Thorough QTc Evaluation and the Safety of Supratherapeutic Doses of Odanacatib in Healthy Subjects

Assessing risk for QTc interval prolongation in a thorough QTc study is a standard recommendation when evaluating new chemical entities. As part of the clinical development program for odanacatib, an oral selective inhibitor of cathepsin K previously in development for the treatment of osteoporosis, 2 clinical studies in healthy subjects assessed pharmacokinetics and overall safety (including potential for delayed ventricular repolarization) of a supratherapeutic dose. In study 1, subjects received a supratherapeutic dose regimen of odanacatib (300 mg on day 1, then daily multiple doses of 25 mg to day 21) or placebo. In study 2 (days 1-4), subjects received the odanacatib supratherapeutic dose regimen or moxifloxacin (positive control, single 400-mg dose on day 4; matching placebo for odanacatib/moxifloxacin) or placebo. All doses were administered with a high-fat meal. In study 1 (N = 12), the supratherapeutic dosing regimen achieved exposure ∼3.5-fold of the proposed therapeutic dose (50 mg once weekly) and was sufficiently well tolerated to permit assessment in the thorough QTc study (study 2). In study 2 (N = 116), the primary objective was placebo-corrected change from baseline in QTcF interval (Fridericia's correction), assessed by replicate electrocardiograms (12-lead Holter recordings; days -1 through 7). Supratherapeutic odanacatib dosing was not associated with increased risk of prolonged QT interval, unlike moxifloxacin (confirming assay sensitivity). Pooled safety data across both studies suggested that the safety profile of odanacatib at high exposures was similar to placebo, with a small clustering of oral cavity adverse events. Odanacatib was not associated with increased risk of prolonged QT interval.

Incidence of hypersensitivity and anaphylaxis with sugammadex

STUDY OBJECTIVE

To evaluate the incidence of hypersensitivity and anaphylaxis after administration of sugammadex.

DESIGN

Retrospective analysis.

SETTING

Sugammadex clinical development program and post-marketing experience.

PATIENTS

Surgical patients and healthy volunteers who received sugammadex or placebo/comparator with anesthesia and/or neuromuscular blockade (NMB).

INTERVENTIONS

Sugammadex administered as 2.0 mg/kg at reappearance of the second twitch, 4.0 mg/kg at 1-2 post-tetanic count, or 16.0 mg/kg at 3 min after rocuronium 1.2 mg/kg.

MEASUREMENTS

Three analytical methods were used: 1) automated MedDRA queries; 2) searches of adverse events (AEs) consistent with treatment-related hypersensitivity reactions as diagnosed by the investigator; and 3) a retrospective adjudication of AEs suggestive of hypersensitivity by a blinded, independent adjudication committee (AC). In addition, a search of all post-marketing reports of events of hypersensitivity was performed, and events were retrospectively adjudicated by an independent AC. Anaphylaxis was determined according to Sampson Criterion 1.

MAIN RESULTS

The pooled dataset included 3519 unique subjects who received sugammadex and 544 who received placebo. The automated MedDRA query method showed no apparent increase in hypersensitivity or anaphylaxis with sugammadex as compared to placebo or neostigmine. Similarly, there was a low overall incidence of AEs of treatment-related hypersensitivity (<1%), with no differences between sugammadex and placebo or neostigmine. Finally, the retrospective adjudication of AEs suggestive of hypersensitivity showed a low incidence of hypersensitivity (0.56% and 0.21% for sugammadex 2 mg/kg and 4 mg/kg, respectively), with an incidence similar to subjects who received placebo (0.55%). There were no confirmed cases of anaphylaxis in the pooled studies. During post-marketing use, spontaneous reports of anaphylaxis occurred with approximately 0.01% of sugammadex doses.

CONCLUSIONS

Subjects who received sugammadex with general anesthesia and/or NMB had a low overall incidence of hypersensitivity, with no apparent increase in hypersensitivity or anaphylaxis with sugammadex as compared to placebo or neostigmine.

