Risk of intracerebral hemorrhage associated with phenprocoumon exposure: a nested case-control study in a large population-based German database

Risk for intracranial hemorrhage in individuals after mild traumatic brain injury who are taking serotonergic antidepressants

Background

Serotonergic antidepressants may predispose to bleeding, but little is known of the risk for traumatic intracranial bleeding.

Methods

This was a prospective case-control study of 218 patients with mild traumatic brain injuries (TBI) who were treated at a Finnish tertiary trauma hospital. Injury-related information and clinical findings were prospectively collected in the emergency department. Detailed pre-injury health history was collected from electronic medical records. Information on the use of serotonergic antidepressants was attained from the Finnish national prescription registry. All head CT scans were reviewed by a neuroradiologist based on the Common Data Elements. Cases were patients with traumatic intracranial hemorrhage on head CT. Controls were patients from the same cohort, but without traumatic intracranial lesions on CT. The proportion with traumatic intracranial bleeding for patients on serotonergic antidepressant medication was compared to the proportion for patients not on serotonergic medication.

Results

The study cohort consisted of 24 cases with traumatic intracranial bleeding and 194 injured controls. The median age of the sample was 70 years (interquartile range = 50-83). One fifth (21.6%) of all the patients were taking a serotonergic antidepressant. Of the patients on an antidepressant, 10.6% (5/47) had an acute hemorrhagic lesion compared to 11.1% (19/171) of those who were not on an antidepressant (p = 0.927). In the regression analysis, traumatic intracranial hemorrhage was not associated with antidepressant use.

Conclusion

Serotonergic antidepressant use was not associated with an increased risk of traumatic intracranial hemorrhage after a mild TBI. The patients in this relatively small cohort were mostly middle-aged and older adults. These factors limit the generalizability of the results in younger patients with mild TBI.

Pharmacokinetics of Phenprocoumon in Emergency Situations-Results of the Prospective Observational RADOA-Registry (Reversal Agent Use in Patients Treated with Direct Oral Anticoagulants or Vitamin K Antagonists Registry)

Background: Phenprocoumon has been used as an oral anticoagulant in patients with thromboembolic disease for more than 40 years. So far its pharmacokinetics have not been analyzed in emergency situations. Methods: Phenprocoumon-treated patients with major bleeding or urgent surgery were included in a prospective, observational registry. Phenprocoumon drug concentrations were analyzed in samples, collected as part of routine care using ultraperformance liquid chromatography tandem mass spectrometry. Moreover, anticoagulant intensity and drug half-life (t1/2) were calculated. Results: 115 patients were included. Phenprocoumon levels declined over time with a half-life of 5.27 and 5.29 days in patients with major bleedings (n = 82) and with urgent surgery (n = 33). Baseline phenprocoumon levels were 2.2 times higher in the bleeding group compared to the surgery group (1.92 vs. 0.87 ng/mL, p < 0.0001). International normalized ratio (INR) values decreased rapidly during the first 24 h. In 27.6% of patients a rebound of INR (recurrent increase > 1.5) was observed which was associated with significantly increased bleeding rates (22% vs. 4.2% in patients with or without INR rebound, p = 0.012). Conclusions: In emergency situations, the long half-life of phenprocoumon may cause INR rebound and associated recurrent bleedings. Optimal management may need to include repeated vitamin K supplementation over days.

