Empirical validation of the reverse parametric waiting time distribution and standard methods to estimate prescription durations for warfarin

PURPOSE

In many prescription databases, the duration of treatment for the single prescription is not recorded. This study aimed to validate 2 different types of approaches for estimating prescription durations, using the oral anticoagulant warfarin as a case.

METHODS

The approaches undergoing empirical validation covered assumptions of a fixed daily intake of either 0.5 or 1.0 defined daily dose (DDD), as well as estimates based on the reverse parametric waiting time distribution (rWTD), with different sets of covariates. We converted estimates of prescription duration to daily dose and compared them to prescribed daily dose as recorded in a clinical registry (using Bland-Altman plots). Methods were compared based on their average prediction error (logarithmic scale) and their limit of agreement ratio (ratio of mean error ± 1.96 SD after transformation to original scale).

RESULTS

Estimates of daily doses were underestimated by 19% or overestimated by 62% when assumptions of 0.5 or 1.0 DDD were applied. The limit of agreement ratio was 6.721 for both assumptions. The rWTD-based approaches performed better when using the estimated mean value of the inter-arrival density, yielding on average negligible bias (relative difference of 0 to 2%) and with limit of agreement ratios decreasing upon additional covariate adjustment (from 6.857 with no adjustment to 4.036 with the fully adjusted model).

CONCLUSIONS

Comparing the different methods, the rWTD algorithm performed best and led to unbiased estimates of prescribed doses and thus prescription durations and reduced misclassification on the individual level upon inclusion of covariates.

Using the "proportion of patients covered" and the Kaplan-Meier survival analysis to describe treatment persistence

PURPOSE

Standard Kaplan-Meier (KM) survival analysis is often used to study treatment persistence estimating the proportion of patients who have not yet experienced a treatment break by a given day after treatment initiation. This method only allows patients to be studied until their first treatment break. The "proportion of patients covered" (PPC) method is another approach to study treatment persistence. It measures the proportion of live patients currently covered by treatment. We aimed to describe the PPC method, show how the KM survival analysis and the PPC method can describe treatment persistence, and discuss the interpretation/application of the methods.

METHODS

We identified new users of statins, selective serotonin reuptake inhibitors, hormone replacement therapy, and ibuprofen. We used KM estimates and the PPC to describe persistence in the 3 years post treatment initiation, using a grace period of 90 days to define a treatment break.

RESULTS

Three years after statin initiation, approximately 40% of patients were still in continuous treatment (KM survival) and 60% of patients still alive were in current treatment (PPC). Corresponding numbers were 12% and 25% for selective serotonin reuptake inhibitors and 9% and 29% for hormone replacement therapy. At 1 year, numbers were 5% and 10% for ibuprofen. The PPC showed markedly less variability than the KM survival analysis with different choices of grace periods.

CONCLUSIONS

The KM survival analysis and the PPC method can be used to study different aspects of treatment persistence. Together, they provide a more complete picture of treatment persistence and drug use patterns.

Use of prescription drugs among women diagnosed with epithelial ovarian cancer in Denmark

INTRODUCTION

Epithelial ovarian cancer patients often suffer from chronic diseases requiring drug treatment. We assessed temporal patterns of drug use among women with ovarian cancer.

MATERIAL AND METHODS

We identified all postmenopausal women with epithelial ovarian cancer in Denmark 2005-2012 and a comparison cohort of age-matched women without cancer. We calculated rates of new drug treatment and total drug use and examined use of new and prevalent drugs before and after diagnosis. Analyses were stratified by histological type and stage of epithelial ovarian cancer.

RESULTS

We identified 2742 patients. The rate of new drug treatment increased from 3 to 5 months before diagnosis and peaked in the first month after diagnosis at 99 new types of drug therapy per 100 individuals (mainly antiemetics, proton-pump inhibitors, hypnotics, and opioids). Although declining, the rate of new drug use remained substantially higher among epithelial ovarian cancer patients than among controls throughout the 3-year postdiagnosis follow-up period. The number of prevalent drugs increased slightly from a median of 4 drugs (interquartile range 2-7) before diagnosis to 5 drugs (interquartile range 2-8) shortly after the diagnosis. The use of preventive drugs decreased only slightly after diagnosis. In stratified analyses, we found limited variation according to histological type, whereas patterns were slightly more pronounced among women with nonlocalized disease compared with localized disease.