Odanacatib Pharmacokinetics Comparison Between Chinese and Non-Chinese Postmenopausal Women

Odanacatib (ODN), an oral selective inhibitor of cathepsin K, was an investigational agent previously in development for the treatment of osteoporosis. In this phase 1 open-label study, 12 healthy Chinese postmenopausal women received single-dose ODN 50 mg on day 1 and multiple-dose ODN 50 mg once weekly on days 15, 22, 29, and 36 under fasted conditions. Pharmacokinetic (PK) parameters were evaluated on days 1 and 36. Multiple-dose area under the concentration-time profile (AUC_0-168h ) and maximum plasma concentration (C_max ) were compared with historical data from 9 non-Chinese postmenopausal women who also received ODN 50 mg once weekly for 4 weeks. Median time to C_max (t_max ) was 3 and 4 hours following single- and multiple-dose administration, respectively. The arithmetic mean ± SD terminal half-life was 81.0 ± 14.0 and 106.7 ± 14.4 hours following single- and multiple-dose administration, respectively. Comparison of multiple-dose PK parameters showed that the geometric mean ratios (Chinese/non-Chinese) and 95%CIs for AUC_0-168h and C_max were 0.81 (0.55-1.19) and 0.87 (0.69-1.11), respectively. All adverse events were mild, none were serious, and none led to discontinuation. Single- and multiple-dose PKs of ODN 50 mg in Chinese postmenopausal women were generally similar to those previously reported in non-Chinese postmenopausal women.

On-the-road driving performance the morning after bedtime use of suvorexant 15 and 30 mg in healthy elderly

RATIONALE

Suvorexant is a first-in-class orexin receptor antagonist for treating insomnia. There is a general concern that hypnotics may impair next-morning driving ability.

OBJECTIVE

The objective of this study was to evaluate next-morning driving performance in older adults after single and repeated doses of suvorexant.

METHODS

Double-blind, randomized, placebo-controlled, 4-period crossover study in 24 healthy volunteers (10 females), aged 65-80 years. Subjects were treated with suvorexant (15 and 30 mg) for eight consecutive nights, zopiclone 7.5 mg nightly on days 1 and 8, and placebo. Driving performance was assessed on days 2 and 9 (9 h after dosing) using a 1-h standardized highway driving test in normal traffic, measuring standard deviation of lateral position (SDLP). Drug-placebo differences in SDLP >2.4 cm were considered to reflect clinically meaningful driving impairment.

RESULTS

Driving performance as measured by SDLP was not impaired following suvorexant. Mean drug-placebo differences in SDLP following suvorexant 15 and 30 mg on day 2 and 9 were 0.6 cm or less. Their 90 % CIs were all below the threshold of 2.4 cm for clinical relevance and included zero, indicating effects were not clinically meaningful or statistically significant. Symmetry analysis showed no significant differences between the number of participants who had SDLP differences >2.4 cm and those who had SDLP differences <-2.4 cm following suvorexant.

CONCLUSIONS

There was no clinically meaningful residual effect of suvorexant 15 and 30 mg on next-morning driving (9 h after bedtime dosing) in healthy older adults, as assessed by mean changes in SDLP and by the number of participants on drug versus placebo that exceeded a predetermined threshold for clinically meaningful impairment.

Psychomotor effects, pharmacokinetics and safety of the orexin receptor antagonist suvorexant administered in combination with alcohol in healthy subjects

A double-blind crossover study investigated psychomotor effects, pharmacokinetics, and safety of the orexin receptor antagonist suvorexant with and without alcohol. Healthy adults (n=31) were randomized to receive placebo or suvorexant (40 mg) plus placebo solution or alcohol (0.7 g/kg) in each of four treatments (single doses; morning administration). The US Food and Drug Administration approved suvorexant dose is 10 mg (up to 20 mg) daily. Pharmacodynamic effects were assessed using tests of digit vigilance (DVT; primary endpoint), choice reaction time, digit symbol substitution, numeric working memory, immediate/delayed word recall, body sway and subjective alertness. Suvorexant alone did not significantly affect DVT reaction time, but did impact some pharmacodynamic tests. Suvorexant with alcohol increased reaction time versus either alone (mean difference at 2 h: 44 ms versus suvorexant, p<0.001; 24 ms, versus alcohol, p<0.05) and had additive negative effects on tests of vigilance, working/episodic memory, postural stability and alertness. No effects of suvorexant alone or with alcohol were observed by 9 h. No important changes in pharmacokinetic parameters were observed upon co-administration. All treatments were generally well tolerated without serious adverse events. In conclusion, co-administration of 40 mg suvorexant and 0.7 g/kg alcohol had additive negative psychomotor effects. Patients are advised not to consume alcohol with suvorexant.

On-the-Road Driving Performance the Morning after Bedtime Use of Suvorexant 20 and 40 mg: A Study in Non-Elderly Healthy Volunteers

STUDY OBJECTIVE

To evaluate next-morning driving performance in adults younger than 65 years, after single and repeated doses of suvorexant 20 and 40 mg.

DESIGN

Double-blind, placebo-controlled, 4-period crossover study.

