Dual therapy with an oral non-vitamin K antagonist and a P2Y12 inhibitor vs triple therapy with aspirin, a P2Y12 inhibitor and a vitamin K antagonist for the treatment of diabetes mellitus patients with co-existing atrial fibrillation following percutaneous coronary intervention: A meta-analysis

BACKGROUND

In this analysis, we aimed to compare the efficacy and safety of dual therapy (DT) with a non-vitamin K oral anticoagulant (NOAC) and an adenosine diphosphate receptor antagonist (P2Y12 inhibitor) vs triple therapy (TT) with aspirin, a P2Y12 inhibitor and a vitamin K antagonist for the treatment of diabetes mellitus (DM) patients with co-existing atrial fibrillation (AF) following percutaneous coronary intervention (PCI).

METHODS

Medical Literature Analysis and Retrieval System Online (MEDLINE), http://www.ClinicalTrials.gov, Excerpta Medical data BASE (EMBASE), Web of Science, Cochrane Central and Google Scholar were the searched databases. Studies that were randomized trials or observational studies comparing DT vs TT for the treatment of DM patients with co-existing AF following PCI were included in this analysis. The adverse cardiovascular outcomes and bleeding events were the endpoints. This meta-analysis was carried out by the RevMan version 5.4 software. Risk ratios (RR) with 95% confidence intervals (CI) were used to represent data and interpret the analysis.

RESULTS

A total number of 4970 participants were included whereby 2456 participants were assigned to the DT group and 2514 participants were assigned to the TT group. The enrollment period varied from year 2006 to year 2018. Our current results showed that major adverse cardiac events (RR: 1.00, 95% CI: 0.84-1.20; P = .98), mortality (RR: 1.08, 95% CI: 0.78-1.48; P = .66), myocardial infarction (RR: 1.02, 95% CI: 0.74-1.42; P = .90), stroke (RR: 0.94, 95% CI: 0.53-1.67; P = .84) and stent thrombosis (RR: 1.09, 95% CI: 0.56-2.10; P = .80) were similar with DT versus TT in these patients. However, the risks for total major bleeding (RR: 0.66, 95% CI: 0.54-0.82; P = .0001), total minor bleeding (RR: 0.74, 95% CI: 0.64-0.85; P = .0001), Thrombolysis in Myocardial Infarction (TIMI) defined major bleeding (RR: 0.58, 95% CI: 0.35-0.95; P = .03), TIMI defined minor bleeding (RR: 0.62, 95% CI: 0.42-0.92; P = .02), intra-cranial bleeding (RR: 0.34, 95% CI: 0.13-0.95; P = .04) and major bleeding defined by the International Society on Thrombosis and Hemostasis (RR: 0.68, 95% CI: 0.51-0.90; P = .008) were significantly higher with TT.

CONCLUSIONS

DT with a NOAC and a P2Y12 inhibitor was associated with significantly less bleeding events without increasing the adverse cardiovascular outcomes when compared to TT with aspirin, a P2Y12 inhibitor and a Vitamin K antagonist for the treatment of DM patients with co-existing AF following PCI. Hence, DT is comparable in efficacy, but safer compared to TT. This interesting hypothesis will have to be confirmed in future studies.

Factors associated to adequate time in therapeutic range with oral vitamin K antagonists in Tunisia

INTRODUCTION

  The quality of chronic anticoagulation and predictor factors of poor anticoagulant control in patients under acenocoumarol were unknown in North Africa.

METHODS

It is an observational study, carried out between November 2015 and November 30, 2016. The international normalized ratio (INR) values were prospectively obtained, and TTR was calculated using the Rosendaal method.

RESULTS

Overall, 215 patients were included in this study, with a mean age of 63±0,8 years. The prevalence of poor anticoagulation control was 78.1%; 95% CI [72.2-83.2] (168 patients with TTR less than 65%). The median TTR with the Rosendaal method was 44.4%. After multivariate adjustment, variables significantly associated with adequate anticoagulation level were: history of ischemic stroke (Adjusted OR equal to 4.3, 95% CI: 1.4-12.9), associated prescription of antiplatelet therapy (Adjusted OR equal to 3.5, 95% CI: 1.1-11.2), daily prescribed dose of coumarins less than 6 mg (Adjusted OR equal to 6.4, 95% CI: 1.1- 36) and lower risk of bleeding assessed as HAS-BLED score (Adjusted OR: 0.5, 95% CI: 0.3-0.8).

