Safety, Tolerability, and Pharmacokinetics of Single and Multiple Ascending Intravenous Infusions of PF-07304814 (Lufotrelvir) in Participants Hospitalized With COVID-19

BACKGROUND

An urgent need remains for antiviral therapies to treat patients hospitalized with COVID-19. PF-07304814-the prodrug (lufotrelvir) and its active moiety (PF-00835231)-is a potent inhibitor of the SARS-CoV-2 3CL protease.

METHOD

Eligible participants were 18 to 79 years old and hospitalized with confirmed COVID-19. This first-in-human phase 1b study was designed with 2 groups: single ascending dose (SAD) and multiple ascending dose (MAD). Participants could receive local standard-of-care therapy. In SAD, participants were randomized to receive a 24-hour infusion of lufotrelvir/placebo. In MAD, participants were randomized to receive a 120-hour infusion of lufotrelvir/placebo. The primary endpoint was to assess the safety and tolerability of lufotrelvir. The secondary endpoint was to evaluate the pharmacokinetics of lufotrelvir and PF-00835231.

RESULTS

In SAD, participants were randomized to receive 250 mg lufotrelvir (n = 2), 500 mg lufotrelvir (n = 2), or placebo (n = 4) by continuous 24-hour infusion. In MAD, participants were randomized to receive 250 mg lufotrelvir (n = 7), 500 mg lufotrelvir (n = 6), or placebo (n = 4) by continuous 120-hour infusion. No adverse events or serious adverse events were considered related to lufotrelvir. At doses of 250 and 500 mg, concentrations for the prodrug lufotrelvir and active moiety PF-00835231 increased in a dose-related manner. Unbound concentrations of the lufotrelvir active metabolite reached steady state approximately 2- and 4-fold that of in vitro EC90 following 250- and 500-mg doses, respectively.

CONCLUSIONS

These safety and pharmacokinetic findings support the continued evaluation of lufotrelvir in clinical studies. Clinical Trials Registration. ClinicalTrials.gov NCT04535167.

Innovative Randomized Phase I Study and Dosing Regimen Selection to Accelerate and Inform Pivotal COVID-19 Trial of Nirmatrelvir

Coronavirus disease 2019 (COVID-19) is a continued leading cause of hospitalization and death. Safe, efficacious COVID-19 antivirals are needed urgently. Nirmatrelvir (PF-07321332), the first orally bioavailable, severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) Mpro inhibitor against the coronaviridae family, has demonstrated potent preclinical antiviral activity and benign safety profile. We report safety, tolerability, and pharmacokinetic data of nirmatrelvir with and without ritonavir as a pharmacokinetic enhancer, from an accelerated randomized, double-blind, placebo-controlled, phase I study. Two interleaving single-ascending dose (SAD) cohorts were evaluated in a three-period crossover. Multiple-ascending dose (MAD) with nirmatrelvir/ritonavir twice daily (b.i.d.) dosing was evaluated over 10 days in five parallel cohorts. Safety was assessed, including in a supratherapeutic exposure cohort. Dose and dosing regimen for clinical efficacy evaluation in phase II/III clinical trials were supported by integrating modeling and simulations of SAD/MAD data with nonclinical data and a quantitative systems pharmacology model (QSP). In SAD, MAD, and supratherapeutic exposure cohorts, nirmatrelvir/ritonavir was safe and well-tolerated. Nirmatrelvir exposure and half-life were considerably increased by ritonavir, enabling selection of nirmatrelvir/ritonavir dose and regimen for phase II/III trials (300/100 mg b.i.d.), to achieve concentrations continuously above those required for 90% inhibition of viral replication in vitro. The QSP model suggested that a 5-day regimen would significantly decrease viral load in SARS-CoV-2-infected patients which may prevent development of severe disease, hospitalization, and death. In conclusion, an innovative and seamless trial design expedited establishment of phase I safety and pharmacokinetics of nirmatrelvir/ritonavir, enabling high confidence in phase II/III dose selection and accelerated pivotal trials' initiation (NCT04756531).

Achieving end-to-end success in the clinic: Pfizer's learnings on R&D productivity

Over the past decade, Pfizer has focused efforts to improve its research and development (R&D) productivity. By the end of 2020, Pfizer had achieved an industry-leading clinical success rate of 21%, a tenfold increase from 2% in 2010 and well above the industry benchmark of ∼11%. The company had also maintained the quality of innovation, because 75% of its approvals between 2016 and 2020 had at least one expedited regulatory designation (e.g., Breakthrough Therapy). Pfizer’s Signs of Clinical Activity (SOCA) paradigm enabled better decision-making and, along with other drivers (biology and modality), contributed to this productivity improvement. These laid a strong foundation for the rapid and effective development of the Coronavirus 2019 (COVID-19) vaccine with BioNTech, as well as the antiviral candidate Paxlovid™, under the company’s ‘lightspeed’ paradigm.

