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

Tailoring oral anticoagulant treatment in the era of multi-drug therapies for PAH and CTEPH

The use of oral anticoagulants in the management of pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH) presents distinct therapeutic challenges and benefits. In PAH, the benefits of oral anticoagulation are uncertain, with studies yielding mixed results on their efficacy and safety. Conversely, oral anticoagulants are a cornerstone in the treatment of CTEPH, where their use is consistently recommended to prevent recurrent thromboembolic events. The choice between vitamin K antagonists (VKAs) and direct oral anticoagulants (DOACs) remains a significant clinical question, as each type presents advantages and potential drawbacks. Furthermore, drug-drug interactions (DDIs) with concomitant PAH and CTEPH treatments complicate anticoagulant management, necessitating careful consideration of individual patient regimens. This review examines the current evidence on oral anticoagulant use in PAH and CTEPH and discusses the implications of DDIs within a context of multi-drug treatments, including targeted drugs in PAH.

The impact of acute diarrhea on the coagulation status of patients with vitamin K antagonists

Acute diarrhea is associated with a reduced absorption of both vitamin K antagonists (VKA) and vitamin K itself. To date, the net effect on the coagulation status of subjects with VKA remains elusive. We performed a systematic retrospective single-center analysis using an electronic data extraction approach to identify subjects with plasmatic anticoagulation (either VKA or direct oral anticoagulant (DOAC)) and diarrhea in a German University Hospital over a period of eight years. Acute diarrhea and complete documentation of coagulation status on admission were defined as inclusion criteria, anticoagulation other than VKA/DOAC and obvious inadherence as exclusion criteria. Subjects with VKA/DOAC admitted for hypertension served as control group. Data extraction yielded 356 subjects with gastrointestinal diagnoses and 198 hypertensive subjects, 55 and 83 of whom fulfilled all in- and exclusion criteria. INR values of subjects with VKA were significantly higher in subjects with diarrhea than in hypertensive controls (4.3 ± 3.7 vs. 2.3 ± 0.7, p < 0.001). The distribution of subjects having INR values lower, higher or within the target range differed significantly among groups with a substantially higher prevalence of overanticoagulation in the diarrhea group (46.4% vs. 14.3%, p < 0.001). In a multinomial logistic regression model, acute diarrhea was significantly associated with overanticoagulation (odds ratio 7.2, 95% confidence interval 2.163–23.921; p < 0.001), whereas age, sex, creatinine, and indication of anticoagulation were not (p > 0.05 each). Acute diarrhea is associated with a highly increased risk for overanticoagulation in patients with VKA. Thus, gastroenteritis necessitates a close monitoring of INR in order to identify subjects needing a temporary pause of VKA therapy.

Rationale and design of a European epidemiological post-authorization safety study (PASS) program: rivaroxaban use in routine clinical practice

BACKGROUND

Rivaroxaban is a highly selective factor Xa inhibitor approved for use in Europe for multiple indications.

STUDY DESIGN AND METHODS

The European rivaroxaban epidemiological post-authorization safety study (PASS) program consists of seven complementary observational studies. For four of the studies, data are obtained from health-care databases in the UK, the Netherlands, Germany, and Sweden. These database studies describe patterns of rivaroxaban use and patient characteristics over time, and investigate safety and effectiveness outcomes in new users of rivaroxaban using a cohort analysis and nested case-control analysis. To put these results in context, safety outcomes are also analyzed in new users of standard of care. In addition, a modified prescription event monitoring study conducted in the early post-launch phase in primary care, and two specialist cohort event monitoring studies that investigated rivaroxaban use in the secondary care hospital setting, systematically collected drug utilization and safety data via questionnaires completed by health-care professionals in the UK.

DISCUSSION

The European rivaroxaban epidemiological PASS is a comprehensive program of complementary studies generating evidence from patients treated in routine clinical practice that will expand our understanding of the risk-benefit profile of rivaroxaban.

Improving antibacterial prescribing safety in the management of COPD exacerbations: systematic review of observational and clinical studies on potential drug interactions associated with frequently prescribed antibacterials among COPD patients

Background

Guidelines advise the use of antibacterials (ABs) in the management of COPD exacerbations. COPD patients often have multiple comorbidities, such as diabetes mellitus and cardiac diseases, leading to polypharmacy. Consequently, drug–drug interactions (DDIs) may frequently occur, and may cause serious adverse events and treatment failure.

Objectives

(i) To review DDIs related to frequently prescribed ABs among COPD patients from observational and clinical studies. (ii) To improve AB prescribing safety in clinical practice by structuring DDIs according to comorbidities of COPD.

