Estradiol and weight are covariates of paracetamol clearance in young women.

AIM: Paracetamol clearance differs between pregnant and non-pregnant women and between women with or without specific oral contraceptives (OCs). However, an association between female sex hormones and paracetamol clearance has never been explored. METHODS: In total, 49 women at delivery, 8 female control subjects without OC use, historical data of 14 women taking OCs, and 15 postpartum observations with and without OCs were pooled to explore covariates of paracetamol clearance. All received a single intravenous 2-gram paracetamol dose, and blood samples were collected up to 6 h after dosing. High-performance liquid chromatography was used to quantify paracetamol. The area under the curve to time infinity (AUC0-∞) was determined and clearance (l/h·m(2)) was calculated by dose/ AUC0-∞. In addition, estradiol and progesterone were quantified by ELISA with electro-chemiluminescence. RESULTS: Median paracetamol clearance at delivery was significantly higher when compared to postpartum or non-pregnant women (11.9 vs. 6.42 and 8.4 l/h·m(2), at least p < 0.05), while an association between paracetamol clearance and estradiol was observed (R = 0.494, p < 0.0001). In non-pregnant subjects, there was no impact of OC exposure on paracetamol clearance. Multiple regression revealed a linear association (Radj = 0.41, p < 0.001) between paracetamol clearance and weight (p = 0.0462) and estradiol (p < 0.0001). CONCLUSION: Estradiol and weight in part explain the variation in paracetamol clearance in young women.

Does the unfavorable pharmacokinetic and pharmacodynamic profile of the iNOS inhibitor GW273629 lead to inefficacy in acute migraine?

The objective of this study was to investigate the pharmacodynamics and pharmacokinetics of a single dose of GW273629, a selective iNOS inhibitor, given during and outside a migraine attack. GW273629 1500 mg was administered to 15 migraine patients both ictally and interictally. Nasal and exhaled nitric oxide (NO), plasma 3-nitrotyrosine, and nitrates were measured to assess systemic NO production. In addition, pharmacokinetics and treatment response were assessed. Data are mean (95% confidence interval [CI]). Plasma 3-nitrotyrosine was higher ictally: 11.96 (8.22, 15.71) ictally versus 2.74 (2.24, 3.24) ng/10 mg interictally (P < .0001). Exhaled and nasal NO showed a similar trend: 12.5 (6.5, 18.6) and 62.2 (41.5, 82.8) ppb ictally versus 9.9 (6.3, 13.4) ppb and 52.5 (38.5, 66.0) ppb interictally, respectively. Early absorption of GW273629 (AUC(0-2) [90% CI]) was reduced by 41 (22, 55)% during an attack. There was no improvement of headache or associated symptoms. Migraine headache is associated with reduced early absorption of GW273629 and excess NO production. In this open-label study, GW273629 was ineffective in the treatment of acute migraine.

Calcitonin gene-related peptide8-37 antagonizes capsaicin-induced vasodilation in the skin: evaluation of a human in vivo pharmacodynamic model.

The purpose of this study was to identify the mediators involved in capsaicin-induced vasodilation in the human skin and to evaluate a pharmacodynamic model for the early clinical evaluation of calcitonin gene-related peptide (CGRP) receptor antagonists. Dermal blood flow (DBF) response of the forearm skin to topically applied capsaicin was measured using laser Doppler perfusion imaging in 22 subjects. The effect of intra-arterially administered CGRP(8-37) (1200 ng . min(-1) . dl(-1) forearm), indomethacin (5 mug . min(-1) . dl(-1) forearm), and N(G)-monomethyl-l-arginine (l-NMMA; 0.2 mg . min(-1) dl(-1) forearm), and orally administered aprepitant (375 mg) on capsaicin-induced dermal vasodilation was assessed. Furthermore, the diurnal variation of the DBF response to capsaicin was studied. CGRP(8-37) inhibited the capsaicin-induced DBF increase: 217(145, 290)% in infused versus 370 (254, 486)% in the noninfused arm [mean (95% CI); p = 0.004]. In contrast, indomethacin, l-NMMA, aprepitant, and the time of assessment did not affect the DBF response to capsaicin. Thus, capsaicin-induced vasodilation in the human forearm skin is largely mediated by CGRP, but not by vasodilating prostaglandins, nitric oxide, or substance P. The response to capsaicin does not display a circadian rhythm. A pharmacodynamic model is proposed to evaluate CGRP receptor antagonists in humans in vivo.