SETTING

Maastricht University, The Netherlands.

PARTICIPANTS

28 healthy volunteers (15 females), aged 23 to 64 years.

INTERVENTIONS

Suvorexant (20 and 40 mg) for 8 consecutive nights; zopiclone 7.5 mg nightly on day 1 and 8; placebo.

MEASUREMENTS

Performance on day 2 and 9 (9 h after dosing) using a one-hour standardized highway driving test in normal traffic, measuring standard deviation of lateral position (SDLP). Drug-placebo changes in SDLP > 2.4 cm were considered to reflect meaningful driving impairment.

RESULTS

Mean drug-placebo changes in SDLP following suvorexant 20 and 40 mg were 1.01 and 1.66 cm on day 2, and 0.48 and 1.31 cm on Day 9, respectively. The 90% CIs of these changes were all below 2.4 cm. Symmetry analysis showed that more subjects had SDLP changes > 2.4 cm than < -2.4 cm following suvorexant 20 and 40 mg on day 2, and following suvorexant 40 mg on day 9. Four female subjects requested that a total of 5 driving tests--all following suvorexant--stop prematurely due to self-reported somnolence.

CONCLUSIONS

As assessed by mean changes in standard deviation of lateral position (SDLP), there was no clinically meaningful residual effect of suvorexant in doses of 20 and 40 mg on next-morning driving (9 h after bedtime dosing) in healthy subjects < 65 years old. There may be some individuals who experience next-day effects, as suggested by individual changes in SDLP and prematurely stopped tests.

CLINICAL TRIAL REGISTRATION

clinicaltrials.gov NCT01311882.

Effects of the orexin receptor antagonist suvorexant on respiration during sleep in healthy subjects

Suvorexant is an orexin receptor antagonist for treating insomnia. The maximum approved dose in the United States and Japan is 20 mg. We evaluated suvorexant effects on respiration during sleep in a randomized, double-blind, 3-period crossover study of healthy adult men (n = 8) and women (n = 4) ≤ 50 years old who received single-dose suvorexant 40 mg, 150 mg, and placebo. Respiration during sleep was measured by oxygen saturation (SpO2 , primary end point) and the Apnea Hypopnea Index (AHI). The study was powered to detect a reduction greater than 5% in SpO2 . There was no effect of suvorexant on mean SpO2 during sleep. The mean (90%CI) treatment differences versus placebo were -0.3 (-1.2-0.6) for 40 mg and 0.0 (-0.9-0.9) for 150 mg. There were no dose-related trends in individual SpO2 values. Mean SpO2 was >96% for all treatments during total sleep time and during both non-REM and REM sleep. There was no effect of either suvorexant dose on AHI. The mean (90%CI) treatment differences versus placebo were 0.8 (-0.7-2.3) for 40 mg and -0.2 (-1.7-1.3) for 150 mg. Suvorexant was generally well tolerated; there were no serious adverse experiences or discontinuations. These data from healthy subjects suggest that suvorexant lacks clinically important respiratory effects during sleep at doses greater than the maximum recommended dose for treating insomnia.

Lack of meaningful effect of ridaforolimus on the pharmacokinetics of midazolam in cancer patients: model prediction and clinical confirmation

Ridaforolimus, a unique non-prodrug analog of rapamycin, is a potent inhibitor of mTOR under development for cancer treatment. In vitro data suggest ridaforolimus is a reversible and time-dependent inhibitor of CYP3A. A model-based evaluation suggested an increase in midazolam area under the curve (AUC(0- ∞)) of between 1.13- and 1.25-fold in the presence of therapeutic concentrations of ridaforolimus. The pharmacokinetic interaction between multiple oral doses of ridaforolimus and a single oral dose of midazolam was evaluated in an open-label, fixed-sequence study, in which cancer patients received a single oral dose of 2 mg midazolam followed by 5 consecutive daily single oral doses of 40 mg ridaforolimus with a single dose of 2 mg midazolam with the fifth ridaforolimus dose. Changes in midazolam exposure were minimal [geometric mean ratios and 90% confidence intervals: 1.23 (1.07, 1.40) for AUC(0-∞) and 0.92 (0.82, 1.03) for maximum concentrations (C(max)), respectively]. Consistent with model predictions, ridaforolimus had no clinically important effect on midazolam pharmacokinetics and is not anticipated to be a perpetrator of drug-drug interactions (DDIs) when coadministered with CYP3A substrates. Model-based approaches can provide reasonable estimates of DDI liability, potentially obviating the need to conduct dedicated DDI studies especially in challenging populations like cancer patients.

