Diplopia following sub-tenon's anaesthesia: an unusual complication.

Diplopia is a rare but well recognised complication following retrobulbar and peribulbar local anaesthesia but it has not been widely reported following sub-tenon's local anaesthesia (STLA). We report on a 76-year-old woman who developed vertical diplopia after left phacoemulsification. She had received a STLA. She had left hypotropia measuring 30 prism diopters for near and distance. She was managed with occlusion but there was no improvement in her findings over 6 months. Ocular motility opinion was then sought and a presumptive diagnosis of inferior rectus fibrosis was made. She subsequently underwent a left inferior rectus recession using adjustable sutures. Postoperatively she had a residual left hypotropia measuring 8 prism dioptres and single vision. Possible causes of inferior rectus fibrosis include muscle damage during traumatic sub-tenon's block or myotoxicity due to local anaesthetic agents. This case highlights the importance of close supervision of inexperienced staff administering regional anaesthetics.

Pharmacokinetic and pharmacodynamic modeling of a copper-selective chelator (TETA) in healthy adults.

The population pharmacokinetics (PK) and pharmacodynamics (PD) of triethylenetetramine (TETA) dihydrochloride (trientine, GC811007) administered orally as 100-, 300-, 600-, or 1800-mg twice-daily doses were assessed in healthy adult male and female volunteers. This study was a randomized, double-blind, placebo-controlled, group-sequential, dose-escalating design. Forty participants, 10 per dose level (8 receiving TETA, 2 receiving placebo), received twice-daily doses for 14 consecutive days. A 2-compartment model for the PK and a linear direct effect model for drug-induced copper excretion (PD) were employed. The population PK/PD model was applied using the NONMEM software. Covariates tested were glomerular filtration rate (GFR), body weight, and gender. Multiple daily doses of TETA were safe and generally well tolerated. The linear 2-compartment model with first-order absorption well characterized the serum concentration data. Although its role was small, GFR had a statistically significant (P < .05) influence on systemic clearance (CL/F). The augmentation of copper excretion was well described by a direct linear model in which the slope was related to GFR and gender (P < .001). The intersubject coefficient of variation was 22.2% for slope (SL) and 82.5% for intercept (ER0). TETA has consistent single/multiple-dose pharmacokinetics and dose-proportional and serum concentration-proportional effects on enhancing copper excretion.

Appetite and food intake results from phase I studies of anamorelin.

BACKGROUND: Loss of appetite and body weight are potentially devastating, highly prevalent cancer complications. The ghrelin receptor is a mediator of appetite and metabolism, and anamorelin is a novel, orally administered ghrelin receptor agonist. Effects on appetite and food intake may influence body-weight gain but can be difficult to measure in multi-site studies. Here, we summarize two single-centre trials. METHODS: Both trials were phase I, randomized, double-blind, placebo-controlled, partly/wholly crossover studies of healthy young adults. Study 102 tested single anamorelin doses of 1-20 mg. Assessments included post-dose self-ratings on 100 mm visual analogue scales for hunger, anticipated eating pleasure, and anticipated quantity of food consumption. Study 101 tested single 10, 25, and 50 mg doses. Assessments included the same scales plus caloric intake beginning 4 h post-dose. RESULTS: Study 102 treated 16 male subjects (mean age, 26.3 years). Mean hunger scores generally increased after all treatments, with significant differences from placebo (P < 0.05) in the 5 mg anamorelin group at 0.5 and 1 h post-dose (+8.2 and +13.2 mm). Results for other scales were similar. Study 101 treated nine male subjects (mean age, 26.3 years). Pooled findings for anamorelin 25 and 50 mg vs. placebo showed significant mean increases in hunger scores at all but 1 pre-prandial time point, including the first assessment, 0.5 h post-dose (+10.9 vs. +0.7 mm, P = 0.0077), and the last assessment, 4 h post-dose (+32.7 vs. +7.0 mm, P = 0.0170), with a significant mean 18.4% increase vs. placebo in caloric intake (P = 0.0148). CONCLUSIONS: In single-centre studies of healthy adults, single anamorelin doses of 1-20 mg elicited modest increases in hunger, and single doses of 25 and 50 mg achieved significant increases in hunger and caloric intake. The findings are consistent with dose-related weight gain reported in a prior phase I study as well as multi-centre findings in cachectic cancer patients and expand the evidence supporting anamorelin as a potential intervention.

