EP42675, a synthetic parenteral dual-action anticoagulant: pharmacokinetics, pharmacodynamics, and absence of interactions with antiplatelet drugs

BACKGROUND

EP42675 is a first-in-class, synthetic, parenteral, anticoagulant combining in a single molecule a direct thrombin inhibitor and an indirect factor Xa(FXa) inhibitor.

OBJECTIVES

To investigate the safety, pharmacokinetics, and pharmacodynamics of EP42675 and its interaction with aspirin, clopidogrel, and unfractionated heparin (UFH).

SUBJECTS AND METHODS

In study 1, healthy male subjects were administered intravenously single-ascending doses (1-10 mg) of EP42675 or placebo. In study 2, healthy male subjects were administered intravenously a single dose of 5 mg EP42675 on day 1 followed by oral administration of aspirin (100 mg) and clopidogrel (75 mg) once daily from day 8 to 21. On day 15, a second dose of 5 mg EP42675 was administered, and subjects were then randomized to receive a single dose of UFH (30 or 60 IU kg(-1) ) or placebo.

RESULTS AND CONCLUSIONS

Mild bleedings were the only drug-related adverse events. EP42675 pharmacokinetics were dose-proportional and characterized by a low clearance, a small volume of distribution, a long terminal half-life. EP42675 pharmacodynamics were characterized by a long-lasting, dose-dependent increase in activated clotting time, ecarin clotting time, thrombin time, anti-FXa activity, activated partial thromboplastin time, prothrombin time, and a decrease in endogenous thrombin potential, measured by a thrombin generation test. Dose-dependent additive effects were seen with UFH on coagulation tests. EP42675 had no additive effect on the inhibition of platelet aggregation induced by aspirin and clopidogrel. These results warrant further clinical development of this new class of anticoagulant.

Population pharmacokinetics (PPK) of eribulin mesylate in patients with locally advanced or metastatic breast cancer (MBC)

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Background: Eribulin mesylate (E7389) is a non-taxane microtubule dynamics inhibitor with a novel mechanism of action. A study was conducted to evaluate efficacy, safety and pharmacokinetics of eribulin at a dose of 1.4 mg/m2 for locally advanced or MBC in patients previously treated with an anthracycline, a taxane, and capecitabine. Methods: Eribulin was administered intravenously over 2–5 minutes at a dose of 1.4 mg/m2 on days 1 and 8 of a 21- day cycle to 291 patients. Four plasma samples were collected between 5 min and 120 hours after the first dose. Plasma eribulin concentrations were determined by LC/MS/MS. A total of 774 samples, from 209 patients with complete dose and sampling information were included in the PPK analysis, which was conducted using nonlinear mixed effects modeling (NONMEM). Results: Eribulin PKs were best described by a three-compartment model, with elimination from the central compartment. Distribution was rapid and elimination slow. For a typical patient with AST<ULN and CLCR=101mL/min (Cockroft-Gault), clearance (CL) was 2.98 L/h and central volume of distribution 3.72 L (V1). Volumes and inter-compartmental clearances for the two peripheral compartments were 3.60 L (V2), 126 L (V3), 2.7 L/h (Q2) and 5.6 L/h (Q3). Inter-patient variability on CL was 57%, and ranged from 26- 98% for other parameters. Residual error was 21% (proportional). CL was on average 38% lower in patients with AST>ULN and positively correlated with renal function. The covariate effects only explained a minor fraction of inter-patient variability in this single study dataset. Conclusions: Eribulin PKs were described by a three-compartment model with rapid distribution and slow elimination. Appreciable interpatient PK variability exists, a minor fraction of which was explained by measures of liver and renal function.