Covariates of tramadol disposition in the first months of life.

BACKGROUND: Data on contributors to between-individual variability in overall tramadol clearance and O-demethyl tramadol (M1) formation in preterm neonates and young infants are limited. METHODS: A population pharmacokinetic analysis of tramadol and M1 was undertaken using non-linear mixed effects model. Covariate analysis included weight, postmenstrual age (PMA), postnatal age (PNA), creatinaemia, (cardiac) surgery, cardiac defect, and cytochrome (CYP)2D6 polymorphisms, classified by CYP2D6 activity score. RESULTS: In 57 patients (25-54 weeks PMA), 593 observations were collected. Tramadol clearance was described using a two-compartment, zero-order input, first-order elimination linear model. An additional compartment was used to characterize M1. Tramadol clearance at term age was 17.1 litre h(-1) (70 kg)(-1) (CV, 37.2%). Size (37.8%) and PMA (27.3%) contribute to this variability. M1 formation clearance (CL2M1, i.e. the contribution of M1 synthesis to M clearance) was 4.11 litre h(-1) (70 kg)(-1) (CV, 110.9%) at term age. Size and PMA were the major contributors to the variability (52.7%); the CYP2D6 activity score contributes 6.4% to this variability. CONCLUSIONS: Overall tramadol clearance estimates confirm earlier reports while CL2M1 variability is explained by size, PMA, and CYP2D6 polymorphisms. The CL2M1 is very low in preterm neonates, irrespective of the CYP2D6 polymorphism with subsequent rapid maturation. The slope of this increase depends on the CYP2D6 activity score. The current pharmacokinetic observations suggest a limited micro-opioid receptor-mediated analgesic effect of M1 in preterm neonates and a potential CYP2D6 polymorphism-dependent effect beyond term age.

Inter-individual variability in propofol pharmacokinetics in preterm and term neonates.

BACKGROUND: To document covariates which contribute to inter-individual variability in propofol pharmacokinetics in preterm and term neonates. METHODS: Population pharmacokinetics were estimated (non-linear mixed effect modelling) based on the arterial blood samples collected in (pre)term neonates after i.v. bolus administration of propofol (3 mg kg(-1), 10 s). Covariate analysis included postmenstrual age (PMA), postnatal age (PNA), gestational age, weight, and serum creatinine. RESULTS: Two hundred and thirty-five arterial concentration-time points were collected in 25 neonates. Median weight was 2930 (range 680-4030) g, PMA 38 (27-43) weeks, and PNA 8 (1-25) days. In a three-compartment model, PMA was the most predictive covariate for clearance (P<0.001) when parameterized as [CL(std).(PMA/38)(11.5)]. Standardized propofol clearance (CL(std)) at 38 weeks PMA was 0.029 litre min(-1). The addition of a fixed value in neonates with a PNA of >/=10 days further improved the model (P<0.001) and resulted in the equation [CL(std).(PMA/38)(11.5) +0.03] for neonates >/=10 days. Values for central volume (1.32 litre), peripheral volume 1 (15.4 litre), and peripheral volume 2 (1.29 litre) were not significantly influenced by any of the covariates (P>0.001). CONCLUSIONS: PMA and PNA contribute to the inter-individual variability of propofol clearance with very fast maturation of clearance in neonatal life. This implicates that preterm neonates and neonates in the first week of postnatal life are at an increased risk for accumulation during either intermittent bolus or continuous administration of propofol.