An open-label clinical trial of the effects of age and gender on the pharmacodynamics, pharmacokinetics and safety of the ghrelin receptor agonist anamorelin.

PURPOSE: To assess the effect of age and gender on the pharmacokinetics (PK) of the ghrelin receptor agonist anamorelin. METHODS: Three demographic cohorts of healthy subjects were enrolled in this single-center, open-label study. Subjects received a single oral dose (25 mg) of anamorelin HCl. Serial blood samples were collected over 24 hours to assess anamorelin PK and circulating growth hormone (GH) levels. Data were compared with a reference cohort. RESULTS: Anamorelin was rapidly absorbed in all cohorts; peak concentrations were observed 30-45 minutes and 2-4 hours post-dose, which declined biexponentially with mean terminal half-lives of 6-7 hours. An age effect on Cmax and AUC∞ was not apparent; however, mean AUC∞ values were approximately 1.8-1.9-fold higher in the female cohorts than in the reference male cohort. GH increase was rapid and virtually identical in both sexes, though attenuated in elderly subjects. No clinically significant safety or tolerability findings were observed. CONCLUSIONS: While PK parameters do suggest higher exposure in females, this effect is considered to be modest given the variability of the 6-8 subjects per cohort. Moreover, no such effect was observed in the pharmacodynamic responses, thus, dose adjustment for age and gender is considered unnecessary.

Pharmacokinetic and pharmacodynamic interactions between diltiazem and methylprednisolone in healthy volunteers.

OBJECTIVES: The pharmacokinetics and pharmacodynamics after administration of methylprednisolone alone, diltiazem alone, and both drugs jointly were assessed in healthy volunteers. METHODS: An unblinded, controlled, fixed-sequence, 2-period study was carried out in 5 healthy white men who received a single dose of intravenous methylprednisolone, 0.3 mg/kg, on day 2, followed by diltiazem alone, 180 mg, on days 5, 6, and 7, with joint dosing of both drugs on day 8. Methylprednisolone and diltiazem disposition was assessed from plasma concentrations. Pharmacodynamic factors were assessed by plasma cortisol and T-helper and T-suppressor lymphocytes by means of extended indirect response models. RESULTS: The clearance of methylprednisolone was significantly reduced in the presence of diltiazem (25.2 L/h versus 16.8 L/h), resulting in a longer half-life (2.28 hours versus 3.12 hours) and increased area under the plasma concentration-time curve (AUC) (871 ng x h/mL versus 1299 ng x h/mL). The AUC of diltiazem was unchanged in the presence of methylprednisolone. No significant intrinsic pharmacodynamic differences were observed for methylprednisolone versus methylprednisolone-diltiazem. The 50% inhibitory concentration values were 0.446 ng/mL versus 0.780 ng/mL for cortisol, 9.20 ng/mL versus 10.7 ng/mL for T-helper cells, and 18.5 ng/mL versus 20.9 ng/mL for T-suppressor cells (P >.05). Greater net suppression, as indicated by the area between the effect curve and suppression ratios, was observed for the methylprednisolone-diltiazem combination versus methylprednisolone alone, which was attributed to reduced elimination of methylprednisolone. CONCLUSIONS: Controlled-delivery diltiazem, 180 mg, significantly increased methylprednisolone AUC and half-life and reduced clearance, lending to greater systemic exposure to the steroid. However, significant differences between 50% inhibitory concentration values for methylprednisolone when given alone and for methylprednisolone in combination with diltiazem were not seen, which implies no change in cortisol or cell-trafficking sensitivity in the presence of diltiazem.

Effects of aprepitant on cytochrome P450 3A4 activity using midazolam as a probe.