Placebo- and amitriptyline-controlled evaluation of central nervous system effects of the NK1 receptor antagonist aprepitant and intravenous alcohol infusion at pseudo-steady state

Recent interest in NK1 receptor antagonists has focused on a potential role in the treatment of drug addiction and substance abuse. In the present study, the potential for interactions between the NK1 receptor antagonist aprepitant and alcohol, given as an infusion at a target level of 0.65 g/L, was evaluated. Amitriptyline was included as positive control to provide an impression of the profile of central nervous system (CNS) effects. In a double-blind, randomized, placebo- and amitriptyline-controlled study, the pharmacokinetics and CNS effects of aprepitant and alcohol were investigated in 16 healthy volunteers. Cognitive and psychomotor function tests included the visual verbal learning test (VVLT), Bond and Lader visual analogue scales (VAS), digit symbol substitution test (DSST), visual pattern recognition, binary choice reaction time, critical flicker fusion (CFF), body sway, finger tapping, and adaptive tracking. Alcohol impaired finger tapping and body sway. Amitriptyline impaired DSST performance, VAS alertness, CFF, body sway, finger tapping, and adaptive tracking. No impairments were found after administration of aprepitant. Co-administration of aprepitant with alcohol was generally well tolerated and did not cause significant additive CNS effects, compared with alcohol alone. Therefore, our study found no indications for clinically relevant interactions between aprepitant and alcohol.

A single supratherapeutic dose of ridaforolimus does not prolong the QTc interval in patients with advanced cancer

Purpose

This dedicated QTc study was designed to evaluate the effect of the mammalian target of rapamycin inhibitor, ridaforolimus, on the QTc interval in patients with advanced malignancies.

Methods

We conducted a fixed-sequence, single-blind, placebo-controlled study. Patients (n = 23) received placebo on day 1 and a single 100-mg oral dose of ridaforolimus on day 2 in the fasted state. Holter electrocardiogram (ECG) monitoring was performed for 24 h after each treatment, and blood ridaforolimus concentrations were measured for 24 h after dosing. The ECGs were interpreted in a blinded fashion, and the QT interval was corrected using Fridericia’s formula (QTcF). After a washout of at least 5 days, 22 patients went on to receive a therapeutic regimen of ridaforolimus (40 mg orally once daily for 5 days per week).

Results

The upper limit of the two-sided 90 % confidence interval for the placebo-adjusted mean change from baseline in QTcF was <10 ms at each time point. No patient had a QTcF change from baseline >30 ms or QTcF interval >480 ms. Geometric mean exposure to ridaforolimus after the single 100-mg dose was comparable to previous experience with the therapeutic regimen. There appeared to be no clear relationship between individual QTcF change from baseline and ridaforolimus blood concentrations. Ridaforolimus was generally well tolerated, with adverse events consistent with prior studies.

Conclusions

Administration of the single 100-mg dose of ridaforolimus did not cause a clinically meaningful prolongation of QTcF, suggesting that patients treated with ridaforolimus have a low likelihood of delayed ventricular repolarization.

Electronic supplementary material

The online version of this article (doi:10.1007/s00280-012-1942-7) contains supplementary material, which is available to authorized users.

Next-day residual effects of gaboxadol and flurazepam administered at bedtime: a randomized double-blind study in healthy elderly subjects

OBJECTIVE

To evaluate the next-day residual effects of the novel hypnotic, gaboxadol, following bedtime dosing in healthy elderly subjects.

METHODS

Healthy women (N = 15) and men (N = 10) aged 65-79 years received a single bedtime (22:00 h) dose of gaboxadol 10 mg, flurazepam 30 mg (positive control), and placebo in a randomized, double-blind, crossover study. Measures of information processing and psychomotor performance (choice reaction time, critical flicker fusion, digit symbol substitution, compensatory tracking, body sway), memory (immediate and delayed word recall), and daytime sleepiness (Multiple Sleep Latency Test), as well as subjective ratings (line analog rating scales, Leeds Sleep Evaluation Questionnaire), were obtained starting at 07:00 h the following morning. Adverse events were recorded.

RESULTS

Gaboxadol did not show next-day impairments versus placebo on any pharmacodynamic measures whereas the positive control, flurazepam, did show impairments versus placebo on most measures. Gaboxadol showed improvements versus placebo on some measures including subjective rating of next-day alertness/clumsiness on the Leeds Sleep Evaluation Questionnaire. Gaboxadol was generally well-tolerated; there were no serious adverse experiences and no subjects discontinued due to an adverse experience.

