Spontaneous intracranial bleeding in two patients with congenital afibrinogenaemia and the role of replacement therapy.

Congenital afibrinogenaemia and hypofibrinogenaemia are rare disorders of haemostasis. In this case report the problems posed in the management of two patients with fibrinogen levels less than 0.1g L(-1) and who developed intracranial bleeding are considered. The value of fibrinogen concentrate and the role of prophylaxis is also discussed.

Clopidogrel and drug metabolism: absence of effect on hepatic enzymes in healthy volunteers.

The influence of clopidogrel 75 mg, given once daily for 10 days on hepatic P-450 mixed function oxidases, was examined by assessing its effect on the disposition of antipyrine, on urinary 6-betahydroxycortisol (6beta-OHC) and on the plasma activity of gamma-glutamyl transpeptidase. This double-blind, randomized, placebo-controlled study was conducted in two parallel groups of 10 healthy young volunteers. Subjects were required to fast for 12 hours before and for 4 hours after dosing. Antipyrine 10 mg/kg was administered in the morning, two days before treatment (day -2) and 24 hours after the last dose of clopidogrel or placebo. Plasma levels of antipyrine, and urinary excretion of antipyrine, 3-hydroxymethyl-antipyrine and nor-antipyrine were measured over 36 hours post-drug for pharmacokinetic determinations. Bleeding time and platelet aggregation induced by 5 microM of ADP were measured before treatment (baseline) and at regular intervals after dosing during treatment. Clopidogrel treatment had a marked effect on platelet aggregation and bleeding time. No significant change in the disposition of antipyrine was observed after the ingestion of clopidogrel over 10 days: mean AUC ratio (+/-SEM) for plasma antipyrine was 1.021+/-0.023 for the clopidogrel group versus 1.001+/-0.019 for the placebo group; mean day 10/day -2 t 1/2 ratios were 1.019+/-0.018 and 1.027+/-0.023, respectively. Urinary excretions of antipyrine and metabolites were unchanged by clopidogrel compared to placebo. The changes in plasma cortisol concentrations, 6beta-OHC excretion and serum gamma-glutamyl transpeptidase activities observed at the end of treatment were fully comparable between the two treatment groups. Thus, the different tests showed no evidence of hepatic enzyme induction by clopidogrel in a pharmacologically effective dose regimen.

Clopidogrel bioavailability: absence of influence of food or antacids.

Two open, randomized, crossover bioavailability studies were carried out to assess the influence of concurrent antacid medication and food on the bioavailability of clopidogrel. A fed/fasting study was conducted in 12 elderly male subjects. Each subject took a single 75 mg dose of clopidogrel on two occasions-in the morning after an overnight fast, either during a standardized breakfast, or with breakfast delayed by 4 hours after dosing. A washout period of 7 days was observed between the two dosings. Twelve healthy male subjects participated in the antacid study. They fasted overnight and for 4 hours after dosing and took a single 75 mg dose of clopidogrel at 8:00 a.m. on two occasions separated by a washout period of 14 days. For one dose, Maalox 2 x 400 mg tablets were taken 1 hour before the clopidogrel dose. Pharmacokinetic parameters of SR26334, the main circulating metabolite of clopidogrel, were derived from plasma concentrations of the latter compound determined before and at regular intervals over 36 hours after dosing. For the fed/fasting study, mean Cmax values (+/-SD) were 2.7+/-0.62 mg/L and 2.1+/-0.96 mg/L for the fasting state and the fed state, respectively and the 90% CI of Cmax ratio was [0.57 - 0.97]. Mean AUC(0-obs) values (AUC to the last observed value) were 7.1+/-1.6 mg.h/L and 7.4+/-1.64 mg.h/L, respectively, and the 90% Cl of AUC ratios were [0.90 - 1.02] and [0.89 - 0.97], respectively. For the antacid study, mean Cmax values were 2.6+/-0.84 mg/L and 2.5+/-0.87 mg/L for the no-antacid regimen and the antacid regimen, respectively, and the 90% CI of Cmax ratio was [0.74 - 1.16]. Mean AUC(0-obs) values were 6.3+/-1.34 mg.h/L and 5.8+/-1.33 mg.h/L, respectively, and the 90% CI of AUC ratios was [0.89+/-0.97]. Thus, exposure to SR26334, and therefore net absorption of clopidogrel, was not significantly modified by food or by prior antacid ingestion.