BACKGROUND: Aprepitant is a neurokinin(1) receptor antagonist that enhances prevention of chemotherapy-induced nausea and vomiting when added to conventional therapy with a corticosteroid and a 5-hydroxytryptamine(3) (5-HT(3)) antagonist. Because aprepitant may be used with a variety of chemotherapeutic agents and ancillary support drugs, which may be substrates of cytochrome P450 (CYP) 3A4, assessment of the potential of this drug to inhibit CYP3A4 activity in vivo is important. The effect of aprepitant on in vivo CYP3A4 activity in humans with oral midazolam used as a sensitive probe of CYP3A4 activity was evaluated in this study. METHODS: In this open-label, randomized, single-period study, 16 healthy male subjects were enrolled. Subjects received one of two oral aprepitant regimens for 5 days (8 subjects per regimen): (1) 125 mg aprepitant on day 1 and then 80 mg/d on days 2 to 5 or (2) 40 mg aprepitant on day 1 and then 25 mg/d on days 2 to 5. All subjects also received a single oral dose of midazolam, 2 mg, at prestudy (3 to 7 days before aprepitant treatment) and on days 1 and 5 (1 hour after aprepitant administration). RESULTS: Coadministration of midazolam and 125/80 mg aprepitant increased the midazolam area under the plasma concentration-time curve by 2.3-fold on day 1 (P <.01) and by 3.3-fold on day 5 (P <.01), as compared with midazolam alone (prestudy). The 125/80-mg regimen of aprepitant also increased the midazolam maximum observed concentration by 1.5-fold on day 1 (P <.05) and by 1.9-fold on day 5 (P <.01). The midazolam half-life values increased from 1.7 hours (prestudy) to 3.3 hours on both day 1 and day 5. Coadministration of 40/25 mg aprepitant and midazolam did not result in significant changes in the midazolam area under the plasma concentration-time curve, maximum observed concentration, and half-life at either day 1 or day 5. CONCLUSIONS: The 5-day 125/80-mg regimen of aprepitant produced moderate inhibition of CYP3A4 activity in humans, as measured with the use of midazolam as a probe drug.

Effects of the neurokinin1 receptor antagonist aprepitant on the pharmacokinetics of dexamethasone and methylprednisolone.

BACKGROUND: Aprepitant is a neurokinin(1) receptor antagonist that, in combination with a corticosteroid and a 5-hydroxytryptamine(3) receptor antagonist, has been shown to be very effective in the prevention of chemotherapy-induced nausea and vomiting. At doses used for the management of chemotherapy-induced nausea and vomiting, aprepitant is a moderate inhibitor of cytochrome P4503A4 and may be used in conjunction with corticosteroids such as dexamethasone and methylprednisolone, which are substrates of cytochrome P4503A4. The effects of aprepitant on the these 2 corticosteroids were evaluated. METHODS: Study 1 was an open-label, randomized, incomplete-block, 3-period crossover study with 20 subjects. Treatment A consisted of a standard oral dexamethasone regimen for chemotherapy-induced nausea and vomiting (20 mg dexamethasone on day 1, 8 mg dexamethasone on days 2 to 5). Treatment B was used to examine the effects of oral aprepitant (125 mg aprepitant on day 1, 80 mg aprepitant on days 2 to 5) on the standard dexamethasone regimen. Treatment C was used to examine the effects of aprepitant on a modified dexamethasone regimen (12 mg dexamethasone on day 1, 4 mg dexamethasone on days 2 to 5). All subjects also received 32 mg ondansetron intravenously on day 1 only. Study 2 was a double-blind, randomized, placebo-controlled, 2-period crossover study with 10 subjects. Subjects in one group received a regimen consisting of 125 mg methylprednisolone intravenously on day 1 and 40 mg methylprednisolone orally on days 2 to 3. Subjects in the other group received oral aprepitant (125 mg aprepitant on day 1, 80 mg aprepitant on days 2 to 3) in addition to the methylprednisolone regimen. RESULTS: In study 1, the area under the concentration-time curve from 0 to 24 hours (AUC(0-24)) of oral dexamethasone on days 1 and 5 after the standard dexamethasone plus ondansetron regimen (treatment A) was increased 2.2-fold (P <.010) with coadministration of aprepitant (treatment B). Coadministration of aprepitant with the modified dexamethasone plus ondansetron regimen (treatment C) resulted in an AUC0-24 for dexamethasone similar to that observed after the standard dexamethasone plus ondansetron regimen (treatment A). In study 2, aprepitant increased the AUC0-24 of intravenous methylprednisolone 1.3-fold on day 1 (P <.010) and increased the AUC0-24 of oral methylprednisolone 2.5-fold on day 3 (P <.010). CONCLUSIONS: Coadministration of aprepitant with dexamethasone or methylprednisolone resulted in increased plasma concentrations of the corticosteroids. These findings suggest that the dose of these corticosteroids should be adjusted when given with aprepitant.