CONCLUSIONS

A single oral bedtime dose of gaboxadol 10 mg did not have next-day residual effects in healthy elderly subjects, as measured by a range of pharmacodynamic assessments, in contrast to the clear impairments produced by flurazepam 30 mg.

Effects of aprepitant on the pharmacokinetics of ondansetron and granisetron in healthy subjects

BACKGROUND

The neurokinin-1-receptor antagonist aprepitant, when given in combination with a corticosteroid and a 5-hydroxytryptamine type 3 (5-HT(3))-receptor antagonist, has been shown to be effective for the prevention of acute and delated chemotherapy-induced nausea and vomiting (CINV).

OBJECTIVE

Two studies were conducted to determine whether concomitant administration of aprepitant altered the pharmacokinetic profiles of ondansetron and granisetron, two 5-HT(3)-receptor antagonists commonly used as antiemetic therapy for CINV.

METHODS

The 2 studies were randomized, open-label, crossover trials conducted in healthy subjects aged between 18 and 46 years. Study 1 involved the following 2 treatment regimens: aprepitant 375 mg PO, dexamethasone 20 mg PO, and ondansetron 32 mg IV on day 1, followed by aprepitant 250 mg PO and dexamethasone 8 mg PO on days 2 through 5; and dexamethasone 20 mg PO and ondansetron 32 mg IV on day 1, followed by dexamethasone 8 mg PO on days 2 through 5. Study 2 involved the following 2 treatment regimens: aprepitant 125 mg PO with granisetron 2 mg PO on day 1, followed by aprepitant 80 mg PO on days 2 and 3; and granisetron 2 mg PO on day 1 only. Individual plasma samples were used to estimate area under the plasma concentration-time curve from time zero to infinity (AUC(0- infinity )), peak plasma concentration, and apparent terminal elimination half-life (t(12)) of both ondansetron and granisetron.

RESULTS

Study 1 included 19 subjects (10 women, 9 men), and study 2 included 18 subjects (11 men, 7 women). Coadministration of aprepitant 375 mg produced a small but statistically significant increase in the AUC(0- infinity ) for intravenous ondansetron (from 1268.3 to 1456.5 ng.h/mL; P = 0.019), with no significant effect on peak concentration at the end of the infusion (360.8 ng/mL with aprepitant vs 408.4 ng/mL without) or t(12) (5.0 vs 4.5 hours, respectively). Coadministration of aprepitant 125 mg/80 mg did not alter the mean pharmacokinetic characteristics of oral granisetron (AUC(0- infinity ), 101.4 ng.h/mL with aprepitant vs 92.2 ng.h/mL without; maximum plasma concentration, 9.0 ng/mL with and without aprepitant; time to maximum plasma concentration, both 3.0 hours; t(12), 6.5 vs 6.9 hours, respectively).

CONCLUSION

Concomitant administration of aprepitant had no clinically significant effect on the mean pharmacokinetic characteristics of either ondansetron or granisetron in these healthy subjects.

Tissue penetration by ertapenem, a parenteral carbapenem administered once daily, in suction-induced skin blister fluid in healthy young volunteers

The penetration of 1 g of intravenous ertapenem once daily for 3 days in suction-induced skin blisters was evaluated. Ten forearm blisters were formed (n = 12) 12 h prior to the last dose. Concentrations of ertapenem in blister fluid exceeded 4 micro g/ml (the MIC at which 90% of the isolates tested are eliminated) for the entire dosing interval. The area under the concentration-time curve for 0 to 24 h ratio of blister fluid to plasma was 61% (90% confidence interval, 56, 65%) suggesting good blister penetration.

Pharmacokinetics of ertapenem in healthy young volunteers

Ertapenem (INVANZ) is a new once-a-day parenteral beta-lactam antimicrobial shown to be effective as a single agent for treatment of various community-acquired and mixed infections. The single- and multiple-dose pharmacokinetics of ertapenem at doses up to 3 g were examined in healthy young men and women volunteers. Plasma and urine samples collected were analyzed using reversed-phase high-performance liquid chromatography with UV detection. Ertapenem is highly bound to plasma protein. The protein binding changes from approximately 95% bound at concentrations of <50 micro g/ml to approximately 92% bound at concentrations of 150 micro g/ml (concentration at the end of a 30-min infusion following the 1-g dose). The nonlinear protein binding of ertapenem resulted in a slightly less than dose proportional increase in the area under the curve from 0 h to infinity (AUC(0- infinity )) of total ertapenem. The single-dose AUC(0- infinity ) of unbound ertapenem was nearly dose proportional over the dose range of 0.5 to 2 g. The mean concentration of ertapenem in plasma ranged from approximately 145 to 175 micro g/ml at the end of a 30-min infusion, from approximately 30 to 34 micro g/ml at 6 h, and from approximately 9 to 11 micro g/ml at 12 h. The mean plasma t(1/2) ranged from 3.8 to 4.4 h. About 45% of the plasma clearance (CL(P)) was via renal clearance. The remainder of the CL(P) was primarily via the formation of the beta-lactam ring-opened metabolite that was excreted in urine. There were no clinically significant differences between the pharmacokinetics of ertapenem in men and women. Ertapenem does not accumulate after multiple once-daily dosing.