Overview of the Clinical Pharmacology of Ertugliflozin, a Novel Sodium-Glucose Cotransporter 2 (SGLT2) Inhibitor

Ertugliflozin, a selective inhibitor of sodium-glucose cotransporter 2 (SGLT2), is approved in the US, EU, and other regions for the treatment of adults with type 2 diabetes mellitus (T2DM). This review summarizes the ertugliflozin pharmacokinetic (PK) and pharmacodynamic data obtained during phase I clinical development, which supported the registration and labeling of this drug. The PK of ertugliflozin was similar in healthy subjects and patients with T2DM. Oral absorption was rapid, with time to peak plasma concentrations (T_max) occurring at 1 h (fasted) and 2 h (fed) postdose. The terminal phase half-life ranged from 11 to 18 h and steady-state concentrations were achieved by 6 days after initiating once-daily dosing. Ertugliflozin exposure increased in a dose-proportional manner over the tested dose range of 0.5–300 mg. Ertugliflozin is categorized as a Biopharmaceutical Classification System Class I drug with an absolute bioavailability of ~ 100% under fasted conditions. Administration of the ertugliflozin 15 mg commercial tablet with food resulted in no meaningful effect on ertugliflozin area under the plasma concentration–time curve (AUC), but decreased peak concentrations (C_max) by 29%. The effect on C_max is not clinically relevant and ertugliflozin can be administered without regard to food. Mild, moderate, and severe renal impairment were associated with a ≤ 70% increase in ertugliflozin exposure relative to subjects with normal renal function, and no dose adjustment in renal impairment patients is needed based on PK results. Consistent with the mechanism of action of SGLT2 inhibitors, 24-h urinary glucose excretion decreased with worsening renal function. In subjects with moderate hepatic impairment, a decrease in AUC (13%) relative to subjects with normal hepatic function was observed and not considered clinically relevant. Concomitant administration of metformin, sitagliptin, glimepiride, or simvastatin with ertugliflozin did not have clinically meaningful effects on the PK of ertugliflozin or the coadministered medications. Coadministration of rifampin decreased ertugliflozin AUC and C_max by 39% and 15%, respectively, and is not expected to affect efficacy in a clinically meaningful manner. This comprehensive evaluation supports administration to patients with T2DM without regard to prandial status and with no dose adjustments for coadministration with commonly prescribed drugs, or in patients with renal impairment or mild-to-moderate hepatic impairment based on ertugliflozin PK.

End-to-end application of model-informed drug development for ertugliflozin, a novel sodium-glucose cotransporter 2 inhibitor

Model-informed drug development (MIDD) is critical in all stages of the drug-development process and almost all regulatory submissions for new agents incorporate some form of modeling and simulation. This review describes the MIDD approaches used in the end-to-end development of ertugliflozin, a sodium-glucose cotransporter 2 inhibitor approved for the treatment of adults with type 2 diabetes mellitus. Approaches included (1) quantitative systems pharmacology modeling to predict dose-response relationships, (2) dose-response modeling and model-based meta-analysis for dose selection and efficacy comparisons, (3) population pharmacokinetics (PKs) modeling to characterize PKs and quantify population variability in PK parameters, (4) regression modeling to evaluate ertugliflozin dose-proportionality and the impact of uridine 5'-diphospho-glucuronosyltransferase (UGT) 1A9 genotype on ertugliflozin PKs, and (5) physiologically-based PK modeling to assess the risk of UGT-mediated drug-drug interactions. These end-to-end MIDD approaches for ertugliflozin facilitated decision making, resulted in time/cost savings, and supported registration and labeling.

Pharmacokinetics and Pharmacodynamics of Ertugliflozin in Healthy Japanese and Western Subjects

Ertugliflozin, a sodium-glucose cotransporter 2 inhibitor, is approved for treatment of type 2 diabetes. This randomized, double-blind (sponsor-open) study in healthy Japanese subjects and open-label study in Western subjects assessed ertugliflozin pharmacokinetics and pharmacodynamics. Cohort A received 3 ascending single doses of ertugliflozin (1, 5, and 25 mg; n = 6 Japanese, n = 6 Western) or placebo (n = 3 Japanese) under fasted conditions. Cohort B received multiple once-daily doses of ertugliflozin 25 mg (n = 6 Japanese) or placebo (n = 3 Japanese) for 7 days under fed conditions. For Japanese subjects in Cohort A, maximum plasma concentrations (C_max ) were observed 1 to 1.5 hours after dosing, and apparent mean terminal half-life was 12.4 to 13.6 hours. The ratios of the geometric means (Japanese/Western) for ertugliflozin 1-, 5-, and 25-mg single doses were 95.94%, 99.66%, and 90.32%, respectively, for area under the plasma concentration-time curve and 107.59%, 97.47%, and 80.04%, respectively, for C_max . Area under the plasma concentration-time curve and C_max increased in a dose-proportional manner. For Cohort B, C_max was observed 2.5 hours after dosing (days 1 and 7), and steady state was reached by day 4. The 24-hour urinary glucose excretion was dose dependent. Ertugliflozin was generally well tolerated. There were no meaningful differences in exposure, urinary glucose excretion, and safety between Japanese and Western subjects.

