Review article: The pharmacological properties and clinical use of valdecoxib, a new cyclo-oxygenase-2-selective inhibitor

Cyclo-oxygenase-2-selective inhibitors produce less gastric damage than conventional non-steroidal anti-inflammatory drugs. Valdecoxib is a new orally administered cyclo-oxygenase-2-selective inhibitor, recently approved for use in osteoarthritis, rheumatoid arthritis and primary dysmenorrhoea in the USA. The drug has been evaluated in more than 60 clinical studies involving more than 14 000 patients and healthy volunteers. The analgesic efficacy of valdecoxib at a dose of 10 mg once daily in both osteoarthritis and rheumatoid arthritis is superior to that of placebo and similar to that of traditional non-steroidal anti-inflammatory drugs. Valdecoxib is effective in single doses of up to 40 mg for the alleviation of acute menstrual pain and has a rapid onset of action (within 30 min) and a long duration of analgesia (up to 24 h). Valdecoxib is well tolerated and has safety advantages compared with traditional non-steroidal anti-inflammatory drugs in terms of less gastrointestinal toxicity and a lack of an effect on platelet function. The incidence of adverse effects involving the kidney (fluid retention, oedema and hypertension) is similar to that of non-selective, non-steroidal anti-inflammatory drugs.

Analysis of formulation and food effect on the absorption of metoclopramide

OBJECTIVES

Assessment of the relative and absolute bioavailability of immediate release and sustained release formulations of metoclopramide. Assessment of the effect of a high-fat meal on the pharmacokinetics of sustained release metoclopramide.

MATERIAL AND METHODS

In a balanced 4-way crossover study in 16 healthy male volunteers, a sustained release (SR) formulation of metoclopramide was compared with a solution for injection (A) and an immediate release tablet (B). The SR formulation was administered after a fasting period (C) as well as after a high-fat meal (D). A single dose of 30 mg metoclopramide was investigated in each treatment. Metoclopramide concentrations were determined by HPLC.

RESULTS

The absolute bioavailability of the sustained release formulation (fasting state) was 58% and thus about 17% lower than the bioavailability of the immediate release formulation. Comparing the treatments C (sustained release, fasting state) and D (sustained release, high-fat meal) no significant influence of food on the absorption of sustained release metoclopramide could be detected.

Psychosocial and traditional risk factors in early ischaemic heart disease: cross-sectional correlates

BACKGROUND

Psychosocial/emotional distress has been repeatedly found to be a correlate of the onset/aggravation of ischaemic heart disease.

METHODS

Eighty-three patients (63 men and 20 women) with known coronary artery disease who entered an aggressive lifestyle modification programme were administered a clinical/demographic history and the Symptom Checklist 90--Revised at baseline. Several measures of social isolation/alienation (shyness/self-consciousness, feeling lonely, feeling abused and overall) were derived from the the Symptom Checklist 90--Revised.

RESULTS

Univariate tests of the association of known cardiovascular risk factors and the Symptom Checklist 90--Revised scales with age at initial diagnosis yielded several significant results for history of hypercholesterolaemia (P = 0.018), history of hypertension (P = 0.030), somatization (P = 0.007), obsessive-compulsive (P = 0.009), depression (P = 0.006), anxiety (P = 0.021), hostility (P = 0.003), paranoia (P = 0.050), psychoticism (P = 0.029), the Global Severity Index (P = 0.007), the Positive Symptom Distress Index (P = 0.005), the Positive Symptom Total Score (P = 0.003) and feeling abused (P = 0.037). Only history of hypertension, history of hypercholesterolaemia and the hostility scale (overall F = 6.08 and P = 0.0009) emerged as unique correlates of age at initial diagnosis in a multiple regression using only the significant univariate predictors.

CONCLUSIONS

Psychosocial factors are sufficiently confounded with one another that they lose their predictive value once one is entered in the equation. High scores on the hostility scale were associated with a 5.7 year differential in age at initial diagnosis. The younger a patient is at initial diagnosis, the more likely he/she is to have high levels of emotional distress.

Chest pain and the treatment of psychosocial/emotional distress in CAD patients

Treatment of psychosocial/emotional distress as a strategy for diminishing chest pain in such patients remains entirely unutilized in standard care. Sixty-three patients with known or suspected CAD were entered in an aggressive lifestyle modification program. Patients completed the Symptom Checklist 90-Revised (SCL90R) at the diagnostic interview session, at 3 and at 12 months. Statistically significant drops were observed on multiple scales of the SCL90R at both 3 and 12 months. An item from the SCL90R was used as a proxy for angina. Multiple measures of emotional distress at baseline were found to correlate with chest pain at baseline, but not a number of traditional cardiovascular risk factors. The chest pain item displayed improvement at both 3 and 12 months. Improvement on all scales of the SCL90R correlated with improvement in chest pain. It may be possible to control chest pain in some CAD patients with psychosocial interventions.