Methods

We conducted a systematic review by searching PubMed and Embase up to 8 February 2018 for clinical trials, cohort and case–control studies reporting DDIs of ABs used for COPD. Study design, subjects, sample size, pharmacological mechanism of DDI and effect of interaction were extracted. We evaluated levels of DDIs and quality of evidence according to established criteria and structured the data by possible comorbidities.

Results

In all, 318 articles were eligible for review, describing a wide range of drugs used for comorbidities and their potential DDIs with ABs. DDIs between ABs and co-administered drugs could be subdivided into: (i) co-administered drugs altering the pharmacokinetics of ABs; and (ii) ABs interfering with the pharmacokinetics of co-administered drugs. The DDIs could lead to therapeutic failures or toxicities.

Conclusions

DDIs related to ABs with clinical significance may involve a wide range of indicated drugs to treat comorbidities in COPD. The evidence presented can support (computer-supported) decision-making by health practitioners when prescribing ABs during COPD exacerbations in the case of co-medication.

Drug-drug interactions with metronidazole and itraconazole in patients using acenocoumarol

PURPOSE

Various population-based cohort studies have shown that antimicrobial agents increase the risk of overanticoagulation in patients using coumarins. In this study, we assessed this association in hospitalized patients.

METHODS

We included all patients hospitalized in the Spaarne Gasthuis (Haarlem/Hoofddorp, the Netherlands), who started using an antimicrobial agent during acenocoumarol treatment or vice versa between 1 January 2015 and 1 July 2019. Patients were followed from start of concomitant therapy until 48 h after termination of the concomitant therapy or discharge, whichever came first. We analyzed the association between the antimicrobial agents and the risk of overanticoagulation, defined as an interpolated INR above 6, using Cox regression analysis. We corrected for multiple testing with the Bonferroni correction. Patients who started using acenocoumarol and amoxicillin/clavulanic acid were used as reference group.

RESULTS

In the study population, sixteen antimicrobial agents were started frequently concomitantly with acenocoumarol treatment. We included 2157 interaction episodes in 1172 patients. Patients who started using the combination of co-trimoxazole (HR 3.76; 95% CI 1.47-9.62; p = 0.006), metronidazole (HR 2.55; 95% CI 1.37-4.76; p = 0.003), or itraconazole (HR 4.11; 95% CI 1.79-9.45; p = 0.001) concomitantly with acenocoumarol treatment had an increased risk of overanticoagulation compared with patients using acenocoumarol and amoxicillin/clavulanic acid concomitantly. The associations for metronidazole (p = 0.045) and itraconazole (p = 0.015) remained statistically significant after correction for multiple testing.

CONCLUSION

Co-trimoxazole, metronidazole, and itraconazole increase the risk of overanticoagulation in patients using acenocoumarol. These combinations should be avoided if possible or otherwise acenocoumarol doses should be reduced and INR measured more frequently.

Drug interactions with oral anticoagulants in German nursing home residents: comparison between vitamin K antagonists and non-vitamin K antagonist oral anticoagulants based on two nested case-control studies

BACKGROUND

Vitamin K antagonists (VKAs) are susceptible to drug-drug interactions. Non-VKA oral anticoagulants (NOACs) have a decreased sensitivity to pharmacokinetic interactions and might be therefore considered superior in patients treated with multiple drugs. The objective of this study was to compare the risk of serious bleeding associated with interacting drugs in German nursing home residents treated with VKA or NOAC.

METHODS

Using claims data of new nursing home residents aged ≥ 65 years (2010-2014) we conducted separate nested case-control analyses within two cohorts of patients treated with VKA or NOAC, respectively. Cases were defined as patients hospitalized for serious bleeding. For each case, up to 20 controls were selected by risk-set sampling. Conditional logistic regression was used to obtain confounder-adjusted odds ratios (aORs) and 95% confidence intervals (CI) for the risk of bleeding associated with VKA or NOAC use and interacting drugs compared with the use of the respective oral anticoagulant alone.

RESULTS

Among 127,227 new nursing home residents, 16,804 patients received oral anticoagulation. Based on 372 cases and 7281 matched controls, the highest risk of bleeding in VKA users was observed for the concomitant use of antibiotics (aOR 3.00; CI 2.11-4.27) vs. VKA use alone, followed by non-steroidal anti-inflammatory drugs (1.66; 1.13-2.43). Among 243 NOAC cases and 4776 matched controls, elevated risks for bleeding were observed for the use of heparins (2.05; 1.25-3.36) and platelet inhibitors (1.92; 1.36-2.72).

