Stroke with intermittent atrial fibrillation: incidence and predictors during aspirin therapy. Stroke Prevention in Atrial Fibrillation Investigators.
(41/1963)
OBJECTIVE: This study was performed to characterize the risk of stroke in elderly patients with recurrent intermittent atrial fibrillation (AF). BACKGROUND: Although intermittent AF is common, relatively little is known about the attendant risk of stroke. METHODS: A longitudinal cohort study was performed comparing 460 participants with intermittent AF with 1,552 with sustained AF treated with aspirin in the Stroke Prevention in Atrial Fibrillation studies and followed for a mean of two years. Independent risk factors for ischemic stroke were identified by multivariate analysis. RESULTS: Patients with intermittent AF were, on average, younger (66 vs. 70 years, p < 0.001), were more often women (37% vs. 26% p < 0.001) and less often had heart failure (11% vs. 21%, p < 0.001) than those with sustained AF. The annualized rate of ischemic stroke was similar for those with intermittent (3.2%) and sustained AF (3.3%). In patients with intermittent AF, independent predictors of ischemic stroke were advancing age (relative risk [RR] = 2.1 per decade, p < 0.001), hypertension (RR = 3.4, p = 0.003) and prior stroke (RR = 4.1, p = 0.01). Of those with intermittent AF predicted to be high risk (24%), the observed stroke rate was 7.8% per year (95% confidence interval 4.5 to 14). CONCLUSIONS: In this large cohort of AF patients given aspirin, those with intermittent AF had stroke rates similar to patients with sustained AF and similar stroke risk factors. Many elderly patients with recurrent intermittent AF have substantial rates of stroke and likely benefit from anticoagulation. High-risk patients with intermittent AF can be identified using the same clinical criteria that apply to patients with sustained AF. (+info)
Prediction of pharmacokinetic drug/drug interactions from In vitro data: interactions of the nonsteroidal anti-inflammatory drug lornoxicam with oral anticoagulants.
(42/1963)
CYP2C9 is involved in the metabolism of the oral anticoagulants warfarin, phenprocoumon, and acenocoumarol. It is also responsible for the 5'-hydroxylation of the nonsteroidal anti-inflammatory drug lornoxicam. Therefore, lornoxicam and the oral anticoagulants are potential inhibitors of their metabolism. Their inhibitory potency was investigated in microsomes from six human livers. An approach to predict pharmacokinetic interactions of lornoxicam from in vitro inhibition data was developed. Where possible, the forecasts were verified by comparison with data from clinical interaction studies. The following increases in steady-state plasma concentrations or areas under the plasma concentration-time curve of the oral anticoagulants by concomitant lornoxicam medication were predicted (values in parentheses are for healthy volunteers): (S)-warfarin, 1. 58-fold (1.32-fold for racemate); racemic-acenocoumarol, 1.28-fold (1.09-fold); (R)-acenocoumarol, 1.10-fold (1.0-fold); racemic-phenprocoumon, 1.11-fold (1.18-fold); and (S)-phenprocoumon, 1.13-fold (1.24-fold). Lornoxicam 5'-hydroxylation was competitively inhibited in vitro by both phenprocoumon (K(i) = 1.2 +/- 0.4 microM) and acenocoumarol (K(i) = 5.5 +/- 3.5 microM). The present results indicate that relatively close predictions of the interactions of lornoxicam with oral anticoagulants from in vitro data are possible under the assumption that hepatic lornoxicam concentrations are similar to its total plasma concentrations. The degree of pharmacokinetic interactions exhibited by oral anticoagulants and lornoxicam is dependent on the respective contribution of CYP2C9 to their total clearance. (+info)
A systematic review of drug induced ocular reactions in diabetes.
(43/1963)
AIMS: To conduct a systematic review of drug induced adverse ocular effects in diabetes to determine if this approach identified any previously unrecognised adverse drug effects; to make a preliminary assessment of the feasibility of this approach in identifying adverse drug reactions; and to assess the current accessibility of this information to prescribing physicians. METHODS: Literature search of online biomedical databases. The search strategy linked eye disorders with adverse drug reactions and diabetes. Source journals were classified as medical, pharmaceutical, diabetes related, or ophthalmological. It was determined whether the reactions identified were recorded in drug datasheets and the British National Formulary. RESULTS: 63 references fulfilled the selection criteria, of which 45 were considered to be relevant to the study. The majority of these were case reports but cross sectional surveys, case-control and cohort studies, and review articles were also identified. 61% of the reactions were not recorded in the British National Formulary and 41% were not recorded in the datasheets. 55% appeared in specialist ophthalmology journals. CONCLUSIONS: This is a feasible approach to the identification of adverse drug reactions. Adverse reactions not listed in the most commonly used reference sources were found. The majority were published in specialist ophthalmology journals which might not be seen by prescribing physicians. (+info)
Warfarin-induced artery calcification is accelerated by growth and vitamin D.