Blood pressure-lowering effect of the sodium glucose co-transporter-2 inhibitor ertugliflozin, assessed via ambulatory blood pressure monitoring in patients with type 2 diabetes and hypertension

This study compared the blood pressure-lowering effect of ertugliflozin (1, 5, 25 mg), hydrochlorothiazide (HCTZ; 12.5 mg) and placebo in 194 patients with type 2 diabetes mellitus and hypertension for 4 weeks using ambulatory blood pressure monitoring. Endpoints (change from baseline to week 4) were: 24-h mean systolic blood pressure (SBP; primary); daytime, night-time, seated predose SBP, 24-h, daytime, night-time, seated predose diastolic blood pressure, 24-h urinary glucose excretion and fasting plasma glucose (FPG; secondary). Safety and tolerability were monitored. Significant decreases in placebo-corrected 24-h mean SBP (-3.0 to -4.0 mmHg) were recorded for all doses of ertugliflozin (for HCTZ, this was -3.2 mmHg). Daytime, but not night-time SBP was consistently reduced. Ertugliflozin produced dose-dependent significant decreases in FPG and increases in urinary glucose excretion. No notable changes in plasma renin activity or urinary aldosterone were seen. The most common adverse events were urinary tract infection, genital fungal infection, upper respiratory tract infection and musculoskeletal pain.

Dose-ranging efficacy and safety study of ertugliflozin, a sodium-glucose co-transporter 2 inhibitor, in patients with type 2 diabetes on a background of metformin

AIM

To investigate the efficacy and safety of ertugliflozin, in a phase II dose-ranging study, in patients with type 2 diabetes mellitus (T2DM) inadequately controlled on metformin.

METHODS

A total of 328 patients [mean T2DM duration, 6.3 years; mean glycated haemoglobin (HbA1c), 8.1%] were randomized to once-daily ertugliflozin (1, 5, 10, 25 mg), sitagliptin (100 mg) or placebo, for 12 weeks. The primary efficacy endpoint was change from baseline to week 12 in HbA1c concentration and the secondary efficacy endpoints were changes from baseline to week 12 in body weight, fasting plasma glucose (FPG) and systolic/diastolic blood pressure (SBP/DBP). Safety and tolerability were also monitored.

RESULTS

Ertugliflozin (1-25 mg/day) produced significant reductions in HbA1c concentration [placebo-corrected least-squares mean (LSM) -0.45% (1 mg) to -0.72% (25 mg); p ≤ 0.002, similar to sitagliptin (-0.76%; p = 0.0001)], FPG (LSM -1.17 to -1.90 mmol/l; p < 0.0001) and body weight (-1.15 to -2.15%; p < 0.0001). The LSM SBP decreased by -3.4 to -4.0 mmHg from baseline with ertugliflozin 5-25 mg/day. No reductions in body weight or blood pressure were observed with sitagliptin. After randomization, 2.7% of patients (9/328) withdrew because of adverse events (AEs); the frequency of AEs was evenly distributed across groups. No dose-related increase in AE frequency occurred with ertugliflozin. Hypoglycaemia was reported in 5 (1.5%) randomized participants (all in the ertugliflozin group). The frequency of urinary tract infection was 3.2% for ertugliflozin (pooled across groups), 1.8% for sitagliptin, 7.4% for placebo, and the frequency of genital fungal infections was 3.7% for ertugliflozin (pooled) versus 1.9% for placebo.

CONCLUSION

Ertugliflozin (1-25 mg/day) improved glycaemic control, body weight and blood pressure in patients with T2DM suboptimally controlled on metformin, and was well tolerated.

The orexin antagonist SB-649868 promotes and maintains sleep in men with primary insomnia

STUDY OBJECTIVES

To assess the acute effects of SB-649868 in male subjects with Primary Insomnia with regard to (1) objective and subjective sleep parameters, (2) safety and tolerability, (3) next-day residual effects.

DESIGN

Multicenter, randomized, double-blind, placebo-controlled crossover study using a complete set of Williams orthogonal Latin Squares

SETTING

9 sleep centers in Germany

PATIENTS

52 male subjects with a diagnosis of primary insomnia (difficulty in sleep initiation and maintenance) confirmed by polysomnography

INTERVENTIONS

SB-649868 (10, 30, 60 mg) and placebo administered after dinner 90 minutes before bedtime

MEASUREMENTS AND RESULTS

Sleep effects assessed by polysomnography during 2 consecutive nights and by sleep questionnaires completed by subjects after each night at the sleep laboratory. Safety and tolerability were assessed by adverse events collection, electrocardiogram (ECG), vital signs, laboratory tests. Next-day residual effects were assessed by Digit Symbol Substitution Test, and modified Verbal Learning Memory Test administered at "lights on" after night 2. SB-649868 significantly reduced latency to persistent sleep, wake after sleep onset (WASO), and increased total sleep time (TST) compared to placebo. A dose-dependent effect was observed. A dose-dependent increase in absolute and percent REM sleep and reduction in REM sleep latency was observed mainly at the 60-mg dose. SB-649868 was well tolerated with inconsistent next day residual effects. SB-649868 sleep effects were correlated with SB-649868 circulating levels.