[Table: see text]

CNS effects of sumatriptan and rizatriptan in healthy female volunteers

This study investigates the CNS effects of sumatriptan and rizatriptan, with temazepam as an active comparator, in healthy female volunteers. Sixteen volunteers completed a randomized, double-blind, crossover study and on four separate occasions received either 100 mg sumatriptan, 20 mg rizatriptan or 20 mg temazepam. The main parameters were eye movements, EEG, body sway, visual analogue scales and a cognitive test battery. Rizatriptan and sumatriptan decreased saccadic peak velocity by 18.3 (95% CI: 5.7, 30.8) and 15.0 (2.2, 27.9) degrees/sec, respectively, about half the decrease induced by temazepam (35.0 (22.1, 47.8) degrees/sec). Body sway increased (30% for rizatriptan (16%, 45%) and 14% for sumatriptan (1%, 27%), respectively). Temazepam caused larger, similar effects. In contrast to temazepam, sumatriptan and rizatriptan decreased reaction times of recognition tasks and increased EEG alpha power (significant for sumatriptan, 0.477 (0.02, 0.935). Therapeutic doses of sumatriptan and rizatriptan caused CNS effects indicative of mild sedation. For EEG and recognition reaction times the effects were opposite to temazepam, indicating central stimulation.

Modeling and stimulation for clinical trial design involving a categorical response: a phase II case study with naratriptan

PURPOSE

The overall aim of the present study was to investigate retrospectively the feasibility and utility of model-based clinical trial simulation as applied to the clinical development of naratriptan with effect measured on a categorical scale.

METHODS

A PK-PD model for naratriptan was developed by using information gathered from previous naratriptan and sumatriptan preclinical and clinical trials. The phase IIa naratriptan data were used to check the PK-PD model in its ability to describe future data. A further PK-PD model was developed by using the phase IIa naratriptan data, and a phase IIb trial was designed by simulation with the use of Matlab. The design resulting from clinical trial simulation was compared with that derived by using D-optimal design.

RESULTS

The PK-PD model showed reasonable agreement with the data observed in the phase IIa naratriptan clinical trial. Clinical trial simulation resulted in a design with four or five arms at 0 mg, 2.5 and/or 5 mg, 10 mg, and 20 mg, PD measurements to be taken at 0, 2, and 4 or 6 h and at least 150 patients per arm. A sub-D-optimal design resulted in two dosing arms at 0 and 10 mg and PD measurements to be taken at 1 and 2 h.

CONCLUSIONS

Clinical trial simulation is a useful tool for the quantitative assessment of the influence of the controllable factors and is the only tool for the quantitative assessment of the uncontrollable factors on the power of a clinical trial.

Pharmacokinetics of naratriptan in adolescent subjects with a history of migraine

Naratriptan is a novel 5-HT1 agonist developed to treat acute migraine. The study objective was to characterize the pharmacokinetics of oral naratriptan in adolescent migraine patients outside a migraine attack. Subjects received a single 2.5 mg naratriptan tablet. Serial serum samples for naratriptan concentrations were collected over 24 hours. Blood pressure, pulse rate, and 12-lead ECG were recorded at baseline and at regular intervals after dosing. Seven patients--3 males and 4 females, 12 to 16 years of age--received drug and completed the study. The geometric mean and 95% confidence interval maximum concentration (Cmax) was 8.0 ng/mL (5.9-10.7), elimination half-life (t1/2) was 4.9 hours (4.5-5.4), area under the concentration-time curve (AUC) was 74.6 ng.h/mL (56.6-98.2), and apparent total clearance (Cl/F) was 558.8 mL/min (424.3-735.9). The median time to maximal concentration (tmax) was 4 hours, with a range of 1.5 to 4. Blood pressure, pulse rate, and ECG parameters did not change significantly from baseline. No serious adverse events or subject withdrawal after drug administration occurred. Oral naratriptan pharmacokinetic parameters in adolescents were similar to values reported in adults. Naratriptan doses for adolescents older than 12 years of age would be expected to be similar to adult doses.

Effect of encapsulation on absorption of sumatriptan tablets: data from healthy volunteers and patients during a migraine

BACKGROUND

Some comparative trials of selective serotonin 1B/ID-agonists in migraine have reported -15% lower efficacy for sumatriptan tablets than that reported in placebo-controlled trials.

OBJECTIVE

This study was designed to test the hypothesis that the encapsulation methods used to mask active drug may delay absorption of sumatriptan from dosing to 2 hours after dosing (the traditional end point in clinical trials of migraine treatment), an effect that may be enhanced by migraine-associated gastric stasis.