CONCLUSIONS

Drug use among postmenopausal women with epithelial ovarian cancer was substantial and varied considerably in relation to the time of cancer diagnosis, although only limited changes were seen in the use of preventive medicines.

Hydrochlorothiazide use and risk for Merkel cell carcinoma and malignant adnexal skin tumors: A nationwide case-control study

BACKGROUND

Hydrochlorothiazide use has been associated with markedly increased risk for squamous cell carcinoma. No previous studies have investigated the association between hydrochlorothiazide use and the risk for Merkel cell carcinoma (MCC) and malignant adnexal skin tumors (MAST).

OBJECTIVE

To examine the association between hydrochlorothiazide use and the risk for MCC and MAST.

METHODS

Using Danish nationwide health registries, we identified all patients with incident MCC or MAST during 2004-2015 and matched the cases individually to cancer-free population controls by risk set sampling. Using conditional logistic regression, we estimated the odds ratios (ORs) and confidence intervals (CIs) associated with cumulative use of hydrochlorothiazide.

RESULTS

The adjusted ORs for MCC and MAST associated with high use (≥50,000 mg) of hydrochlorothiazide was 2.3 (95% CI 1.1-4.8) and 3.6 (95% CI 1.9-7.0), respectively, which increased to 3.3 (95% CI 1.3-8.3) and 5.6 (95% CI 2.4-13.3), respectively, with highest use (≥100,000 mg). We found no increased risk for these tumors in analyses of drugs with similar indications as hydrochlorothiazide, except there was a tendency toward an increased risk for MCC associated with the use of furosemide (OR 1.9, 95% CI 0.9-4.0).

LIMITATIONS

No data on sun exposure was available.

CONCLUSION

Hydrochlorothiazide use is associated with an increased risk for MCC and MAST.

Clinical events preceding switching and discontinuation of oral anticoagulant treatment in patients with atrial fibrillation

Aims

Switching between oral anticoagulants and treatment discontinuation are common events related to therapy with non-vitamin K antagonist oral anticoagulants (NOACs). However, knowledge on the reasons leading to these treatment changes is scarce. The aim of this study was to identify clinical events preceding anticoagulant switching and NOAC discontinuation during oral anticoagulant therapy in patients with atrial fibrillation.

Methods and results

We performed a nationwide register-based study including Danish atrial fibrillation patients initiating a NOAC between August 2011 and February 2016 (n = 50 623). We explored potential reasons leading to changes in anticoagulant treatment by identifying clinical events preceding switches from vitamin K antagonists (VKA) to NOAC, switches from NOAC to VKA, and discontinuations of NOACs. Among 23 531 anticoagulant users changing treatment, we identified 13 295 switches from VKA to NOAC, 5206 switches from NOAC to VKA, and 8995 discontinuations of NOACs. Approximately half of all treatment changes were preceded by a hospitalization. A relevant specific clinical event or procedure was identified prior to 18.3% of switches from VKA to NOAC, prior to 23.0% of switches from NOAC to VKA, and prior to 26.6% of discontinuations. Switches from VKA to NOAC were most often preceded by thromboembolic events (7.0%), whereas cardioversion was the most common specific event prior to a switch from NOAC to VKA (11.4%). Discontinuations were most often preceded by bleeding events (7.6%).

Conclusion

For about one in five patients, treatment changes during anticoagulant therapy were preceded by a major clinical event. However, the majority of patients changed treatment for reasons not recorded in health registries.

Use of Non-Vitamin K Antagonist Oral Anticoagulants 2008-2016: A Danish Nationwide Cohort Study