Improving estimates of exposures for epidemiologic studies of plutonium workers

Epidemiologic studies of nuclear facilities usually focus on relations between cancer and doses from external penetrating radiation, and describe these exposures with little detail on measurement error and missing data. We demonstrate ways to document complex exposures to nuclear workers with data on external and internal exposures to ionizing radiation and toxic chemicals. We describe methods for assessing internal exposures to plutonium and external doses from neutrons; the use of a job exposure matrix for estimating chemical exposures; and methods for imputing missing data for exposures and doses. For plutonium workers at Rocky Flats, errors in estimating neutron doses resulted in underestimating the total external dose for production workers by about 16%. Estimates of systemic deposition do not correlate well with estimates of organ doses. Only a small percentage of workers had exposures to toxic chemicals, making epidemiologic assessments of risk difficult.

Risk factors that may adversely modify the natural history of the pediatric pronated foot

Flatfoot is one of the most common conditions seen in pediatric podiatry practice. There is no universally accepted definition for flatfoot. Flatfoot is a term used to describe a recognizable clinical deformity created by malalignment at several adjacent joints. Clinically, a flatfoot is one that has a low or absent longitudinal arch. Determining flexibility (physiologic) or rigidity (pathologic) is the first step in management. A flexible flat foot will have an arch that is present in open kinetic chain (off weight-bearing) and lost in closed kinetic chain (weight-bearing). A rigid flatfoot has loss of the longitudinal arch height in open and closed kinetic chain. According to Mosca, "The anatomic characteristics of a flatfoot are excessive eversion of the subtalar complex during weight-bearing with plantarflexion of the talus, plantarflexion of the calcaneus in relation to the tibia, a dorsiflexed and abducted navicular and a supinated forefoot." Normally developing infants have a flexible flatfoot and gradually develop a normal arch during the first decade of life. When evaluating an infant for a pronated condition, the examiner must also consider other risk factors that may affect the foot in its overall development. These contributing factors will play a role in the development of a treatment plan. The risk factors include ligamentous laxity, obesity, rotational deformities, tibial influence, pathological tibia varum, equinus, presence of an os tibiale externum, and tarsal coalitions. The authors realize other less significant factors exist but are not as detrimental to the foot as the primary ones discussed in depth. The primary risk factors that affect the pronated foot have been outlined. The clinician should always examine for these conditions when presented with a child exhibiting pronatory changes. A thorough explanation to the parents as to the consequential effects of these risk factors and their effects on the pediatric pronated foot is paramount to providing an acceptable comprehensive treatment program. Children often are noncompliant with such treatments as stretching and orthotic maintenance. The support of the parents is crucial to maintaining an effective treatment program continued at home.

The steady-state disposition of indinavir is not altered by the concomitant administration of clarithromycin

STUDY OBJECTIVES

To evaluate the safety and potential pharmacokinetic interaction between indinavir and clarithromycin.

STUDY METHODS

In a randomized, three-period, crossover fashion, 12 healthy adults received the following for 1 week: 800 mg oral indinavir sulfate every 8 hours with placebo, 500 mg oral clarithromycin every 12 hours with placebo, and indinavir sulfate with clarithromycin. Plasma indinavir, clarithromycin, and 14-hydroxyclarithromycin concentrations were determined after the last dose in each treatment period.

RESULTS

Administration of indinavir sulfate with clarithromycin caused a statistically significant increase in four pharmacokinetic parameters: a 58% increase in plasma indinavir concentrations at 8 hours (P = .029), a 47% increase in values for clarithromycin area under the plasma concentration versus time curve from time zero to the last measured concentration [AUC(0-12h); P = .0002], and 49% and 48% decreases in 14-hydroxyclarithromycin AUC(0-12h) and maximum plasma concentration (Cmax) values, respectively (P = .0001 and P = .0001). These effects are not considered to be clinically significant in view of the insignificant effects on the values for indinavir area under the plasma concentration versus time curve from time zero to the last measured concentration [AUC(0-8h)] and Cmax, as well as the safety profile of clarithromycin.