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.

Clopidogrel compatibility with concomitant cardiac co-medications: a study of its interactions with a beta-blocker and a calcium uptake antagonist.

The safety and pharmacodynamic compatibility of clopidogrel with medications commonly used in patients with atherosclerosis, such as, a beta-adrenergic receptor antagonist (atenolol) and a calcium uptake inhibitor (nifedipine) were assessed. Atenolol and nifedipine interactions with clopidogrel were studied in patients with peripheral arterial obstructive disease taking a well-established regimen of nifedipine (N group of 6 patients) and in patients with coronary artery disease taking a well-established regimen of either atenolol (A group of 8 patients) or of atenolol and nifedipine (AN group of 8 patients). The study was conducted as a double-blind, randomized, crossover comparison of clopidogrel, 75 mg once daily, and placebo treatment for 7 days, with a 14-day washout between treatments. Pharmacodynamic interactions between atenolol and nifedipine, either alone or in combination, and clopidogrel were assessed primarily on the clinical control of angina or hypertension and, secondarily, by comparing the extent of inhibition of ADP (5 microM)-induced platelet aggregation achieved between the 3 groups. The mean number of anginal episodes per patient during the placebo week was 1.50, 9.0 and 11.5 in the A, N and AN groups, respectively; during the week of clopidogrel treatment, it was 1.39, 7.3 and 9.0, respectively, indicating no change in occurrence. Likewise, review of the use of nitrates (long or short acting) did not suggest any major change in usage during any period of the study. ECGs did not change between the three recording times (at screening and at the end of each treatment period). Vital signs were also unchanged throughout. Percent inhibition of platelet aggregation on day 7 was 31% in the N group, 39% in the A group, 28% in the AN group, and 33% overall. In conclusion, the coadministration of clopidogrel did not interfere with the clinical control of hypertension or angina established with atenolol or nifedipine, or both. Clopidogrel retained its full antiplatelet effect, and there were no safety problems caused by the coadministration.

Effects of ticlopidine in AV-fistula surgery in uremia. Fistula Study Group.

Two hundred and fifty-eight patients with uremia who were offered surgery for placement of an arteriovenous fistula for hemodialysis were recruited in nine regional dialysis centers. The patients were randomized to receive the platelet aggregation inhibitory compound ticlopidine, 250 mg b.d., or matching placebo. Study medication was targeted at 7, minimum 3, days before scheduled surgery and continued for 28 days after surgery. The overall rate of occlusion was 41/260 evaluable operations (16%), 25/131 (19%) in the placebo group and 16/129 (12%) in the ticlopidine group. The risk of early occlusion was a non-significant 35% lower in the ticlopidine group. Limited risk factor analysis did not clearly identify any subgroup other than females at greater risk of early thrombosis nor any subgroup deriving particular benefit from ticlopidine treatment.

Aspirin: benefit and risk in thromboprophylaxis.

Aspirin is often perceived either as a harmless panacea or as a useless poison which causes endless, needless trouble. We have carefully reviewed the literature on all aspects of aspirin and find that neither view is justified. Regular use of even low-dose aspirin (150 mg/day or less) may lead to clinically-important adverse events, particularly haemorrhage. The risk of such an event is considerably outweighed by the benefit for patients with a significant risk of a thromboembolic event. For individuals without a clear risk of thrombosis or thromboembolism, the balance is more even: indiscriminate aspirin-taking is to be discouraged.

Piperacillin-tazobactam as empiric monotherapy in febrile neutropenic patients with haematological malignancies.