We aimed to provide detailed utilization data on the total use of non-vitamin K antagonist oral anticoagulants (NOACs) since their introduction in 2008. Using the nationwide Danish National Prescription Registry, we identified all individuals filling prescriptions for NOACs 2008-2016. We reported the development in incident and prevalent users and explored baseline characteristics and treatment persistence according to treatment indication. A total of 126,691 NOAC users were identified within the Danish population of 5.7 million inhabitants. The annual incidence and prevalence increased rapidly reaching 10 and 17 per 1000 individuals in 2016. Patients received NOACs due to atrial fibrillation (AF) (43%), venous thromboembolism (VTE) prophylaxis after arthroplastic surgery (17%), VTE (12%) and no registered indication (28%). The most frequently used NOAC was rivaroxaban (n = 52,431), followed by dabigatran (n = 47,067), apixaban (n = 27,116) and edoxaban (n = 77). The proportion of AF and VTE patients initiating low-dose NOACs were between 23% and 50%. Patients treated with NOAC for VTE primarily received rivaroxaban. We observed a trend towards increased use of apixaban and rivaroxaban at the expense of dabigatran. Treatment persistence was highly dependent on treatment indication. Persistence to NOAC after 3 years was only 62% in AF compared to 28% for VTE. We documented an accelerating increase in the use of all four NOACs in the first 8 years after introduction. We have identified areas requiring further attention, including reasons for missing indications, potential inappropriate dosing and low long-term persistence with NOACs in patients with AF.

Oral Immunosuppressive Treatment of Myasthenia Gravis in Denmark: A Nationwide Drug Utilization Study, 1996-2013

Although immunosuppressants in the treatment of myasthenia have been available for several decades, population-based studies describing drug utilization in myasthenia patients are scarce. We aimed in this study to describe the treatment of myasthenia in Denmark in more recent years with emphasis on use of oral immunosuppressant agents. We identified a nationwide cohort of incident myasthenia patients in Denmark from 1996 to 2013 and tracked their use of drugs over the entire period using data from nationwide registers. Patients with myasthenia were classified according to utilization of specific immunosuppressants (e.g. prednisolone) as 'never user' or 'ever user'. We used Kaplan-Meier (K-M) and proportion of patients covered (PPC) curves to describe treatment onset and termination. We identified 928 patients (52% female) with incident myasthenia in the study period. Overall, 638 (69%) were treated with prednisolone and 506 (55%) with azathioprine. Treatment with prednisolone and azathioprine within 2 years of myasthenia diagnosis was initiated in 462 (56%) and 366 (45%). Only one of four myasthenia patients (n = 231) did not receive oral immunosuppressive treatment at any time in the study period. Prednisolone was stopped in most patients, whereas treatment with azathioprine was often continued throughout follow-up. In conclusion, we found that treatment of myasthenia in Denmark in recent years corresponded well to the expected clinical course of myasthenia and that most patients underwent long-term immunosuppression.

Risk of lactic acidosis in type 2 diabetes patients using metformin: A case control study

BACKGROUND

Metformin constitutes first-line treatment of type 2 diabetes mellitus. It is presumed to have lactic acidosis as a dangerous, but rare, side effect.

OBJECTIVES

To estimate the incidence rate of lactic acidosis in patients with type 2 diabetes mellitus as well as to estimate the relative risk of lactic acidosis associated with metformin treatment.

METHODS

This is a population-based combined cohort and case-control study among patients with type 2 diabetes mellitus who were acutely admitted with lactic acidosis at Odense University Hospital, Denmark; in the period from 1st June 2009 to 1st October 2013. The patients included as cases were all acutely hospitalized with lactic acidosis (pH <7.35 and lactate ≥2.0 mmol/l). For each case, we identified 24 age- and sex-matched controls sampled from the same cohort with type 2 diabetes mellitus. The use of metformin identified by using a prescription database. Analyses included multivariable logistic regression and adjusting for predefined confounding: renal function, HbA1c, comorbidity and diabetes duration.

RESULTS

Our cohort included 10,652 patients with type 2 diabetes mellitus with a median age of 74 years, and 51.5% were male. During follow-up, 163 individuals were hospitalized with lactic acidosis, corresponding to an incidence rate of 391/100,000 person years. Use of metformin was not associated with lactic acidosis: adjusted odds ratio was 0.79 (95%CI 0.54-1.17).

CONCLUSION

Among patients with type 2 diabetes mellitus, the incidence rate of acute hospitalization with lactic acidosis was 391/100,000 person years. Use of metformin did not increase the risk of lactic acidosis. However, comorbidity seems to be an important risk factor.