CONCLUSION

The data demonstrate the sleep-promoting properties of the orexin antagonist SB-649868 in male patients with insomnia.

Phase I studies on the safety, tolerability, pharmacokinetics and pharmacodynamics of SB-649868, a novel dual orexin receptor antagonist

The orexin system plays a major role in the integration of metabolic and circadian influences that drive wakefulness. This paper describes initial Phase I trials of a novel dual orexin receptor antagonist SB-649868 that has demonstrated preclinical potential for treatment of sleep disorders. The trial designs included a single ascending dose escalation study (dose range: 10-80 mg in the fed and fasted states) and a multiple repeat dose study (dose range: 5-30 mg in the fed state) enrolling a total of 103 male volunteer subjects. SB-649868 was well tolerated at all doses in this study population, with mechanism-related adverse events (e.g. somnolence and fatigue) observed in a majority of subjects after 60 and 80 mg single doses. Although total drug exposure was similar in the fed and fasted states, the rate, but not the extent, of absorption increased in the fed state, resulting in an increased C(max). The typical estimated half-life of SB-649868 was 3-6 h - comparable with currently used hypnotic agents. Repeated administration of SB-649868 dose-dependently increased exposure to simvastatin (10 mg), suggesting CYP3A4 inhibition ranging from very mild (5 mg) to strong (30 mg). Evening dosing resulted in significant dose-dependent improvement in latency to persistent sleep, total sleep time and wake after sleep onset as measured by polysomnography. Next-morning testing did not detect evidence of residual cognitive effects. Results of these trials support further investigation of SB-649868 and other dual orexin receptor antagonists as potentially effective and well-tolerated treatments for patients with sleep disorders.

Within-subject comparison of striatal D2 receptor occupancy measurements using [123I]IBZM SPECT and [11C]Raclopride PET

Antipsychotic-induced D2 receptor occupancy values tend to be lower when measured with [(123)I]IBZM SPECT than with [(11)C]Raclopride PET. To clarify this issue, D2 receptor occupancy was measured in the same subjects using both techniques. Twenty patients with schizophrenia on monotherapy with risperidone (n=7; 3-9 mg/d), olanzapine (n=5; 5-20 mg/d) or clozapine (n=8; 150-450 mg/d) at stable doses, and ten healthy volunteers (HV) underwent both a [(123)I]IBZM SPECT and a [(11)C]Raclopride PET examinations in random order on different days within a week. Patients with schizophrenia were scanned at a fixed interval after last dose administration. Quantification of receptor availability was performed using the most conventional methods from the literature: the tissue ratio derived specific uptake ratios (SUR) were used for SPECT, and simplified reference tissue model (SRTM) derived binding potentials (BP(ND)) for PET. Analysis was performed using both occipital cortex and cerebellum as reference regions for both modalities. Striatal D2 receptor occupancy was measured as the percentage reduction of [(123)I]IBZM SUR or [(11)C]Raclopride BP(ND) compared to the population average measured in HV using the same modality. Occupancy values measured by SPECT were lower than those measured with PET, by 12.4% and 13.8% when occipital cortex and cerebellum were used as reference regions. This difference should be taken in consideration when interpreting reported antipsychotic striatal D2 receptor occupancy values from the literature.

Pharmacokinetics and time-course of D(2) receptor occupancy induced by atypical antipsychotics in stabilized schizophrenic patients

The (123)I-IBZM SPECT measured D(2) receptor occupancy (D(2)RO) in chronically dosed, stabilized schizophrenic patients and its relationship with antipsychotic (AP) pharmacokinetics (PK) over time is still unclear. The aims of this study were: 1) To define the relationship between striatal D(2) receptor occupancy (D( 2)RO) and plasma concentration (C(P)) in stabilized schizophrenic patients on clinically relevant doses using (123)I-IBZM SPECT; 2) To investigate the time course of AP-induced D(2)RO and corresponding C(P). Forty-six schizophrenic patients on their clinically required doses of risperidone, olanzapine, clozapine or quetiapine were included. D( 2)RO and C(P) were measured over time following a sparse-sampling experimental design, and individual PK and D(2)RO-time profiles were estimated using a population approach. Observed striatal D(2)RO and C(P) ranges were 28-75% and 9.4-60.5 ng/mL for risperidone, 22-84% and 8.6-89.5 ng/mL for olanzapine, 5-53% and 41.6-818.2 ng/mL for clozapine and 0-64% and 37.9-719.6 ng/mL for quetiapine. A PK-D(2)RO relationship was found for the four APs. D(2)RO pattern over time was stable for risperidone, olanzapine and clozapine but fluctuating for quetiapine. Stabilized schizophrenic patients show a wide range of both D(2)RO and C(P) at clinically effective doses of the four AP, suggesting that clinical response to these AP may be maintained with D(2)RO below 65%. D(2)RO patterns over time differ between AP. These results should be considered for accurate interpretation of D(2)RO measurements, proper design of studies and optimization of drug regimens for patients on AP treatment.