The efficacy of piperacillin-tazobactam as first line empiric therapy was assessed in 54 febrile neutropenic episodes in 42 patients (27 male, 15 female) with haematological malignancy. Nineteen (35%) episodes were bacteraemias (15 Gram-positive, 4 Gram-negative), 5 (9%) were clinically documented (Hickman line sites) and 30 (56%) were pyrexias of unknown origin. Study therapy was initiated after a median of 4 days of neutropenia (range 1-30). Eighteen (33%) episodes responded to piperacillin-tazobactam without a need for treatment modification. Four (7%) episodes initially responded to piperacillin-tazobactam but required treatment modification for fungal superinfection. Of the 19 bacteraemias, 6 (32%) were eradicated or presumed eradicated by piperacillin-tazobactam. Of the 32 (60%) episodes which failed to respond to piperacillin-tazobactam, 11 (34%) responded to anti-fungal therapy; 14 (44%) responded to a glycopeptide and 5 (16%) responded to a second-line broad spectrum antibacterial agent. Two (6%) patients died, both in the presence of progressive malignancy. There was no significant toxicity associated with piperacillin-tazobactam. We conclude that piperacillin-tazobactam is effective as empiric monotherapy in neutropenic fever and may reduce the requirement for glycopeptides.

Effects of ticlopidine administered to healthy volunteers on platelet function in whole blood.

Ticlopidine is thought to be a selective inhibitor of ADP-induced platelet function. Here we have investigated the effects of ticlopidine on platelet function in whole blood induced by ADP and by other platelet agonists. Whole blood was used because it was considered that ADP derived from red cells might act synergistically with other platelet agonists to enhance platelet responses, and that ticlopidine might interfere with this process. Measurements were performed using blood from 16 healthy volunteers before ticlopidine administration, after taking ticlopidine 250 mg daily for 10 days, after taking ticlopidine 250 mg twice daily for a further 10 days, and after 14 days off treatment. Ticlopidine proved to be a very effective inhibitor of the platelet aggregation induced by ADP; it was most effective in enhancing the reversibility of the aggregation response. The drug modestly but significantly reduced streptokinase, adrenaline, collagen, sodium arachidonate, PAF and U46619 - induced platelet aggregation. The drug significantly reduced the extent of the release reaction (14C-5HT release) induced by ADP, streptokinase, PAF, ristocetin and sodium arachidonate, and also reduced the extent of the synergistic 14C-5HT release induced by combinations of ADP and PAF, ADP and adrenaline and PAF and adrenaline. The various inhibitory effects of ticlopidine were evident after treatment with 250 mg daily but were more pronounced after 250 mg twice daily. All values had returned to normal after 14 days off treatment. Ticlopidine had no effect on serum thromboxane B2 production nor on several parameters of coagulation and fibrinolysis. We conclude that ticlopidine is an effective inhibitor of ADP-induced platelet aggregation and also the platelet aggregation and 14C-5HT release induced in whole blood by a number of platelet agonists and combinations of agonists. These latter effects are probably mainly via a selective effect on ADP. The inhibitory effects of the drug are dose-related.

Reduction of requirement for leg vascular surgery during long-term treatment of claudicant patients with ticlopidine: results from the Swedish Ticlopidine Multicentre Study (STIMS).

OBJECTIVE: To study the effect of long-term treatment of the platelet inhibitor ticlopidine as secondary prevention against the need of vascular surgery in patients with intermittent claudication. DESIGN: The Swedish Ticlopidine Multicentre Study (STIMS), was conducted in six medical and surgical clinics of university hospitals in Sweden. METHODS: 687 claudicants were randomised to ticlopidine 250 mg bd or placebo and vascular surgery events were recorded prospectively over a 7-year period. Cox proportional hazards models of risk for leg vascular surgery were constructed using drug treatment and 11 putative risk factors for vascular disease as covariates. Surgical event-free survivals were compared by Kaplan-Meier analysis. RESULTS: The overall rate of first operations was 2.4% per annum. More than half of these operations were in the aortoiliac region. One-quarter of patients operated during the period required further operations but amputation was rare. Ticlopidine treatment reduced the need for vascular reconstructive surgery by about half, both in intention-to-treat and on-treatment analyses (unadjusted relative risks 0.486, 95% CI 0.317-0.745; p < 0.001; 0.493, 95% CI 0.290-0.841: p < 0.01, respectively). In Cox model analysis only male sex was confirmed as a risk factor for surgery. Previous peripheral arterial surgery was the strongest predictor of the need for surgery. None of the risk factors examined interacted statistically with the effect of treatment with ticlopidine. CONCLUSION: In patients with intermittent claudication it seems possible to prevent the need for future vascular surgery by the use of platelet inhibition with ticlopidine.

