A pharmacokinetic/pharmacodynamic investigation: assessment of edivoxetine and atomoxetine on systemic and central 3,4-dihydroxyphenylglycol, a biochemical marker for norepinephrine transporter inhibition.

Inhibition of norepinephrine (NE) reuptake into noradrenergic nerves is a common therapeutic target in the central nervous system (CNS). In noradrenergic nerves, NE is oxidized by monoamine oxidase to 3,4-dihydroxyphenylglycol (DHPG). In this study, 40 healthy male subjects received the NE transporter (NET) inhibitor edivoxetine (EDX) or atomoxetine (ATX), or placebo. The pharmacokinetic and pharmacodynamic profile of these drugs in plasma and cerebrospinal fluid (CSF) was assessed. In Part A, subjects received EDX once daily (QD) for 14 or 15 days at targeted doses of 6mg or 9mg. In Part B, subjects received 80mg ATX QD for 14 or 15 days. Each subject received a lumbar puncture before receiving drug and after 14 or 15 days of dosing. Plasma and urine were collected at baseline and after 14 days of dosing. Edivoxetine plasma and CSF concentrations increased dose dependently. The time to maximum plasma concentration of EDX was 2h, and the half-life was 9h. At the highest EDX dose of 9mg, DHPG concentrations were reduced from baseline by 51% at 8h postdose in CSF, and steady-state plasma and urine DHPG concentrations decreased by 38% and 26%, respectively. For 80mg ATX, the decrease of plasma, CSF, or urine DHPG was similar to EDX. Herein we provide clinical evidence that EDX and ATX decrease DHPG concentrations in the periphery and CNS, presumably via NET inhibition. EDX and ATX concentrations measured in the CSF confirmed the availability of those drugs in the CNS.

[Assessment of afobazole effects on diazepam withdrawal-induced anxiety in rats].

Long-term administration of benzodiazepines is known to be associated with drug dependence. The aim of the present work was to investigate the effects of non-benzodiazepine anxiolytic afobazole in the treatment of benzodiazepine withdrawal syndrome. Male outbred rats were treated with either diazepam (4.0 mg/kg, i.p.) or vehicle for 30 days and then abruptly withdrawn for 48 h. Animals were tested in the elevated plus maze test. In addition, neurochemical shifts were evaluated in the selected brain structures (striatum, hippocampus, hypothalamus, and frontal cortex) during diazepam withdrawal. Withdrawn animals made fewer entries and spent less time on the open arms than did vehicle-treated rats and demonstrated a decrease in the dopamine level in striatum as compared with vehicle and diazepam-treated ones. Afobazole (5.0 mg/kg, i.p.) effectively (i) ameliorated withdrawal-induced anxiety, returning behavioral pattern in the elevated plus maze test up to levels comparable to that in vehicle-treated animals, and (ii) increased withdrawal-reduced dopamine level (+23.8%, p < 0.05) in striatum. It is suggested that afobazole, due to its multitarget receptor action, can be useful in the diazepam withdrawal-induced anxiety blockade through modulation of dopaminergic system activity.

A clinical and pharmacologic assessment of once-daily versus twice-daily dosing for rivaroxaban.

Altering doses and regimens of a drug has consequences for the drug's pharmacokinetic and pharmacodynamic profile. Based on a half-life of 5-13 h, it is expected that the Factor Xa inhibitor rivaroxaban would be best suited to a twice-daily rather than a once-daily dose regimen. However, although rivaroxaban is used as a twice-daily regimen for the initial treatment of venous thromboembolism (VTE) and secondary prevention after acute coronary syndromes, the approved dosing is once-daily for prevention of VTE after orthopaedic surgery, long-term secondary prevention of VTE and stroke prevention in patients with non-valvular atrial fibrillation. Rivaroxaban dosing was based on the evaluation of the efficacy and safety of several rivaroxaban doses and regimens in phase II trials. A clear overall advantage of twice-daily dosing compared with once-daily dosing was not documented for indications for which once-daily dosing was subsequently selected. Once-daily dosing was therefore selected for these indications because it is expected to be associated with better compliance than twice-daily dosing, and potentially, with improved outcomes. These studies and data obtained with another Factor Xa inhibitor, edoxaban, in addition to previous experience with low molecular weight heparins, indicate that the clinical impact of once-daily versus twice-daily doses on outcome in terms of efficacy and safety cannot be reliably predicted from pharmacology data, e.g. elimination half-life, obtained during pre-clinical and early phase I clinical studies but rather should be ascertained empirically in phase II and III clinical trials.

Qualitative GC-MS assessment of TCP and TAMORF elimination in rats.