Stress and other psychosocial characteristics of patients with psychogenic nonepileptic seizures

Research on psychogenic nonepileptic seizures (PNES) has focused on childhood abuse, but less is known about other stressors and psychosocial risk factors. The authors compared 25 patients with PNES with 33 control subjects with epilepsy on stressful life events and other risk factors for somatoform disorders. Compared with control subjects, patients with PNES reported significantly more prevalent and stressful negative life events (including adulthood abuse) and more current rumination, stress-related diseases, somatic symptoms, bodily awareness, and marginally more anxiety and depression. However, the relationship of many of these variables to PNES was accounted for by life stress. Groups did not differ on illness worry, alexithymia, or psychotic symptoms. The results suggest that PNES are part of a larger pattern of somatic symptoms responses to a wide range of negative events, including stress in adulthood.

Psychological factors affecting a medical condition: ischemic coronary heart disease

The criteria for scientific validation of the entities currently subsumed under the DSM-IV category of "Psychological Factors Affecting a Medical Condition" have never been clearly enumerated. Historically, its precursor category ("Psychophysiological Disorder") was rarely used, and predicated upon clinical observation of personality styles among patients with specific physical illnesses, or clinical observations relating psychosocial events and symptom exacerbation. Because of logical flaws with either of these methods, clarification of the most rigorous criteria for demonstrating a cause-effect relationship is necessary. With the increase in well-designed and carefully executed epidemiological and treatment studies, this diagnostic category has evolved into an arena where cutting-edge insights and therapies are becoming available for a growing variety of medical conditions, especially ischemic coronary heart disease. The present article reviews the nature of the scientific evidence necessary to accept an etiological or aggravating role for psychological events.

On-line immunoaffinity extraction and HPLC analysis of flunitrazepam and its main metabolites in serum

A sensitive, simple, and rapid method for the determination of flunitrazepam and its major metabolites (7-aminoflunitrazepam, 7-acetamidoflunitrazepam, and norflunitrazepam) in serum and plasma is presented. The on-line procedure uses an immobilized, highly reusable antibody against benzodiazepines for selective extraction from serum followed by analysis by high-performance liquid chromatography with ultraviolet detection. This reliable method provides a limit of detection of 1 ng/mL serum, and results are obtained in less than 40 min.

Determination of flunitrazepam and its main metabolites in serum and urine by HPLC after mixed-mode solid-phase extraction

A rapid and sensitive method is presented for the simultaneous determination of flunitrazepam, norflunitrazepam, 7-aminoflunitrazepam, and 7-acetamidoflunitrazepam in serum, plasma, and urine. The compounds were extracted by a mixed-mode solid-phase procedure following analysis by high-performance liquid chromatography and ultraviolet detection and using methylclonazepam as the internal standard. The method revealed high recoveries and showed good precision and linearity for all compounds. The limit of detection was at least 1 ng/ml serum (plasma) for all compounds.

Retrospective analysis of the effects of psychotherapeutic interventions on outcomes of psychogenic nonepileptic seizures

PURPOSE

Uncertainty exists regarding the effectiveness of psychotherapy in patients with psychogenic nonepileptic seizures (PNES). We retrospectively reviewed the outcomes of therapeutic interventions in a cohort of patients with PNES.

METHODS

We identified patients with PNES by outpatient video-EEG (VEEG) between 1992 and 1996. We retrospectively analyzed the effects on outcomes of various types of interventions for PNES administered at random, using a structured interview and review of medical records. Patients with subjective events and severe psychosis were excluded. Patients who required inpatient monitoring because the outpatient VEEG was inconclusive were also excluded.

RESULTS

One hundred patients were diagnosed with PNES between 1992 and 1996: 61 patients completed the study. The average age was 43.3 years, and 90% were female. Nine (15%) had had PNES <1 year, and 7 (11%) had epilepsy. Eleven of 16 patients (68%) who received five or more counseling sessions, including showing the videotaped recording of the nonepileptic spell (13 of 16) by the comprehensive epilepsy program (CEP) psychotherapist had cessation (7 of 16) or reduction (4 of 16) of their episodes. Eleven of 15 patients (73%) who received only the feedback and care of their CEP neurologists had similar favorable outcome. Twelve of 25 patients (48%) who received counseling by a non-CEP psychotherapist or psychiatrist had cessation (10 of 25) or reduction (2 of 25) of episodes. Five patients who received no feedback or intervention had no improvement (4 of 5) or worsening (1 of 5) of the PNES.