Selective Serotonin Reuptake Inhibitors and Intracerebral Hemorrhage Risk and Outcome

Background and Purpose- Selective serotonin reuptake inhibitors (SSRIs) have a well-established association with bleeding complications and conflicting reports on outcome after stroke. We sought to evaluate whether pre-intracerebral hemorrhage (ICH) SSRI use increased ICH risk and post-ICH SSRI use improved ICH outcome. Methods- Through post hoc analysis of the ERICH study (Ethnic/Racial Variations of Intracerebral Hemorrhage), SSRI use was categorized into no use, pre-ICH only, pre- and post-ICH use (termed "continuous"), and post-ICH only (termed "new"). Using multivariable modeling, associations were sought between pre-ICH SSRI use and ICH risk in the case-control set, and associations between post-ICH SSRI use and 3-month outcome were analyzed in the ICH case set. Exploratory analyses sought to assess influence of race/ethnicity in models. Results- The final study cohort consisted of 2287 ICH cases and 2895 controls. Pre-ICH SSRI use was not associated with ICH risk (odds ratio, 0.824 [95% CI, 0.632-1.074]) nor potentiation of ICH risk with anticoagulant or antiplatelet use. New post-ICH SSRI use was associated with unfavorable modified Rankin Scale score at 3 months after ICH (odds ratio, 1.673 [95% CI, 1.162-2.408]; P=0.006) in multivariable analyses. Additional propensity score analysis indicated a similar trend but did not reach statistical significance (P=0.107). When stratified by race/ethnicity, multivariable modeling demonstrated reduced ICH risk with pre-ICH SSRI use in Hispanics (odds ratio, 0.513 [95% CI, 0.301-0.875]; P=0.014), but not non-Hispanic whites or blacks, and no associations between post-ICH SSRI use and 3-month outcome in any racial/ethnic group. Conclusions- In a large multiethnic cohort, pre-ICH SSRI use was not associated with increased ICH risk, but post-ICH SSRI use was associated with unfavorable 3-month neurological outcome after ICH. Registration- URL: https://www.clinicaltrials.gov; Unique identifier: NCT01202864.

The impact of selective serotonin reuptake inhibitors on the risk of intracranial haemorrhage: A systematic review and meta-analysis

Introduction

Observational studies have suggested increased risk of intracranial haemorrhage (ICrH) in patients receiving selective serotonin reuptake inhibitors (SSRIs). We sought to clarify the impact of SSRIs on ICrH, accounting for study methodology.

Patients and methods

A comprehensive search of Medline, Embase and the Cochrane Library from 1960 to December 2017 identified studies comparing SSRIs with control. The outcomes (first-ever and recurrent ICrH) were meta-analysed using a random effects model.

Results

Twenty-four observational studies and three randomised trials were available for meta-analysis, totalling 4,844,090 patient-years of follow-up. Those receiving SSRIs were more likely to be female (p = 0.01) and have depression (p < 0.001). Compared to controls, SSRI users had a significantly increased risk of ICrH (relative risk (RR) 1.26, 95%CI 1.11-1.42). Although SSRI use was associated with increased ICrH risk in those without previous ICrH (RR 1.31, 95%CI 1.15-1.48), this was not the case in those with previous ICrH (RR 0.95, 95%CI 0.83-1.09). Sensitivity analysis according to the bleeding definition reported demonstrated that although 'haemorrhagic stroke' was associated with SSRIs (RR 1.40, 95%CI 1.13-1.72), intracerebral haemorrhage was not (RR 1.11, 95%CI 0.86-1.42). Additional sensitivity analyses demonstrated a stronger association between SSRIs and ICrH in studies with a high (p < 0.001) compared to low risk of bias (p = 0.09) and with retrospective (p < 0.001) compared to prospective (p=0.31) study designs.

Discussion

Although SSRIs are associated with an increased risk of ICrH, the association is partly accounted for by important biases and other methodological limitations in the available observational data.

Conclusion

Our findings suggest there is insufficient high-quality data to advise restriction of SSRIs because of concern regarding ICrH risk.