Roflumilast Usage from 2010 to 2016: A Danish Nationwide Drug Utilization Study

Roflumilast, a phosphodiesterase-4-inhibitor, is marketed as add-on treatment to inhaled bronchodilators and corticosteroids in COPD patients with frequent exacerbations. Although marketed since 2010, usage pattern of roflumilast for an entire nation has not previously been explored. This study aimed to estimate the total utilization of roflumilast in Denmark during 2010 to 2016, using the Danish nationwide health registers. We identified 1573 individuals (47% males) who used roflumilast during the study period, of whom 705 (45%) redeemed only one prescription. Of all patients initiating roflumilast, 67% discontinued treatment within the first year. The rate of treatment initiation decreased 73% from 2011 (7.5/100,000 person-years) to 2016 (2.0/100,000 person-years) concurrent with a stable prevalence of 3.0-4.0/100,000 persons throughout the study period. The median duration of roflumilast use was 76 days. Patients with severe comorbidity tended to exhibit a lower degree of early discontinuation (Charlson Comorbidity Index 3+: odds ratio [OR]: 0.59; 95% confidence interval [CI] 0.33-1.04), as well as patients with a COPD-related admission within a year prior to roflumilast initiation (OR 0.62; 95% CI 0.49-0.80). The decreasing incidence and high level of early roflumilast discontinuation could be due to lack of benefit, a low awareness of romiflulast's indication among physicians, secondary to a challenging prescribing procedure or to adverse effects.

Considerations for Pharmacoepidemiological Studies of Drug-Cancer Associations

In this MiniReview, we provide general considerations for the planning and conduct of pharmacoepidemiological studies of associations between drug use and cancer development. We address data sources, study design, assessment of drug exposure, ascertainment of cancer outcomes, confounder adjustment and future perspectives. Aspects of data sources include assessment of complete history of drug use and data on dose and duration of drug use, allowing estimates of cumulative exposure. Outcome data from formal cancer registries are preferable, but cancer data from other sources, for example, patient or pathology registries, medical records or claims are also suitable. The two principal designs for observational studies evaluating drug-cancer associations are the cohort and case-control designs. A key challenge in studies of drug-cancer associations is the exposure assessment due to the typically long period of cancer development. We present methods to examine early and late effects of drug use on cancer development and discuss the need for employing 'lag-time' in order to avoid reverse causation. We emphasize that a new-user study design should always be considered. We also underline the need for 'dose-response' analyses, as drug-cancer associations are likely to be dose-dependent. Generally, studies of drug-cancer associations should explore risk of site-specific cancer, rather than cancer overall. Additional differentiation may also be crucial for organ-specific cancer with various distinct histological subtypes (e.g., lung or ovary cancer). We also highlight the influence of confounding factors and discuss various methods to address confounding, while emphasizing that the choices of methods depend on the design and specific objectives of the individual study. In some studies, use of active comparator(s) may be preferable. Pharmacoepidemiological studies of drug-cancer associations are expected to evolve considerably in the coming years, due to the increasing availability of long-term data on drug exposures and cancer outcomes, the increasing conduct of multinational studies, allowing studies of rare cancers and subtypes of cancer, and methodological improvements specifically addressing cancer and other long-term outcomes.

A smartphone application supporting patients with psoriasis improves adherence to topical treatment: a randomized controlled trial

BACKGROUND

Adherence to topical psoriasis treatments is low, which leads to unsatisfactory treatment results. Smartphone applications (apps) for patient support exist but their potential to improve adherence has not been systematically evaluated.

OBJECTIVES

To evaluate whether a study-specific app improves adherence and reduces psoriasis symptoms compared with standard treatment.

METHODS

We conducted a randomized controlled trial (RCT, clinicaltrials.gov registration: NCT02858713). Patients received once-daily medication [calcipotriol/betamethasone dipropionate (Cal/BD) cutaneous foam] and were randomized to no app (n = 66) or app intervention (n = 68) groups. In total, 122 patients (91%) completed the 22-week follow-up. The primary outcome was adherence, which was defined as medication applied ≥ 80% of days during the treatment period and assessed by a chip integrated into the medication dispenser. Secondary outcomes were psoriasis severity measured by the Lattice System Physician's Global Assessment (LS-PGA) and quality of life, measured using the Dermatology Life Quality Index (DLQI) at all visits.