METHODS

Two randomized, open-label, 2-way crossover trials were conducted to evaluate the absorption and bioequivalence of conventional 50-mg sumatriptan tablets and encapsulated 50-mg sumatriptan tablets in supine, fasted, healthy volunteers (Glaxo Wellcome protocol SUM40270) and supine patients experiencing a migraine (Glaxo Wellcome protocol SUM40268). Absorption was assessed by calculating the area under the plasma concentration-time curve from dosing to 2 hours after dosing (AUC2) and the times to first measurable plasma concentration, 10 ng/mL, 20 ng/mL, and maximum plasma concentration. Data for the AUC from time zero to infinity and maximum plasma concentration were used to assess standard bioequivalence, which is considered to occur when the 90% CIs for the geometric mean treatment ratios (test/reference) fall between 0.8 and 1.25.

RESULTS

Study 1 included 26 healthy subjects (73% men, 27% women; mean age, 39.1 years), and study 2 included 30 patients with migraine (67% women, 33% men; mean age, 42.7 years). Sumatriptan absorption was delayed with the encapsulated tablet compared with the conventional tablet 0 to 2 hours after dosing, particularly during a migraine. AUC2 values with encapsulated sumatriptan compared with the conventional tablet were 21% lower in healthy volunteers (ratio of capsule/tablet, 0.79; 90% CI, 0.588-1.050) and 27% lower in patients experiencing a migraine (ratio of capsule/tablet, 0.73; 90% CI, 0.519-1.023). Standard bioequivalence was demonstrated in both healthy volunteers and patients experiencing a migraine.

CONCLUSIONS

Encapsulation delayed absorption of sumatriptan 0 to 2 hours after dosing, particularly during a migraine. This delay in absorption of the encapsulated form may account for the lower efficacy of sumatriptan in some comparative studies.

A population pharmacokinetic-pharmacodynamic analysis of repeated measures time-to-event pharmacodynamic responses: the antiemetic effect of ondansetron

This paper presents and illustrates methodology for specifying, estimating, and evaluating a predictive model for repeated measures time-to-event responses. The illustrative example specifies a model of the antiemetic effect vs. concentration relationship for the 5-HT3 antagonist ondansetron in the human ipecac model for emesis. A key part of this model is a time-dependent log hazard function for emesis that is increased by ipecac administration and decreased by ondansetron concentration. The model is fit using an approximate maximum likelihood method. The data consist of the time free of emeses and, for those individuals with emetic episodes, the time(s) of the episode(s). Model evaluation is accomplished using residual plots adapted to time-to-event data and a "posterior predictive check" wherein observed data statistics are compared to those obtained from data simulated from the fitted model. The ondansetron concentration required to obtain a 50% reduction in the hazard of emesis is estimated to be 1.4 +/- 0.2 ng/ml, and the rate constant for elimination of ipecac-induced hazard is 1.5 +/- 0.2 hr-1.

Mixed effect modeling of sumatriptan pharmacokinetics during drug development: II. From healthy subjects to phase 2 dose ranging in patients

Sumatriptan is indicated for the treatment of migraine attack and cluster headache; it is currently marketed as a subcutaneous injection, nasal spray, and oral tablet. New formulations are under consideration. The knowledge of sumatriptan absorption, combined with PK/PD information would help the design of more efficient formulations. In this perspective, we attempted to model the absorption of sumatriptan by population PK analysis. Data following administration by the intravenous (i.v.), the subcutaneous (s.c.), and the oral (po) route in healthy subjects were analyzed. A large database with full kinetic profiles was constituted. Sumatriptan was administered to 215 healthy subjects (i.v., s.c., and po) and to 143 migraine sufferers (po). The mean age was 31 years (18-86 years) in healthy subject population and was 38 years (18-65 years) in migraine patients. The mean weights were 74 kg (54-104 kg) and 66 kg (38-136 kg) in healthy subjects and migraine patients, respectively, and the mean heights were 176 cm (157-193 cm) and 164 cm (152-183 cm) in healthy subjects and migraine patients, respectively. A NONMEN analysis was performed using a two-compartment disposition model. Oral absorption was modeled with a first-order input followed by a zero-order input. Less biased results were obtained using the FOCE method. The total clearance and the distribution volume at steady state were 71.2 L/hr and 94.5 L after i.v. dosing and 68.7 L/hr and 109 L after inclusion of the s.c. and po data. The absorption phase appeared to last for about 5 hr. The interindividual variability of the main PK parameters was low: It was around 20% for the total clearance and around 30% for the distribution volume at steady state. Although significant, the combination of age and height on clearance did not decrease considerably the interindividual variability of this parameter (decrease of 2.2%); nor was it possible to establish clearly if a migraine attack has an effect on drug absorption because of the sampling scheme during absorption. Simulations have shown that it would have been possible to estimate all the PK parameters with a data set reduced to one quarter of its actual number of samples.