Pharmacokinetics and Pharmacodynamics of Omarigliptin, a Once-Weekly Dipeptidyl Peptidase-4 (DPP-4) Inhibitor, After Single and Multiple Doses in Healthy Subjects.

The pharmacokinetics (PK) and pharmacodynamics (PD) of omarigliptin, a novel once-weekly DPP-4 inhibitor, were assessed following single and multiple doses in healthy subjects. Absorption was rapid, and food did not influence single-dose PK. Accumulation was minimal, and steady state was reached after 2 to 3 weeks. Weekly (area under the curve) AUC and Cmax displayed dose proportionality within the dose range studied at steady state. The average renal clearance of omarigliptin was ∼2 L/h. DPP-4 inhibition ranged from ∼77% to 89% at 168 hours following the last of 3 once-weekly doses over the dose range studied. Omarigliptin resulted in ∼2-fold increases in weighted average postprandial active GLP-1. Omarigliptin acts by stabilizing active GLP-1, which is consistent with its mechanism of action as a DPP-4 inhibitor. Administration of omarigliptin was generally well tolerated in healthy subjects, and both the PK and PD profiles support once-weekly dosing. A model-based assessment of QTc interval risk from the single ascending dose study predicted a low risk of QTc prolongation within the likely clinical dose range, a finding later confirmed in a thorough QT trial.

Vascular effects of 5-HT1B/1D-receptor agonists in patients with migraine headaches.

OBJECTIVES: Second-generation triptans are believed to have fewer cardiovascular effects than sumatriptan. This was investigated in vivo by comparing the vascular effects of equipotent therapeutic dosages of selective 5-HT1B/1D-receptor agonists. METHODS: Sixteen patients with migraine headaches completed a double-blind, placebo-controlled, four-way crossover study. With ultrasonography and applanation tonometry used 1.5 hours after the oral intake of sumatriptan (50 mg), rizatriptan (10 mg), zolmitriptan (2.5 mg), or placebo arterial vessel wall properties, blood flow and pressure waveforms were measured in common carotid, brachial, and temporal arteries. At the brachial artery, flow-induced vasodilation (an endothelium-dependent process) was evaluated, and blood pressures were recorded. RESULTS: Mean arterial pressure, 91 +/- 2 mm Hg after placebo, increased (P < .05) by 4% to 6% after administration of each triptan. Each active treatment decreased (P < .001) both brachial and carotid artery diameter. Isobaric compliance of the brachial artery, 0.077 +/- 0.010 mm2/kPa after placebo, decreased (P < .01) by 11% +/- 8%, 11% +/- 11%, and 23% +/- 7% after administration of sumatriptan, rizatriptan, and zolmitriptan, respectively. Isobaric compliance of the carotid artery was 1.31 +/- 0.10 mm2/kPa after placebo (no change). Zolmitriptan was the only triptan that decreased temporal artery diameter significantly (by 12% +/- 3%, P < .001). The resistance of the temporal artery vascular bed increased after administration of sumatriptan (by 26% +/- 11%, P < .05) and zolmitriptan (by 40% +/- 9%, P = .001). Flow-induced vasodilation was unaffected. CONCLUSIONS: Selective 5-HT1B/1D-receptor agonists induce vasoconstriction and decrease compliance of conduit arteries. These effects are more pronounced at muscular (temporal, brachial) compared with elastic (carotid) arteries. Resistance is only increased at the temporal artery vascular bed, suggesting cranioselectivity for resistance vessels. Endothelial function is not differently affected by any of the triptans tested.

Effects of enteric-coated, low-dose aspirin on parameters of platelet function.