RESULTS

Intention-to-treat analyses using regression was performed. More patients in the intervention group were adherent to Cal/BD cutaneous foam than those in the nonintervention group at week 4 (65% vs. 38%, P = 0·004). The intervention group showed a greater LS-PGA reduction than the nonintervention group at week 4 (mean 1·86 vs. 1·46, P = 0·047). A similar effect was seen at weeks 8 and 26, although it did not reach statistical significance.

CONCLUSIONS

This RCT demonstrates that the app improved short-term adherence to Cal/BD cutaneous foam treatment and psoriasis severity.

Effect of copayment policies on initial medication non-adherence according to income: a population-based study

Objective

Copayment policies aim to reduce the burden of medication expenditure but may affect adherence and generate inequities in access to healthcare. The objective was to evaluate the impact of two copayment measures on initial medication non-adherence (IMNA) in several medication groups and by income level.

Design

A population-based study was conducted using real-world evidence.

Setting

Primary care in Catalonia (Spain) where two separate copayment measures (fixed copayment and coinsurance) were introduced between 2011 and 2013.

Participant

Every patient with a new prescription issued between 2011 and 2014 (3 million patients and 10 million prescriptions).

Outcomes

IMNA was estimated throughout dispensing and invoicing information. Changes in IMNA prevalence after the introduction of copayment policies (immediate level change and trend changes) were estimated through segmented logistic regression. The regression models were stratified by economic status and medication groups.

Results

Before changes to copayment policies, IMNA prevalence remained stable. The introduction of a fixed copayment was followed by a statistically significant increase in IMNA in poor population, low/middle-income pensioners and low-income non-pensioners (OR from 1.047 to 1.370). In high-income populations, there was a large statistically non-significant increase. IMNA decreased in the low-income population after suspension of the fixed copayment and the introduction of a coinsurance policy that granted this population free access to medications (OR=0.676). Penicillins were least affected while analgesics were affected to the greatest extent. IMNA to medications for chronic conditions increased in low/middle-income pensioners.

Conclusion

Even nominal charge fixed copayment may generate inequities in access to health services. An anticipation effect and expenses associated with IMNA may have generated short-term costs. A reduction in copayment can protect from non-adherence and have positive, long-term effects. Copayment scenarios could have considerable long-term consequences for health and costs due to increased IMNA in medication for chronic physical conditions.

A cohort study on the risk of lymphoma and skin cancer in users of topical tacrolimus, pimecrolimus, and corticosteroids (Joint European Longitudinal Lymphoma and Skin Cancer Evaluation - JOELLE study)

Background

There is a concern that topical tacrolimus and pimecrolimus, indicated for second-line treatment of atopic dermatitis, may increase the risk of lymphoma and skin cancer, particularly in children.

Objective

The aim of this study was to compare incidence rates (IRs) of lymphoma and skin cancer between new users of topical tacrolimus or pimecrolimus and users of moderate- to high-potency topical corticosteroids (TCSs) and untreated subjects.

Methods

This is a multicenter cohort study with frequency matching by strata of propensity scores in population databases in the Netherlands, Denmark, Sweden, and the UK. IR ratios (IRRs) were estimated using Mantel–Haenszel methods for stratified analysis.

Results

We included 19,948 children and 66,127 adults initiating tacrolimus, 23,840 children and 37,417 adults initiating pimecrolimus, 584,121 users of TCSs, and 257,074 untreated subjects. IRs of lymphoma per 100,000 person-years were 10.4 events in children and 41.0 events in adults using tacrolimus and 3.0 events in children and 27.0 events in adults using pimecrolimus. The IRR (95% confidence interval [CI]) for lymphoma, tacrolimus versus TCSs, was 3.74 (1.00–14.06) in children and 1.27 (0.94–1.71) in adults. By lymphoma type, the highest IRR was 3.17 (0.58–17.23) for Hodgkin lymphoma in children and 1.76 (95% CI, 0.81–3.79) for cutaneous T-cell lymphoma (CTCL) in adults. For pimecrolimus versus TCSs, the highest IRR was 1.31 (95% CI, 0.33–5.14) for CTCL in adults. Compared with untreated subjects, adults using TCSs had a higher incidence of CTCL (IRR, 10.66; 95% CI, 2.60–43.75). Smaller associations were found between tacrolimus and pimecrolimus use and the risk of malignant melanoma or nonmelanoma skin cancer.