(44/1963)
The present studies demonstrate that growth and vitamin D treatment enhance the extent of artery calcification in rats given sufficient doses of Warfarin to inhibit gamma-carboxylation of matrix Gla protein, a calcification inhibitor known to be expressed by smooth muscle cells and macrophages in the artery wall. The first series of experiments examined the influence of age and growth status on artery calcification in Warfarin-treated rats. Treatment for 2 weeks with Warfarin caused massive focal calcification of the artery media in 20-day-old rats and less extensive focal calcification in 42-day-old rats. In contrast, no artery calcification could be detected in 10-month-old adult rats even after 4 weeks of Warfarin treatment. To directly examine the importance of growth to Warfarin-induced artery calcification in animals of the same age, 20-day-old rats were fed for 2 weeks either an ad libitum diet or a 6-g/d restricted diet that maintains weight but prevents growth. Concurrent treatment of both dietary groups with Warfarin produced massive focal calcification of the artery media in the ad libitum-fed rats but no detectable artery calcification in the restricted-diet, growth-inhibited group. Although the explanation for the association between artery calcification and growth status cannot be determined from the present study, there was a relationship between higher serum phosphate and susceptibility to artery calcification, with 30% higher levels of serum phosphate in young, ad libitum-fed rats compared with either of the groups that was resistant to Warfarin-induced artery calcification, ie, the 10-month-old rats and the restricted-diet, growth-inhibited young rats. This observation suggests that increased susceptibility to Warfarin-induced artery calcification could be related to higher serum phosphate levels. The second set of experiments examined the possible synergy between vitamin D and Warfarin in artery calcification. High doses of vitamin D are known to cause calcification of the artery media in as little as 3 to 4 days. High doses of the vitamin K antagonist Warfarin are also known to cause calcification of the artery media, but at treatment times of 2 weeks or longer yet not at 1 week. In the current study, we investigated the synergy between these 2 treatments and found that concurrent Warfarin administration dramatically increased the extent of calcification in the media of vitamin D-treated rats at 3 and 4 days. There was a close parallel between the effect of vitamin D dose on artery calcification and the effect of vitamin D dose on the elevation of serum calcium, which suggests that vitamin D may induce artery calcification through its effect on serum calcium. Because Warfarin treatment had no effect on the elevation in serum calcium produced by vitamin D, the synergy between Warfarin and vitamin D is probably best explained by the hypothesis that Warfarin inhibits the activity of matrix Gla protein as a calcification inhibitor. High levels of matrix Gla protein are found at sites of artery calcification in rats treated with vitamin D plus Warfarin, and chemical analysis showed that the protein that accumulated was indeed not gamma-carboxylated. These observations indicate that although the gamma-carboxyglutamate residues of matrix Gla protein are apparently required for its function as a calcification inhibitor, they are not required for its accumulation at calcification sites. (+info)
A primary care evaluation of three near patient coagulometers.
(45/1963)
AIM: To compare the reliability and relative costs of three international normalised ratio (INR) near patient tests. MATERIALS: Protime (ITC Technidyne), Coaguchek (Boehringer Mannheim), and TAS (Diagnostic Testing). METHODS: All patients attending one inner city general practice anticoagulation clinic were asked to participate, with two samples provided by patients not taking warfarin. A 5 ml sample of venous whole blood was taken from each patient and a drop immediately added to the prepared Coaguchek test strip followed by the Protime cuvette. The remainder was added to a citrated bottle. A drop of citrated blood was then placed on the TAS test card and the remainder sent to the reference laboratory for analysis. Parallel INR estimation was performed on the different near patient tests at each weekly anticoagulation clinic from July to December 1997. RESULTS: 19 patients receiving long term warfarin treatment provided 62 INR results. INR results ranged from 0.8-8.2 overall and 1.0-5.7 based on the laboratory method. Taking the laboratory method as the gold standard, 12/62 results were < 2.0 and 2/62 were > 4.5. There were no statistical or clinically significant differences between results from the three systems, although all near patient tests showed slightly higher mean readings than the laboratory, and 19-24% of tests would have resulted in different management decisions based on the machine used in comparison with the laboratory INR value. The cost of the near patient test systems varied substantially. CONCLUSIONS: All three near patient test systems are safe and efficient for producing acceptable and reproducible INR results within the therapeutic range in a primary care setting. All the systems were, however, subject to operator dependent variables at the time of blood letting. Adequate training in capillary blood sampling, specific use of the machines, and quality assurance procedures is therefore essential. (+info)
A comparison of a low-dose warfarin induction regimen with the modified Fennerty regimen in elderly inpatients.