BACKGROUND: Aspirin is widely used as an anti-thrombotic drug; however, it has been suggested that enteric-coated formulations of aspirin may be less bioavailable and less effective as anti-thrombotic agents. AIM: To assess the effect of a formulation of enteric-coated, low-dose (81 mg) aspirin on serum generated thromboxane B2 and platelet aggregation in healthy subjects. METHODS: Twenty-four subjects participated in a double-blind, randomized, placebo-controlled, parallel-group, multiple-dose study. Twelve subjects in each of two groups received a daily oral dose of enteric-coated aspirin (81 mg) or matching placebo for 7 days. Serum thromboxane B2 and platelet aggregation (using 1 mm arachidonic acid and 1 microg/mL collagen as agonists) were measured 1-3 days prior to day 1, on day 1 (prior to therapy) and 4 h after the last dose on day 7. RESULTS: After seven daily doses of enteric-coated aspirin, the mean percentage inhibition from baseline of ex vivo generated serum thromboxane B2 was 97.4%, compared with a 7.8% increase after placebo treatment. The mean percentage inhibition of arachidonic acid- and collagen-induced platelet aggregation was 97.9% and 70.9%, respectively, following enteric-coated aspirin, compared with - 1.0% and 2.7%, respectively, after placebo. CONCLUSIONS: The anti-platelet effects of multiple, daily, low-dose aspirin (as assessed by inhibition of serum thromboxane B2 and platelet aggregation) are not adversely affected by enteric coating.

Impact of antihypertensive treatment on quality of life: comparison between bisoprolol and bendrofluazide.

OBJECTIVES: To compare quality of life with the selective beta1-blocker bisoprolol and the thiazide diuretic bendrofluazide in patients with mild to moderate hypertension. DESIGN AND SETTING: Multi centric, randomised, double-blind, two-way crossover study carried out at six general practice centres. SUBJECTS: Eighty-one patients with newly diagnosed or previously treated hypertension, who had a mean diastolic blood pressure (BP) of 95-120 mm Hg after receiving placebo for 4-6 weeks. INTERVENTIONS: In random order, patients received bisoprolol (5 mg once daily) or bendrofluazide (2. 5 mg once daily) for 8 weeks. MAIN OUTCOME MEASURES: Quality of life and antihypertensive effect. RESULTS: Decrease in systolic/diastolic BP did not differ between bisoprolol (10 +/- 2/13 +/- 1 mm Hg) and bendrofluazide (9 +/- 2/11 +/- 1 mm Hg). Between bisoprolol and bendrofluazide neither in the intention-to-treat nor in the efficacy analysis any difference was found in quality of life variables, such as Health Status Index, somatic symptoms, anxiety, depression, total psychiatric morbidity, cognitive symptoms and hostility score. Compared to baseline the Health Status Index improved (P < 0.05) during bisoprolol. None of the other investigated quality of life variables changed compared to baseline. No patients dropped out during bisoprolol or bendrofluazide treatment. Although, the total number of reported adverse events appeared lower during bendrofluazide than during bisoprolol treatment, it is unclear whether drug related adverse events also differ between the two drugs. CONCLUSIONS: At equipotent antihypertensive dosages, the effect of an 8-week treatment on quality of life does not differ between the selective beta1-blocker bisoprolol and the thiazide diuretic bendrofluazide.

Weight, pregnancy and oral contraceptives affect intravenous paracetamol clearance in young women.

OBJECTIVES: Because of the extensive variability in paracetamol clearance in young women, published data were pooled with newly collected observations in search of covariates of paracetamol pharmacokinetics (PK) within this specific population. SUBJECTS AND METHODS: PK estimates and clinical characteristics [pregnant, weight, exposure to oral contraceptives (OC)] in young women following IV loading dose (2 g paracetamol) were pooled, using a non-compartmental linear disposition model in individual time-concentration profiles. Data were reported by median and range. Rank correlation was used to link clearance (l/h) to weight, Mann Whitney U test to compare clearance (l/h.m-2) between subgroups (pregnant, OC exposure). Finally, a multiple regression model with clearance (l/h) in all women and all non-pregnant women was performed. RESULTS: Based on 73 paracetamol PK estimates, a 8-fold variability in clearance (range 7.1-62.2 l/h) was documented, in part explained by a correlation (r2=0.36) between clearance (l/h) and weight. Clearance (l/h and l/h.m-2) and distribution volume (l) at delivery (n=36) were higher compared to non-pregnant observations. In non-pregnant women, women on OC (n=20) had a higher paracetamol clearance (l/h.m-2) compared to women (n=17) not on OC (p = 0.023). Weight (p = 0.0043) and pregnancy (p = 0.02) were independent variables (r=0.56) of paracetamol clearance (l/h). In non-pregnant women, weight (p = 0.009) and OC exposure (p = 0.03) were independent variables (r=0.51). CONCLUSIONS: Weight, pregnancy and OC result in higher clearance of IV paracetamol in young women. Besides compound specific relevance, these findings also unveil covariates of drug metabolism in young women.