Early clinical experience with subcutaneous naratriptan in the acute treatment of migraine: a dose-ranging study

Naratriptan is a novel, potent agonist at the 5HT1B/1D receptor. A total of 335 migraine patients were treated in this randomized, double-blind, placebo-controlled, dose-ranging, in-clinic study, to evaluate the efficacy, safety and tolerability of five doses of subcutaneous (sc) naratriptan (0.5, 1, 2.5, 5 or 10 mg) in comparison with sc sumatriptan (6 mg) and placebo in the acute treatment of a moderate/severe migraine attack. Headache relief [reduction of headache severity from moderate or severe (grade 2/3) to mild or none (grade 1/0)] at 1 and 2 h after each dose, was reported by a statistically significantly higher proportion of patients for all doses of sc naratriptan and sc sumatriptan (6 mg) than for placebo. The percentages of patients with headache relief at 2 h post-dose were: naratriptan (0.5 mg) 65%, (1 mg) 75%, (2.5 mg) 83%, (5 mg) 94% and (10 mg) 91%; sumatriptan (6 mg) 89%; placebo 41%, (P < 0.005). The earliest report of a statistically significant difference compared with placebo for the times assessed was with sc naratriptan (10 mg) at 10 min post-dose (P = 0.023). The percentages of patients reporting adverse events were dose-related; sc naratriptan (0.5 mg) 33%, (1 mg) 29%, (2.5 mg) 43%, (5 mg) 59% and (10 mg) 71%; sc sumatriptan 53%; placebo 22%. There were no clinically significant changes in electrocardiogram (ECG), vital signs or laboratory parameters. Systemic exposure increased proportionally to the dose, the absorption of sc naratriptan was rapid (tmax = 10 min) and the half-life was 5 h. In conclusion, sc naratriptan was an effective and well-tolerated acute treatment for migraine. Copyright 1998 Lippincott Williams & Wilkins

Comparative clinical pharmacokinetics of single doses of sumatriptan following subcutaneous, oral, rectal and intranasal administration

Sumatriptan, a 5-HT1 receptor agonist active for the acute treatment of migraine, is currently available as subcutaneous injection and oral tablets. Rectal or intranasal formulations may offer advantages over those marketed. This study compared the pharmacokinetics of sumatriptan via all four routes. Usual absorption parameters were described and the rate of absorption was assessed using deconvolution technics. There were no statistical differences between the non-parenteral routes for tmax or Cmax/AUCinfinity. However, Cmax and AUCtmax were statistically greater with the suppository than with the tablet, but there was no difference between intranasal and oral routes. The highest rate of absorption occurred earlier with the intranasal than with the oral route. Relative to the subcutaneous route, the bioavailability for the suppository was greater than for intranasal spray and oral tablet. The amount of sumatriptan excreted in the urine unchanged was similar for all routes. Sumatriptan in this study was well tolerated.

Safety, tolerability, and pharmacokinetics of sumatriptan in healthy subjects following ascending single intranasal doses and multiple intranasal doses