CONCLUSIONS

The combination of indinavir sulfate and clarithromycin is generally well tolerated and can be coadministered without dose adjustment.

Concurrent administration of the erythromycin breath test (EBT) and oral midazolam as in vivo probes for CYP3A activity

Given the prominent role of CYP3A in the metabolism of drugs, it is important to identify whether new chemical entities will affect this enzyme system and produce clinically relevant drug interactions. This study evaluated concomitant administration of intravenous [14C N-methyl] erythromycin (3 microCi) (erythromycin breath test; EBT) and 2 mg oral midazolam as probes of systemic and of systemic plus presystemic CYP3A activity, respectively. Twelve males received the probes in a two-period crossover fashion: one period included the probes on two occasions, 5 days apart; in the second period, 200 mg ketoconazole was given orally 2 hours prior to the probes. The within-subject CV for EBT (%14CO2/h) and midazolam AUC0-last was 4.9% and 16.9%, respectively. Ketoconazole reduced %14CO2/h by 43% and increased midazolam AUC0-last by approximately fivefold. In a nonrandomized third period (N = 5), ketoconazole was given simultaneously with midazolam (no EBT); midazolam AUC0-last was similar whether ketoconazole was given 2 hours prior to or simultaneously with the midazolam. The low midazolam dose was generally well tolerated; mild sedation was occasionally seen. Concurrent administration of the EBT and oral midazolam is a sensitive and reproducible tool to screen new chemical entities for potentially important CYP3A interactions.

Lack of polymorphism of the conversion of losartan to its active metabolite E-3174 in extensive and poor metabolizers of debrisoquine (cytochrome P450 2D6) and mephenytoin (cytochrome P450 2C19)

OBJECTIVE

Losartan was given to subjects with known phenotypes of the polymorphic enzymes CYP2D6 and CYP2C19 to study any possible influence on the metabolism of the drug.

METHODS

Plasma concentrations of losartan and E-3174 were studied after oral intake of 50 mg losartan in 24 healthy, male, Swedish Caucasian subjects who were extensive or poor metabolizers (EM/PM) of debrisoquine [cytochrome P450 2D6 (CYP2D6)] or mephenytoin [cytochrome P450 2C19 (CYP2C19)].

RESULTS

The areas under the curve (AUCinfinity) of losartan and E-3174 did not differ between poor and extensive metabolizers of debrisoquine or mephenytoin, respectively.

CONCLUSION

About 14% of the antihypertensive drug losartan is metabolized to the active carboxylic acid metabolite E-3174, which contributes to the effect of losartan. The present study suggests that CYP2D6 and CYP2C19 are not involved to any major extent in the in vivo conversion of losartan to E-3174.

Effect of fluconazole on indinavir pharmacokinetics in human immunodeficiency virus-infected patients

To evaluate a potential pharmacokinetic interaction of coadministration of fluconazole, and indinavir, a human immunodeficiency virus (HIV) protease inhibitor, 13 patients were enrolled in a multiple-dose, three-period, placebo-controlled, crossover study. Patients were randomly assigned to receive indinavir at 1,000 mg every 8 h for 7 1/3 days (with fluconazole placebo), fluconazole at 400 mg once daily for 8 days (with indinavir placebo), and indinavir with fluconazole in combination. The pharmacokinetics of both drugs were measured on day 8 of each treatment period. The peak concentration in plasma (Cmax) and the time to reach Cmax were obtained by inspection, and the area under curve (AUC) was calculated for indinavir and fluconazole for each treatment period in which the respective drugs were administered. There was a marginally (P = 0.08) statistically significant decrease in the AUC from 0 to 8 h (AUC(0-8)) for indinavir when it was administered with fluconazole. However, the magnitudes of the decreases in Cmax and the concentration at 8 h postdosing (C8) were not as great as the decrease in AUC(0-8). Although the 90% confidence interval for the geometric mean ratio was within the hypothesized limits, the clinical significance is not clear. Indinavir coadministration with fluconazole had no statistically (P > 0.5) or clinically significant effect on the Cmax and C8 of indinavir. Fluconazole coadministration with indinavir had no statistically or clinically significant effect on the pharmacokinetics of fluconazole. One patient was discontinued because of mild to moderate abdominal pain and diarrhea while on indinavir and fluconazole in combination. No serious adverse experience according to the results of laboratory tests was noted. Total bilirubin levels in serum were mildly increased in most patients treated with indinavir. This was not clinically significant and was not affected by the coadministration of fluconazole. Although the values of the pharmacokinetic parameters for indinavir decrease in the presence of fluconazole, indinavir and fluconazole can be administered concomitantly to HIV-infected patients without adjustment of the dose of either drug, and both drugs are generally well tolerated.