Nerve agents are highly toxic organophosphorus (OP) compounds. They inhibit acetylcholinesterase (AChE), an enzyme that hydrolyses acetycholine (ACh) in the nervous system. Pathophysiological changes caused by OP poisonings are primarily the consequence of surplus ACh on cholinergic receptors and in the central nervous system. Standard treatment of OP poisoning includes combined administration of carbamates, atropine, oximes and anticonvulsants. In order to improve therapy, new compounds have been synthesised and tested. Tenocyclidine (TCP) and its adamantane derivative 1-[2-(2-thienyl)-2-adamantyl] morpholine (TAMORF) have shown interesting properties against soman poisoning. In this study, we developed a qualitative GC-MS method to measure elimination of TCP and TAMORF through rat urine in order to learn more about the mechanisms through which TCP protects an organism from OP poisoning and to determine the duration of this protective effect. GC-MS showed that six hours after treatment with TCP, rat urine contained only its metabolite 1-thienylcyclohexene, while urine of rats treated with TAMORF contained both TAMORF and its metabolites.

Human percutaneous absorption of a direct hair dye comparing in vitro and in vivo results: implications for safety assessment and animal testing.

Although in vitro skin absorption studies often detect small residues of applied test material in the epidermis/dermis, it is uncertain whether the residue is within the living skin. We studied the dermal absorption of a hair dye hydroxyanthraquinone-aminopropyl methyl morpholinium methosulphate (HAM) in human skin in vivo and in vitro. In vivo, skin (back and scalp) received 0.5% HAM in a commercial formulation at 20microg/cm2 After 0.5 or 48h, skin was tape stripped, followed by cyanoacrylate biopsies (CAB). Sebum from scalp sites was collected for 48h. In vitro, skin was treated with 20mg/cm2 dye for 0.5h, penetration determined after 24h. In vivo, at 0.5h, total recovery (back) was 0.67microg/cm2 (tape strips+CAB). Fluorescence microscopy showed HAM in the hair follicle openings (HFO). At 0.5h, scalp tape strips contained 1.80microg/cm2, HFO 0.82microg/cm2. At 48h, HFO contained 0.21microg/cm2, sebum 0.80microg/cm2. In vivo, skin residues were in the non-living skin and eliminated via desquamation and sebum secretion. In vitro, the SC contained 1.50microg/cm2, epidermis/dermis 0.86microg/cm2, receptor fluid<0.04microg/cm2, a total of 0.90microg/cm2 was considered to be bioavailable. In vitro epidermis/dermis residues were nearly identical to those located in non-living skin in vivo. In conclusion, in vitro percutaneous penetration studies may produce seemingly bioavailable material , which raises the need for a Threshold of Skin Absorption (TSA) addressing a negligible dermal absorption in order to avoid unnecessary in vivo toxicity studies on substances that produce no significant human systemic exposure.

A combined approach to drug metabolism and toxicity assessment.

The challenge of predicting the metabolism or toxicity of a drug in humans has been approached using in vivo animal models, in vitro systems, high throughput genomics and proteomics methods, and, more recently, computational approaches. Understanding the complexity of biological systems requires a broader perspective rather than focusing on just one method in isolation for prediction. Multiple methods may therefore be necessary and combined for a more accurate prediction. In the field of drug metabolism and toxicology, we have seen the growth, in recent years, of computational quantitative structure-activity relationships (QSARs), as well as empirical data from microarrays. In the current study we have further developed a novel computational approach, MetaDrug, that 1) predicts metabolites for molecules based on their chemical structure, 2) predicts the activity of the original compound and its metabolites with various absorption, distribution, metabolism, excretion, and toxicity models, 3) incorporates the predictions with human cell signaling and metabolic pathways and networks, and 4) integrates networks and metabolites, with relevant toxicogenomic or other high throughput data. We have demonstrated the utility of such an approach using recently published data from in vitro metabolism and microarray studies for aprepitant, 2(S)-((3,5-bis(trifluoromethyl)benzyl)-oxy)-3(S)phenyl-4-((3-oxo-1,2,4-triazol-5-yl)methyl)morpholine (L-742694), trovofloxacin, 4-hydroxytamoxifen, and artemisinin and other artemisinin analogs to show the predicted interactions with cytochromes P450, pregnane X receptor, and P-glycoprotein, and the metabolites and the networks of genes that are affected. As a comparison, we used a second computational approach, MetaCore, to generate statistically significant gene networks with the available expression data. These case studies demonstrate the combination of QSARs and systems biology methods.