MRK-409 (MK-0343), a GABAA receptor subtype-selective partial agonist, is a non-sedating anxiolytic in preclinical species but causes sedation in humans.

MRK-409 binds to α1-, α2-, α3- and α5-containing human recombinant GABA(A) receptors with comparable high affinity (0.21-0.40 nM). However, MRK-409 has greater agonist efficacy at the α3 compared with α1 subtypes (respective efficacies relative to the full agonist chlordiazepoxide of 0.45 and 0.18). This compound readily penetrates the brain in rats and occupies the benzodiazepine site of GABA(A) receptors, measured using an in vivo [(3)H]flumazenil binding assay, with an Occ(50) of 2.2 mg/kg p.o. and a corresponding plasma EC(50) of 115 ng/mL. Behaviourally, the α3-preferring agonist efficacy profile of MRK-409 produced anxiolytic-like activity in rodent and primate unconditioned and conditioned models of anxiety with minimum effective doses corresponding to occupancies, depending on the particular model, ranging from ∼35% to 65% yet there were minimal overt signs of sedation at occupancies greater than 90%. In humans, however, safety and tolerability studies showed that there was pronounced sedation at a dose of 2 mg, resulting in a maximal tolerated dose of 1 mg. This 2 mg dose corresponded to a C(max) plasma concentration of 28 ng/mL, which, based on the rodent plasma EC(50) for occupancy of 115 ng/mL, suggested that sedation in humans occurs at low levels of occupancy. This was confirmed in human positron emission tomography studies, in which [(11)C]flumazenil uptake following a single dose of 1 mg MRK-409 was comparable to that of placebo, indicating that occupancy of GABA(A) receptor benzodiazepine binding sites by MRK-409 was below the limits of detection (i.e. <10%). Taken together, these data show that MRK-409 causes sedation in humans at a dose (2 mg) corresponding to levels of occupancy considerably less than those predicted from rodent models to be required for anxiolytic efficacy (∼35-65%). Thus, the preclinical non-sedating anxiolytic profile of MRK-409 did not translate into humans and further development of this compound was halted.

Preclinical and clinical pharmacology of TPA023B, a GABAA receptor α2/α3 subtype-selective partial agonist.

In the accompanying paper we describe how MRK-409 unexpectedly produced sedation in man at relatively low levels of GABA(A) receptor occupancy (∼10%). Since it was not clear whether this sedation was mediated via the α2/α3 or α1 GABA(A) subtype(s), we characterized the properties of TPA023B, a high-affinity imidazotriazine which, like MRK-409, has partial agonist efficacy at the α2 and α3 subtype but is an antagonist at the α1 subtype, at which MRK-409 has weak partial agonism. TPA023B gave dose- and time-dependent occupancy of rat brain GABA(A) receptors as measured using an in vivo [(3)H]flumazenil binding assay, with 50% occupancy corresponding to a respective dose and plasma drug concentration of 0.09 mg/kg and 19 ng/mL, the latter of which was similar to that observed in mice (25 ng/mL) and comparable to values obtained in baboon and man using [(11)C]flumazenil PET (10 and 5.8 ng/mL, respectively). TPA023B was anxiolytic in rodent and primate (squirrel monkey) models of anxiety (elevated plus maze, fear-potentiated startle, conditioned suppression of drinking, conditioned emotional response) yet had no significant effects in rodent or primate assays of ataxia and/or myorelaxation (rotarod, chain-pulling, lever pressing), up to doses (10 mg/kg) corresponding to occupancy of greater than 99%. In man, TPA023B was well tolerated at a dose (1.5 mg) that produced occupancy of >50%, suggesting that the sedation previously seen with MRK-409 is due to the partial agonist efficacy of that compound at the α1 subtype, and highlighting the importance of antagonist efficacy at this particular GABA(A) receptor population for avoiding sedation in man.