CONCLUSION

The quality of anticoagulation management with VKA among outpatients who received acenocoumarol was suboptimal. Strategies should be undertaken by clinicians and patients to improve the quality of anticoagulation, to address challenges to adverse cardiovascular outcomes in individuals treated with chronic anticoagulation.

Emerging Tools for Stroke Prevention in Atrial Fibrillation

Ischaemic strokes resulting from atrial fibrillation (AF) constitute a devastating condition for patients and their carers with huge burden on health care systems. Prophylactic treatment against systemic embolization and ischaemic strokes is the cornerstone for the management of AF. Effective stroke prevention requires the use of the vitamin K antagonists or non-vitamin K oral anticoagulants (NOACs). This article summarises the latest developments in the field of stroke prevention in AF and aims to assist physicians with the choice of oral anticoagulant for patients with non-valvular AF with different risk factor profile.

Assessment of toxicity and coagulopathy of brodifacoum in Japanese quail and testing in wild owls

Based on detection of hepatic residues, scavenging and predatory non-target raptors are widely exposed to second generation anticoagulant rodenticides (SGARs). A small proportion, generally <10%, of tested birds are diagnosed as acutely poisoned. Little is known, however, of sub-lethal effects of SGARs, such as interaction of clotting capacity with traumatic injury. Assessment of coagulation function of birds submitted live to wildlife rehabilitators or veterinarians may provide a means of establishing the proportion of animals suffering sub-lethal coagulopathies, as well as identifying individuals requiring treatment. As a first step in exploring the potential of this approach, we dosed Japanese quail (Coturnix japonica) with the SGAR, brodifacoum, at 0, 0.8, 1.4, 1.9, and 2.5 mg/kg and sampled birds at 1, 3, 5 and 7 days post-dosing. Prothrombin time (PT), which measures the extrinsic coagulation pathway, was significantly prolonged in 98% of brodifacoum-exposed quail in a dose- and time-dependent manner. 50-fold prolongation of PT occurred at higher brodifacoum dosages and correlated to hemorrhage found at necropsy. Activated clotting time (ACT), a measure of the intrinsic pathway also increased with dose and time. Hemoglobin (Hb) and hematocrit (Hct) decreased dose- and time-dependently at doses ≥1.4 mg/kg with no significant change at 0.8 mg/kg. Reference intervals for PT (10.0-16.2 s), ACT (30-180 s), Hb (9.6-18.4 g/dl), and Hct (34-55%) were established in Japanese quail. Species-specific reference intervals are required as barn owl PT (17-29 s) and quail PT were different. The proportion of brodifacoum-exposed quail with hemorrhage was not correlated with liver residues, but was correlated with PT, suggesting that this assay is a useful indicator of avian anticoagulant rodenticide exposure. PTs measured in free-living barn owls sampled between April 2009 and August 2010 in the lower Fraser Valley of BC do not suggest significant exposure to SGARs.

Potential antiproliferative effect of isoxazolo- and thiazolo coumarin derivatives on breast cancer mediated bone and lung metastases

The study highlights the current progress in the development of coumarin scaffolds for drug discovery as novel anticancer agents in metastatic breast cancer. Eight compounds, combining the coumarin core and five membered heterocycles (isoxazoles and thiazoles) in hydrazinyldiene- -chroman-2,4-diones, were characterized in terms of a potential antiproliferative effect on bone (SCP1833) and lung (SCP4175) metastatic breast cancer cell lines using the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay. Cell viability was evaluated after 48 and 72 h of treatment and the 50 % inhibitory concentrations were determined. The results demonstrated dose- and time-dependent activity, with the most potent molecules having a thiazole moiety, without or with additional methyl group(s) attached to the carbon(s) at position(s) 5 and/or 4 in the thiazole ring. These molecules possessed significantly higher potency against both test cell lines compared to 4-hydroxycoumarin.

Positive selection in the chromosome 16 VKORC1 genomic region has contributed to the variability of anticoagulant response in humans