Clopidogrel--a platelet inhibitor which inhibits thrombogenesis in non-anticoagulated human blood independently of the blood flow conditions.

The goal of the present study was to investigate the effect of 7 and 14 days of daily oral administration of 75 mg clopidogrel on collagen-induced thrombogenesis in flowing non-anticoagulated human blood. Blood was drawn directly from an antecubital vein over immobilised collagen type III fibrils positioned in a parallel-plate perfusion chamber. The wall shear rates at the collagen surface were those characteristic for veins (100 s-1), and for medium sized (650 s-1) and moderately stenosed (2600 s-1) arteries. Clopidogrel ingestion reduced the thrombus volume significantly (p < 0.05) at 100 and 2600 s-1 (39 and 51% respectively). The beta-thromboglobulin plasma levels were reduced concomitantly. However, it was not possible to measure accurately the thrombus volume at 650 s-1, due to loose packing of the platelet thrombi. Transmission electron microscopy substantiated this observation and showed that clopidogrel profoundly reduced the platelet degranulation process (p < 0.005). The inhibitory effect of clopidogrel on platelet consumption by the growing thrombi resulted apparently in higher platelet concentration at the collagen surface, which enhanced the platelet-collagen adhesion at all three shear rates (p < 0.05). Despite the low deposition of fibrin on collagen, clopidogrel reduced significantly the fibrinopeptide A plasma levels and the fibrin deposition at shear rates below 650 s-1. This was apparently a consequence of the reduced platelet recruitment and the lower activation of platelets, since activated platelets in thrombi promote deposition of fibrin.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics of ticlopidine during chronic oral administration to healthy volunteers and its effects on antipyrine pharmacokinetics.

1. The pharmacokinetics of ticlopidine, a novel antithrombotic agent, have been investigated in 10 healthy volunteers dosed orally with the drug (250 mg 12 hourly for 21 days), to determine the basic pharmacokinetic parameters in humans, to investigate its accumulation during repeated administration, and to assess its effects on hepatic drug-metabolizing enzymes. 2. After the first dose, peak plasma concentrations (median 0.31, range 0.08-0.80 mg/l) were generally found at 2 h. The levels decreased rapidly to a median concentration of 0.087 mg/l by 4 h then declined to 0.022 (range less than 0.005-0.128) mg/l at 12 h after administration, with apparent half-lives of approx. 4 h. The median AUC value for this first dosage interval (AUC tau) was 0.97 (range 0.41-3.49) mg h l-1. 3. Pre-dose plasma concentrations indicated that steady state was reached after 5-10 days, and then remained essentially unchanged through to the end of the study. From 30 h after the final dose, drug levels declined exponentially with a median half-life of 28.8 (range less than or equal to 20-50) h. 4. Following the final dose, the median peak concentration and AUC tau were 0.99 (range 0.22-2.12) mg/l and 4.06 (range 0.90-15.2) mg h l-1 respectively. Based on AUC values, the mean accumulation factor +/- SD was 3.73 +/- 1.14. 5. The metabolic status of subjects was assessed by administration of single doses of antipyrine (700 mg orally) 7 days before the first dose of ticlopidine and 2 days after the final dose. Treatment with ticlopidine decreased antipyrine clearance, demonstrating that it inhibited drug-metabolizing enzymes. Significant correlations (r2 = 0.84, p less than 0.01) were found between the AUC values for ticlopidine and antipyrine, indicating that the interindividual variation in the pharmacokinetics of ticlopidine are explained by differences in metabolic clearance.

A common tumour-specific antigen: III. Preparation of small fragments incorporating the cell-sensitizing determinant.

