak plasma concentration (C(max)) were greater between 9 A.M. and 9 P.M. than between 9 P.M. and 9 A.M. (50 and 34 micrograms . hr . ml-1; 6.85 and 4.23 micrograms/ml). Although C(max) values of sulfide were higher after morning doses of sulindac, it was apparent that much of the plasma sulfide after morning doses was actually derived from the previous evening dose. This may be a consequence of circadian rhythm in gallbladder emptying. While renal clearance of sulindac was related to urinary pH, diurnal changes in urinary acidity did not cause the fluctuations in the plasma sulfide. Since once-daily sulindac in the evening is as, if not more, effective than twice-daily drug in sustaining plasma sulfide levels, further studies on the therapeutic efficacy of once-daily dosing are warranted.

Effects of enalapril, a new converting enzyme inhibitor, in hypertension

The new angiotensin converting enzyme inhibitor enalapril maleate was given in single oral doses of 2.5, 5, and 10 mg to 11 hospitalized patients with uncomplicated essential hypertension who were on a 150-mEq sodium diet. All doses of enalapril induced reduction of mean seated diastolic blood pressure (SDBP). The magnitude of the initial SDBP reduction was not dose related, but the duration of effect was longer (greater than 12 hr) after the 5 and 10 mg. After dosing, mean plasma angiotensin converting enzyme activity (ACE) and aldosterone concentration (PAC) fell, while plasma renin activity (PRA) rose. Serum concentrations of the active diacid from of enalapril increased linearly with dosage; ACE was inhibited maximally at concentrations above 10 ng/ml. During repeated dosing in the outpatient trial there was attenuation of the antihypertensive effect (12 to 24 hr after dosing) in eight of 10 patients. Despite dose increases only two patients achieved SDBP control (less than or equal to 90 mm Hg). In the five patients in whom 50 mg/day hydrochlorothiazide was added near the end of the trail mean SDBP was further reduced. Enalapril was well tolerated. Further studies of the drug, especially in combination with diuretic, are needed.

A comparative pilot study of enalapril, a new converting enzyme inhibitor, and hydrochlorothiazide in essential hypertension

Eight patients with essential hypertension completed a double-blind, randomly allocated crossover comparison of either 5 or 10 mg enalapril maleate, 50 mg hydrochlorothiazide, or their combination administered once daily during sequential two-week periods. Blood pressure, pulse rate, plasma renin activity, angiotensin-converting enzyme activity, plasma aldosterone concentration, and urinary electrolytes were monitored for 24 hours after placebo and on days 1 and 14 of each treatment period. After two weeks of each treatment, only the combination of enalapril and hydrochlorothiazide significantly lowered the mean seated diastolic blood pressure (SDBP). Likewise, SDBP control (less than or equal to 90 mm Hg) was achieved only after combination therapy; six of the eight patients were controlled by the combination for up to 24 hours. The initial SDBP response to combination therapy differed with the sequence of drug addition; however, by day 14 the responses were comparable, regardless of whether hydrochlorothiazide or enalapril was first given. Mean converting enzyme activity was suppressed by enalapril in all patients, though it did not always correlate with changes in SDBP or plasma aldosterone. Mean plasma renin activity increased, but the increase was significant only on the combination. There were no serious adverse effects.

Low-dose captopril: its use in mild to moderate hypertension unresponsive to diuretic treatment

The effect of low doses (25 mg three times a day) of captopril was evaluated in 16 patients with mild to moderate essential hypertension, previously uncontrolled by hydrochlorothiazide. After a no-treatment period, mean eight-hour seated diastolic blood pressure (SDBP, mm Hg) was 103 +/- 5 on placebo, 95 +/- 8 after a single dose of captopril, 96 +/- 4 after two weeks of captopril alone, and 90 +/- 6 after its combination with hydrochlorothiazide. Though nine patients had at least a 10% fall in SDBP after the initial dose of captopril, only three had a comparable fall after two weeks; after captopril and hydrochlorothiazide, however, 12 patients had such a response. Captopril decreased mean angiotensin-converting enzyme activity and plasma aldosterone, though to a lesser extent with continued therapy. Because its side effects appear dose related, low doses of captopril combined with a diuretic are effective and may be better tolerated.

Determination of norfloxacin, a new nalidixic acid analog, in human serum and urine by high-performance liquid chromatography

A high-performance liquid chromatographic method for the analysis of norfloxacin (MK-366) [1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)3-quinolinecarboxylic acid], a new nalidixic acid analog, in human serum and urine is described. A statistical evaluation of the assay data showed acceptable accuracy and precision for 0.1 to 10.0 micrograms of MK-366 per ml of serum and for 1.0 to 500 micrograms of MK-366 per ml of urine. MK-366 was extracted from serum and urine at pH 7.5 with methylene chloride and back-extracted with sodium hydroxide solution. Chromatography was performed on an anion-exchange column with acetonitrile-phosphate buffer as the mobile phase; UV absorbance was monitored at 273 nm. The method was used to measure MK-366 in clinical specimens.