VKORC1 (vitamin K epoxide reductase complex subunit 1, 16p11.2) is the main genetic determinant of human response to oral anticoagulants of antivitamin K type (AVK). This gene was recently suggested to be a putative target of positive selection in East Asian populations. In this study, we genotyped the HGDP-CEPH Panel for six VKORC1 SNPs and downloaded chromosome 16 genotypes from the HGDP-CEPH database in order to characterize the geographic distribution of footprints of positive selection within and around this locus. A unique VKORC1 haplotype carrying the promoter mutation associated with AVK sensitivity showed especially high frequencies in all the 17 HGDP-CEPH East Asian population samples. VKORC1 and 24 neighboring genes were found to lie in a 505 kb region of strong linkage disequilibrium in these populations. Patterns of allele frequency differentiation and haplotype structure suggest that this genomic region has been submitted to a near complete selective sweep in all East Asian populations and only in this geographic area. The most extreme scores of the different selection tests are found within a smaller 45 kb region that contains VKORC1 and three other genes (BCKDK, MYST1 (KAT8), and PRSS8) with different functions. Because of the strong linkage disequilibrium, it is not possible to determine if VKORC1 or one of the three other genes is the target of this strong positive selection that could explain present-day differences among human populations in AVK dose requirement. Our results show that the extended region surrounding a presumable single target of positive selection should be analyzed for genetic variation in a wide range of genetically diverse populations in order to account for other neighboring and confounding selective events and the hitchhiking effect.

Successful therapy of coumatetralyl rodenticide induced pericardial effusion with pericardiocentesis in a dog

A 5-year-old, intact male, golden retriever was presented with an acute onset of lethargy and respiratory distress. The dog was diagnosed as having rodenticide intoxication with pericardial effusion. Pericardiocentesis was successfully performed and was followed with a blood transfusion. This case suggests that rodenticide intoxication might cause pericardial effusion in dogs.

Notable pink excreta and severe myocardial suppression in superwarfarin (difethialone) intoxication

Patients rarely consult physicians before developing coagulopathy or bleeding in most reported cases of superwarfarin intoxication. A 57-year-old woman ingested red-dyed pellets of anticoagulant rodenticide containing difethialone and warfarin as well as tablets of nitrazepam. Although she presented to the hospital in a comatose state, notable pink-colored excreta hinted at the consumption of anticoagulant rodenticide, which led to the early diagnosis of superwarfarin intoxication. Supplementation of large doses of intravenous and oral vitamin K successfully prevented coagulopathy and bleeding. On the other hand, temporary and reversible myocardial suppression was extremely severe, and required the introduction of percutaneous cardiopulmonary support.

Differential expression of cytochrome P450 genes between bromadiolone-resistant and anticoagulant-susceptible Norway rats: a possible role for pharmacokinetics in bromadiolone resistance

BACKGROUND

Anticoagulant resistance in Norway rats, Rattus norvegicus (Berk.), has been suggested to be conferred by mutations in the VKORC1 gene, encoding the target protein of anticoagulant rodenticides. Other factors, e.g. pharmacokinetics, may also contribute to resistance, however. To examine the involvement of pharmacokinetics in bromadiolone resistance in male and female rats, liver expression profiles of seven cytochrome P450 genes from a Danish bromadiolone-resistant rat strain (with an Y139C-VKORC1 mutation) were compared with profiles from an anticoagulant-susceptible strain.

RESULTS

In the presence of bromadiolone, the Cyp2e1, Cyp2c13, Cyp3a2 and Cyp3a3 genes were significantly overexpressed, while Cyp2c12 expression was suppressed in resistant female rats compared with susceptible females. Relative to susceptible males, resistant males showed significant overexpression of the Cyp2a1, Cyp2e1, Cyp3a2 and Cyp3a3 genes. On exposure to bromadiolone, females had higher Cyp2e1 expression than males, which possibly explains why female rats are generally more tolerant to anticoagulants than male rats.

CONCLUSION

Results suggest that bromadiolone resistance in a Danish strain of Norway rats involves enhanced anticoagulant metabolism catalysed by cytochrome P450-2e1, -3a2 and -3a3. This pharmacokinetically based bromadiolone resistance is to some extent sex differentiated, as female resistance furthermore seems to involve overexpression of cytochrome P450-2c13 and suppression of P450-2c12, whereas male resistance appears to involve P450-2a1 overexpression.

Persistence of bromadiolone anticoagulant rodenticide in Arvicola terrestris populations after field control

This paper documents the exposure pattern of a population of small mammals to bromadiolone over time in a field-scale follow up. This is the first assessment of the field-scale effect of such control operation on the availability of bromadiolone-exposed A. terrestris prey to nontarget predator species. It indicates that an important risk of poisoning of nontarget species does exist during large-scale field control operations with bromadiolone, which is contradictory to results obtained from laboratory experiments in the early 1980s and consistent with the secondary poisoning hazards due to repeated exposure regularly reported during the past 20 years.