The delivery of sumatriptan doses intranasally could add greater flexibility in the treatment of migraine than is possible with the currently available subcutaneous and oral sumatriptan preparations. Two independent double-blind, randomized, placebo-controlled clinical studies were conducted to evaluate the safety, tolerability and pharmacokinetics of intranasally administered sumatriptan following ascending single doses (three different dose levels) and multiple doses. In the four-way, crossover, ascending-dose study, 20 healthy female subjects were randomized to receive on separate occasions single intranasal spray doses of 5, 10, or 20 mg sumatriptan (as the hemisulphate salt) or placebo into one nostril. Adverse events were mild and consisted mainly of bitter taste at the back of the throat and events typical of sumatriptan administered by other routes (headache, lightheadedness and tingling). Area under the plasma sumatriptan concentration versus time curve (AUC infinity) and peak plasma concentration (Cmax) increased with the dose. Dose proportionality was demonstrated between 5 and 10 mg but not across the dose range 5-20 mg. Time to maximum plasma concentration (tmax) was variable due to multiple peaking. The elimination half-life (t1/2), approximately 2 h, was unaffected by the magnitude of dose. In the two-period, multiple-dose, crossover study, 12 healthy adult male and female subjects were randomized to receive either sumatriptan hemisulphate 20 mg or placebo, administered intranasally as a spray three times a day for 4 days. The two dosing periods were separated by 3 to 14 days. Multiple doses of sumatriptan were well tolerated, with no serious adverse events occurring or withdrawals due to adverse events. All patients reported a mild to moderate drug-related disturbance of taste. Nasal examinations remained normal, and olfactory function was unaffected. The AUC over the first 8 h following dosing (AUC8) and fraction of the dose excreted in the urine (fe; 6.2% vs 3.6%) were similar on Days 1 and 4. Day 4 values were significantly higher (p < or = 0.05) for Cmax (16.9 ng/ml vs 13.1 ng/ml), renal clearance (Clr; 19.0 l/h vs 14.2 l/h), and t1/2 (2.18 h vs 1.93 h), and shorter for tmax (0.88 h vs 1.75 h). Some accumulation (22%) occurred over the 4 days of dosing. Serum concentrations of the pharmacologically inactive indole acetic acid metabolite of sumatriptan were fourfold to fivefold higher than corresponding sumatriptan concentrations. Overall, these studies show that the sumatriptan intranasal spray formulation is well tolerated, allows rapid absorption of sumatriptan, and results in only a clinically insignificant degree of sumatriptan accumulation upon repeated dosing.

Mixed effect modeling of sumatriptan pharmacokinetics during drug development. I: Interspecies allometric scaling

Allometric scaling is an empirical examination of the relationships between the pharmacokinetic parameters and size (usually body weight), but it can also involve brain weight for metabolized drug. Through all species, the protein binding of sumatriptan is similar (14-16%), and its metabolic pathway undergoes extensive oxidative deamination involving the monoamine oxidase A isoenzyme. These similarities across species suggested the possible relevance of an allometric analysis. Toxicokinetic data were collected from rats, pregnant rabbits, and dogs in animal pharmacokinetic studies where sumatriptan was administered intravenously to the animals at doses of 5 mg/kg. 0.25 mg/kg, and 1 mg/kg, respectively. Animal data were pooled and analyzed in one step using a mixed effect modeling (population) approach. The kinetic parameters predicted in any species were close to the observed values by species: 77 L/hr vs. 80 L/hr in man for total clearance, 137 L vs. 119 L for distribution volume at steady state. The value of the mixed effect modeling approach compared to the two-step method was demonstrated especially with the possibility of including covariates to describe the status of animal (e.g., pregnancy) in the model. Knowledge of the animal kinetics, dynamics, and metabolism of a drug contributes to optimal and expeditious development. Valuable information for the design of the first-dose-in-man study may emerge from more creative data analysis based on all the information collected during the preclinical and ongoing nonclinical evaluation of a new drug.

Plasma and skin suction-blister-fluid pharmacokinetics and time course of the effects of oral mizolastine

OBJECTIVE

To investigate plasma and skin suction-blister-fluid pharmacokinetics of oral mizolastine in order to determine whether the drug concentration in the fluid of suction-induced skin blisters could better predict the antihistamine activity than the plasma concentration.

SETTING

Department of Internal Medicine, Université Paris 6.

SUBJECTS

Ten healthy male volunteers.

METHODS

The volunteers (mean age 26.8 years, mean weight 75.8 kg) received a single 10-mg oral dose of mizolastine at 1000 hours. The pharmacokinetic study included 11 plasma and 9 blister fluid samples and blister epidermal-roof specimens. Mizolastine was assayed by high-performance liquid chromatography (HPLC). Each volunteer also received nine intradermal injections of 5 micrograms histamine. Antihistamine activity was assessed as the post-treatment percentages of changes in the histamine-induced relative wheal and flare areas versus baseline.