Pharmacokinetics and pharmacodynamics of a novel nizatidine controlled-release formulation in healthy subjects.

The pharmacokinetics and intragastric pH effects of a novel nizatidine controlled-release (CR) formulation were compared to a currently marketed immediate-release (IR) nizatidine formulation (Axid). The bimodal pulsatile release characteristics of nizatidine CR decreased its Cmax by approximately 42% compared to nizatidine IR while maintaining 90% relative bioavailability; tmax was approximately 1.6 times longer with the CR formulation. These characteristics enabled controlled-release nizatidine to sustain effective plasma drug concentrations for a greater duration than immediate-release nizatidine over the dosing intervals. In multiple doses, the 24-hour AUC ratio for all comparisons of nizatidine CR 150 mg bid, nizatidine CR 300 mg daily, and nizatidine IR 150 mg bid was between 97% and 99%. Mean pH AUC values for nizatidine CR 150 mg bid and nizatidine IR 150 mg bid were similar overall during the 0- to 14-hour and 14- to 24-hour dosing intervals. For the 14- to 24-hour dosing interval, nizatidine CR 150 mg maintained gastric pH over 3.0 and 4.0 for 42% and 27% of the time compared to 39% and 23% for nizatidine IR, respectively. Nizatidine CR 300 mg, compared to the 150-mg CR and IR regimens, had a greater effect on increasing evening intragastric pH, thus providing support for the potential utility of nizatidine CR 300 mg dosed at night in alleviating nocturnal symptoms of gastroesophageal reflux disease.

Pharmacokinetics and safety of a single oral dose of once-daily alfuzosin, 10 mg, in male subjects with mild to severe renal impairment.

The effect of renal impairment on the safety and pharmacokinetics of a once-daily formulation of alfuzosin, 10 mg, was evaluated. In an open, single-dose study, 26 volunteers, ages 18 to 65 years, were classified as having normal renal function (n = 8) or mild (n = 6), moderate (n = 6), or severe (n = 6) renal impairment. Mean Cmax values increased by a factor of 1.20, 1.52, and 1.20 in subjects with mild, moderate, or severe renal impairment, respectively, compared with controls. Values for AUC(0-infinity) were 1.46, 1.47, and 1.44, respectively. The t(1/2z) was increased only in the group with severe renal impairment. Emergent vasodilatory adverse events were reported by 4 of 26 subjects. No discontinuations due to adverse events occurred. Laboratory parameters were satisfactory in all groups. In conclusion, once-daily alfuzosin, 10 mg, could be safely administered to patients with impaired renal function, and dosage adjustment does not seem necessary.

Dose equivalency evaluation of major corticosteroids: pharmacokinetics and cell trafficking and cortisol dynamics.