Effect of bromadiolone on haematology, liver and kidney in Mus musculus

Bromadiolone, a second generation anticoagulant rodenticide was tested on Mus musculus to evaluate its effects on blood, liver and kidney at varied time intervals of 6, 12, 24 and 48 hrs. Groups of six animals each were selected for experiment. Animals were administered with bromadiolone in the form of bait at 6, 12, 24 and 48 hrs time intervals. Control animals were maintained for each time interval. After each time interval the experiment and the control animals were sacrificed and the effect of bromadiolone on blood, liver and kidney were studied.

Whole-carcass residues of the rodenticide difenacoum in anticoagulant-resistant and -susceptible rat strains (Rattus norvegicus)

The present study investigated the whole-carcass residue carried by resistant and susceptible laboratory rat strains following 5, 10, or 20 d of feeding on a diet of 25 mg difenacoum/kg bait. The mean whole-carcass residue of difenacoum was determined by high-performance liquid chromatography to be between 0.52 and 0.74 mg/kg body weight in all three rat strains tested. These values were considerably lower than some comparable data previously reported for other species and second-generation rodenticides as well as from mathematical models. The whole-carcass residue of extractable (i.e., nonrefractory) parent compound carried by highly resistant rats fed for 20 d (0.74 mg/kg body wt) is unlikely to present a significantly increased risk to predators compared to the amount carried by susceptible rats after 5 d of feeding (0.52 mg/kg body wt). However, resistant rats are more likely to be available for predation and to be carrying a whole-carcass residue of anticoagulant throughout the duration of a control program.

Superwarfarin and Glass Ingestion with Prolonged Coagulopathy Requiring High-Dose Vitamin K1Therapy

A 23-year-old man was brought to the emergency department after eating four boxes of brodifacoum-containing rodenticide over a 4-day interval and pieces from approximately two bottles of glass over the previous 2 weeks. He was asymptomatic but his prothrombin time was markedly elevated with an international normalized ratio (INR) of 37.8. A plain abdominal film showed diffuse radiopaque foreign bodies, presumably glass, in the large and distal small intestines. Treatment for ingested glass consisted of stool softeners and bulk-forming laxatives. The patient developed mild gingival bleeding and received fresh frozen plasma (FFP) infusions and vitamin K1 orally. At a vitamin K1 dosage of 300 mg/day, the INR corrected to less than 2.0 and the patient was discharged taking that dosage. He returned 26 days later with hematuria and flank pain, and his INR was 189. He was administered FFP and packed red blood cells, and his vitamin K1 dosage was increased to 800 mg/day; his INR returned to baseline. Compliance with taking the vitamin K1, which required ingestion of 60-160 tablets/day, was a serious problem, requiring numerous follow-up calls and visits to the patient at home and work. At 5-month follow he was doing well. Compliance with large daily doses of vitamin K1 for treatment of "superwarfarin" ingestion may be poor because of the duration of treatment and large number of pills required. A more concentrated formulation may be advantageous for management of patients with brodifacoum poisoning.

Oral Anticoagulant Therapy in Venous Thromboembolism

The main objective of treatment of venous thromboembolism (VTE) is the prevention of the extension, embolization, and recurrence of thrombosis. The long-term aim is to prevent late recurrences and the post-thrombotic syndrome. Heparin and oral anticoagulants (OACs) have been the cornerstones of VTE treatment in the last 30 years. Low molecular weight heparins (LMWHs) have been introduced more recently in the treatment of the acute phase of VTE, and they have allowed the home treatment of deep vein thrombosis (DVT) in selected cases. The optimal duration of OAC therapy after VTE is still controversial. Several studies have been conducted, and several are ongoing with the aim to stratify patients into risk categories for recurrence. Patients at high risk are candidates for long-term oral anticoagulation as the benefits of extended oral anticoagulation would outweigh the risk of bleeding. Patients are currently stratified into risk categories on the basis of clinical characteristics of the VTE event: (1) first or recurrent event; (2) idiopathic or due to a transient risk factor such as surgery, trauma, hormonal therapy, or immobilization; (3) presence of active cancer; (4) location (proximal DVT and/or pulmonary embolism, PE, or distal DVT); and (5) presence of known hereditary or acquired thrombophilia. Patients with distal VTE or VTE due to a transient risk factor are at a low risk of recurrence and short-term anticoagulation is indicated (3 months). Patients with an idiopathic event or with known thrombophilic defects such as FV Leiden or the G20210A prothrombin mutation are candidates for a longer course of therapy (6 months). Patients with cancer, antiphospholipid antibodies syndrome, recurrent idiopathic event, antithrombin deficiency, protein C or protein S deficiency, homozygosity for FV Leiden, and double heterozygosity are candidates for extended long-term anticoagulation. More recently, studies have indicated that other factors such as D-dimer levels after the discontinuation of OAC therapy or the residual vein thrombosis could be additional predictive factors for recurrences. In patients with VTE and cancer, oral anticoagulation poses a higher risk of bleeding, and such patients are more prone to recurrences. Alternative treatment with LMWH could be safer and more effective in these patients.