Pharmacokinetics, pharmacodynamics, and safety of a prostaglandin D2 receptor antagonist.

Laropiprant is a selective antagonist of the prostaglandin D(2) (PGD(2)) receptor subtype 1 (DP1). Three double-blind, randomized, placebo-controlled studies evaluated the safety, tolerability, pharmacokinetics, and pharmacodynamics of single and multiple oral doses of laropiprant in healthy male volunteers. Single doses up to 900 mg and multiple doses up to 450 mg were generally well tolerated. Laropiprant exhibited dose-proportional pharmacokinetics. Oral absorption is rapid (T(max)=0.8-2.0 h) and the terminal half-life is approximately 12-18 h. The pharmacokinetics of laropiprant was not affected by food. Single doses of 6 mg and higher were effective in suppressing PGD(2)-induced cyclic AMP accumulation in platelets, demonstrating laropiprant target engagement with DP1. Laropiprant has detectable off-target antagonist effects at the thromboxane A(2) receptor but no clinically significant effect on collagen-induced platelet aggregation or bleeding times with multiple doses up to 200 mg.

Increased C-reactive protein in young adult patients with migraine.

Interictal serum C-reactive protein (CRP) was measured in 50 young adult patients with migraine and compared with 50 controls. The median CRP level was 1.42 mg/l in patients with migraine and 0.90 mg/l in controls (P = 0.03). This finding supports the role of inflammation in migraine, but needs confirmation in larger controlled studies. Prospective studies may establish whether measurements of CRP can identify patients with migraine at risk for cardiovascular events.

Reproducibility of the capsaicin-induced dermal blood flow response as assessed by laser Doppler perfusion imaging.

AIMS: Part I: to establish the dose and appropriate application site of capsaicin on the human forearm in order to produce a robust and reproducible dermal blood flow (DBF) response. Part II: to evaluate the within-subject arm-to-arm and period-to-period reproducibility. METHODS: Both parts consisted of two study visits. In part I, placebo and 100, 300 and 1000 microg capsaicin were applied at four predefined sites on the volar surface of both forearms. Placebo and capsaicin doses were randomized and balanced by site between subjects. Changes in DBF were assessed by laser Doppler perfusion imaging up to 60 min after capsaicin application. In part II, only 1000 microg capsaicin was applied on the proximal forearm and changes in DBF assessed up to 30 min (t(30)). DBF response was expressed as percent change from baseline +/- SD and the corresponding AUC(0-30). Reproducibility assessment included calculation of the concordance correlation coefficient (CCC). RESULTS: Part I (n = 12 subjects): compared with placebo, 300 and 1000 microg capsaicin increased DBF (P < 0.05) at all time points except at 10 min. This increase was reproducible at the two most proximal sites from the 30-min time point onwards when compared between arms (CCC >or= 0.8, i.e. substantial to almost perfect reproducibility). In part II (n = 11), t(30) averaged 390 +/- 120% and arm-to-arm reproducibility was almost perfect (CCC = 0.91) for AUC(0-30). CONCLUSIONS: Capsaicin induces a reproducible within-subject arm-to-arm increase in DBF. We provide a non-invasive pharmacodynamic model in humans to test antagonists of mediators involved in capsaicin-induced dermal vasodilation, including calcitonin gene-related peptide antagonists.