RESULTS

Mizolastine mean Cmax (SD) and median tmax were, respectively, 380 ng.ml-1 and 0.8 h in plasma, and 21.8 ng.ml-1 and 10 h in blister fluid. Mizolastine could not be quantified in the epidermis. The maximal histamine-induced relative flare inhibition was 72.5% and was attained at the median time of 3 h post-dosing and therefore was delayed by 2.2 h with respect to the plasma tmax. Mean relative wheal inhibition, although lower, showed the same time profile. A direct relationship could not be found between drug concentrations in blister fluid and antihistamine activity. Simulated concentrations in the peripheral compartment better explain the maximum inhibition effect on flare, observed 3 h post-dosing, with a flatter hysteresis loop obtained when plotting relative flare inhibition versus plasma or blister-fluid drug concentrations.

CONCLUSION

The mizolastine concentrations in the skin suction-blister fluid were not predictive of the antihistamine activity.

Reduction of hyperglycemia after oral glucose load by the new alpha 2-adrenergic receptor antagonist SL 84.0418 in healthy subjects

OBJECTIVE

To assess the antihyperglycemic activity of a new peripherally acting alpha 2-adrenergic receptor antagonist, SL 84.0418 in healthy volunteers

METHODS

This was a randomized, double-blind crossover study. The effects of 10, 50, and 100 mg SL 84.0418 on blood glucose, plasma insulin, C-peptide, glucagon, epinephrine, and norepinephrine were investigated in comparison with placebo and 5 mg glipizide before and after an oral glucose challenge (75 gm).

RESULTS

Peak blood glucose and area under the blood-glucose curve were dose-dependently reduced by SL 84.0418; the extent of this reduction was similar with 100 mg SL 84.0418 and glipizide. Glipizide but not SL 84.0418 decreased nadir blood glucose. Plasma insulin and C-peptide were increased by glipizide but not by SL 84.0418. Treatments did not modify plasma glucagon. Plasma epinephrine increased during glipizide treatment and plasma norepinephrine increased during treatment with 50 and 100 mg SL 84.0418. Systolic and diastolic blood pressure were moderately enhanced by 50 and 100 mg SL 84.0418. Adverse effects reflecting alpha 2-adrenergic receptor blockade occurred more frequently with 100 mg SL 84.0418. The adverse effect profile of 50 mg SL 84.0418 was not different from that observed with glipizide.

CONCLUSION

The alpha 2-adrenergic receptor antagonist SL 84.0418 dose dependently reduced the increase in blood glucose after glucose load without modification of plasma insulin. It may represent an alternative to sulfonylureas in the treatment of non-insulin-dependent diabetes mellitus. Further studies are needed to assess its efficacy and tolerability in non-insulin-dependent patients.

Pharmacodynamics and pharmacokinetics of mizolastine (SL 85.0324), a new nonsedative H1 antihistamine

The antihistaminic activity, clinical safety, and pharmacokinetics of mizolastine (SL 85.0324) were studied in a 5-way, double-blind crossover study of ten healthy volunteers with doses of 1 to 75 mg. Inhibition of the histamine-induced wheal and flare showed clear dose-dependent antihistaminic activity beginning from the 2-mg dose with a maximum attained between 10 and 20 mg. The onset of action was rapid (one hour) and the effect persisted for more than 24 hours after a 10-mg dose or more. Mizolastine was well tolerated at doses up to 75 mg; subjective and objective signs of transient sedative activity were not observed at doses below 30 mg. The pharmacokinetic profile (rapid absorption with Tmax congruent to 1 h and elimination T1/2 of about eight hours) parallels the pharmacodynamic activity. Within the considered dose range, the pharmacokinetics was linear with no saturation phenomena.