Pharmacokinetics and pharmacodynamics of landiolol hydrochloride, an ultra short-acting beta1-selective blocker, in a dose escalation regimen in healthy male volunteers.

OBJECTIVES: We conducted a randomized, double-blind, placebo-controlled study to evaluate the pharmacokinetics and pharmacodynamics of landiolol hydrochloride in a dose escalation regimen in healthy male volunteers. METHODS: We set two-dose escalation regimen (LM and MH groups) using three different doses [L (low): 0.03 mg/kg/min (1 min) loading-->0.01 mg/kg/min (10 min) continuous, M (medium): 0.06 mg/kg/min (1 min) loading-->0.02 mg/kg/min (10 min) continuous, H (high): 0.125 mg/kg/min (1 min) loading-->0.04 mg/kg/min (10 min) continuous]. Sixteen subjects were allocated randomly to the LM, MH, and placebo groups (n=6, 6, and 4, respectively). RESULTS: In both the LM and MH groups, the blood concentration of landiolol hydrochloride changed within a constant range from 2 minutes after initiation of administration to just before the higher dose escalation. By 2 minutes following the higher dose escalation, the concentration of landiolol hydrochloride reached C(max), and reached almost steady state levels until 6 minutes following administration of the higher dose. The t(1/2) of landiolol hydrochloride was 3.5 minutes. The heart rates and blood pressures of subjects administered landiolol hydrochloride decreased, but there were no adverse events in any subject. CONCLUSIONS: The concentration of landiolol hydrochloride rapidly reached steady state levels, and rapidly dissipated after completion of administration.

Aprepitant: a novel antiemetic for chemotherapy-induced nausea and vomiting.

OBJECTIVE: To evaluate the safety and efficacy of aprepitant in the prevention of acute and delayed chemotherapy-induced nausea and vomiting (CINV). DATA SOURCES: MEDLINE and PubMed database searches were conducted from 1966 to May 2004 using the following search terms: aprepitant, Emend, substance P, neurokinin-1, chemotherapy, nausea, vomiting, L-754,030, and MK-869. STUDY SELECTION AND DATA EXTRACTION: Large, randomized Phase II and III clinical trials examining the use of aprepitant for CINV, as well as all published drug interaction studies with aprepitant, were included and reviewed. Data lacking in published trials were supplemented with the manufacturer product information. DATA SYNTHESIS: The pharmacokinetics of aprepitant are favorable for once-daily oral dosing. Based on the results of published clinical trials, aprepitant appears to augment the effects of corticosteroids and 5-HT3 antagonists when given prior to highly emetogenic chemotherapy, including cisplatin. Aprepitant appears to have the most benefit in the prevention of delayed CINV and in preventing emesis rather than nausea. Data in pediatric patients, patients undergoing stem-cell transplantation, and those receiving multiple-day or moderately emetogenic chemotherapy are lacking. Common adverse effects are limited to hiccups, asthenia, and diarrhea. More serious but rare adverse effects include neutropenia. Because aprepitant is a CYP3A4 substrate, a 3A4 inhibitor and inducer, and a 2C9 inducer, close monitoring for drug interactions is warranted. CONCLUSIONS: Triple antiemetic therapy with aprepitant, a corticosteroid, and a 5-HT3 antagonist appears to provide improved efficacy in the prevention of emesis in patients receiving highly emetogenic chemotherapy. Due to its novel mechanism of action and demonstrated efficacy in this combination, aprepitant should be considered for formulary addition.

Peroral sustained-release film-coated pellets as a means to overcome physicochemical and biological drug-related problems. II. Bioavailability and tolerance assessment in dogs.

Sustained-release (SR) dosage forms consisting of pellets coated with different pH-sensitive film layers, previously optimized in vitro with regard to pH independence of their drug release characteristics, were evaluated in vivo after single administration to Beagle dogs. In vivo performances were compared to those of a nonoptimized SR matrix tablet and a reference instant release (IR) capsule, in terms of the observed plasma pharmacokinetic profiles for the parent drug (ucb 11056) and its primary metabolite (ucb 26201), the bioavailability results, and the drug tolerance data. All SR dosage forms were seen to be effective in prolonging the relatively short biological half-life of the compound and in reducing the incidence of concentration-related side-effects, e.g., emesis, and of behavioral symptoms, e.g., restlessness, discomfort, and indisposition. The film-coated SR pellets offer a number of advantages over the monolithic SR matrix system in terms of a drug delivery pattern less dependent on pH changes in the gastrointestinal (GI) tract, a higher flexibility for adjusting and controlling the pharmacokinetic profiles, and a consequently more efficient approach for keeping all concentration-related side-effects under control.