CONCLUSIONS

Psychotherapy or feedback provided by CEP professionals with experience in epilepsy and PNES improves outcome and may be superior to other or no interventions.

Investigation on the bioequivalence of 2 oral preparations containing spironolactone and furosemide

The bioequivalence of 2 formulations containing spironolactone and furosemide was determined. The test preparation was Spironolacton 50 plus Heumann tablets, a new generic spironolactone preparation, developed by Heumann Pharma GmbH, the reference preparation was Osyrol 50-Lasix capsules, Hoechst AG. The study was designed as a randomized 2-period, 2-sequence, crossover study. A daily dose of 50 mg spironolactone and 20 mg furosemide was administered over 5 days to 24 healthy volunteers in the fasting state. Plasma samples were assayed for spironolactone, its 2 active metabolites canrenone and 7alpha-thiomethylspirolactone, and furosemide by HPLC. Statistical analysis was performed by ANOVA and by nonparametric methods. Because spironolactone was rapidly eliminated from plasma, its pharmacokinetics could only be evaluated with regard to maximum plasma levels. This parameter did slightly miss the criteria for bioequivalence. For canrenone and 7alpha-thiomethylspirolactone bioequivalence was given. For furosemide the test formulation was found to be equivalent concerning the extent of bioavailability. Bioequivalence with regard to maximum concentrations could not be shown. However, from the point of view of pharmacodynamics, this finding may not necessarily be of clinical relevance.

Analysis of metabolites--a new approach to bioequivalence studies of spironolactone formulations

The aldosterone antagonist spironolactone undergoes extensive and complex biotransformation. For investigation of bioequivalence of 2 oral spironolactone formulations, Spironolacton 50 Heumann and Aldactone 50, the pharmacokinetics and bioequivalence of the parent drug and 2 predominant active metabolites, canrenone and 7 alpha-thiomethylspirolactone, were determined in a 2-way crossover study in 24 young healthy male volunteers after multiple oral dosing of 100 mg once daily. Plasma samples were measured by a newly developed HPLC assay and individual pharmacokinetic parameters of the 3 compounds were calculated by use of noncompartmental techniques. Statistical analysis was performed by ANOVA and nonparametric methods. Spironolactone was rapidly cleared from plasma. Therefore, only Css,max and tss,max were determined. Concerning Css,max bioequivalence was found with 90% classical shortest confidence interval ranging from 80.7-112.4%. The intrasubject variability for Css,max was determined to be 28.1%. Higher and persisting concentrations were observed for the metabolites. For canrenone 90% classical shortest confidence intervals were calculated as 95.4-105.0% for AUCss,tau, as 92.9-105.8% for Css,max, and as 89.1-106.3% for peak trough fluctuation (PTF). In the case of 7 alpha-thiomethylspirolactone the values were 84.2-103.0% for AUCss,tau, 77.0-98.6% for Css,max, and 85.0-100.4% for PTF. For tss,max nonparametric 90% confidence intervals were determined as 0.00 to 1.50 h for spironolactone and canrenone and as -0.50 to 1.00 h for 7 alpha-thiomethylspirolactone. The intraindividual variability was below 30% for all pharmacokinetic parameters in the case of the metabolites. Thus, bioequivalence of the test and the reference formulation can be concluded. The study suggests the inclusion of parent compound and metabolites for bioequivalence testing of spironolactone formulations. Intraindividual subject variability was clearly diminished by investigating bioequivalence under steady-state conditions.