Muscle glucose transport and phosphorylation in type 2 diabetic, obese nondiabetic, and genetically predisposed individuals

Our objectives were to quantitate insulin-stimulated inward glucose transport and glucose phosphorylation in forearm muscle in lean and obese nondiabetic subjects, in lean and obese type 2 diabetic (T2DM) subjects, and in normal glucose-tolerant, insulin-resistant offspring of two T2DM parents. Subjects received a euglycemic insulin (40 mU.m(-2).min(-1)) clamp with brachial artery/deep forearm vein catheterization. After 120 min of hyperinsulinemia, a bolus of d-mannitol/3-O-methyl-d-[(14)C]glucose/d-[3-(3)H]glucose (triple-tracer technique) was given into brachial artery and deep vein samples obtained every 12-30 s for 15 min. Insulin-stimulated forearm glucose uptake (FGU) and whole body glucose metabolism (M) were reduced by 40-50% in obese nondiabetic, lean T2DM, and obese T2DM subjects (all P < 0.01); in offspring, the reduction in FGU and M was approximately 30% (P < 0.05). Inward glucose transport and glucose phosphorylation were decreased by approximately 40-50% (P < 0.01) in obese nondiabetic and T2DM groups and closely paralleled the decrease in FGU. The intracellular glucose concentration in the space accessible to glucose was significantly greater in obese nondiabetic, lean T2DM, obese T2DM, and offspring compared with lean controls. We conclude that 1) obese nondiabetic, lean T2DM, and offspring manifest moderate-to-severe muscle insulin resistance (FGU and M) and decreased insulin-stimulated glucose transport and glucose phosphorylation in forearm muscle; these defects in insulin action are not further reduced by the combination of obesity plus T2DM; and 2) the increase in intracelullar glucose concentration under hyperinsulinemic euglycemic conditions in obese and T2DM groups suggests that the defect in glucose phosphorylation exceeds the defect in glucose transport.

Characterization of the SPECT 5-HT2A receptor ligand 123I-R91150 in healthy volunteers: part 2--ketanserin displacement

As part of the radioiodinated 4-amino-N-1-[3-(4-fluorophenoxy)propyl]-4-methyl-4-piperidinyl]5-iodo-2-methoxybenzamide ((123)I-R91150) characterization study, ketanserin challenges were performed on healthy volunteers with the aim of assessing the specificity of (123)I-R91150 binding to subtype 2A of the 5-hydroxytryptamine receptor (5-HT(2A)), the sensitivity of (123)I-R91150 SPECT in measuring ligand displacement, the relationship between ketanserin plasma concentrations and (123)I-R91150 displacement, and the suitability of the cerebellum as a reference region for quantification.

METHODS

Dynamic SPECT was performed on 6 healthy men (mean age +/- SD, 21 +/- 0.89 y) from the time of (123)I-R91150 injection until 470 min afterward. Ketanserin was administered intravenously at 210 min after injection at 3 doses: 0.1 mg/kg (n = 2), 0.05 mg/kg (n = 2), and 0.015 mg/kg (n = 2). Blood samples for measurement of ketanserin plasma concentrations were drawn. MRI was performed on all subjects and coregistered to the SPECT data for region-of-interest drawing on cortical regions and cerebellum. The simplified reference tissue model (SRTM) was considered the gold standard for quantification, and results were compared with those obtained with the tissue ratio method (TR). The percentage (123)I-R91150 displacement was calculated with both methods as the percentage difference between baseline and postketanserin scans.

RESULTS

Depending on the cerebral regions with the maximum ketanserin dose studied, SRTM and TR mean displacements were 57.1%-95.4% and 71.9%-101.2%, respectively, for the 0.1 mg/kg dose; 51.7%-91.4% and 56.7%-102.8%, respectively, for the 0.05 mg/kg dose; and 7.7%-54.5% and 13.8%-47.0%, respectively, for the lowest dose, 0.015 mg/kg. A good correlation was found between the 2 methods. No ketanserin-induced displacement was observed in the cerebellum time-activity curves, supporting the use of the cerebellum as a reference region. The relationship between displacement and ketanserin plasma concentration fit with a rectangular hyperbola, with a 5.6 ng/mL concentration associated with 50% of the maximum displacement (EC(50)). EC(50) values calculated using occupancies derived both with SRTM and with TR were in good agreement.

CONCLUSION

(123)I-R91150 SPECT is sensitive enough to measure ketanserin dose-dependent displacement in cerebral regions rich in 5-HT(2A) receptors. These results support the selectivity of (123)I-R91150 for 5-HT(2A) receptors and its use as a SPECT ligand for measurements of drug-induced 5-HT(2A) receptor occupancy in humans.