Robust versus consistent variance estimators in marginal structural Cox models

In survival analyses, inverse-probability-of-treatment (IPT) and inverse-probability-of-censoring (IPC) weighted estimators of parameters in marginal structural Cox models are often used to estimate treatment effects in the presence of time-dependent confounding and censoring. In most applications, a robust variance estimator of the IPT and IPC weighted estimator is calculated leading to conservative confidence intervals. This estimator assumes that the weights are known rather than estimated from the data. Although a consistent estimator of the asymptotic variance of the IPT and IPC weighted estimator is generally available, applications and thus information on the performance of the consistent estimator are lacking. Reasons might be a cumbersome implementation in statistical software, which is further complicated by missing details on the variance formula. In this paper, we therefore provide a detailed derivation of the variance of the asymptotic distribution of the IPT and IPC weighted estimator and explicitly state the necessary terms to calculate a consistent estimator of this variance. We compare the performance of the robust and consistent variance estimators in an application based on routine health care data and in a simulation study. The simulation reveals no substantial differences between the 2 estimators in medium and large data sets with no unmeasured confounding, but the consistent variance estimator performs poorly in small samples or under unmeasured confounding, if the number of confounders is large. We thus conclude that the robust estimator is more appropriate for all practical purposes.

The Potential of High-Dimensional Propensity Scores in Health Services Research: An Exemplary Study on the Quality of Care for Elective Percutaneous Coronary Interventions

OBJECTIVE

Evaluating the potential of the high-dimensional propensity score (HDPS) to control for residual confounding in studies analyzing quality of care based on administrative health insurance data.

DATA SOURCE

Secondary data from 2004 to 2009 from three German statutory health insurance providers.

STUDY DESIGN

We conducted a retrospective cohort study in patients with elective percutaneous coronary interventions (PCIs) and compared the mortality risk between the in- and outpatient setting using Cox regression. Adjustment for predefined confounders was performed using conventional propensity score (PS) techniques. Further, an HDPS was calculated based on predefined and empirically selected confounders from the database.

PRINCIPAL FINDINGS

Conventional PS methods showed a decreased mortality risk for outpatient compared to inpatient PCIs, while trimming of patients with nonoverlap in the HDPS distribution and weighting resulted in a comparable risk. Most comorbidities were less prevalent in the HDPS-trimmed population compared to the original one.

CONCLUSION

The HDPS methodology may reduce residual confounding by rendering the studied cohort more comparable through restriction. However, results cannot be generalized for the entire study population. To provide unbiased results, full assessment of all unmeasured confounders from proxy information in the database would be necessary.

Comparative risk for cardiovascular diseases of dipeptidyl peptidase-4 inhibitors vs. sulfonylureas in combination with metformin: Results of a two-phase study

AIMS

The aim was to assess whether the use of additional data from the Disease Management Program (DMP) diabetes mellitus type 2 to minimize the potential for residual confounding will alter the estimated risk of either myocardial infarction, ischemic stroke or heart failure in patients with type 2 diabetes using sulfonylureas compared to dipeptidyl peptidase-4 (DPP-4) inhibitors in addition to metformin based on routine health care data.

METHODS

We conducted a nested two-phase case-control study using claims data of one German health insurance from 2004 to 2013 (phase 1) and data of the DMP from 2010 to 2013 (phase 2). Adjusted odds ratios (ORs) for the combined cardiovascular event myocardial infarction, ischemic stroke or heart failure were calculated using a two-phase logistic regression.

RESULTS

Phase 1 comprised 3179 patients (289 cases; 2890 controls) and phase 2 comprised 1968 patients (168 cases; 1800 controls). We observed an adjusted OR of 0.83 for the combined cardiovascular event (95% CI: 0.61-1.13).

CONCLUSIONS

We observed a non-significantly reduced risk for cardiovascular diseases in patients using DPP-4 inhibitors compared to sulfonylureas in addition to metformin. This finding was not altered by the inclusion of additional information of the DMP in the analysis. However, due to the low power of this study, further studies are needed to reproduce our findings.