(46/1963)
OBJECTIVES: To compare a new low-dose warfarin induction regimen with the Fennerty regimen in elderly inpatients. DESIGN: Age-stratified, randomized prospective study. SUBJECTS: 120 age-stratified elderly inpatients. INTERVENTIONS: Each patient was randomized to either the new induction regimen or to a modified Fennerty regimen. MAIN OUTCOMES MEASURES: Days to therapeutic International Normalized Ratio (INR >2); days in the therapeutic range (INR 2-3) during induction; number of patients with INR >4.5; ability of day 4 INR to predict day 8 warfarin dose. RESULTS: The mean time to therapeutic INR was longer for the new induction regimen than modified Fennerty regimen in patients aged 65-75 years [4.6 (mean) +/- 1.6 (SD) days vs 3.8 +/- 0.8 days; P = 0.03] and in patients aged >75 years (4.5 +/- 1.4 days vs 3.5 +/- 0.7 days; P = 0.003). Patients spent more time in the therapeutic INR range with the new induction regimen [3.0 +/- 1.3 days vs 2.7 +/- 1.3 days (P = 0.03) for those aged 65-75 years and 2.9 +/- 1.1 days vs 2.4 +/- 1.3 days (P = 0.04 for those aged >75 years]. Fewer patients using the new regimen had INRs >4.5 in the first 8 days [1 (3%) vs 6 (20%) for 65-75 years (P < 0.05) and 1 (3%) vs 11 (37%) for >75 years (P < 0.01)]. The ability to predict the maintenance dose to within 1 mg was 55% for both regimens. CONCLUSION: The low-dose regimen has important clinical advantages over the Fennerty regimen for anticoagulating elderly inpatients. (+info)
Laboratory evaluation of WBA 8119 as a rodenticide for use against warfarin-resistant and non-resistant rats and mice.
(47/1963)
Feeding tests were carried out in the laboratory to evaluate WBA 8119 as a potential new rodenticide against wild common rats (Rattus norvegicus), ship rats (R. rattus) and house mice (Mus musculus). The results obtained are compared with data previously obtained for difenacoum, another member of the same series of 4-hydroxycoumarin anticoagulants. With warfarin-resistnat and non-resistant common rats, complete kills were obtained using a concentration of 0-0005% for 2 days, or 0-001% for 1 day: a 1-day test at 0-0005% killed 6 out of 10 and 17 out of 20 of the two types respectively. At 0-0005% complete kills of resistant ship rats were obtained after 2 days exposure and of resistant house mice after 1 day, but at 0-002% for 2 days there was some survival. Non-resistant ship rats and house mice were all killed after 2 days feeding on 0-002% bait. In 2-day palatability tests, R. norvegicus showed no significant aversion to the poison at 0-002% and 100% mortality was obtained. The poison was significantly unpalatable to R. rattus at 0-005% and to M. musculus at 0-005% and 0-002%, although with the last species these concentrations gave complete kills. It is concluded that WBA 8119 has greater activity than other known anticoagulants against the three commensal species examined. The laboratory results suggest that concentrations between 0-0005% and 0-002% would be suitable for field use against common rats, and between 0-002% and 0-005% for ship rats and house mice. (+info)
Trials of the anticoagulant rodenticide WBA 8119 against confined colonies of warfarin-resistant house mice (Mus musculus L.).
(48/1963)
The efficacy of the newly developed anticoagulant rodenticide WBA 8119 was evaluated against the house mouse (Mus musculus L.) using individual and family groups of warfarin-resistant animals. WBA 8119 at 0-002%, 0-005% and 0-01% in pinhead oatmeal bait gave complete kills of mice in 'no-choice' feeding tests carried out in cages and small pens. In replicated 21-day treatments on families of mice confined in larger pens conditioned to feeding on plain foods, the overall mortalities obtained using the three formulated poison baits were 71/72, 62/63 and 57/57 respectively. The results of the WBA 8119 toxicity tests are considered in relation to previous findings on other anticoagulant rodenticides, particularly difenacoum. In equivalents tests, WBA 8119 performed better than difenacoum. The data thus suport the laboratory findings that WBA 8119 is the most active anticoagulant so far tested for the control of warfarin-resistant house mice. (+info)