Integrin α11ß1 regulates cancer stromal stiffness and promotes tumorigenicity and metastasis in non-small cell lung cancer.

Integrin α11ß1 is a stromal cell-specific receptor for fibrillar collagens and is overexpressed in carcinoma-associated fibroblasts (CAFs). We have investigated its direct role in cancer progression by generating severe combined immune deficient (SCID) mice deficient in integrin α11 (α11) expression. The growth of A549 lung adenocarcinoma cells and two patient-derived non-small cell lung carcinoma (NSCLC) xenografts in these α11 knockout (α11(-/-)) mice was significantly impeded, as compared with wild-type (α11(+/+)) SCID mice. Orthotopic implantation of a spontaneously metastatic NCI-H460SM cell line into the lungs of α11(-/-) and α11(+/+) mice showed significant reduction in the metastatic potential of these cells in the α11(-/-) mice. We identified that collagen cross-linking is associated with stromal α11 expression, and the loss of tumor stromal α11 expression was correlated with decreased collagen reorganization and stiffness. This study shows the role of integrin α11ß1, a receptor for fibrillar collagen in differentiation of fibroblasts into CAFs. Furthermore, our data support an important role for α11 signaling pathway in CAFs, promoting tumor growth and metastatic potential of NSCLC cells and being closely associated with collagen cross-linking and the organization and stiffness of fibrillar collagen matrices.

Inhibitory effect of telmisartan on the blood pressure response to angiotensin II challenge.

Telmisartan is a new angiotensin receptor antagonist possessing potent, selective, and insurmountable inhibitory activity specific to the angiotensin II type 1 (AT 1 ) receptor. The current study was performed to determine the inhibition of the angiotensin II pressor response by telmisartan in 48 healthy volunteers challenged with hypertension-inducing doses of i.v. angiotensin II. Subjects were challenged with this dose of angiotensin II at intervals between 0.25 and 48 h after double-blind single-dose oral administration of telmisartan 20 mg (n = 12), 40 mg (n = 12), or 80 mg (n = 12) or placebo (n = 12) in parallel groups. Diastolic and systolic blood pressure and pulse rate were recorded continuously using a servophotoplethysmograph. Urine samples were collected during the study for urinalysis. Tolerability of telmisartan, in comparison with placebo, was also monitored throughout the study. Telmisartan 20-80 mg dose dependently inhibited the increase in diastolic and systolic blood pressure induced by angiotensin II. Telmisartan 40 mg produced 80.1% maximum inhibition, and with 80 mg 89.6% maximum inhibition of diastolic blood pressure was achieved. Inhibition was apparent after 0.3-1.1 h and was still observed 48 h after administration for all telmisartan doses. The inhibitory effect of telmisartan 20, 40, and 80 mg, 48 h after dosing was significantly greater than that of placebo. A > 25% inhibition of the angiotensin II response on diastolic blood pressure was detected until 26.9, 35.4, and 40.5 h, respectively, after telmisartan 20 mg, 40 mg, and 80 mg. Anti-clockwise hysteresis was observed, indicating a delay and longer persistence of effect than to be expected from the plasma concentration-time course. The slow dissociation of telmisartan from the receptor probably contributed to this hysteresis. The incidence of adverse events was comparable in telmisartan-and placebo-treated subjects and was not dose dependent. In conclusion, telmisartan 40 mg provides rapid-onset, well-tolerated, and near-maximal inhibition of angiotensin II-induced hypertension, with maintenance of the inhibitory effect for 48 h.

Identifying a cohort of patients with early-stage breast cancer: a comparison of hospital discharge and primary data.

BACKGROUND: Hospital discharge data are a potential source of information for quality of care; however, they lack detailed clinical data. OBJECTIVES: To assess the usefulness of hospital discharge data for describing patterns of care. RESEARCH DESIGN: Cohort study comparing hospital discharge data with data collected from medical records and patients. PATIENTS: Women diagnosed with early-stage breast cancer in Massachusetts and Minnesota (1993-1995). MEASURES: The percentage of patients in the primary data set who did not match a record in the discharge data set, and the percentage of patients in the discharge data set who did not match a record in the primary data set. Odds ratios for appearing in one data set, but not the other according to patient and hospital characteristics. RESULTS: For patients in the primary data set, 26.9% from Massachusetts and 13.2% from Minnesota did not match a record in the discharge data set. In both states, factors associated with failure to match to the discharge data included receipt of breast conserving surgery, shorter length of stay, and treatment hospital. For patients in the discharge data set, 43.4% in Massachusetts and 30.3% in Minnesota did not match a patient in the primary data set. In both states, factors associated with failure to match to the primary data included treatment hospital and the presence of positive lymph nodes. CONCLUSIONS: Hospital discharge data were fairly sensitive when linked to patients with early-stage breast cancer who were identified through hospital records. The discharge data lacked specificity, however. If discharge data are used to characterize patterns care for inpatients with early stage disease, estimates are likely to be inaccurate due to the inclusion of unsuitable patients in the denominator used to calculate procedure rates.