Pregnancy outcome after maternal poisoning with brodifacoum, a long-acting warfarin-like rodenticide

BACKGROUND

Brodifacoum is a potent warfarin-like anticoagulant used in many rat-poisoning products. Its availability has led to several reported human ingestions, none previously reported in pregnancy.

CASE

A woman presented at 22 weeks' gestation in hemorrhagic diathesis, attributed to the ingestion of rat poison containing brodifacoum several days earlier. Aggressive vitamin K therapy controlled the maternal coagulopathy, and no fetal hemorrhage was observed by sonography. Her subsequent prenatal course and delivery were unremarkable, and she was delivered of a healthy infant, who has remained well for at least 1 year.

CONCLUSION

In this patient, brodifacoum ingestion in pregnancy caused substantial maternal hemorrhage, but no fetal hemorrhage or teratogenic effects were observed.

Brodifacoum rodenticide ingestion in a patient with shigellosis

Factitious disorders are characterized by the intentional feigning or induction of signs and/or symptoms in order to assume the sick role. The spectrum of diseases and symptoms simulated is extensive. Although some patients may seek only the gratifications of the sick role, typically patients seek health care for their afflictions. We report the case of a woman with a history of numerous unexplainable illnesses and laboratory findings who had shigellosis. On routine evaluation, a severe prothrombin coagulopathy was discovered and later determined to be caused by brodifacoum, a "superwarfarin" drug found in potent rodenticides. The patient was successfully treated with daily vitamin K. She continued to deny intentional or accidental ingestion but did consent to psychiatric treatment.

Combined superwarfarin and ethylene glycol ingestion. A unique case report with misleading clinical history

A markedly elevated prothrombin time (PT) and activated partial thromboplastin time (APTT) were observed in a 24-year-old man who was admitted with a history of ethylene glycol ingestion. Further laboratory evaluation suggested that the coagulopathy was related to acquired factor deficiencies. The PT and APTT improved transiently on usual doses of vitamin K, but rapidly became abnormal again. The coagulopathy was controlled only after large doses of vitamin K for at least 37 days. On further questioning, the patient admitted to consuming a large quantity of a rodenticide. The second generation anticoagulant rodenticides (superwarfarins) result in a potent and prolonged anticoagulant effect by reducing the activity of the vitamin K dependent factors (II, XII, IX, and X). To our knowledge, this is the first reported concomitant ingestion of both ethylene glycol and a superwarfarin compound. This case serves to illustrate how a logical laboratory evaluation can lead to the proper diagnosis, despite a misleading clinical history.

The long-term effects of the rodenticide, brodifacoum, on blood coagulation and vitamin K metabolism in rats

1. The long-term (30 days) effects of a single dose of brodifacoum (0.2 mg kg-1, orally) on blood clotting activity and on liver parameters of the vitamin K cycle were investigated in rats. Maximal effect on blood clotting activity was seen on day one. On day seven blood clotting activity had returned to normal. 2. Liver microsomal vitamin KO reductase activity was maximally suppressed (10% of control activity) on day one, steadily recovered to about 40% on day 15 to remain at that level. The same time course was seen for the number of microsomal warfarin binding sites. 3. The persistent inhibition of the vitamin K cycle was also verified in vivo; following vitamin K administration (10 mg kg-1, i.v.) on day 30, the brodifacoum-treated rats accumulated vitamin KO in the liver. 4. Although clotting factor synthesis was normal, brodifacoum-treated rats were highly sensitive to warfarin. 5. Brodifacoum rapidly accumulated in the liver until the saturation of the microsomal binding site. Brodifacoum binding to the target prevented its elimination from the liver; liver content on day 30 was not different from day 7. 6. The results show (1) an over capacity for the hepatocellular vitamin K cycle, (2) a dissociation of the vitamin K epoxidation and the vitamin K-dependent carboxylation, (3) the 'superwarfarin' rodenticides to be extremely persistent due to their binding to the target.