Multiple dose pharmacokinetics of paroxetine in children and adolescents with major depressive disorder or obsessive-compulsive disorder

The current study examined the pharmacokinetics (PK), safety, and tolerability of paroxetine after repeated multiple oral dosing in children and adolescents with major depressive or obsessive-compulsive disorder. In this 6-week, open-label, repeat dose, dose-rising study, 62 patients (27 children and 35 adolescents) were treated with paroxetine 10 mg/day for the first 2 weeks of the study, 20 mg/day for the next 2 weeks, and 30 mg/day for the final 2 weeks. Pharmacokinetic sampling and safety assessments occurred at baseline and subsequently on the final treatment day of each dosing level. Between-patient variability in PK was pronounced at the 10 mg dose level, but markedly reduced at higher doses. A supra-proportional increase in plasma concentrations with increasing dose was evident in both age groups. Data for C(max) and AUC(0-24) indicated that, at each dose level, paroxetine steady-state systemic exposure was higher in children than in adolescents. The differences between age groups, however, diminished with each increasing dose, and were virtually abolished when differences in weight among different age groups were considered. Stepwise regression analysis indicated that both oral clearance and volume of distribution were highly dependent on paroxetine dose, cytochrome P4502D6 genotype, and weight (p<0.0001), but not age or sex. Paroxetine was generally safe and well tolerated in both age groups, with the most frequently observed adverse events being largely consistent with those observed in prior paroxetine studies of adult psychiatric patients. Certain gastrointestinal and behavioral activation events (aggressive reaction and nervousness) were reported more frequently in the youngest age group.

Characterization of a 7% carbon dioxide (CO2) inhalation paradigm to evoke anxiety symptoms in healthy subjects

The present study is aimed at characterizing the carbon dioxide (CO2) procedure in healthy subjects to achieve reliable provocation of anxiety symptoms. Thirty healthy subjects inhaled in single-blind both compressed air and 7% CO2 mixture. Panic Symptom List (PSLIII-R), Visual Analogue Scale-Anxiety (VAS-A), State Anxiety Inventory (STAI-Y/1), respiratory parameters and skin conductance were measured. 'Responders' were classified depending on PSLIII-R scores after CO2. Twelve out of the 21 'responders' performed a second test to assess test-retest repeatability. In 21 subjects Delta%VAS-A (45.4 +/- 32.1) and PSLIII-R (pre-test 2.3 +/-2.1, post-test 17.5 +/- 8.2) but not STAI-Y/1, significantly increased during CO2 inhalation. Respiratory Rate, Minute Volume, end-Tidal CO2 and skin conductance rose in 'responders'. Repeatability was studied with Bland-Altman plots, revealing mean difference between tests close to 0 for both Delta%VAS-A and PSLIII-R. Among physiologic parameters, end-Tidal CO2 and Respiratory Rate showed good repeatability, with a within-subject CV of 9.2% and 6%, respectively. The challenge produced measurable response in healthy subjects. Good test-retest repeatability was observed in 'responders'. These data indicate that the test can be suitable for testing putative anti-panic or anxiolytic drugs in clinical studies using a within subject, crossover design.

Modeling airflow-related shear stress during heterogeneous constriction and mechanical ventilation

Ventilator-induced lung injury has been proposed as being caused by overdistention and closure and reopening of small airways and alveoli. Here we investigate the possibility that heterogeneous constriction increases airflow-related shear stress to a dangerously high level that may be sufficient to cause injury to the epithelial cells during mechanical ventilation. We employed an anatomically consistent model of the respiratory system, based on Horsfield morphometric data, and solved for the time evolution of pressure and flow along the airway tree during mechanical ventilation. We simulated constant-flow ventilation with passive expiration in two different conditions: baseline and highly heterogeneous constriction. The constriction was applied with two strategies: establishing a simple diameter reduction or adding also a length shortening. The shear stress distribution on airway walls was analyzed for airways ranging from the trachea to the acini. Our results indicate that 1). heterogeneous constriction can amplify the maximal values of shear stress up to 50-fold, with peak values higher than 0.6 cmH2O; 2). the highest shear stress is found in pathways constricted by 60-80%; 3). simultaneous diameter reduction and shortening amplifies the shear stresses by three- to fourfold, with shear stresses reaching 2 cmH2O; and 4). there is a range of airways (diameters from 0.6 to 0.3 mm at baseline) that appear to be at risk of very high stresses. We conclude that elevated airflow-related shear stress on the epithelial cell layer can occur during heterogeneous constriction and conjecture that this may constitute a mechanism contributing to ventilator-induced lung injury.