Mephenytoin as a probe for CYP2C19 phenotyping:effect of sample storage, intra-individual reproducibility and occurrence of adverse events.

AIMS: To further evaluate mephenytoin as a probe for CYP2C19 phenotyping. METHODS: Healthy subjects (n = 2638) were phenotyped using the urinary (S)-mephenytoin to (R)-mephenytoin ratio. This method was evaluated for (a) the stability of the S/R-ratio following sample storage, (b) the intraindividual reproducibility of the ratio, and (c) the occurrence of adverse events. RESULTS: After prolonged storage, the S/R-ratio of samples from extensive metabolisers (EM) increased up to 85%. In 1.5% of the cases (1 out 66), this led to incorrect classification of phenotype. In EMs, but not in poor metabolisers (PMs), the S/R-ratio increased after acid treatment. The intraindividual reproducibility of the mephenytoin phenotyping procedure was 28%. No major side-effects were observed and there was no relationship between the incidence of side-effects and the phenotype of the subject. CONCLUSIONS: After prolonged storage the S/R-ratio significantly increased in EMs and, although low, the risk of incorrect classification should not be ignored. Our data support the use of mephenytoin as a safe drug for CYP2C19 phenotyping.

An optimized methodology for combined phenotyping and genotyping on CYP2D6 and CYP2C19.

A method for simultaneous phenotyping and genotyping for CYP2D6 and CYP2C19 was tested. Six healthy volunteers were selected (three extensive and three poor metabolisers for CYP2D6). CYP2D6 was probed with dextromethorphan and metoprolol and CYP2C19 was probed with omeprazole. Blood samples were collected and analysed for dextromethorphan, dextrorphan, metoprolol, alpha-hydroxymetoprol, omeprazole and 5-hydroxyomeprazole by HPLC. Genotyping was performed for both CYP2D6 and CYP2C19. Generally, plasma levels could be measured up to 8 h post-dose except for alpha-hydroxymetoprolol in poor metabolizers (PMs) and dextromethorphan in extensive metabolizers (EMs) (35% below quantification limit). The correlation between the metabolic ratio based on timed individual measurements and the metabolic ratio based on the AUC0-12 values was significant at 3 h post-dose for all probes. In conclusion, the following procedure is suggested: administer metoprolol (100 mg) and omeprazole (40 mg); after 3 h, take a blood sample to assess the genotype and the metabolic ratio for CYP2D6 (metoprolol over alpha-hydroxymetoprolol) and CYP2C19 (omeprazole over 5-hydroxyomeprazole) in plasma. With this procedure, all necessary information on the individual CYP2D6 and CYP2C19 metabolising capacity can be obtained in a practical, single-sample approach.

The prevalence of CYP2D6 and CYP2C19 genotypes in a population of healthy Dutch volunteers.

AIM: This study was performed in a sample of the Dutch population to estimate the prevalence of noncoding mutations of CYP2D6 and CYP2C19 as obtained by genotyping. In addition, the predictability of the genotyping strategy was assessed. METHODS: The CYP2D6 and CYP2C19 status of 765 unrelated healthy volunteers was evaluated. Dextromethorphan and mephenytoin were used for determining the phenotypes. Genotyping was performed by PCR on the most common null alleles for CYP2D6 (except for CYP2D6*5) and CYP2C19. RESULTS: For CYP2D6, the most frequently observed null allele was CYP2D6*4, which accounted for 89% of all null alleles. The prevalence of poor metabolizers (PMs) in healthy volunteers was 5.5%, which was lower than that found previously by phenotyping (8.0%; chi2 test P = 0.009). For CYP2C19*2 and CYP2C19*3, the frequencies were 13.3% and 0.2%, respectively. The S:R ratio was significantly higher in heterozygous subjects (S:R ratio 0.22) than in homozygous wild type subjects (S:R ratio 0.11). Comparison of all subjects below 45 years showed a significantly higher S:R ratio in the female ones compared to the male ones, especially in heterozygous subjects (S:R ratio 0.39 vs. 0. 19; P < 0.001). CONCLUSIONS: The frequencies of CYP2D6 and CYP2C19 allelic variants were in accordance with other European populations. Assessment of *3, *4, *6, *7, and *8 alleles for CYP2D6, and *2 and *3 for CYP2C19, predicted the phenotype with an accuracy of over 98.6%. A gene-dose effect was found for CYP2C19. CYP2C19 heterozygous female subjects had a decreased CYP2C19 activity that may be at least partly due to the use of oral contraceptives.