The effect of MK-0524, a prostaglandin D(2) receptor antagonist, on prostaglandin D (2)-induced nasal airway obstruction in healthy volunteers.

INTRODUCTION: Nasal congestion in allergic rhinitis results from tissue edema and vasodilatation in the nasal mucosa. Of the mediators released by mast cells in response to allergens, prostaglandin (PG) D(2) is regarded as the most potent inducer of nasal congestion. Intranasal administration of PGD(2) reproduces the nasal blockade experienced by patients with seasonal allergic rhinitis (SAR) via its action on the PGD(2) (DP) receptor to induce nasal vasodilatation. Intranasal challenge with PGD(2) can be a useful tool for evaluating DP-receptor antagonists. OBJECTIVE: The main purpose of this study was to examine the ability of MK-0524, a DP receptor antagonist in development for the treatment of SAR, to block PGD(2) induced nasal congestion in healthy volunteers. METHODS: To this end, a double-blind, placebo-controlled, randomized, 3-period study was performed in 15 healthy subjects. During each period, subjects received MK-0524 25 mg, MK-0524 100 mg or placebo qd for 3 days. Twenty-four hours following the last dose, nasal provocations with PGD(2) were performed to determine the PD(75), which is the intranasal dose of PGD(2) that provokes a 75% increase in baseline total nasal airway resistance as performed by active anterior rhinomanometry. RESULTS: Following treatment with MK-0524, the PD(75) (mean+/-SD) was significantly shifted from 15.8 +/- 18.3 mug/nostril during the placebo period to more than 512 mug/nostril both following the 25- and 100-mg (maximum challenge dose tested) dose regimen. CONCLUSION: Whether this >45 fold increase in PD(75) will induce a clinically meaningful effect of MK-0524 will require clinical study in participants with SAR.

Forearm vascular response to nitric oxide and calcitonin gene-related peptide: comparison between migraine patients and control subjects.

The forearm vascular response to nitric oxide (NO) and calcitonin gene-related peptide (CGRP) was investigated in 10 migraine patients and 10 matched control subjects. Changes in forearm blood flow (FBF) during intrabrachial infusion of: (i) serotonin (releasing endogenous NO), (ii) sodium nitroprusside (SNP, exogenous NO-donor), and (iii) CGRP were measured using venous occlusion plethysmography. Flow-mediated dilation (FMD) of the brachial artery, a measure for the endogenous release of NO reactive to occlusion, was measured using ultrasound and expressed as percentage change vs. baseline diameter. FBF ratio (i.e. FBF in the infused over the control arm) at baseline (1.1 +/- 0.1) did not differ between both populations. Serotonin, SNP and CGRP induced a dose-dependent increase (P < 0.001) in FBF ratio in controls (to 2.8 +/- 0.3, 6.7 +/- 1.4 and 6.9 +/- 1.2 at the highest dose, respectively) and migraineurs (2.5 +/- 0.4, 5.6 +/- 0.8 and 6.5 +/- 1.3, respectively); these ratios did not differ between both groups. FMD was comparable in control subjects (5.8 +/- 1%) and migraine patients (5.2 +/- 1%). Based on the forearm vascular response to NO and CGRP, migraine patients do not display generalized changes in vascular function.

Effect of aprepitant on the pharmacokinetics and pharmacodynamics of warfarin.