Conclusion

Use of topical tacrolimus and pimecrolimus was associated with an increased risk of lymphoma. The low IRs imply that even if the increased risk is causal, it represents a small excess risk for individual patients. Residual confounding by severity of atopic dermatitis, increased monitoring of severe patients, and reverse causation could have affected the results.

Use of Dicloxacillin and Risk of Pregnancy among Users of Oral Contraceptives

The antibiotic dicloxacillin has been shown to induce drug-metabolizing CYP enzymes to a clinically relevant extent. In this study, we investigated whether the use of dicloxacillin confers an increased risk of unwanted pregnancy among oral contraceptive users. The study population comprised Danish women falling pregnant (1997-2015) during oral contraceptive use, defined as having filled a prescription for an oral contraceptive within 120 days both before and after the estimated date of conception. Data were analysed using a case-crossover approach. For each woman, we assessed the use of dicloxacillin preceding the date of conception and during 10 previous control periods and estimated the odds ratio for such unintended pregnancies associated with the use of dicloxacillin. Among 364 women using dicloxacillin prior to conception, 40 (11%) were exposed to dicloxacillin at the time of conception, yielding an odds ratio (OR) associating use of dicloxacillin to unintended pregnancy of 1.18 (95% CI 0.84-1.65). Supplementary and sensitivity analyses generally returned similar estimates, except for a slightly increased risk among users of progestogen-only oral contraceptives (OR 1.83, 95% CI 0.63-5.34). Analysis of other antibiotics as negative controls yielded results close to unity (ORs ranging from 0.83 to 1.13). In conclusion, our study found no evidence for an increased risk of oral contraceptive failure when using dicloxacillin. However, acknowledging study limitations, we suggest the use of supplementary barrier methods during treatment with dicloxacillin, until our findings are confirmed in further studies.

Use of attention-deficit/hyperactivity disorder medication among older adults in Denmark

AIMS

Knowledge on the use of attention-deficit/hyperactivity disorder (ADHD) medication among older adults is limited. We hypothesized that ADHD medication is used off-label in adults aged ≥50 years as part of palliative care in e.g. cancer patients. The aim of this study was to describe the use of ADHD medication among adults aged ≥50 years in Denmark.

METHODS

Using the Danish health registries, we identified new users ≥50 years of ADHD medication during 2000-2012. We estimated the annual incidence of ADHD medication use and ADHD diagnoses. We described new users of ADHD medication according to co-medication, comorbidities and assessed the 1-year cumulative mortality rate. A posthoc analysis allowed us to include new users until 2015.

RESULTS

We identified 6690 new users of ADHD medication from 2000 to 2012. From 2000 to 2015 we observed an increase in the incidence of ADHD medication use from 12.5 to 30.3 per 100 000 person-years. However, the incidence rate decreased from 2010 to 2015. Throughout the study period, the incidence rate of ADHD diagnoses was low (overall prevalence among new users ≤2%). Opioids were the most frequent comedication used (used by 54%), while cancer was the most frequent diagnosis preceding treatment (prevalence of 52%). The 1-year cumulative mortality was 50%, primarily driven by patients with a preceding cancer diagnosis.

CONCLUSION

There was an increase in the incidence of ADHD medication use in adults aged ≥50 years from 2000-2010 and a decreasing incidence from 2010-2015. Our results suggest that ADHD medication is used off-label in older adults as part of palliative care.

Dicloxacillin induces CYP2C19, CYP2C9 and CYP3A4 in vivo and in vitro

AIM

The aim of this study was to study potential cytochrome P450 (CYP) induction by dicloxacillin.

METHODS

We performed an open-label, randomized, two-phase, five-drug clinical pharmacokinetic cocktail crossover study in 12 healthy men with and without pretreatment with 1 g dicloxacillin three times daily for 10 days. Plasma and urine were collected over 24 h and the concentration of all five drugs and their primary metabolites was determined using a liquid chromatography coupled to triple quadrupole mass spectrometry method. Cryopreserved primary human hepatocytes were exposed to dicloxacillin for 48 h and changes in gene expression and the activity of CYP3A4, CYP2C9, CYP2B6 and CYP1A2 were investigated. The activation of nuclear receptors by dicloxacillin was assessed using luciferase assays.