Design, methods, and evaluation directions of a multi-access service for the management of diabetes mellitus patients

Recent advances in information and communication technology allow the design and testing of new models of diabetes management, which are able to provide assistance to patients regardless of their distance from the health care providers. The M2DM project, funded by the European Commission, has the specific aim to investigate the potential of novel telemedicine services in diabetes management. A multi-access system based on the integration of Web access, telephone access through interactive voice response systems, and the use of palmtops and smart modems for data downloading has been implemented. The system is based on a technological platform that allows a tight integration between the access modalities through a middle layer called the multi-access organizer. Particular attention has been devoted to the design of the evaluation scheme for the system: A randomized controlled study has been defined, with clinical, organizational, economic, usability, and users' satisfaction outcomes. The evaluation of the system started in January 2002. The system is currently used by 67 patients and seven health care providers in five medical centers across Europe. After 6 months of usage of the system no major technical problems have been encountered, and the majority of patients are using the Web and data downloading modalities with a satisfactory frequency. From a clinical viewpoint, the hemoglobin A1c (HbA1c) of both active patients and controls decreased, and the variance of HbA1c in active patients is significantly lower than the control ones. The M2DM system allows for the implementation of an easy-to-use, user-tailored telemedicine system for diabetes management. The first clinical results are encouraging and seem to substantiate the hypothesis of its clinical effectiveness.

A telemedicine support for diabetes management: the T-IDDM project

In the context of the EU funded Telematic Management of Insulin-Dependent Diabetes Mellitus (T-IDDM) project, we have designed, developed and evaluated a telemedicine system for insulin dependent diabetic patients management. The system relies on the integration of two modules, a Patient Unit (PU) and a Medical Unit (MU), able to communicate over the Internet and the Public Switched Telephone Network. Using the PU, patients are allowed to automatically download their monitoring data from the blood glucose monitoring device, and to send them to the hospital data-base; moreover, they are supported in their every day self monitoring activity. The MU provides physicians with a set of tools for data visualization, data analysis and decision support, and allows them to send messages and/or therapeutic advice to the patients. The T-IDDM service has been evaluated through the application of a formal methodology, and has been used by European patients and physicians for about 18 months. The results obtained during the project demonstration, even if obtained on a pilot study of 12 subjects, show the feasibility of the T-IDDM telemedicine service, and seem to substantiate the hypothesis that the use of the system could present an advantage in the management of insulin dependent diabetic patients, by improving communications and, potentially, clinical outcomes.

A morphometric model of lung mechanics for time-domain analysis of alveolar pressures during mechanical ventilation

In this study we propose, and implement in the time domain, an anatomically consistent model of the respiratory system in critical care conditions that allows us to evaluate the impact of different ventilator strategies as well as of constrictive pathologies on the time course of acinar pressures and flows. We discuss the simplifications of the original Horsfield structure (Horsfield, K., et al. Models of the human bronchial tree. J. Appl. Physiol. 31:207-217, 1971), which were needed to enable the model implementation. The model has a binary tree structure including large airways represented as a combination of wall compliance and laminar resistance, small airways that have the same arrangement but can be heterogeneously constricted, and alveolar compartments that are viscoelastic second-order models to represent the stress adaptation behavior of lung tissue. We have described patient-ventilator interactions modeling the ventilator and the endotracheal tube. In conclusion this model makes it possible to investigate realistically the effect of homogeneous versus heterogeneous constrictive pathologies and the impact of different ventilatory patterns on pressure and flow distribution at the acinar level in the mechanically ventilated patient.

On-line monitoring of intrinsic PEEP in ventilator-dependent patients

Measurement of the intrinsic positive end-expiratory pressure (PEEP(i)) is important in planning the management of ventilated patients. Here, a new recursive least squares method for on-line monitoring of PEEP(i) is proposed for mechanically ventilated patients. The procedure is based on the first-order model of respiratory mechanics applied to experimental measurements obtained from eight ventilator-dependent patients ventilated with four different ventilatory modes. The model PEEP(i) (PEEP(i,mod)) was recursively constructed on an inspiration-by-inspiration basis. The results were compared with two well-established techniques to assess PEEP(i): end-expiratory occlusion to measure static PEEP(i) (PEEP(i, st)) and change in airway pressure preceding the onset of inspiratory airflow to measure dynamic PEEP(i) (PEEP(i,dyn)). PEEP(i, mod) was significantly correlated with both PEEP(i,dyn) (r = 0.77) and PEEP(i,st) (r = 0.90). PEEP(i,mod) (5.6 +/- 3.4 cmH(2)O) was systematically >PEEP(i,dyn) and PEEP(i,st) (2.7 +/- 1.9 and 8.1 +/- 5.5 cmH(2)O, respectively), in all the models without external PEEP. Focusing on the five patients with chronic obstructive pulmonary disease, PEEP(i,mod) was significantly correlated with PEEP(i,st) (r = 0.71), whereas PEEP(i,dyn) (r = 0.22) was not. When PEEP was set 5 cmH(2)O above PEEP(i,st), all the methods correctly estimated total PEEP, i.e., 11.8 +/- 5.3, 12.5 +/- 5.0, and 12.0 +/- 4.7 cmH(2)O for PEEP(i,mod), PEEP(i,st), and PEEP(i,dyn), respectively, and were highly correlated (0.97-0.99). We interpreted PEEP(i,mod) as the lower bound of PEEP(i,st) and concluded that our method is suitable for on-line monitoring of PEEP(i) in mechanically ventilated patients.