Evaluation of analytical and clinical performance of a dual-probe phenotyping method for CYP2D6 polymorphism and CYP3A4 activity screening.

A bioanalytical method for the determination of dextromethorphan (DEX) and its metabolites dextrorphan (DTX), 3-methoxymorphinan (3MM), and 3-hydroxymorphinan (3HM) in human urine was developed for CYP2D6 phenotyping and CYP3A4 activity measurements in clinical pharmacology studies using dextromethorphan administered in a drinking solution as substrate. The method was evaluated by thorough conventional validation and by a cross-validation of the method with a previously applied method for dextromethorphan and dextrorphan only (CYP2D6 phenotyping). Cross-validation with the former method showed no significant differences in measured concentrations of volunteer samples. This guaranteed the consistency of epidemiologic data in the database collected from two methods. For the CYP2D6 and CYP3A4 evaluations, the clinical parameters are ratios of concentrations. It appeared that severe variance in individual concentrations generally did not influence the variance of ratios significantly, because experimental errors in concentrations of two analytes proved to correlate considerably. For CYP2D6 values around the antimodes, the chance of a misclassification is very small. The chance of classifying an extensive metabolizer as a poor metabolizer or vice versa is negligible. For CYP3A4 activity determinations it was concluded that in general a change in dextromethorphan/3-methoxymorphinan (DEX/3MM) ratios of 10% or more as detected with the current method, is a significant increase or decrease in the activity of CYP3A4. The authors concluded that they had obtained an analytically valid and clinically reliable bioanalytical method for the determination of dextromethorphan and its metabolites dextrorphan, 3-methoxymorphinan, and 3-hydroxymorphinan in human urine for CYP2D6 phenotyping and CYP3A4 activity measurements for clinical pharmacology studies.

Dysphagia lusoria: clinical aspects, manometric findings, diagnosis, and therapy.

OBJECTIVE: The lusorian artery is a rare anomaly of the right subclavian artery. This artery arises from the aortic arch distal of the left subclavian artery, crossing the midline behind the esophagus. Normally this anomaly causes no symptoms. Sometimes dysphagia first appears above the age of 40 yr. METHODS: In the period of 1992-1997, the diagnosis of an aberrant right subclavian artery was made in five patients with dysphagia who were referred to a small community hospital. A sixth patient had a right-sided aorta with an aberrant left subclavian artery. RESULTS: Endoscopy revealed a pulsating impression in the esophagus of three patients. Four patients had coexisting esophageal abnormalities. Barium contrast examination of the esophagus showed a characteristic diagonal impression at the level of the fourth thoracic vertebra in all patients. Computed tomography and angiography confirmed the diagnosis and excluded aneurysms. Manometric investigation of the esophagus revealed nonspecific abnormalities in five patients. Drug treatment was sufficient in three patients (mean follow-up, 6.2 yr). Three patients were operated upon because of persistent dysphagia. Through a cervical approach the artery was ligated near its root and connected with the right carotid artery. Postoperatively two patients became symptom-free, the other patient still has intermittent dysphagia. CONCLUSION: Dysphagia can be caused by a rare anomaly of the subclavian artery. The diagnosis can be overlooked at endoscopy, but barium contrast study of the esophagus will reveal the abnormality. In patients with coexisting esophageal abnormalities the finding may be incidental and specific conservative treatment may be sufficient. Manometry cannot be used to diagnose this condition or to predict surgical outcome. When the symptoms are intractable, surgical correction should be considered even if coexisting esophageal abnormalities are present.

Absorption, metabolism, and excretion of intravenously and orally administered [14C]telmisartan in healthy volunteers.