Surreptitious ingestion of a long-acting vitamin K antagonist/rodenticide, brodifacoum: clinical and metabolic studies of three cases

The vitamin K metabolism of three patients with factitious purpura due to brodifacoum ingestion was studied. These patients, who presented with bleeding disorders due to deficiency of the vitamin K-dependent blood clotting proteins, were refractory to vitamin K1 at standard doses and required fresh frozen plasma to control bleeding until large doses of vitamin K1 were used. Metabolic studies demonstrated a blockade in vitamin K utilization, consistent with the presence of a vitamin K antagonist, but the patients denied use of anticoagulants. Warfarin assays were negative. We show that the factitious purpura in each patient was due to the surreptitious ingestion of brodifacoum, a potent second generation long-acting vitamin K antagonist used as a rodenticide. The coagulopathies responded to long-term therapy with large doses of vitamin K1. The serum elimination half-time for brodifacoum ranged from 16 to 36 days in these patients. The anticoagulant effect is of long duration, requiring chronic vitamin K treatment. With increasing availability of new rodenticides, factitious purpura due to surreptitious ingestion of these potent vitamin K antagonists is emerging as a new problem, previously associated with warfarin, with important implications for diagnosis and treatment.

Algorithm for short-term prescription of phenprocoumon

Data from the start of anticoagulation therapy using the coumarin derivative phenprocoumon were obtained retrospectively for 101 patients, and the correct long-term maintenance dose (MD) of the drug was determined. The average loading dose was 23.2 +/- 7.8 mg and the average MD 2.14 +/- 0.99 mg. The physician's prescription on discharge tended to underestimate the true MD by 0.29 +/- 0.64 mg. Significant positive correlations with MD were noted for loading dose and weight and negative correlations for age, serum creatinine, initial prothrombin ratio, and length of treatment pause (days) for patients receiving an excessive loading dose. Using stepwise variance analysis, an algorithm was obtained that predicted the MD: MD = -0.7 + loading dose/10 - treatment pause/7 - age/60 + initial prothrombin ratio. The accuracy (0.02 +/- 0.54 mg) was similar to that of the discharging physician. The algorithm required an average observation period of 5.4 days and the physician's estimate 12.4 days. It is suggested that the use of the algorithm would lead to shorter hospitalization without loss of treatment accuracy.

Trial of low-dose aspirin plus dipyridamole versus anticoagulants for prevention of aortocoronary vein graft occlusion

In a prospective randomised trial, 249 patients who had aortocoronary vein bypass surgery were assigned either to a platelet inhibitory drug regimen or to standard anticoagulant therapy. Treatment was replaced by placebo in half of the patients in each group after 3 months. The platelet inhibitory drug regimen--very low-dose aspirin combined with dipyridamole--was as effective as standard anticoagulant therapy to prevent early and late graft occlusion. Death, myocardial infarction, and severe bleeding occurred significantly more often in patients receiving anticoagulants, whereas mild drug-related gastrointestinal and cerebral side-effects were more common in patients taking platelet inhibitory drugs. Antithrombotic treatment should be continued for at least 1 year after coronary artery bypass graft surgery.

[Anticoagulation with phenprocoumon in early childhood: dosage, complications, effectiveness]

The dose-response relationship of the Vitamine-K-antagonist Phenprocoumon (Marcumar) was studied in a group of 11 children and 10 adults receiving anticoagulation postoperatively after mechanical valve replacement. The dose in children was found to be lineally correlated to the body surface area and similar to that in adults (saturation dose: 16.0 +/- 3.2 mg/m2; maintenance dose: 11.2 +/- 1.6 mg/m2/week). During the follow up period (265 patient months) one child died from mitral valve thrombosis, two children developed traumatic haematomas, and in one child interactions with 2 other drugs were observed. The incidence of thrombembolism or serious bleeding complications was 4.5 and 9.0 instances per 100 patient-years, respectively. The efficiency of prothrombin time control was established over a six months period and showed 70.3% of the values within, 23.% above, and 6.5% below the therapeutic range. During this period, the prothrombin time was measured 2.5 times per patient and month at the average. We conclude from our experience, that an anticoagulation therapy with Phenprocoumon can be performed in children with only mildly elevated risk of bleeding complications as effectively as in adults provided it is monitored closely.