Passage of cefotaxime and ceftriaxone into cerebrospinal fluid of patients with uninflamed meninges

Cefotaxime and ceftriaxone have proven to be effective in pyogenic infections of the central nervous system. Since in some bacterial central nervous system infections the blood-cerebrospinal fluid (CSF) barrier is either minimally impaired or recovers in the course of the illness, we studied the penetration of both antibiotics in the absence of inflamed meninges. Patients who had undergone external ventriculostomies for noninflammatory occlusive hydrocephalus received either cefotaxime (2 g/30 min) or ceftriaxone (2 g/30 min) to treat extracerebral infections. Serum and CSF were drawn repeatedly after the first dose. With ceftriaxone, they were also drawn after the last dose. The concentrations of cefotaxime, its metabolite desacetylcefotaxime, and ceftriaxone were determined by high-performance liquid chromatography with UV detection. Maximum concentrations of cefotaxime in CSF were reached 0.5 to 8 h (median = 3 h; n = 6) after the end of the infusion and ranged from 0.14 to 1.81 mg/liter (median = 0.44 mg/liter; n = 6). Maximum levels of ceftriaxone in CSF ranging from 0.18 to 1.04 mg/liter (median = 0.43 mg/liter; n = 5) were seen 1 to 16 h (median = 12 h; n = 5) after the infusion. The elimination half-life of cefotaxime in CSF was 5.0 to 26.9 h (median = 9.3 h; n = 5), and that of ceftriaxone was 15.7 to 18.4 h (median = 16.8 h; n = 3). It is concluded that after a single dose of 2 g, maximal concentrations of cefotaxime and ceftriaxone in CSF do not differ substantially. The long elimination half-lives guarantee uniform concentrations in CSF. These concentrations reliably inhibit highly susceptible bacteria but cannot be relied on to inhibit staphylococci and penicillin G-resistant Streptococcus pneumoniae.

Quinolone antibacterial agents: relationship between structure and in vitro inhibition of the human cytochrome P450 isoform CYP1A2

The inhibitory effect of 44 quinolone antibacterials and derivatives (common structure, 4-oxoquinoline-3-carboxylic acid) on cytochrome P450 isoform CYP1A2 activity was tested using human liver microsomes and caffeine 3-demethylation as a specific test system for this enzyme. By direct comparison of molecules differing structurally in only one position, the following structure-activity relationships were found. 3'-Oxo derivatives had a reduced or similar activity and M1 metabolites (cleavage of piperazinyl substituent) had a greater inhibitory activity, compared with the parent molecule. Alkylation of the 7-piperazinyl substituent resulted in a reduced inhibitory potency. Naphthyridines with an unsubstituted piperazinyl group at position 7 displayed a greater inhibitory potency than did corresponding quinoline derivatives. Derivatives with a fluorine substitution at position 8 had only a minor effect. Molecular modeling studies with inhibitors and caffeine showed that it is possible to explain the potency of the quinolones to inhibit CYP1A2 on a molecular level. The keto group, the carboxylate group, and the core nitrogen at position 1 are likely to be the most important groups for binding to the active site of CYP1A2, because the molecular electrostatic potential of all inhibitors is very similar to that of caffeine in these regions. The presence of a piperazinyl substituent, however, seems to be no prerequisite for inhibitory potency. Finally, an equation to estimate the potency to inhibit CYP1A2 was developed by quantitative structure-activity relationship analysis.

Inhibitory potency of quinolone antibacterial agents against cytochrome P450IA2 activity in vivo and in vitro

Inhibition of cytochrome P450IA2 activity is an important adverse effect of quinolone antibacterial agents. It results in a prolonged half-life for some drugs that are coadministered with quinolones, such as theophylline. The objective of the study described here was to define the parameters for quantifying the inhibitory potencies of quinolones against cytochrome P450IA2 in vivo and in vitro and to investigate the relationship between the results of both approaches. Cytochrome P450IA2 activity in vitro was measured by using the 3-demethylation rate of caffeine (500 microM) in human liver microsomes. The inhibitory potency of a quinolone in vitro was determined by calculating the decrease in the activity of cytochrome P450IA2 caused by addition of the quinolone (500 microM) into the incubation medium. The mean values (percent reduction of activity without quinolone) were as follows: enoxacin, 74.9%; ciprofloxacin, 70.4%; nalidixic acid, 66.6%; pipemidic acid, 59.3%; norfloxacin, 55.7%; lomefloxacin, 23.4%; pefloxacin, 22.0%; amifloxacin, 21.4%; difloxacin, 21.3%; ofloxacin, 11.8%; temafloxacin, 10.0%; fleroxacin, no effect. The inhibitory potency of a quinolone in vivo was defined by a dose- and bioavailability-normalized parameter calculated from changes of the elimination half-life of theophylline and/or caffeine reported in previously published studies. Taking the pharmacokinetics of the quinolones into account, it was possible to differentiate between substances with and without clinically relevant inhibitory effects by using results of in vitro investigations. The in vitro test described here may help to qualitatively predict the relevant drug interactions between quinolones and methylxanthines that occur during therapy.