The study was conducted in healthy male volunteers to evaluate the absorption, metabolic pattern, and mode of elimination of telmisartan, a nonpeptide angiotensin II receptor antagonist. [14C]telmisartan was administered orally in solution as a single 40 mg dose to 5 subjects. A further 5 subjects received short-term intravenous infusion of [14C]telmisartan 40 mg. Measurement of total 14C radioactivity in plasma showed that about 50% was absorbed following oral administration, with maximum plasma concentration observed after 0.5 to 1 hour. Absolute bioavailability was 43%. On average, 84% of total radioactivity in plasma reflected the parent compound. The remainder of total radioactivity could be ascribed to the glucuronide conjugate of telmisartan, which represented the only metabolite in man. About 99.5% of telmisartan was bound to plasma protein, mainly to albumin and alpha-1-acid glycoprotein. Telmisartan was reversibly distributed into erythrocytes. More than 90% of administered dose was excreted within 120 hours, and the excretion balance was complete 144 hours after dosing. Radioactivity was almost exclusively (> 98%) excreted via the feces; urinary excretion accounted for < 1% of the dose, irrespective of the route of administration. In the small fraction excreted into urine, the glucuronide conjugate of telmisartan was predominant. Although some telmisartan glucuronide was detected in plasma, only unchanged drug was identified in the feces. No changes in vital signs, electrocardiogram, or clinical laboratory tests were detected following telmisartan administration, and adverse events, predominantly unrelated to treatment and of mild intensity, were infrequent. One subject fainted and, on another occasion, reported faintness; these events were probably due to the antihypertensive action of the intravenous study medication.

Steady-state pharmacodynamics and pharmacokinetics of warfarin in the presence and absence of telmisartan in healthy male volunteers.

The effects of multiple-dose telmisartan on the steady-state pharmacodynamics and pharmacokinetics of warfarin were assessed in 12 healthy young males in an open-label, single-period study conducted over 30 days. Subjects received loading doses of oral once-daily warfarin on days 1 to 5, which were individually adjusted at days 6 and/or 9 to attain stable predose prothrombin time values (INRpre) of between 1.2 and 1.8 by the end of medication phase 1 (day 14). From days 15 to 24 (medication phase 2), subjects received oral once-daily telmisartan 120 mg in addition to individualized oral doses of once-daily warfarin. On days 25 to 31 (medication phase 3), oral once-daily warfarin was again administered alone at individualized doses. Under steady-state conditions, INRpre remained unchanged during medication phases 1, 2, and 3. The difference between phases 1 and 3 was -0.04 (95% confidence interval [CI]: -0.7 to 0.10) and between phases 2 and 1 was 0.03 (95% CI: -0.11 to 0.10). Mean trough plasma warfarin concentrations (Cpre) were stable during medication with warfarin alone but showed a small, although statistically significant, decrease during the combined-medication phase. The point estimate of the ratio of phase 2/phase 1 was 0.89 (95% CI: 0.84 to 0.95). The decrease in Cpre did not result in decreased anticoagulation. This suggests that the extent of pharmacokinetic interaction between telmisartan and warfarin is limited, and since telmisartan had no effect on INRpre and the concomitant medication was well tolerated, there is no evidence for a clinically relevant interaction between telmisartan and warfarin.

The effect of telmisartan on the steady-state pharmacokinetics of digoxin in healthy male volunteers.