Studies on the fate of flocoumafen in the Japanese quail (Coturnix coturnix japonica)

1. 14C-Flocoumafen, administered to Japanese quail as a single oral or i.p. dose, was rapidly and extensively eliminated in excreta; most was eliminated within 24 h. Extensive metabolism of the rodenticide was seen, with at least 8 metabolites detected; unchanged flocoumafen comprised 9% dose. The elimination kinetics and metabolic profiles were qualitatively similar after oral and i.p. dosing. 2. The major metabolites (60% dose) were labile to beta-glucuronidase, liberating aglycones with identical chromatographic mobilities to those of the unchanged flocoumafen isomers. 3. Radioactivity was retained mostly in the liver; largely as unchanged flocoumafen associated with the mitochondrial and microsomal fractions. Elimination of radioactivity from most tissues was biphasic with an initially rapid depletion (5 days) followed by a slow terminal elimination phase. The elimination half life from liver was greater than 100 days. 4. Livers of quail receiving extended dietary exposure to flocoumafen at 5, 15 and 50 ppm had concentrations of flocoumafen (1.0 nmol/g) that were independent of dose, indicating a capacity-limited binding site. These hepatic concentrations were similar to those after a single oral dose and were also similar to those in rats. The data indicate the presence in quail liver of a saturable high affinity flocoumafin binding site with similar characteristics and capacity to that in the rat. 5. The selective toxicity of flocoumafen to rats (highly toxic) and quail (moderately toxic) appears to arise from differences in metabolism rather than from anticoagulant binding in the liver. When hepatic binding sites of rats are saturated anticoagulant action becomes lethal, whereas quail are able to survive and extensively metabolize the compound.

The percutaneous fate of the rodenticide flocoumafen in the rat: role of non-biliary intestinal excretion

1. Appreciable penetration of radioacticity occurred through rat skin following percutaneous administration of 14C-flocoumafen. At 7 days after dosing 12% of the administered radioactivity remained at the site of application, while 25% was located in the liver as unchanged flocoumafen. 2. Excretion of flocoumafen metabolites via the urine accounted for 10% dose over the 7 day experiment, this is some 30-fold greater than that seen after a single oral dose. 3. Unchanged flocoumafen comprised the major product detected in faeces. Biliary elimination was a very minor route of excretion and did not account for all of the unmodified flocoumafen present in faeces. 4. Considerable amounts of unchanged flocoumafen found associated with the contents of the large intestine after intraperitoneal administration to rats fitted with biliary fistulae indicates that, in the intact rat, flocoumafen enters the intestine by a non-biliary intestinal excretion mechanism.

Elimination and accumulation of the rodenticide flocoumafen in rats following repeated oral administration

1. Following multiple oral administration of 14C-flocoumafen to rats at 0.02 and 0.1 mg/kg per week, appreciable cellular accumulation was seen in the liver. 2. Residues in the liver increased with dose throughout the duration of the experiment (14 weeks) at the low dose, but reached a plateau after 4 weeks at the high dose. The major component was unchanged flocoumafen together with a minor polar metabolite seen also in faeces. 3. The data suggest the presence in rat liver of a saturable high-affinity binding site for flocoumafen and a second binding site of lower affinity. 4. Lethal anticoagulant action occurs only when the binding sites have become saturated. 5. A range of haematological and clinical chemistry measurements failed to predict the onset of anticoagulant toxicity seen in the high dose treatment group. 6. Flocoumafen was not extensively metabolised; at the low dose, approximately 30% of the cumulative administered dose was eliminated in the faeces within 3 days of each dosing, mainly as unchanged rodenticide. At the high dose, this value ranged from 18% after the first dose to 59% after the tenth dose. 7. Two more polar metabolites and a lipophilic compound were minor products in faeces. Amounts of the polar products increased with cumulative dosage received. The urinary route of elimination was a very minor one (less than 1.6%) at both doses.

The in vivo effects of oral anticoagulants in man: comparison between liver and non-hepatic tissues

The in vivo effects of oral anticoagulant therapy with 4-hydroxycoumarins on various vitamin K-dependent enzyme systems in man were compared. In hepatic microsomes obtained from donors who has been treated with 4-hydroxycoumarins for more than 6 months, the vitamin K 2,3 epoxide reductase activity and the DTT-dependent vitamin K quinone reductase activity were diminished to 35% and 20% of the corresponding normal values. In the non-hepatic tissues, only a small decrease in vitamin K 2,3 epoxide reductase activity could be demonstrated, while no differences were found in the vitamin K quinone reductase activities. In none of the tissues a significant increase of noncarboxylated precursor proteins was observed, whereas also vitamin K hydroquinone-dependent carboxylase activities seemed to be unaffected by the anticoagulant treatment.