Nocturnal profile of growth hormone secretion during sleep induced by zolpidem: a double-blind study in young adults and children

Overnight blood sampling for repeated growth hormone (GH) assays, regarded as the most physiological assessment of GH status, may induce some disturbances in patients' sleep and then in the evaluation of GH secretion. We studied the influence of a hypnotic drug, zolpidem (10 mg), on nocturnal GH profiles (GH peak, time to first and maximum GH peak, area under the curve, mean integrated concentration) over two nights at a 7-day interval, in a double-blind cross-over design in a group of 12 young adult volunteers (27.9 +/- 4.3 years), and in a group of 12 children (10.8 +/- 2.3 years) with short stature, in a parallel double-blind study. Mean GH profiles showed no difference between zolpidem-treated subjects and placebo-treated controls, either in adults or in children. Although in these experimental conditions, sleep onset latency was significantly reduced with zolpidem in the adult volunteers, the mean time to first GH peak remained unchanged. Furthermore, GH profile did not relate with sleep duration, sleep onset latency or number of awakenings. A hypnotic drug, such as zolpidem, given at bedtime, is therefore devoided of effect on nocturnal GH profile and may be used in young children for overnight blood sampling when needed.

Combined low-dose acetylsalicylic acid and dihydroergotamine in migraine prophylaxis. A double-blind, placebo-controlled crossover study

The efficacy of the combination of dihydroergotamine (10 mg) with acetylsalicylic acid (80 mg) (DHE + ASA) in the prophylaxis of migraine was studied in a double-blind, placebo-controlled crossover trial (8 weeks twice). Of 45 patients who entered the study, 38 completed it. The number of attacks was significantly (p = 0.003) reduced during active treatment (11.5 +/- 6.2) compared with placebo (16.6 +/- 9.9). The mean duration, the mean severity, and the mean score for symptomatic acute medication of attacks did not differ significantly. The overall assessment made by the patients themselves was in favor of DHE + ASA (p = 0.001). These results indicate a moderately beneficial effect of the dihydroergotamine/low-dose acetylsalicylic acid combination in migraine prophylaxis.

Simultaneous modeling of pharmacokinetics and pharmacodynamics with a nonparametric pharmacodynamic model

We describe a variation on an approach to simultaneous modeling of pharmacokinetics (PK) and pharmacodynamics (PD). Both approaches model the often-observed time lag between plasma drug concentration (Cp) and drug effect (E) in non-steady-state experiments by postulating an E site whose concentration (Ce) is kinetically linked to Cp by a first-order process. With the linking model, the time lag can be removed from the data and the underlying concentration-response (Ce-E) relationship can be estimated. The original method requires the analyst to postulate a particular parametric form for the Ce-E model, whereas ours does not. It estimates the rate constant of the linking model as the value that causes the hysteresis curve (Ce vs E points connected in time order) to collapse to a single curve that represents the (empirical) Ce-E relationship. The method is presented as an algorithm and is tested by means of simulation and a real-world example. The results suggest that the method can faithfully estimate the Ce-E curve for a variety of PD models and degrees of experimental error when its basic assumption of time-invariant PD holds.

[Pharmacokinetic and clinical investigation of amoxicillin administered intravenously in the newborn ]

Neonatal antibiotherapy involves special requirements which justify carrying out a clinical and pharmacokinetic investigation of amoxicillin. Our study concerns 34 newborn babies prone to infection divided in 3 groups: 26 newborns at gestational age; 6 hypotrophic and slightly premature newborns (age: 34 at 37 weeks); 1 highly premature baby (28 weeks, 0,9 kg). After direct IV drip of 33 mg/kg, 4 plasma concentrations analyses at time 0,5 1, 3, 8 hours, as well as an analysis of the urine from 0 to 8 hours are carried out by method of disk diffusion in nutrient agar. The main pharmacokinetics parameters are the following: half-live elimination time: 5.l4 +/- 3.43 hours; volume of distribution: 1.38 +/- 1.13 l/kg; total clearance: 0.211 +/- 0.277 l/kg/h. There is no correlation between birth weight and the parameters studied. However in the case of hypotrophic baby the volume of distribution is higher than for the child born after full gestation and may be partly correlated with the weight at birth. The same holds for clearance (correlation index of 0.66 and 0.59 respectively). The extreme variability of the pharmacokinetics parameters for newborn babies leads the authors to recommend a minimum dose of 150 mg/kg per day spread over 3 or 4 injections per day.