A multiple-dose, open-label, two-period, crossover randomized study was conducted in 12 healthy male volunteers to investigate the effect of multiple-dose telmisartan on the steady-state pharmacokinetics of digoxin. On day 1 of a 7-day medication period, subjects received a loading dose of digoxin 0.5 mg in the morning, followed by an evening dose of digoxin 0.25 mg, either alone or together with telmisartan 120 mg administered in the morning. On the subsequent 6 days, either digoxin 0.25 mg or digoxin 0.25 mg together with telmisartan 120 mg was administered once daily in the morning. Each 7-day medication period was separated by a washout period of > or = 14 days. A steady-state plasma concentration-time profile was assessed for digoxin during each period and for telmisartan during the period with the combined treatment. Multiple-dose telmisartan administered with digoxin resulted in higher serum digoxin concentrations than those observed after digoxin given alone. Geometric mean AUC144-168, Cmax, and Cmin values for digoxin when given in combination with telmisartan were higher by 22%, 50%, and 13%, respectively, compared with values when given alone. However, the 90% confidence interval for the geometric mean of Cmin was within the predefined 80% to 125% range of no interaction. During combination medication, digoxin tmax was shorter and Cmax/AUC144-168 increased, suggesting that the rise in digoxin Cmax may be due to more rapid drug absorption. Study medications were well tolerated, with the incidence, nature, and intensity of adverse events being similar during both medication periods. Also, no changes in vital signs or clinical laboratory tests were observed during the study. Although there was some evidence for a pharmacokinetic interaction between digoxin and telmisartan found in this study, the safety and tolerability of digoxin were unaffected by concurrent administration of telmisartan in the study population. Since any symptoms of overdose are related only to steady state and not peak concentrations and due to the fact that there was a lack of effect on serum trough levels of digoxin in this study, it is unlikely that the findings have any clinical relevance. The magnitude of increase in digoxin concentrations is comparable with increases observed with administration of calcium antagonists, carvedilol, ACE inhibitors such as captopril, and antiarrhythmic drugs such as amiodarone, quinidine, and propafenone. Monitoring of serum digoxin concentrations should be considered when patients first receive telmisartan and in the event of any changes in telmisartan dose.

[Free air below the diaphragm: not always an acute surgical problem]. / Vrije lucht onder het diafragma: niet altijd een acuut chirurgisch probleem.

In three patients, two males aged 66 and 67 years with among other disorders chronic obstructive pulmonary disease (COPD) and one woman aged 24 years with a history of intestinal surgery and current abdominal pain, the chest X-ray showed free air below the diaphragm. The two males had no major abdominal symptoms, but they did have pneumonia. All were treated conservatively. Of the males, one died from pneumonia, the other recovered. The woman presented recurrent symptoms and was subjected to extensive diagnostic examinations. This revealed a marked sigmoid perforation which was repaired, after which the symptoms did not recur. Pneumoperitoneum indicates rupture or perforation of a hollow viscus in up to 90%. In these cases, prompt surgical management is the therapy of choice. In at least 10% free air under the diaphragm is due to causes which do not require surgical treatment. These causes can be divided into intra-abdominal, intrathoracic, gynaecological and iatrogenic diseases. Conservative management should only be considered if followed by frequent and intensive evaluation of the patient's condition.

Absorption, metabolism and excretion of a single oral dose of (14)C-repaglinide during repaglinide multiple dosing.

OBJECTIVE: The present study was designed to assess the disposition of (14)C-repaglinide in whole blood, plasma, urine and faeces, and to measure the total recovery of drug-related material in urine and faeces after a single 2-mg oral dose of (14)C-repaglinide during multiple dosing. METHODS: In this single-centre, open-label, phase-I trial, six healthy male volunteers received 2 mg of the prandial glucose regulator, repaglinide, four times daily for 13 days, 15 min before meals. On the morning of day 7, breakfast was omitted and the dose was given as an oral solution containing 2 mg of (14)C-repaglinide. RESULTS: After oral dosing, a mean peak plasma concentration of repaglinide of 27.74 ng. ml(-1) (range: 16.84-36.65 ng. ml(-1)) was observed with a time to peak concentration of 0.5 h. Approximately 20% of repaglinide and its associated metabolites were distributed into red blood cells. No measurable (14)C-radioactivity was present in whole blood samples 6 h after dosing. Within 96 h of dosing with (14)C-repaglinide, 90% of the administered dose appeared in the faeces and 8% was excreted in urine. In the plasma, the major compound was repaglinide (61%). In the urine, the major metabolites were unidentified polar compounds, the aromatic amine (M(1)) (24%), and the dicarboxylic acid (M(2)) (22%). In the faeces, the major metabolite was M(2) (66% of administered dose). Therefore, repaglinide was excreted predominantly as metabolites and the major in vivo metabolite of repaglinide in humans was M(2). During regular dosing for 6 days, the morning plasma trough levels of repaglinide were, with very few exceptions, almost always too low to measure, indicating the absence of accumulation at this dose of 2 mg four times daily. Repaglinide was well tolerated, and there were no episodes of hypoglycaemia. CONCLUSION: After oral dosing with repaglinide, the mean peak plasma concentration was rapidly attained and, thereafter, plasma concentrations decreased promptly. The major route of excretion was via the faeces. These properties make repaglinide a suitable insulin secretagogue for all patients with type-2 diabetes who retain sufficient beta-cell function.