The integrity of current corticosteroid dose equivalency tables, as assessed by mechanistic models for cell trafficking and cortisol dynamics, was investigated in this study. Single, presumably equivalent, doses of intravenous hydrocortisone, methylprednisolone, dexamethasone, and oral prednisolone were given to 5 white men, according to total body weight, in a 5-way crossover, placebo-controlled study. Pharmacodynamic (PD) response-time profiles for T helper cells, T suppressor cells, neutrophils, and adrenal suppression were evaluated by extended indirect response models. For adrenal suppression, prednisolone appears to be less potent than methylprednisolone or dexamethasone. A good correlation was found between the estimated in vivo EC50 values and relative receptor affinity (equilibrium dissociation constants normalized to dexamethasone). Area under the effect curves of all PD responses was calculated using a linear-trapezoidal method. Although T helper cell trafficking and adrenal suppression achieved significant differences by repeated-measures ANOVA (p = 0.014 and 0.022), post hoc analysis using the Bonferroni method revealed no difference between treatments. Although limited by the use of single doses and a relatively small sample size, this study applies mechanistic models for several biomarkers showing that currently used dosing tables reflect reasonable dose equivalency relationships for four corticosteroids.

Evaluation of methods for improving precision of blood pressure measurements in phase I clinical trials.

Small sample sizes are typically incorporated in early Phase I clinical studies, which may lead to insignificant changes in safety parameters such as blood pressure. Therefore, it is paramount to identify an optimal, noninvasive method of accurately measuring blood pressure and an appropriate analysis strategy yielding the smallest variability. The goals of this study were (1) to compare the variability between automated and manual blood pressure measurements, (2) to determine whether triplicate blood pressure measurements were independent of one another, and (3) to assess how the number of blood pressure readings affects variability and study sample size. Twenty healthy volunteers were enrolled in this randomized, two-way crossover study. Each subject received three incremental infusions of phenylephrine or normal saline on separate days to simulate blood pressure variability. The mean systolic blood pressure readings with the automated device were consistently higher than the manual device by 3 to 5 mmHg. Conversely, the mean diastolic blood pressure readings with the automated device were consistently 3 to 5 mmHg lower than the manual device. However, the variability and absolute change in blood pressure were essentially identical with manual and automated methods. No systematic order effects such as the first blood pressure reading always being higher were detected, suggesting that the triplicate readings were independent of one another and that an interval of 2 minutes between readings is adequate. Compared to a single measurement, collecting blood pressure in triplicate results in a 40% lower sample size needed to detect a 5-mmHg difference in systolic blood pressure.

Evaluation of potential inductive effects of aprepitant on cytochrome P450 3A4 and 2C9 activity.

The NK(1) receptor antagonist aprepitant (EMEND(R)), developed for use in combination with a 5HT(3) receptor antagonist and a corticosteroid to prevent highly emetogenic chemotherapy-induced nausea and vomiting (CINV), has been shown to have a moderate inhibitory effect as well as a possible inductive effect on cytochrome P450 (CYP) 3A4. Aprepitant has been noted to produce modest decreases in plasma S(-)-warfarin concentrations, suggesting potential induction of CYP2C9. Because metabolism of some chemotherapeutic agents may involve CYP3A4, the potential inductive effect of the CINV dosing regimen of aprepitant on this metabolic pathway was evaluated using intravenous midazolam, a sensitive probe substrate of CYP3A4. The time course of induction of CYP2C9 by aprepitant was also evaluated using oral tolbutamide, a probe substrate of CYP2C9. In this double-blind, randomized, placebo-controlled, single-center study, 24 healthy subjects were randomized (12 subjects per group) to receive either an aprepitant 3-day regimen (aprepitant 125 mg p.o. on day 1 and aprepitant 80 mg p.o. on days 2 and 3) or matching placebo. All subjects also received probe drugs (midazolam 2 mg i.v. and tolbutamide 500 mg p.o.) once prior to aprepitant dosing (baseline) and again on days 4, 8, and 15. The ratio (aprepitant/placebo) of the geometric mean area under the plasma concentration curve (AUC) fold-change from baseline for midazolam was 1.25 on day 4 (p < 0.01), 0.81 on day 8 (p < 0.01), and 0.96 on day 15 (p = 0.646). The ratio (aprepitant/placebo) of the geometric mean AUC fold-change from baseline for tolbutamide was 0.77 on day 4 (p < 0.01), 0.72 on day 8 (p < 0.001), and 0.85 on day 15 (p = 0.05). Assessed using intravenous midazolam as a probe, aprepitant 125/80 mg p.o. administered over days 1 to 3 produced clinically insignificant weak inhibition (day 4) and induction (day 8) of CYP3A4 activity and no effect on CYP3A4 activity on day 15. Assessed using oral tolbutamide as a probe, the aprepitant regimen also produced modest induction of CYP2C9 activity on days 4 and 8, which resolved nearly to baseline by day 15. Thus, the aprepitant regimen for CINV results in modest, transient induction of CYPs 3A4 and 2C9 in the 2 weeks following administration.