Hepatobiliary elimination of temafloxacin

The biliary excretion of temafloxacin and temafloxacin glucuronide was characterised in this study after administration of a single oral temafloxacin 600mg dose to 8 patients with T-tube drainage of the common bile duct inserted after cholecystectomy or choledochotomy. High performance liquid chromatographic analyses of plasma, urine and bile samples collected during the 72h after temafloxacin administration showed that biliary concentrations of unchanged temafloxacin followed a time-course parallel to plasma concentrations but were 5- to 10-fold higher. Biliary temafloxacin peak concentrations ranged from 18.74 to 64.35 mg/L and time to peak concentrations from 0.71 to 10.23h. Mean hepatobiliary clearance of temafloxacin was 3.10 ml/min (0.19 L/h) when calculated for the unchanged drug and 1.43 ml/min (0.09 L/h) when calculated for its biliary excretion as glucuronic acid conjugates. Patients with higher bile production had markedly higher clearance of both temafloxacin and temafloxacin glucuronide. The elimination time-course of the conjugate in bile generally paralleled those of temafloxacin in bile and plasma, although there was a lag in the rate of appearance of the conjugate in bile. Biliary excretion of unchanged temafloxacin and temafloxacin glucuronide accounted for approximately 2.2 and 1% of the administered dose, respectively. Thus, it appears that hepatobiliary elimination of temafloxacin and its glucuronide acid accounts for only a small fraction of total temafloxacin clearance. Nonetheless, concentrations attained in the bile are far above the minimum inhibitory concentration values of pathogens relevant in biliary tract infections.

Pharmacokinetics of temafloxacin in patients with liver impairment

A multicentre study was conducted to determine whether liver impairment would alter the pharmacokinetics of temafloxacin, a new fluoroquinolone antimicrobial agent. 16 patients with cirrhosis and 12 healthy volunteers (the control group) received a single oral 600mg dose of temafloxacin. Blood and urine were sampled at frequent intervals after drug administration and assayed by high performance liquid chromatography. The mean age of patients with liver impairment was greater than that of the control group; they also had a lower creatinine clearance and urine output. There was no difference between the groups in either the peak plasma temafloxacin concentration or the time to reach peak concentration. However, the volume of distribution and elimination rate constant of temafloxacin were significantly lower in the group with liver impairment, as were total temafloxacin clearance, renal clearance, and the ratio of renal:creatinine clearance. Nonrenal clearance was similar in patients and controls. Creatinine clearance and urine output were found to account for most of the intersubject variability in total clearance as determined by multiple linear regression analysis. Because the altered temafloxacin pharmacokinetics appear to be primarily due to impaired renal function, this should be the main determinant of temafloxacin dosage in patients with liver disease.

Effects of temafloxacin and ciprofloxacin on the pharmacokinetics of caffeine

A number of quinolone antibacterial agents, particularly enoxacin, pefloxacin, pipemidic acid and ciprofloxacin, are known to decrease the clearance of methylxanthines. The effects of temafloxacin and ciprofloxacin on the pharmacokinetics of caffeine were therefore compared in a 3-way crossover study in 12 healthy young volunteers. Each volunteer received 183mg once-daily doses of caffeine in conjunction with twice-daily placebo, temafloxacin 600mg and ciprofloxacin 750mg in 3 separate phases according to a randomised sequence. A doubling of the area under the plasma concentration-time curve (77.8 vs 31.8 mg/L.h) and terminal-phase half-life (9.7 vs 4.5h) of caffeine were observed in the presence of ciprofloxacin. The magnitude of the reduction in the intrinsic clearance of caffeine produced by ciprofloxacin was greater than that described in the literature for ciprofloxacin and theophylline. This may partly be explained by intertrial differences in dosage and study design. Coadministration of temafloxacin did not have any effect on the pharmacokinetics of caffeine, confirming results of other studies suggesting that this agent does not affect methylxanthine clearance. Accordingly, it appears that restriction of caffeine intake during temafloxacin therapy is not necessary.