Clopidogrel, a novel antiplatelet agent, and digoxin: absence of pharmacodynamic and pharmacokinetic interaction.

The safety, and the pharmacodynamic and pharmacokinetic compatibility of clopidogrel, 75 mg daily, with the cardiac glycoside digoxin, were assessed in 12 healthy male subjects who took digoxin 0.25 mg once daily for 20 days and, in addition, clopidogrel 75 mg once daily from day 11 to day 20, so as to achieve steady-state conditions with both drugs. The drugs were taken after an overnight fast, and a standardized breakfast was served 30 minutes later. Blood samples for digoxin determination were drawn pre-dose on days 1, 8, 9, 10, 18, 19, and 20 of the schedule, and at 0.5, 1, 2, 3, 4, 5, 6, 8, 12, 16, and 24 hours post-dose on days 10 and 20. Urine samples were collected pre-dose and from 0-4, 4-8, 8-12, and 12-24 hours post-dose on days 10 and 20. Platelet aggregation studies were carried out using ADP at 5 micromol/L final concentration as an agonist. Establishment of steady-state plasma concentrations of digoxin on days 8-11 and 18-21 was confirmed by application of Dunnett's test on the trough plasma concentrations. The plasma pharmacokinetics and urinary excretions of digoxin for day 10 and day 20 were very similar: the day 20/day 10 ratios (90% Cl) were 1.1 (0.99; 1.24) for Cmax, 1.0 (0.92; 1.08) for Cmin, 1.02 (0.96; 1.07) for AUC(0-24), and 0.99 (0.94; 104) for urinary excretion. Mean inhibition of ADP-induced platelet aggregation at the end of the clopidogrel treatment period was 34%. The clinical, cardiac, and biological evidence from the study indicated that clopidogrel administration does not enhance digoxin's cardiac effects. Overall, the data indicated that there is no reason to anticipate an interaction when clopidogrel is added to digoxin for long-term management of patients with cardiac disease.

Absorption and mass balance of piperonyl butoxide following an 8-h dermal exposure in human volunteers.

Dermal absorption, metabolism and excretion of piperonyl butoxide (PBO) was studied using 14C-PBO either by itself as a 3% (w/w) solution in isopropyl alcohol or as a 4% (w/w) solution in an aqueous end-use formulation. Each of these two formulations were tested on four young, healthy male volunteers, using a single topical application on the ventral forearm under non-occlusive conditions for an 8-h period. The application sites were thoroughly cleaned with cotton swabs moistened with isopropyl alcohol, then rinsed with isopropyl alcohol. Blood from the ipsilateral and contralateral arms, urine and feces were collected at selected intervals during the 8-h application and through a 120-h post-application period. The application area was also tape-stripped to determine if any of the test material accumulated in the stratum corneum. These samples provided data which permitted insight into the kinetics of penetration and elimination processes of PBO. The absorption of PBO either by itself or formulated was very poor, as demonstrated by the radioactivity excreted in the urine, and radioactivity in the ipsilateral plasma. When dosed by itself, approximately 1.78% of the dose was excreted in the urine. In contrast, only 0.47% of the formulated PBO was excreted in the urine. Trace radioactivity was detected in the feces from both formulations. The absorbed radioactivity was rapidly eliminated in the urine. There was no evidence of accumulation of PBO in the skin as evidenced by low amounts of radioactivity in the tape-strippings. The majority of the applied radioactivity was recovered from the skin surface. Total recovery of the applied radioactivity was 100.86 and 104.22% for PBO and the formulated product respectively. Absorbed PBO was completely metabolized to at least three major metabolites prior to its excretion in the urine. The three metabolites represented over 70% of the excreted radioactivity for PBO. The HPLC retention times for these metabolites are different than that seen in rats. The structures of these metabolites have not been elucidated.

Multiple-dose pharmacokinetics, safety, and tolerability of bosentan, an endothelin receptor antagonist, in healthy male volunteers.