Quality of oral anticoagulation with phenprocoumon in regular medical care and its potential for improvement in a telemedicine-based coagulation service--results from the prospective, multi-center, observational cohort study thrombEVAL

BACKGROUND

The majority of studies on quality of oral anticoagulation (OAC) therapy with vitamin K-antagonists are performed with short-acting warfarin. Data on long-acting phenprocoumon, which is frequently used in Europe for OAC therapy and is considered to enable more stable therapy adjustment, are scarce. In this study, we aimed to assess quality of OAC therapy with phenprocoumon in regular medical care and to evaluate its potential for optimization in a telemedicine-based coagulation service.

METHODS

In the prospective observational cohort study program thrombEVAL we investigated 2,011 patients from regular medical care in a multi-center cohort study and 760 patients from a telemedicine-based coagulation service in a single-center cohort study. Data were obtained from self-reported data, computer-assisted personal interviews, and laboratory measurements according to standard operating procedures with detailed quality control. Time in therapeutic range (TTR) was calculated by linear interpolation method to assess quality of OAC therapy. Study monitoring was carried out by an independent institution.

RESULTS

Overall, 15,377 treatment years and 48,955 international normalized ratio (INR) measurements were analyzed. Quality of anticoagulation, as measured by median TTR, was 66.3% (interquartile range (IQR) 47.8/81.9) in regular medical care and 75.5% (IQR 64.2/84.4) in the coagulation service (P <0.001). Stable anticoagulation control within therapeutic range was achieved in 63.8% of patients in regular medical care with TTR at 72.1% (IQR 58.3/84.7) as compared to 96.4% of patients in the coagulation service with TTR at 76.2% [(IQR 65.6/84.7); P = 0.001)]. Prospective follow-up of coagulation service patients with pretreatment in regular medical care showed an improvement of the TTR from 66.2% (IQR 49.0/83.6) to 74.5% (IQR 62.9/84.2; P <0.0001) in the coagulation service. Treatment in the coagulation service contributed to an optimization of the profile of time outside therapeutic range, a 2.2-fold increase of stabile INR adjustment and a significant decrease in TTR variability by 36% (P <0.001).

CONCLUSIONS

Quality of anticoagulation with phenprocoumon was comparably high in this real-world sample of regular medical care. Treatment in a telemedicine-based coagulation service substantially improved quality of OAC therapy with regard to TTR level, frequency of stable anticoagulation control, and TTR variability.

TRIAL REGISTRATION

ClinicalTrials.gov, unique identifier NCT01809015, March 8, 2013.

Risk of subarachnoid hemorrhage and early case fatality associated with outpatient antithrombotic drug use

BACKGROUND AND PURPOSE

Subarachnoid hemorrhage (SAH) accounts for <7% of all strokes, but is an enormous individual and societal burden. We investigated the risk of SAH associated with prior use of antithrombotic drugs and their influence on 30-day case fatality.

METHODS

We conducted a nested case-control study in a cohort of 13.4 million members of the German Pharmacoepidemiological Research Database. Ten controls were matched to each case hospitalized for SAH between July 2004 and November 2006 by health insurance, year of birth, and sex using risk set sampling. Exposure was assessed for the warfarin analog phenprocoumon, heparin, clopidogrel/ticlopidine, and acetylsalicylic acid. Multivariable-adjusted odds ratios (ORs) for SAH were estimated by conditional logistic regression. Risk factors for 30-day case fatality were assessed in patients with SAH by logistic regression.

RESULTS

The nested case-control study included 2065 SAH cases and 20 649 matched controls. The risk of SAH was significantly increased for phenprocoumon (OR, 1.7; 95% confidence interval [CI], 1.3-2.3), clopidogrel/ticlopidine (OR, 1.7; 95% CI, 1.1-2.5), and for acetylsalicylic acid use (OR, 1.5; 95% CI, 1.2-2.0), but not for outpatient heparin use (OR, 1.2; 95% CI, 0.5-2.7). The early case fatality of 22.8% was associated with an age >70 years (OR, 2.3; 95% CI, 1.8-3.1) and arterial hypertension (OR, 1.3; 95% CI, 1.0-1.6), but not with any of the antithrombotic drugs.