CONCLUSIONS

Concomitant medication needs to be prescribed cautiously and monitored closely in nursing home residents treated with oral anticoagulants.

Clopidogrel Drug Interactions and Serious Bleeding: Generating Real-World Evidence via Automated High-Throughput Pharmacoepidemiologic Screening

Few population-based studies have examined bleeding associated with clopidogrel drug-drug interactions (DDIs). We sought to identify precipitant drugs taken concomitantly with clopidogrel (an object drug) that increased serious bleeding rates. We screened 2000-2015 Optum commercial health insurance claims to identify DDI signals. We performed self-controlled case series studies for clopidogrel plus precipitant pairs, examining associations with gastrointestinal bleeding or intracranial hemorrhage. To distinguish native bleeding effects of a precipitant, we reexamined associations using pravastatin as a negative control object drug. Among 431 analyses, 28 clopidogrel plus precipitant pairs were statistically significantly positively associated with serious bleeding. Ratios of rate ratios ranged from 1.13-3.94. Among these pairs, 13 were expected given precipitant drugs alone increased and/or were harbingers of serious bleeding. The remaining 15 pairs constituted new DDI signals, none of which are currently listed in two major DDI knowledge bases.

Mechanisms and the clinical relevance of complex drug-drug interactions

As a result of an increasing aging population, the number of individuals taking multiple medications simultaneously has grown considerably. For these individuals, taking multiple medications has increased the risk of undesirable drug–drug interactions (DDIs), which can cause serious and debilitating adverse drug reactions (ADRs). A comprehensive understanding of DDIs is needed to combat these deleterious outcomes. This review provides a synopsis of the pharmacokinetic (PK) and pharmacodynamic (PD) mechanisms that underlie DDIs. PK-mediated DDIs affect all aspects of drug disposition: absorption, distribution, metabolism and excretion (ADME). In this review, the cells that play a major role in ADME and have been investigated for DDIs are discussed. Key examples of drug metabolizing enzymes and drug transporters that are involved in DDIs and found in these cells are described. The effect of inhibiting or inducing these proteins through DDIs on the PK parameters is also reviewed. Despite most DDI studies being focused on the PK effects, DDIs through PD can also lead to significant and harmful effects. Therefore, this review outlines specific examples and describes the additive, synergistic and antagonistic mechanisms of PD-mediated DDIs. The effects DDIs on the maximum PD response (E_max) and the drug dose or concentration (EDEC₅₀) that lead to 50% of E_max are also examined. Significant gaps in our understanding of DDIs remain, so innovative and emerging approaches are critical for overcoming them.

Use of oral anticoagulants in German nursing home residents: drug use patterns and predictors for treatment choice

AIMS

Information on utilization of oral anticoagulants (OACs) in nursing homes is scarce. This study aimed to (i) describe OAC use in German nursing home residents, (ii) examine factors influencing whether treatment is initiated with vitamin K antagonists (VKAs) or non-VKA oral anticoagulants (NOACs) and (iii) assess which conditions predict switching to NOAC instead of continuing VKA.

METHODS

Using claims data (2010-2014), we studied a cohort of new nursing home residents aged ≥65 years receiving OAC. Further, OAC use in patients with atrial fibrillation (AF) was examined over the years.

RESULTS

Overall, 16 804 patients (median age: 85 years, 75% female, 44% with renal disease) were included. The majority received phenprocoumon as first OAC (58.0%), followed by rivaroxaban (28.1%). Over the study period, NOAC use increased substantially. Initiating NOAC instead of VKA was predicted by a previous stroke (adjusted odds ratio: 1.76; 95% confidence interval: 1.49-2.08). In contrast, renal disease predicted VKA initiation (0.66; 0.59-0.75) as did the presence of a prosthetic heart valve. Switching from VKA to NOAC was predicted by a stroke (2.55; 2.00-3.24), bleeding events and a recent hospitalization. During 2010-2014, the proportion of AF patients with a CHADS2 score ≥2 receiving OAC increased from 27% to 46%.

CONCLUSIONS

NOACs are increasingly used in German nursing homes, both for initial anticoagulation but also in VKA pre-treated patients. Switching from VKA to NOAC was substantially influenced by aspects such as intended higher effectiveness and safety but probably also practicability due to less blood monitoring.