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.

Influence of a variable overall diameter hydrophilic acrylic sharp-edged single-piece intra-ocular lens on capsule opacification one year after surgery.

BACKGROUND: To investigate the influence of the overall intraocular lens (IOL) diameter on posterior capsule opacification (PCO) formation. METHODS: In this prospective randomized clinical trial, 124 eyes of 62 patients with bilateral age-related cataract were included. Each patient received a Corneal A501D IOL in one eye and a Corneal J501D IOL in the fellow eye. Best corrected visual acuity (BCVA) and digital slitlamp photographs were taken a 1 h, 1 week, 1, 3, 6 and 12 months postoperatively. The amount of PCO was assessed subjectively at the slitlamp and objectively using automated image-analysis software. RESULTS: We found a mean BCVA of 0.81 ± 0.2 for the Corneal A501D group and 0.79 ± 0.21 for the Corneal J501D group. There was no significant difference 12 months after surgery between the two IOLs (p > 0.05). Objective PCO assessment resulted in a mean PCO score (scale 0-10) of 1.65 ± 1.71 was found for the Corneal J501D group and a score of 1.54 ± 1.64 was found for the Corneal A501D group (p > 0.05). The subjective PCO assessment at 1 year resulted in a mean PCO score of 2.0 ± 1.74 in the Corneal J501D group and 2.13 ± 1.64 in the Corneal A501D group (p > 0.05). CONCLUSION: Both investigated IOLs showed good clinical performance regarding PCO and BCVA. Our study suggests that the use of an IOL with variable total diameter seems not to influence the rate of PCO formation.

Pharmacokinetic drug interactions between clobazam and drugs metabolized by cytochrome P450 isoenzymes.