Factors responsible for interindividual differences in the dose requirement of phenprocoumon

The total and unbound plasma concentrations of phenprocoumon and the prothrombin complex activity were determined in 51 patients on phenprocoumon. A 7-fold difference in the dosing rate (10-70 micrograms/kg/day) was required to maintain the prothrombin complex activity at 11-30% of normal. The variation in dosing requirement was mainly due to interindividual differences in the intrinsic clearance of phenprocoumon and only to a minor degree to differences in sensitivity to it. On average patients with myocardial infarction required only 2/3 of the daily dose of phenprocoumon of post cardiac surgery patients and patients with thrombosis and emboli. That difference appeared to be due to higher clearance in surgical patients and to greater resistance to phenprocoumon in patients with thrombosis and emboli. The total clearance in patients varied approximately 5-fold. It was better predicted by the interindividual intrinsic clearance (r = 0.84) than by the unbound fraction (r = 0.15).

Vitamin K antagonism of coumarin intoxication in the rat

An in vitro system which expresses all enzyme activities related to vitamin K-dependent carboxylation of blood clotting factors was prepared from livers of rats overdosed with warfarin, difenacoum and dicumarol respectively. In this system, the activities of the two pathways that are known to produce active reduced vitamin K1 cofactor for the carboxylation reaction were measured. Also the ability of high concentrations of vitamin K1 to overcome inhibition of clotting factor synthesis was studied. In the systems prepared from livers of warfarin and difenacoum intoxicated rats, pathway I was inactive. Vitamin K epoxide reductase was also inactive which strongly suggests that this enzyme catalyzes the activity of pathway I in vivo. Reduction of vitamin K1 by pathway II bypassed the inactive pathway I and resulted in carboxylation activity. This pathway therefore mediates the antidotic effect of vitamin K1 in the coumarin intoxicated liver. In the in vitro system prepared from dicumarol intoxicated livers the activity of pathway I was not significantly affected. Dicumarol however was a strong inhibitor when added to liver microsomes in vitro.

Plasma hypercoagulability after termination of oral anticoagulants

The effect of discontinuation of a long term oral anticoagulant therapy with phenprocoumon on blood clotting parameters has been evaluated in patients in a controlled prospective trial. After termination of phenprocoumon the prothrombin time normalized within 15 days and the thrombotest coagulation value within 57 days. Fibrinopeptide A (FPA) increased significantly during the observation period. FPA release in vitro also rose after discontinuation of anticoagulants. In control patients on a phenprocoumon maintenance therapy no alterations of the above mentioned parameters occurred within the same period. The data indicate that plasma hypercoagulability is found in many patients, orally anticoagulated because of myocardial infarction, when the anticoagulant therapy is discontinued.

Monitoring of oral anticoagulation by an amidolytic factor X assay. A long-term study in 42 patients

The validity of the amidolytic Factor X assay for the control of long term oral anticoagulation (OA) was investigated in 42 patients randomized into 2 groups; PT group (anticoagulant dosage according to PT) and F.X group (anticoagulant dosage based on F.X). An independent expert's dosage according to F.X served for analysis in the former group. In the F.X group the F.X based dosage was considered valid only when not differing by more than 15% from the expert's PT based dosage. Confirming the good correlation between PT and F.X the study further demonstrates that the changes from one control to the next one, delta PT and delta F.X, too, are significantly correlated (r = 0.58, p less than 0.001, n = 217). In over one third of the periods the dosage proposals based on PT and F.X were identical and differed by more than 15% in only 12/217 instances. Our results justify a large trial on the control of OA by the amidolytic F.X assay.

[Coumarin therapy during antirheumatism therapy with sulindac]

Possible interactions between the new non-steroidal antirheumatic drug Sulindac and a coumarin derivative have been investigated. 20 subjects, who required anticoagulation therapy for a variety of medical conditions, were treated for 4 consecutive weeks with Sulindac at varying dosages (200-400 mg per day). Prothrombin time, Thrombotest and bleeding time were not significantly affected by the concurrent administration of Sulindac. It can be concluded that there is no clinically important interaction between phenprocoumon and the doses of sulindac that are considered effective in rheumatic disorders. There were some moderate side effects, only one drop out was registered because of gastro-intestinal bleeding (melaena).

Individualization of drug dosage during long-term treatment with phenprocoumon (Falithrom)

Pharmacokinetic studies were carried out with 3H-phenprocoumon (3H-PPC) during long-term treatment with phenprocoumon (PPC, Falithrom) in 10 female and male patients with thromboembolic diseases. Additionally, 12 mg 3H-PPC were administered per os to 6 male volunteers. Half-life and pattern of urine metabolites were measured and compared with those in patients. The radioactivity decreased independently of the total PPC plasma concentration, which was estimated fluorometrically. An exponential regression with a high coefficient of determination was found between the mean maintenance dose (PPC) and the area under plasma concentration curve of radioactivity. This procedure is considered to be a method to improve long-term treatment with PPC.