Models of subcutaneous insulin kinetics. A critical review

Subcutaneous insulin kinetics is a complex process whose quantitation is needed for a reliable glycemic control in the conventional therapy of insulin-dependent diabetes. The major difficulties in modeling include accounting for the distribution in the subcutaneous depot and transport to plasma. A single model describing in detail the various processes for all the commercially available insulin preparations is not available. Several models however have been proposed which vary in the degree of complexity. Virtually all of them handle the regular insulin preparation while a few handle the intermediate acting and the novel insulin analogues. In this paper we critically review these models.

A case-control study on risk factors for Peyronie's disease

The aim of this study was to investigate the relationship between history of selected diseases, genital traumas, and Peyronie's disease. A hospital-based case-control study was conducted at the Andrologic and Surgical Outpatient Units of the Policlinico Gemelli, Rome, where 134 men with Peyronie's disease and 134 male controls were interviewed. The association between Peyronie's disease and selected characteristics was estimated by means of odds ratios (OR) and 95% confidence intervals (CI). Patients who underwent invasive procedures on the penis (i.e., urethral catheterization, cystoscopy, and transurethral prostatectomy) had a 16-fold increased risk for Peyronie's disease (OR = 16.1, 95% CI: 1.8-142), while a nearly three-fold increase was observed among patients who had genital and/or perineal traumatisms (95% CI: 1.0-7.1). A history of urethritis, uricacidemia, and lipoma was also significantly associated with an increased risk for Peyronie's disease. Twenty-one percent of the cases and none of the controls were affected by Dupuytren's contracture, and 4% of cases and none of the controls reported familial history for Peyronie's disease. The frequency of inflammatory or fibromatous lesions of the genital tract of the partner was significantly higher in men with Peyronie's disease than among controls. These results were consistent when performing a stratified analysis according to the type of controls (i.e., controls affected by urologic or by digestive conditions) to rule out the potential effect of recall bias. The findings of the study lend support to clinical reports stressing the importance of genital traumatisms and genetic conditions in the development of Peyronie's disease.

[Oncocytic carcinoma in a horseshoe kidney]

The Authors report a rare case of oncocytoma in a horseshoe kidney. The diagnostic path needed to assess the precise anatomy of the malformation and tumoral staging is out lined. Oncological problems dealing with oncocytoma are further discussed, together with the technical and surgical issues pertinent to the clinical case.

Neuro-pharmacologic control of bladder voiding. Pharmacologic therapy of detrusor-sphincter dyssynergia concerning 162 patients

The Authors refer to current opinions regarding the neuro-pharmacologic control of bladder voiding. They report their experience concerning 162 patients with detrusor-sphincter dyssynergia: 86 pts were affected by multiple sclerosis and 76 by neurobladder after spinal cord injury.

Anatomo-functional considerations on venogenic impotence

The authors report their clinical experience with cavernosography and cavernosometry on impotent patients. The indications of method and its correct place in the diagnostic workup are underscored. The methods of evaluation are described, highlighting the advantages of a diagnostic pharmacological approach in respect to a near as possible physiological haemodynamic evaluation. Finally they propose a future development for the method, such as the use of PGE1 instead of the commonly employed drugs, and a new classification for the veno-occlusive disease with stage and grade.

Acute idiopathic scrotal oedema: rare disorder or difficult diagnosis?

This study reports our experience in 6 cases of acute idiopathic scrotal oedema. Although children were the primary targets, this pathologic condition was also encountered in adults. Specific diagnosis of acute idiopathic scrotal oedema, opposed to other causes of scrotal swelling, is based on history, an objective examination, velocimetric Doppler exam and echography. Correct diagnosis is important in order to avoid unnecessary surgery. We are inclined to consider acute idiopathic scrotal oedema as an allergic disorder and recommend a follow-up within two days.

Comparison of the reactivity of micro-and macrovessels to noradrenaline and endothelin in rats with renal (2K1C) hypertension

The response to noradrenaline and endothelin in isolated aortae in vitro and mesenteric microvessels in vivo - in situ was studied in 4-week 2K1C hypertensive rats. Enhanced reactivity to noradrenaline was observed in aortae with endothelium isolated from hypertensive rats, whereas in aortae without endothelium, noradrenaline induced similar responses in sham-operated control and hypertensive preparations. Endothelin responses were not altered in aortae with or without endothelium isolated from hypertensive rats. In mesenteric microvessels, both noradrenaline and endothelin evoked higher responses in 2K1C than in control animals. It is suggested that the enhanced reactivity observed could be involved in the maintainance of high blood pressure levels in 2K1C hypertension. The altered reactivity could be due to a dysfunction of the endothelial cells.