The multiple-dose pharmacokinetics, safety, and tolerability of oral bosentan, a selective endothelin receptor antagonist, were investigated in healthy male volunteers. In study A, an ascending-dose, double-blind, placebo-controlled trial, doses of 100, 200, 500, and 1000 mg bosentan or placebo were given once daily for 8 days as tablets (100 and 500 mg dose strength). In study B, a double-blind, placebo-controlled trial, 500 mg tablets of bosentan or placebo tablets were given once daily for 8 days with two additional single intravenous dose administrations of 250 mg bosentan 48 hours before the first and 24 hours after the last oral dose. The drug was very well tolerated. No effects on pulse rate, ECGs, or clinical laboratory tests were observed. Marginal effects on blood pressure were seen in subjects only when standing. The oral bioavailability of bosentan was 43% to 48%, with a small interindividual variability of 20%. Doses above 500 mg did not lead to significant further increases in plasma levels of bosentan. From the first to the last day of the oral treatment phase, plasma concentrations of bosentan decreased by 30% to 40% due to a 2-fold increase in plasma clearance. Absorption and plasma protein binding did not change. The 24-hour urinary excretion of 6 beta-hydroxycortisol was increased in parallel by approximately 1.7-fold, indicating induction of cytochrome P450 3A isozymes. The two metabolites of bosentan reached plasma concentrations well below those of bosentan and will most likely not contribute to the pharmacological activity.

CYP2D6 and CYP2C19 activity in a large population of Dutch healthy volunteers: indications for oral contraceptive-related gender differences.

OBJECTIVE: We examined a large database containing results on CYP2D6 and CYP2C19 activity of 4301 Dutch volunteers phenotyped in the context of various clinical pharmacology studies. METHODS: The subjects were given 22 mg dextromethorphan, 100 mg mephenytoin and 200 mg caffeine. For CYP2D6, the dextromethorphan/dextrorphan metabolic ratios in urine samples taken for a subsequent 8 h were used. Dextromethorphan and dextrorphan were quantified by reversed-phase high performance liquid chromatography. For CYP2C19 similarly obtained (R)-mephenytoin and (S)-mephenytoin ratios were used. (S)-mephenytoin and (R)-mephenytoin were analysed and quantified by enantioselective capillary gas chromatography. In addition, CYP2C19 poor metabolizer (PM) subjects were reanalysed after acidic pre-treatment of urine samples to confirm the PM status. RESULTS: The investigated population mainly comprised Caucasian (98.9%) males (68%). The age ranged from 18 to 82 years. For CYP2D6, it was found that 8.0% of the subjects were PMs. The average metabolic ratio was 0.014 (0.033) for subjects who showed extensive metabolizing activity (EM) and 5.4 (7.6) for PM subjects. For CYP2C19, it was found that 1.8% of the subjects were PMs. The metabolic ratio was 0.162 (0.124) for EM subjects and 1.076 (0.040) for PM subjects. Within the EM group the metabolic ratio in females was significantly lower for CYP2D6 (-20%) and significantly higher for CYP2C19 (+40%) compared with males. For PMs there was no such difference for CYP2D6 (P = 0.79) or CYP2C19 (P = 0.20). Oral contraceptive (OC) use significantly decreased the CYP2C19 activity by 68% for mephenytoin as compared to non-OC using females. CONCLUSIONS: For CYP2D6, the PM incidence (8.0%) is in accordance with literature data. The CYP2C19, PM incidence (1.8%) is low compared to reports from other European countries. For mephenytoin, the acidification procedure has been shown to be very important for the confirmation of CYP2C19 PMs. In EM females compared to EM males, CYP2D6 activity is increased and CYP2C19 activity is reduced. For CYP2C19 in particular this reduction is substantial and most pronounced in the age range from 18 to 40 years. For CYP2C19, the reduced activity is associated with the use of oral contraceptives.

PIP: Cytochrome P (CYP) isoenzymes are known to be important catalysts for oxidative biotransformation of both exogenous and endogenous compounds. This study examined a large database containing phenotyping results on CYP2D6 (dextromethorphan) and CYP2C10 (mephenytoin) activity of 4301 Dutch healthy volunteers phenotyped in the context of various pharmacology studies. The subjects were given 22 mg dextromethorphan, 100 mg mephenytoin, and 200 mg caffeine. For CYP2D6, the dextromethorphan/dextrorphan metabolic ratios in urine samples taken for 8 subsequent hours were used. Dextromethorphan and dextrorphan were quantified by reversed-phase high performance liquid chromatography. For CYPC19, similarly obtained (R)-mephenytoin and (S)-mephenytoin ratios were used, which were analyzed and quantified by enantioselective capillary gas chromatography. In addition, CYP2C19 poor metabolizer (PM) subjects were reanalyzed after acidic pretreatment of urine samples to confirm the PM status. It was found out that 8.0% of the subjects were PMs in the CYP2D6. The average metabolic ratio was 0.014 for subjects who showed extensive metabolizing activity (EM) and 5.4 for PM subjects, while for CYP2C19 1.8% of the subjects were PMs. The metabolic ratio was 0.162 for EM subjects and 1.076 for PM subjects. Within the EM group the metabolic ratio in females was significantly lower for CYP2D6 and significantly higher for CYP2C19 compared with the males. For PMs there was no such difference for CYP2D6. Oral contraceptive use significantly decreased the CYP2C19 activity by 68% for mephenytoin as compared to non-OC-using females.