Old and new oral anticoagulants: Food, herbal medicines and drug interactions

The most commonly prescribed oral anticoagulants worldwide are the vitamin K antagonists (VKAs) such as warfarin. Factors affecting the pharmacokinetics of VKAs are important because deviations from their narrow therapeutic window can result in bleedings due to over-anticoagulation or thrombosis because of under-anticoagulation. In addition to pharmacodynamic interactions (e.g., augmented bleeding risk for concomitant use of NSAIDs), interactions with drugs, foods, herbs, and over-the-counter medications may affect the risk/benefit ratio of VKAs. Direct oral anticoagulants (DOACs) including Factor Xa inhibitors (rivaroxaban, apixaban and edoxaban) and thrombin inhibitor (dabigatran) are poised to replace warfarin. Phase-3 studies and real-world evaluations have established that the safety profile of DOACs is superior to those of VKAs. However, some pharmacokinetic and pharmacodynamic interactions are expected. Herein we present a critical review of VKAs and DOACs with focus on their potential for interactions with drugs, foods, herbs and over-the-counter medications.

Comparative risk of death in older adults treated with antipsychotics: A population-based cohort study

Although the use of antipsychotics has been associated with an increased risk of death, data on the safety of individual substances is scarce. We thus aimed to compare the risk of death in new users of individual antipsychotics aged =>65 years and conducted a cohort study in the German Pharmacoepidemiological Research Database between 2005 and 2011. Patients were followed from initiation of treatment until death, 90 days after cohort entry, end of insurance or the end of the study period. Multivariable cox regression was used to estimate confounder adjusted hazard ratios (aHR) of death for 14 individual antipsychotics compared to risperidone. In sensitivity analyses, we also applied high-dimensional propensity score (HDPS) methods to explore possible unmeasured confounding. In a cohort of 137,713 new users of antipsychotics, a higher risk of death was found for haloperidol (aHR: 1.45; 95% confidence interval: 1.35-1.55), levomepromazine (aHR: 1.34; 1.16-1.54), zuclopenthixol (aHR: 1.32; 1.02-1.72) and to a lesser extent for melperone (aHR: 1.13; 1.07-1.19) compared to risperidone. Lower risks were observed for quetiapine, prothipendyl, olanzapine, tiapride, clozapine, perazine and flupentixol. In subgroup analyses, levomepromazine and chlorprothixene were only associated with a higher risk of death in patients aged =>80 years and with dementia. The application of HDPS methods did not substantially change the results. In conclusion, our study suggests that initiation of haloperidol, levomepromazine, zuclopenthixol and chlorprothixene treatment is associated with an increased risk of death compared to risperidone and should be avoided in older patients except in palliative care when treatment alternatives are available.

Dosing Recommendations for Concomitant Medications During 3D Anti-HCV Therapy

The development of direct-acting antiviral (DAA) agents has reinvigorated the treatment of hepatitis C virus infection. The availability of multiple DAA agents and drug combinations has enabled the transition to interferon-free therapy that is applicable to a broad range of patients. However, these DAA combinations are not without drug-drug interactions (DDIs). As every possible DDI permutation cannot be evaluated in a clinical study, guidance is needed for healthcare providers to avoid or minimize drug interaction risk. In this review, we evaluated the DDI potential of the novel three-DAA combination of ombitasvir, paritaprevir, ritonavir, and dasabuvir (the 3D regimen) with more than 200 drugs representing 19 therapeutic drug classes. Outcomes of these DDI studies were compared with the metabolism and elimination routes of prospective concomitant medications to develop mechanism-based and drug-specific guidance on interaction potential. This analysis revealed that the 3D regimen is compatible with many of the drugs that are commonly prescribed to patients with hepatitis C virus infection. Where interaction is possible, risk can be mitigated by paying careful attention to concomitant medications, adjusting drug dosage as needed, and monitoring patient response and/or clinical parameters.

Risk of bleeding and antibiotic use in patients receiving continuous phenprocoumon therapy. A case-control study nested in a large insurance- and population-based German cohort