Effects of 2 quinolone antibacterials, temafloxacin and enoxacin, on theophylline pharmacokinetics

Certain quinolone and naphthyridone antibacterial agents reduce the clearance of theophylline, posing potential clinical risks for patients maintained on this bronchodilator. Whether temafloxacin also affects theophylline pharmacokinetics was assessed in a randomised double-blind 3-way crossover study in 12 healthy volunteers, using placebo and enoxacin as controls. Each volunteer participated in all 3 phases of the study, receiving theophylline plus daily divided doses of temafloxacin 800mg, enoxacin 800mg, or placebo, orally for 7 days. Aminophylline 200mg (containing 146mg theophylline) was given orally twice daily on the first 4 days. On the fifth morning, theophylline 200mg was administered intravenously, and serial blood and urine samples were collected for the following 72h. Coadministration of enoxacin significantly reduced the metabolic clearance of theophylline (approximately 65%). In contrast, during coadministration of temafloxacin, theophylline pharmacokinetics did not differ significantly from those during coadministration of placebo. No clinically significant adverse events occurred; total reported adverse events during enoxacin-theophylline administration (n = 33) were higher than those reported during temafloxacin-theophylline administration (n = 22) and theophylline alone (n = 23). Administration of temafloxacin to patients on long term theophylline therapy appears to be a safe and rational choice when treatment with a broad spectrum antibiotic is indicated.

Comparative pharmacokinetics of ciprofloxacin and temafloxacin in humans: a review

Temafloxacin is a new antibacterial agent of the fluoroquinolone group. In comparison with ciprofloxacin, the current leading quinolone, temafloxacin shows higher and longer lasting plasma concentrations after equivalent doses due to an almost complete gastrointestinal absorption and a lower total clearance. Temafloxacin absorption is little influenced by food intake. Concomitant administration of antacids should be avoided; a time interval of at least 2 hours should elapse between intake of either quinolone and an antacid. Both quinolones are excreted mainly by the kidney. They differ in tubular secretion, which is high for ciprofloxacin and low for temafloxacin. The overall nonrenal elimination is similar for both compounds. Ciprofloxacin has a slightly higher extent of metabolism, while temafloxacin probably has a higher transintestinal elimination. The biliary excretion of both compounds is in the same range. The longer half-life of temafloxacin enables a once-daily dose regimen, whereas the usual recommended dosage of ciprofloxacin is twice daily. For both quinolones the apparent volumes of distribution per body weight are significantly above unity, indicating good tissue penetration with intracellular uptake. The concentrations in the extracellular fluids are directly related to the corresponding plasma concentrations. The penetration of temafloxacin into the body fluids investigated--tears, nasal secretion, saliva, sweat, prostatic and seminal fluid--in general exceeds that of ciprofloxacin (with the exception of seminal fluid). Unlike ciprofloxacin, there is no drug interaction with methylxanthines. Comparative clinical studies reflecting the complex interrelating factors of host and pathogens are needed to demonstrate the significance of the pharmacokinetic differences between temafloxacin and ciprofloxacin.

Molecular defect (Gla+14----Lys) and its functional consequences in a hereditary factor X deficiency (factor X "Vorarlberg")

Factor X (FX) "Vorarlberg" is a congenital FX deficiency characterized clinically by a mild bleeding tendency. Homozygous individuals have a FX activity of less than 10% in the extrinsic system and 25% in the intrinsic system. FX antigen is 20%. Using molecular techniques, two point mutations were detected in the coding sequence of the FX Vorarlberg gene: a G----A at base pair 160 in exon II resulting in a change of Gla14 (GAA) to Lys (AAA); a G----A at base pair 424 in exon V resulting in a change from Glu102 (GAG) to Lys (AAG). The mutations abolished a TaqI restriction site in exon II and an MnlI site in exon V. To determine whether these mutations are present on one or on both alleles, restriction analyses of amplified exon II and exon V fragments were performed. Analysis of the pedigree showed that the genotype for the mutation on exon II (homozygous versus heterozygous) correlates with the severity of the phenotypic coagulation defect. We therefore conclude that the mutation in exon II is responsible for the functional defect in FX Vorarlberg. We have also purified the mutant FX protein from patient plasma. Purified FX Vorarlberg is indistinguishable from normal FX on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Its activity is 15% of normal FX upon activation with factor VIIa/tissue factor, 75% upon activation with factor IXa/factor VIIIa, and 100% upon activation with RVV. Activation at varying Ca2+ concentrations shows that the affinity of FX Vorarlberg for Ca2+ is decreased. Factor Xa Vorarlberg is able to convert prothrombin at a normal rate but also shows decreased affinity for Ca2+ in this interaction. Upon addition of Ca2+, FX Vorarlberg does not undergo the same conformational change as normal FX. Our data show that FX Vorarlberg has a decreased affinity for Ca2+ which impedes a normal conformational change. This leads to a decreased rate of activation by factor VIIa/tissue factor and by factor IXa. The decrease is much more marked for the extrinsic than for the intrinsic pathway.