Intact cells of various human tumours and tumour cell lines, and acid extracts of various human tumours and normal tissues, each of which react with the lymphocytes of cancer patients as detected by the macrophage electrophoretic mobility (MEM) test, have been subjected to proteolysis. Activity was destroyed by some enzymes, and the apparent molecular size of the active material was reduced by others. An active low-mol.-wt fragment has been partially purified from papain digests of several tumours. Peptides with normal tissue and tumour-characteristic activities have been separated chromatographically from tryptic digests of tumour extracts.

Capillary tube leucocyte adherence inhibition assay for cell-mediated immunity: effects of transient bacterial infection in guinea-pigs.

Adherence of guinea-pig leucocytes to glass, and changes of adherence caused by antigen challenge, were measured during a 3-month period in which an idiogenic, fortuitous bacterial infection passed though the main guinea-pig colony. Expected responses were found in SPF animals, and, at the beginning and end of this period, in stock animals and those immunized with Freund's complete adjuvant with or without added keyhole limpet haemocyanin. During active infection, all non-SPF animals showed enhanced adherence changes whilst SPF animals continued to give expected responses. The implications for use of leucocyte adherence inhibition tests with human subjects are discussed.

Cell surface charge correlation of partition with electrophoresis.

Critical mixtures of aqueous solutions of polymers separate into two or more immiscible phases. Particulate materials distribute in such phase systems generally between one bulk phase and the interface between bulk phases. The distribution is described by a simple partition law, and is quantitatively determined by, inter alia, the nature of the particle surface, particularly net electrical charge. The partition behaviour of various cells, native or modified by treatment with trypsin, neuraminidase or maleic anhydride, correlate strongly with electrophoretic mobility. Partition behaviour and electrophoretic mobility are both dependent upon cell surface charge. Thus, in appropriate conditions, changes in surface charge may be registered as changes in partition.

Cell partition: a study of parameters affecting the partition phenomenon.

Critical mixtures of aqueous solutions of polymers can be separated into two or more immiscible phases. Particulate materials are distributed in such phase systems generally between one bulk phase and the interface between bulk phases. The distribution is described by a simple partition law and is quantitatively determined by temperature, interfacial tensions, the electromotic potential difference between phases and the nature of the particle surface. The effects on transfacial potential differences of varying polymer, NaCl and sodium phosphate concentrations in dextran/polyethylene glycol systems were studied: increase of polyethylene glycol concentration increased the potential; addition of up to 40 mM NaCl progressively reduced the potential to zero: very small (less than 10 mM) concentrations of sodium phosphate buffer increased the potential, but further increase caused a fall in potential, which was less marked than that caused by equivalent concentrations of NaCl. The partition properties of a variety of cells, native or modified by treatment with trypsin, neuraminidase or maleic anhydride, were studied. In systems containing greater than 40 mM NaCl no difference in partition patterns for modifications of each cell type was observed. In systems containing no NaCl the partition pattern was highly dependent on the nature of the modification. From the behaviour of such models, polymer-electrolyte phase systems suitable for study of cell surface modification involving change, or no change, in net surface have been identified.

Electrophoretic separation of esterases of Alaria marcianae (La Rue, 1917) (Trematoda).

1. Disc electrophoresis was used to determine the esterase isoenzymes present in adults of the strigeoid trematode Alaria marcianae (La Rue, 1917). 2. Eight esterase bands were found with alpha-naphthyl acetate as the substrate and Fast Blue RR as the dye. 3. From results obtained with inhibitors, four different types of esterases were tentatively identified; cholinesterase (one band), ali-esterase or B-type (one band), arylesterase or A-type (2 bands) and acetylesterase or C-type (4 bands).

Cell partition. A simple test for lymphocyte sensitisation.

An established method of investigating total surface charge on particulate materials has been applied to the detection of changes in surface charge on macrophages which are induced by supernatants from the interaction of sensitised lymphocytes and appropriate antigen. The method was studied as an alternative to the established but problematical macrophage-electrophoretic-mobility (M.E.M.) test for detecting such changes. This preliminary investigation suggests that the results from subjects with and without malignant disease differ significantly.