OBJECTIVE: To examine the effect of aprepitant on the pharmacokinetics and pharmacodynamics of warfarin. Aprepitant is a neurokinin-1 (NK1)-receptor antagonist developed as an antiemetic for chemotherapy-induced nausea and vomiting. METHODS: This was a double-blind, placebo-controlled, randomized, two-period, parallel-group study. During period 1, warfarin was individually titrated to a stable prothrombin time (expressed as international normalized ratio, INR) from 1.3 to 1.8. Subsequently, the daily warfarin dose remained fixed for 10-12 days. During period 2, the warfarin dose was continued for 8 days, and on days 1-3 administered concomitantly with aprepitant (125 mg on day 1, and 80 mg on days 2 and 3) or placebo. At baseline (day -1 of period 2) and on day 3, warfarin pharmacokinetics was investigated. INR was monitored daily. During period 2, warfarin trough concentrations were determined daily. RESULTS: The study was completed by 22 healthy volunteers (20 men, 2 women). On day 3, steady-state pharmacokinetics of warfarin enantiomers after aprepitant did not change, as assessed by warfarin AUC(0-24 h) and C(max). However, compared with placebo, trough S(-) warfarin concentrations decreased on days 5-8 (maximum decrease 34% on day 8, P<0.01). The INR decreased after aprepitant with a mean maximum decrease on day 8 of 11% versus placebo (P=0.011). CONCLUSION: These data are consistent with a significant induction of CYP2C9 metabolism of S(-) warfarin by aprepitant. Subsequently, in patients on chronic warfarin therapy, the clotting status should be monitored closely during the 2-week period, particularly at 7-10 days, following initiation of the 3-day regimen of aprepitant with each chemotherapy cycle.

No effect of short-term omeprazole intake on acenocoumarol pharmacokinetics and pharmacodynamics.

AIMS: To investigate the effect of omeprazole on the pharmacokinetics of R- and S-acenocoumarol and on their combined anticoagulant activity. METHODS: Eight healthy male subjects completed a double-blind, randomized, placebo-controlled, two-way cross-over study. Subjects were given either omeprazole 40 mg or placebo once daily for 3 days. On day 2 of each study period, a single 10 mg oral dose of racemic acenocoumarol was administered and venous blood samples were collected for pharmacokinetic and pharmacodynamic assessments. A wash-out period of 2 weeks separated the two study periods. RESULTS: The pharmacokinetics of R- and S-acenocoumarol (AUC 3016 +/- 221 and 233 +/- 14 ng ml(-1) h, respectively) did not change after omeprazole (AUC 2929 +/- 256 and 220 +/- 18 ng ml(-1) h, respectively). Anticoagulant activity (INRmax 1.7 +/- 0.1) was unaffected by co-administration of omeprazole (INRmax 1.7 +/- 0.1). CONCLUSIONS: The short-term intake of omeprazole does not affect acenocoumarol pharmacokinetics or pharmacodynamics. These data differ from the results of previous studies on the effect of omeprazole on warfarin, suggesting a different in vivo interaction profile of omeprazole on acenocoumarol than on warfarin. Drug interaction studies with oral anticoagulants should not be restricted to the use of warfarin.

Pneumocystis carinii pneumonia. Review of 32 cases in immunocompromised hosts.

The records of patients in whom Pneumocystis carinii pneumonia (PCP) was diagnosed between January 1989 and December 1991 were reviewed. Thirty-two patients--all immunocompromised--were included in the study: 41% were HIV-positive and 59% HIV-negative. In 23 patients (72%) concomitant pathogens were isolated, most frequently Cytomegalovirus. Presenting symptoms included fever (97%), cough (75%) and dyspnea (63%). All HIV-infected patients had a T4-lymphocyte count below 200/mm3 (or 20%). The majority of patients (80%) treated with trimethoprim-sulfamethoxazole experienced adverse events which were usually well tolerated so that a therapy change was necessary in only 12% of patients. PCP was fatal in 34% of the patients. Respiratory failure requiring mechanical ventilation carries a poor prognosis. The ratio of non-AIDS/AIDS patients infected with PC is increasing. This increase is due to the growing contribution of patients treated with immunosuppressive agents and patients with disease-associated immunodeficiencies other than AIDS. Our study suggests that treatment of PCP is more successful with early diagnosis. In addition, as mortality rate is high in non-AIDS patients, our data suggest that the more frequent use of PCP prophylaxis in patients given immunosuppressive drugs, might reduce the incidence of PCP and PCP related mortality.