CONCLUSIONS

Outpatient antithrombotic drug use was associated with an increased risk of SAH, but no association was observed with early case fatality.

Evaluation of pregnancy outcome records in the German Pharmacoepidemiological Research Database (GePaRD)

PURPOSE

Routine health care data are a valuable source for the assessment of risks of drugs during pregnancy. Therefore, the aim of the current analysis was the evaluation of pregnancy outcome records in German health insurance data.

METHODS

We used the German Pharmacoepidemiologic Research Database including data of more than 15 million insurants (about 18% of the German population). Among 10-49 year-old women, we identified six categories of pregnancy outcomes: term births, preterm births, stillbirths, induced abortions, spontaneous abortions and ectopic pregnancies. In order to assess the validity of these records, we have set our results in relation to representative data for the corresponding outcomes in Germany. We also investigated whether pregnancy markers (diagnoses, procedures or medical services which indicate an existing pregnancy) can be used to identify pregnancies.

RESULTS

In total, we identified 94 261 pregnancy outcomes in 2005. The percentage of births outside hospital (1.2%) and of preterm births (11.6%), the rate of stillbirths (3 per 1000 live births) and the rate of ectopic pregnancies (20 per 1000 live births) agreed well with representative data for Germany. Compared to epidemiological data, the occurrence of spontaneous abortions was underestimated (5.4% of all pregnancies). There were 4.1 induced abortions per 100 live births, compared to 18.1 in national data. Positive predictive values and sensitivities of markers varied across marker categories and for different pregnancy outcomes.

CONCLUSIONS

Completeness of pregnancy outcomes recorded in the database varied by pregnancy outcome. This should be taken into account in studies of drug safety in pregnancy.

Cost-effectiveness of pharmacogenetics in anticoagulation: international differences in healthcare systems and costs

Genotyping patients for CYP2C9 and VKORC1 polymorphisms can improve the accuracy of dosing during the initiation of anticoagulation with vitamin K antagonists (coumarin derivatives). The anticipated degree of improvement in the safety of anticoagulation with coumarins through genotyping may vary depending on the quality of patient care, which varies both with and among countries. The management and the cost of anticoagulant care can therefore influence the cost-effectiveness of genotyping within any given country. In this article, we provide an overview of the cost-effectiveness of pharmacogenetics-guided dosing of coumarin derivatives. We describe the organization of anticoagulant care in the UK, Sweden, The Netherlands, Greece, Germany and Austria, where a genotype-guided dosing algorithm is currently being investigated as part of the EU-PACT trial. We also explore the costs of anticoagulant care for the treatment of atrial fibrillation in these countries.

Bleeding complications and liver injuries during phenprocoumon treatment: a multicentre prospective observational study in internal medicine departments

BACKGROUND

Even after the recent approval of newer oral anticoagulants for clinical use, the vitamin K antagonist phenprocoumon remains an important treatment option for many patients. In order to quantify the hitherto "accepted" risks of phenprocoumon treatment, we analyzed adverse drug reactions (ADRs) that led to hospitalization on the internal medicine wards of four German pharmacovigilance centers.

METHODS

We prospectively analyzed ADRs leading to hospitalization on the internal medicine wards of the hospitals belonging to the German Network of Regional Pharmacovigilance Centers (Rostock, Greifswald, Jena, and the Sophien- und Hufeland-Klinikum in Weimar) in the years 2000 to 2008.