There is major concern about coumarins interacting with various drug classes and increasing the risk of overanticoagulation. The aim of the study was to assess bleeding risk in patients with concurrent use of antibiotics and phenprocoumon, the most widely prescribed coumarin in many European countries. We conducted a nested-case-control study within a cohort of 513,338 incident and continuous phenprocoumon users ≥ 18 years of age using claims data of the statutory health insurance company AOK, covering 30% of the German population. Bleeding risk associated with current use of antibiotics for systemic use (antibacterials/antimycotics) was calculated using conditional logistic regression in 13,785 cases with a bleeding event and 55,140 risk-set sampling-matched controls. Bleeding risk associated with any antibacterial use in phenprocoumon users was significantly increased [odds ratio (OR) 2.37, 95% confidence interval (CI) 2.20-2.56]. The association was stronger for gastrointestinal than for cerebral bleeding (OR 2.09, 95% CI 1.84-2.38 and OR 1.34, 95% CI 1.03-1.74, respectively) and highest for other/unspecified bleeding (OR 2.92, 95% CI 2.62-3.26). Specific antibiotic classes were strongly associated with bleeding risk, e.g. cotrimoxazole (OR 3.86, 95% CI 3.08-4.84) and fluorquinolones (OR 3.13, 95% CI 2.74-3.59), among those highest for ofloxacin (OR 5.00, 95% CI 3.01-8.32). Combined use of phenprocoumon and antimycotics was not significantly associated with bleeding risk. Risk was not significantly modified by age (pint=0.25) or sex (pint=0.96). The association was stronger the closer the antibiotic exposure was to the bleeding event. Among continuous phenprocoumon users, antibiotics - particularly quinolones and cotrimoxazole - should be prescribed after careful consideration due to an increased bleeding risk. Close monitoring of international normalised ratio levels after prescription is recommended.

Causes and timing of delayed bleeding after oral surgery

OBJECTIVES

This study examines a cohort of patients who suffered bleeding requiring hemostatic intervention after oral surgery. The reasons for bleeding and the interval between surgery and onset of bleeding are investigated.

MATERIALS AND METHODS

Between 1998 and 2009, 1,819 cases were eligible for this retrospective study. Factors (independent parameters) influencing the interval (dependent variable) were analyzed using negative binomial count regression models (NegBin II). The significance of each regressor's effect was tested using Wald's test and the total effect using likelihood ratio test.

RESULTS

Of the patients examined, 1,101 (60.1 %) did not take anticoagulants, 394 (21.5 %) took phenprocoumon, 233 (12.7 %) took acetylsalicylic acid, 33 (1.8 %) took clopidogrel, 17 (0.9 %) took more than one anticoagulant, and 78 (4.3 %) had a congenital blood disorder. After simple tooth extraction, 95.3 % suffered bleeding; 69.7 % of extractions were performed in the molar region. Later that day of surgery, 66.0 % of all patients showed bleeding. The bleeding interval was significantly prolonged by anticoagulant therapy with phenprocoumon, by congenital clotting disorders.

CONCLUSIONS

Normal tooth extractions are underestimated for their risk for postoperative bleeding, especially in the molar region. Anticoagulant therapy or congenital blood disorders present oral surgeons with a further challenge.

CLINICAL RELEVANCE

Performing surgery before midday allows surgeons managing postoperative bleeding themselves for a better patient satisfaction. Intensified information about correct postoperative behavior is crucial. Prolonged blood coagulation should intensify follow-up checks. Patients with congenital blood disorders and patients at high risk for bleeding with the need for substitution of platelets or clotting factors should receive inpatient care. More potent, local applicable coagulant agents are required for these patients.

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.

Concurrent use of tramadol and oral vitamin K antagonists and the risk of excessive anticoagulation: a register-based nested case-control study

OBJECTIVES

The objective was to assess whether the concurrent use of tramadol and vitamin K antagonists (VKAs) leads to an increased risk of excessive anticoagulation.

DESIGN

The study was designed as a case-control study, nested within users of VKA and with tramadol use as our main exposure. We used conditional logistic regression to control for potential confounders.

SETTING

Prescription data from primary care were obtained from Odense Pharmacoepidemiological Database (OPED). Information about hospital admissions was obtained from the patient administrative system of Funen County (FPAS).

SUBJECTS

Both cases and controls were selected from users of VKA. Cases were defined by being hospitalised with a main diagnosis indicating excessive anticoagulation. For each case, we selected 15 controls among VKA users, matched by age and sex.

MAIN OUTCOME MEASURE

Odds ratio for experiencing excessive anticoagulation attributable to the use of tramadol.

RESULTS

A total of 178 patients were included, 30 of which were exposed to tramadol, along with 2643 controls, 114 of which were exposed to tramadol. The adjusted odds-ratio for experiencing excessive anticoagulation during use of tramadol was 3.1 (1.9-5.2). This corresponds to, on average, one excess case per 250 treatment years (CI 125-584). The result is potentially confounded by concomitant paracetamol use and the presence of acute illness.

CONCLUSION

Caution is advised when using tramadol in patients using VKA, and if possible, an alternative pain-medication should be used.

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.