Effects of losartan on blood pressure, plasma renin activity, and angiotensin II in volunteers

Losartan is an orally active, nonpeptide angiotensin II (Ang II) (site-1) receptor antagonist. We conducted a multiple-dose study in healthy male volunteers to investigate the tolerability, blood pressure effects, and changes in plasma renin activity (PRA) and plasma Ang II concentration associated with once-daily administration of 100 mg losartan for a week. Subjects were studied on a standardized sodium diet (24-hour urinary sodium excretion, 98 +/- 37 [SD] mEq per 24 hours on the placebo run-in day). Measurements of blood pressure, heart rate, PRA, Ang II, and aldosterone were taken during a placebo run-in day and after single and multiple (7 days) daily doses of losartan (100 mg, n = 10) or placebo (n = 4). Ang II was measured specifically by high performance liquid chromatography coupled with radioimmunoassay. In subjects given losartan, respective decreases (systolic/diastolic) from run-in in supine blood pressure 6 hours after dosing were (mean +/- SD), compared with the placebo run-in day, first dose: -8.8 +/- 9.6/-6.8 +/- 5.0, last dose: -11.6 +/- 8.9/-7.0 +/- 4.8 mm Hg (p < 0.05 for all changes). At this 6-hour time point, corresponding increases from run-in in PRA were from 1.2 +/- 0.6 to 12.0 +/- 6.3 (first dose) and 9.6 +/- 4.9 (last dose) ng angiotensin I per milliliter per hour and in Ang II were from 4.3 +/- 1.7 to 72.4 +/- 33.3 and 45.7 +/- 14.1 pg/mL. All changes in PRA and Ang II were statistically significant within the losartan-treated group, and the biochemical changes were significantly greater than those in the placebo-treated group. The increment in Ang II was less after the last dose than after the first (p < 0.05). The drug was well tolerated by all subjects. These data indicate that, under the conditions of this study, losartan administration (100 mg/day for eight doses over 9 days) results in treatment-related decreases in blood pressure and increases in PRA and Ang II octapeptide.

The influence of amines on various platelet responses

Four amines, galactosamine, mannosamine, histamine and arginine were studied for their effects on platelet aggregation, platelet morphological changes, platelet protein phosphorylation and platelet secretion. Galactosamine inhibited platelet aggregation in response to arachidonic acid and ionophore A23187 but did not inhibit changes in platelet morphology, or in platelet protein phosphorylation in response to these agents and only partially inhibited platelet secretion. The results suggest that galactosamine can be used as a selective inhibitor of platelet-platelet attachment without having a significant effect on intracellular processes. Mannosamine was similar to galactosamine except that it partially suppressed phosphorylation of myosin light chain. Histamine was similar to mannosamine except that some platelet damage was seen in platelets exposed to histamine and arachidonic acid or ionophore A23187. Arginine was non-selective: it suppressed platelet aggregation, secretion and phosphorylation of myosin light chain and a 40 kDa protein (40P) in response to arachidonic acid and ionophore A23187. Arginine was also potent in suppressing platelet morphological changes. When the same four amines were evaluated for their effects on thrombin-induced aggregation; secretion was inhibited concomitantly with inhibition of aggregation. Inhibition of myosin light chain and 40P phosphorylation was evident with galactosamine, suggesting that when thrombin is used as the agonist, galactosamine is not a specific inhibitor of platelet-platelet attachment. These amines therefore have various effects on platelet responses. Under some conditions and with arachidonic acid or ionophore A23187 as agonist, one of them, galactosamine, can be used as a selective inhibitor of platelet-platelet attachment.

Potentiation by endotoxin of responses associated with increases in calcium conductance

Bacterial endotoxin at concentrations of 0.03 mug/ml enhanced the following responses, each of which reflects calcium influx: (1) contraction of spiral intestine retractor muscle of dogfish; (2) amplitude of postsynaptic potential of squid giant synapse as a function of presynaptic depolarization; (3) membrane responses of deep abdominal extensor muscle of crayfish, stimulated intracellularly; and (4) slow transient (calcium) current in trabeculae of frog atrium under voltage clamp. Corticosteroid antagonized the endotoxin effect on the smooth muscle, not on the frog atrial current. One mechanism of action of endotoxin may be to increase transmembrane calcium currents.