RESULTS

The 851 patients hospitalized for a phenprocoumon-associated ADR accounted for 12.4% of the 6887 ADR-related hospitalizations in the period of the study. 723 (85%) were admitted for a hemorrhage, usually in the gastrointestinal tract (482 patients); 8 patients died as a consequence of hemorrhage associated with phenprocoumon exposure. Using drug utilization data for the catchment areas of the participating hospitals, we calculate a rate of 5 to 7 hemorrhages leading to hospitalization in an internal medicine ward per 1000 patient-years under phenprocoumon treatment. One-third of the patients who had a hemorrhage were taking other interacting drugs, mainly inhibitors of platelet aggregation and non-steroidal anti-inflammatory drugs. Among the patients who were taking phenprocoumon because of a history of thromboembolic events or for atrial fibrillation, 60% to 70% of those who had hemorrhages had an international normalized ratio (INR) that was above the upper limit of the therapeutic range. Phenprocoumon-associated impairment of liver function arose in 23 patients (2.7%).

CONCLUSION

In this study, about one-eighth of all ADR-related admissions to hospital internal medicine wards were associated with phenprocoumon. There is a need for a comparative risk-benefit assessment of phenprocoumon and the newer oral anticoagulants under real-life conditions.

Age-specific prevalence, incidence of new diagnoses, and drug treatment of attention-deficit/hyperactivity disorder in Germany

OBJECTIVE

The purpose of this study was to estimate the prevalence and incidence of new diagnoses of attention-deficit/hyperactivity disorder (ADHD) and assess drug treatment of ADHD in the 3-17 year age group in Germany.

METHOD

We analysed data from the German Pharmacoepidemiological Research Database (GePaRD) for the years 2004-2006. The GePaRD includes claim records of 14,000,000 members of four statutory health insurances, representing 17% of the German population. The assessment of ADHD diagnoses was based on International Classification of Diseases version 10 (ICD-10) codes in outpatient and hospital data.

RESULTS

In 2005, the age-standardized prevalence and incidence of new diagnoses were 2.5% and 9/1000 person-years, respectively. Both measures were 3-4 times higher for males than for females. Incidence of new ADHD diagnoses increased linearly up to the age of 8 years for boys and 9 years for girls and decreased abruptly thereafter. In the calendar quarter of the initial ADHD diagnosis, 9.4% (95% confidence interval [CI] 8.9-9.8%) received methylphenidate or atomoxetine and 36.8% (95% CI 36.1-37.6%) received at least one prescription of either drug within the first year. Initiation of drug treatment and choice of drug were similar for both sexes.

CONCLUSIONS

ADHD is a common condition among children and youth in Germany. There are substantial differences by sex in the prevalence and incidence of new ADHD diagnoses, but only a small difference in drug treatment among those diagnosed with ADHD. A relatively low percentage of children receives drug treatment in the first year after the initial diagnosis of ADHD.

[Management and therapy of atrial fibrillation in geriatric patients]

Among geriatric patients, atrial fibrillation is the most common cardiac arrhythmia. In patients over 80 years of age, the prevalence rises to approximately 10%. Atrial fibrillation is associated with serious health implications, including a 2-fold increase in mortality risk and a 5-fold increase in stroke risk. In contrast to these facts, the current guidelines on the management of atrial fibrillation of the European Society of Cardiology (ESC) contain only a short paragraph on these patients. Many relevant clinical aspects go without any comment. Thus, the purpose of our paper is to discuss those special needs of geriatric patients and their physicians which are not mentioned in the guidelines of the ESC. In our review, we discuss rhythm versus rate control, oral anticoagulation, outcome, prevention, falls, adherence, polypharmacy, dementia, nursing home patients, frailty, and geriatric assessment in consideration of geriatric patients. An extended search of the literature on Pubmed served as the basis for this review. Individual aspects of each geriatric patient should be considered when managing these complex patients; however, the complexity of each case must not lead to an individualized therapy that is not in accordance with current guidelines and the literature. A large number of papers which help us to answer most of the clinical questions regarding the management of trial fibrillation in geriatric patients have already been published.