STUDY OBJECTIVE: To investigate potential drug-drug interactions between clobazam and cytochrome P450 (CYP) isoenzyme substrates, inhibitors, and inducers. DESIGN: Two, prospective, open-label, single-center, drug-drug interaction (DDI) studies and a population pharmacokinetics analysis of seven multicenter phase II-III trials. SETTING: Clinical research unit. PARTICIPANTS: Fifty-four healthy adult volunteers were enrolled in the two drug-drug interaction studies; 53 completed the studies. The population pharmacokinetics analysis evaluated data from 171 participants from five studies with healthy volunteers and two studies with patients with Lennox-Gastaut syndrome. Participants in these studies received clobazam and stable dosages of the following antiepileptic drugs: phenobarbital, phenytoin, carbamazepine, valproic acid, lamotrigine, felbamate, or oxcarbazepine. INTERVENTION: In the first drug-drug interaction study, 36 participants received a single oral dose of clobazam 10 mg on day 1, followed by either ketoconazole 400 mg once/day or omeprazole 40 mg once/day on days 17-22, with a single dose of clobazam 10 mg coadministered on day 22, to study the effects of CYP3A4 or CYP2C19 inhibition, respectively, on clobazam and its active metabolite N-desmethylclobazam (N-CLB). In the second study, 18 participants received a drug cocktail consisting of caffeine 200 mg, tolbutamide 500 mg, dextromethorphan 30 mg, and midazolam 4 mg on days 1 and 19, and clobazam 40 mg/day on days 4-19, to study clobazam's effects on CYP1A2, CYP2C9, CYP2D6, and CYP3A4. MEASUREMENTS AND MAIN RESULTS: In the first DDI study, coadministration of ketoconazole (a CYP3A4 inhibitor) and clobazam increased clobazam's area under the concentration time curve from time zero extrapolated to infinity (AUC(0-∞) ) 54% and decreased clobazam's maximum plasma concentration (C(max) ) by 15% versus administration of clobazam alone, but the combination affected these pharmacokinetic parameters for N-CLB to a lesser degree. The CYP2C19 inhibitor omeprazole increased AUC(0-∞) and C(max) of N-CLB by 36% and 15%, respectively, but did not significantly affect the pharmacokinetics of clobazam. At steady state, N-CLB has 3-4 times greater exposure than clobazam. In the second DDI study, no clinically significant drug-drug interactions were observed between clobazam 40 mg and the CYP probe substrates caffeine or tolbutamide. Exposure to midazolam and its 1-hydroxymidazolam metabolite, however, decreased by 27% and increased 4-fold, respectively. Clobazam increased dextromethorphan (CYP2D6) AUC(0-∞) by 95% and C(max) by 59%. In the population pharmacokinetics analysis, stable dosages of common antiepileptic drugs that induce CYP3A4 or CYP2C19, or inhibit CYP2C19, had negligible effects on clobazam or N-CLB. Clobazam did not affect valproic acid or lamotrigine exposures. CONCLUSION: These findings suggest no clinically meaningful drug-drug interactions between clobazam and drugs metabolized by CYP3A4, CYP2C19, CYP1A2, or CYP2C9. Concomitant use of drugs metabolized by CYP2D6 may require dosage adjustment. Clobazam may be administered safely as adjunctive therapy in patients with Lennox-Gastaut syndrome, without meaningful changes in clobazam pharmacokinetics that would require dosage adjustment.

A Single-Dose Bioequivalence and Food Effect Study With Aprepitant and Fosaprepitant Dimeglumine in Healthy Young Adult Subjects.

Fosaprepitant dimeglumine, a lyophilized prodrug, is rapidly converted to aprepitant, a substance P/neurokinin 1 (NK1 ) receptor antagonist. Intravenous (IV) fosaprepitant and oral aprepitant are used in combination with other antiemetics to prevent chemotherapy-induced nausea and vomiting. This randomized, phase 1 study was designed to assess the aprepitant area under the curve (AUC0-∞ ) equivalence of a single, oral 165-mg or 185-mg dose of aprepitant to a single 150-mg fosaprepitant IV dose infused over 20 minutes, and to evaluate the effect of food on the bioavailability of the oral 165-mg and 185-mg aprepitant doses. Plasma samples were analyzed for aprepitant, and linear mixed-effects models were applied to natural log-transformed aprepitant AUC data. A 2 one-sided tests procedure was used to evaluate bioequivalence; the adjusted P values for the AUC0-∞ of both oral doses versus the IV dose were < .05, supporting the hypothesis that each single, oral dose of aprepitant is equivalent to the AUC0-∞ of a single IV infusion of fosaprepitant. Food effect results suggest that dose adjustment would not be necessary with a single oral dose of aprepitant. Single-dose administration of oral 165 mg and 185 mg aprepitant and IV 150 mg fosaprepitant was generally well tolerated.

Relative Bioavailability of an Emulsion Formulation for Omega-3-Acid Ethyl Esters Compared to the Commercially Available Formulation: A Randomized, Parallel-Group, Single-Dose Study Followed by Repeat Dosing in Healthy Volunteers.