Troglitazone has no effect on red cell mass or other erythropoietic parameters.

OBJECTIVE: Troglitazone is a new anti-diabetic agent for the treatment of type 2 diabetes. In placebo-controlled trials troglitazone improves glycaemic control, reduces hyperinsulinaemia and has beneficial effects on blood lipids. However, minor, reversible reductions in erythrocyte count, haemoglobin and haematocrit with no associated clinical symptoms have been observed in some troglitazone-treated patients. The primary objective of the present study was to determine if these changes could be explained by a decrease in red cell mass or change in plasma volume. METHODS: Twenty-four healthy males were randomized in a double-blind manner to troglitazone (200 or 600 mg per day) or placebo for 6 weeks. Blood samples for the measurement of red cell mass and plasma volume were obtained in the 2 weeks prior to treatment and after 6 weeks of treatment. Reticulocyte and erythrocyte counts, haemoglobin and haematocrit were also measured. RESULTS: At the end of the treatment period there were no statistically significant changes in red cell mass. Similarly there were no changes in reticulocyte count, erythropoietin or soluble transferrin receptors. These data indicate that troglitazone does not affect erythropoiesis. In addition, troglitazone was not associated with increased red blood cell destruction or haemolysis. There was a trend towards increased plasma volume in the troglitazone groups: increases of 2.5 ml x kg(-1) (5.7% increase) in the troglitazone 200 mg group and 3.4 ml x kg(-1) (7.8% increase) in the troglitazone 600 mg group were observed compared with placebo. CONCLUSION: These data suggest that dilutional effects related to a modest increase in plasma volume may explain the haematological changes seen in other clinical trials with high doses of troglitazone, although this study has shown that the changes in plasma volume are not statistically significant.

A comparison of the pharmacokinetics and tolerability of riluzole after repeat dose administration in healthy elderly and young volunteers.

The pharmacokinetics and tolerability of the novel antiexcitatory agent, riluzole, were compared in 18 healthy elderly and 18 healthy gender- and weight-matched young volunteers. All participants received riluzole 50 mg twice daily (the recommended dosage for patients with amyotrophic lateral sclerosis), administered orally for 5 days. The pharmacokinetics of riluzole, determined on the morning of the 5th day of dosing, were not significantly affected by age or gender. The mean terminal elimination half-life (t1/2), however, was statistically significant between elderly and young subjects. Riluzole was well tolerated upon repeat dose administration. Headache was the most frequent adverse event reported, and there was no overt difference in the type, frequency, or severity of adverse events between elderly and young volunteers or between genders. In conclusion, these results indicate that no dosage adjustments of riluzole are required in the elderly.

'High throughput' solid-phase extraction technology and turbo ionspray LC-MS-MS applied to the determination of haloperidol in human plasma.

A quantitative method for the analysis of haloperidol in human plasma is described. Sample clean-up was performed by means of solid-phase extraction using 3M Empore extraction disk plates in the 96-well format, automated with a Canberra Packard pipetting robot. Separation was performed by reversed phase high performance liquid chromatography with turbo ionspray tandem mass spectrometric detection by monitoring the decay of protonated haloperidol of m/z 376 to its fragment at m/z 165, versus the decay of protonated haloperidol-D4 at m/z 380 to its fragment at m/z 169. The validated concentration range was from 0.100 to 50.0 ng ml(-1), with an inaccuracy and overall imprecision below 10% at all concentration levels. Validation results on linearity, specificity, precision, accuracy and stability are shown and are found to be adequate. The average sample preparation time for a batch of 96 samples is approximately 50 min. The chromatographic run time is 3 min. A sample throughput of at least 240 samples per day can be achieved.