Regional and temporal variations in coding of hospital diagnoses referring to upper gastrointestinal and oesophageal bleeding in Germany

Background

Health insurance claims data are increasingly used for health services research in Germany. Hospital diagnoses in these data are coded according to the International Classification of Diseases, German modification (ICD-10-GM). Due to the historical division into West and East Germany, different coding practices might persist in both former parts. Additionally, the introduction of Diagnosis Related Groups (DRGs) in Germany in 2003/2004 might have changed the coding. The aim of this study was to investigate regional and temporal variations in coding of hospitalisation diagnoses in Germany.

Methods

We analysed hospitalisation diagnoses for oesophageal bleeding (OB) and upper gastrointestinal bleeding (UGIB) from the official German Hospital Statistics provided by the Federal Statistical Office. Bleeding diagnoses were classified as "specific" (origin of bleeding provided) or "unspecific" (origin of bleeding not provided) coding. We studied regional (former East versus West Germany) differences in incidence of hospitalisations with specific or unspecific coding for OB and UGIB and temporal variations between 2000 and 2005. For each year, incidence ratios of hospitalisations for former East versus West Germany were estimated with log-linear regression models adjusting for age, gender and population density.

Results

Significant differences in specific and unspecific coding between East and West Germany and over time were found for both, OB and UGIB hospitalisation diagnoses, respectively. For example in 2002, incidence ratios of hospitalisations for East versus West Germany were 1.24 (95% CI 1.16-1.32) for specific and 0.67 (95% CI 0.60-0.74) for unspecific OB diagnoses and 1.43 (95% CI 1.36-1.51) for specific and 0.83 (95% CI 0.80-0.87) for unspecific UGIB. Regional differences nearly disappeared and time trends were less marked when using combined specific and unspecific diagnoses of OB or UGIB, respectively.

Conclusions

During the study period, there were substantial regional and temporal variations in the coding of OB and UGIB diagnoses in hospitalised patients. Possible explanations for the observed regional variations are different coding preferences, further influenced by changes in coding and reimbursement rules. Analysing groups of diagnoses including specific and unspecific codes reduces the influence of varying coding practices.

Drug interactions with phenprocoumon and the risk of serious haemorrhage: a nested case-control study in a large population-based German database

PURPOSE

Phenprocoumon is the most frequently used vitamin K antagonist in Germany. The aim of this study was to estimate the risk of serious bleeding as a result of the use of drugs with potential interaction with phenprocoumon.

METHODS

We conducted a nested case-control study in a cohort of 246,220 phenprocoumon users in the German Pharmacoepidemiological Research Database. Cases were patients hospitalised for haemorrhage of different kinds. Ten controls were matched to each case by health insurance, birth year and sex using incidence density sampling. Odds ratios (OR) with 95% confidence intervals (CI) of the risk of serious bleeding associated with combined use of phenprocoumon and potentially interacting drugs versus phenprocoumon alone were estimated using conditional logistic regression analysis. Our analyses considered multiple risk factors, such as bleeding history, other comorbidities or co-medication.

RESULTS

Our study included 2,553 cases and 25,348 matched controls. An increased risk of bleeding was observed for the combined use of phenprocoumon and clopidogrel vs phenprocoumon use alone (OR: 1.83, 95% CI: 1.41-2.36). Antibiotic drugs associated with an increased risk of haemorrhage in the population of phenprocoumon users included the group of quinolones with ORs ranging from 2.74 (95% CI: 1.80-4.18) for ciprofloxacin to 4.40 (95% CI: 2.45-7.89) for levofloxacin, amoxicillin plus clavulanic acid (OR: 2.99, 95% CI: 1.39-6.42) and cotrimoxazole (OR 3.57, 95% CI: 2.36-5.40). Among non-steroidal anti-inflammatory drugs (NSAIDs), ketoprofen and naproxen were associated with the highest risks.

CONCLUSION

Significantly elevated risks of major bleeding were mainly observed for drugs with known pharmacodynamic interaction with phenprocoumon, and less for drugs with possible pharmacokinetic interaction.