LOVAZA (omega-3-acid ethyl esters; eicosapentaenoic acid [EPA]/docosahexaenoic acid [DHA]), with diet, lowers very high triglycerides (≥500 mg/dL) in adults. This study evaluated whether an emulsion formulation (LEM) increases the bioavailability of EPA/DHA compared to the reference formulation (RF) in healthy volunteers. Following relative bioavailability assessment, LEM, RF, and placebo were dosed for 2 weeks. Exposure measurements included plasma-free and total fatty acid (EPA/DHA) concentrations and phospholipid and red blood cell (RBC) incorporation. Following single doses, the dose-normalized EPA plasma-corrected AUCs were 14-fold (total) and 12-fold (free) higher and DHA plasma-corrected AUCs were 10-fold (total) and 13-fold (free) higher for LEM compared to RF. EPA and DHA incorporation into phospholipids increased for all active treatments; the increase was dose dependent for EPA. An 8-fold increase over baseline was observed in EPA incorporation for LEM (4-capsule dose) compared to a 4-fold increase for RF 4 g. DHA incorporation increased to a lesser degree, and RBC incorporation also increased. Pharmacodynamic evaluations revealed slight decreases (-8% to -25%) in the mean fasting triglyceride concentrations in all groups, including placebo, compared to baseline. Following a high-fat meal, no consistent treatment-related effect on the triglyceride profiles was observed. Study treatments were safe and tolerated. In conclusion, LEM improves the oral bioavailability of EPA and DHA.

Effect of casopitant, a novel NK-1 receptor antagonist, on the pharmacokinetics and pharmacodynamics of steady-state warfarin.

Casopitant, a novel NK-1 receptor antagonist under investigation for the prevention of postoperative and chemotherapy-induced nausea and vomiting, is a weak to moderate inhibitor of CYP3A and a moderate inducer of CYP2C9 in vitro. Furthermore, both CYP enzymes are involved in the metabolism of R- and S-warfarin, respectively. This clinical study was conducted to explore the potential drug-drug interaction between casopitant and warfarin. In total, 97 healthy participants were enrolled and 54 completed the study. Participants received individualized daily dosing of warfarin to an international normalized ratio (INR) of 1.3 to 2.3 over a 14-day period (period 1). Immediately following period 1, participants entered period 2 and were randomized to receive either regimen A (oral casopitant [150 mg day 1, 50 mg days 2 and 3] and warfarin [days 1-10]) or regimen B (oral casopitant 60 mg and warfarin [days 1-14]). INR assessments were performed daily. The steady-state C(max) and AUC of R- and S-warfarin were not altered by regimen A, but R-warfarin AUC was increased 1.31-fold (90% confidence interval [CI]: 1.22, 1.41), and S-warfarin AUC was increased 1.27-fold (90% CI: 1.18, 1.38) on day 14 in regimen B. Steady-state INR values were not affected by either casopitant regimen.

Ketoconazole and rifampin significantly affect the pharmacokinetics, but not the safety or QTc interval, of casopitant, a neurokinin-1 receptor antagonist.

Casopitant, an antiemetic, is a neurokinin-1 receptor antagonist metabolized primarily by cytochrome P450 3A4 (CYP3A4). Three phase 1 studies with 131 healthy subjects examined the impact of a strong CYP3A inhibitor (ketoconazole) and inducer (rifampin) on the pharmacokinetics and safety of casopitant. Oral casopitant was administered alone (study 1, 100-mg single dose; study 2, 150 mg on day 1, 50 mg on days 2 and 3; study 3, 150-mg single dose) with either 400 mg daily of oral ketoconazole or 600 mg daily of oral rifampin. Ketoconazole increased the maximum observed plasma concentration (C(max)) and area under the plasma concentration time curve to the last sampling time, t (AUC(0-t)) of single-dose casopitant 2.7-fold and 12-fold and increased the C(max) of 3-day casopitant 2.5-fold on day 1 and 2.9-fold on day 3, whereas AUC((0-tau)) increased 4.3-fold on day 1 and 5.8-fold on day 3. Neither safety signals nor prolongation of Fredericia-corrected QT was observed at these increased exposures in study 2. Repeat-dose rifampin reduced the C(max) and AUC((0-t)) of casopitant 96% and 90%, respectively. These clinical studies confirmed the role of CYP3A in the metabolism and disposition of casopitant. Coadministration of casopitant with strong inhibitors of CYP3A is likely to increase plasma exposure of casopitant, whereas coadministration with strong inducers of CYP3A is likely to decrease casopitant exposure and compromise efficacy.