RESULTS

A total of 10 days of treatment with dicloxacillin resulted in a clinically and statistically significant reduction in the area under the plasma concentration-time curve from 0 to 24 h for omeprazole (CYP2C19) {geometric mean ratio [GMR] [95% confidence interval (CI)]: 0.33 [0.24, 0.45]}, tolbutamide (CYP2C9) [GMR (95% CI): 0.73 (0.65, 0.81)] and midazolam (CYP3A4) [GMR (95% CI): 0.54 (0.41, 0.72)]. Additionally, other relevant pharmacokinetic parameters were affected, indicating the induction of CYP2C- and CYP3A4-mediated metabolism by dicloxacillin. Investigations in primary hepatocytes showed a statistically significant dose-dependent increase in CYP expression and activity by dicloxacillin, caused by activation of the pregnane X receptor.

CONCLUSIONS

Dicloxacillin is an inducer of CYP2C- and CYP3A-mediated drug metabolism, and we recommend caution when prescribing dicloxacillin to users of drugs with a narrow therapeutic window.

Effect of an In-Hospital Multifaceted Clinical Pharmacist Intervention on the Risk of Readmission: A Randomized Clinical Trial

IMPORTANCE

Hospital readmissions are common among patients receiving multiple medications, with considerable costs to the patients and society.

OBJECTIVE

To determine whether a multifaceted pharmacist intervention based on medication review, patient interview, and follow-up can reduce the number of readmissions and emergency department (ED) visits.

DESIGN, SETTING, AND PARTICIPANTS

This randomized clinical multicenter study (Odense Pharmacist Trial Investigating Medication Interventions at Sector Transfer [OPTIMIST]) enrolled patients from September 1, 2013, through April 23, 2015, with a follow-up of 6 months completed on October 31, 2015. Consecutive medical patients in an acute admission ward who were 18 years or older and who used 5 or more medications were invited to participate. Of 1873 patients invited to participate, 1499 (80.0%) accepted. The medication review and patient interview were conducted in the hospital and followed up in collaboration with primary care. Analysis was based on intention to treat.

INTERVENTIONS

The patients were randomized into 3 groups receiving usual care (no intervention), a basic intervention (medication review), and an extended intervention (medication review, 3 motivational interviews, and follow-up with the primary care physician, pharmacy, and nursing home).

MAIN OUTCOMES AND MEASURES

The prespecified primary outcomes were readmission within 30 or 180 days and ED visits within 180 days. The primary composite end point was readmission or an ED visit within 180 days. Secondary outcomes were drug-related readmissions within 30 and 180 days after inclusion, and all-cause mortality and drug-related mortality.

RESULTS

A total of 1467 patients (679 men [46.3%] and 788 women [53.7%]; median age, 72 years; interquartile range, 63-80 years) were part of the primary analysis, including 498 randomized to usual care, 493 randomized to the basic intervention, and 476 randomized to the extended intervention. The extended intervention had a significant effect on the numbers of patients who were readmitted within 30 days (hazard ratio [HR], 0.62; 95% CI, 0.46-0.84) or within 180 days (HR, 0.75; 95% CI, 0.62-0.90) after inclusion and on the number of patients who experienced the primary composite end point (HR, 0.77; 95% CI, 0.64-0.93). The study showed a nonsignificant reduction in drug-related readmissions within 30 days (HR, 0.65; 95% CI, 0.39-1.09) and within 180 days (HR, 0.80; 95% CI, 0.59-1.08) after inclusion and in deaths (HR, 0.83; 95% CI, 0.22-3.11). The number needed to treat to achieve the primary composite outcome for the extended intervention (vs usual care) was 12.

CONCLUSIONS AND RELEVANCE

A multifaceted clinical pharmacist intervention may reduce the number of ED visits and hospital readmissions.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT03079375.

Proton-pump inhibitors among adults: a nationwide drug-utilization study

BACKGROUND

The use of proton-pump inhibitors (PPIs) has grown worldwide, and there are concerns about increased unsubstantiated long-term use. The aim of the study was to describe the real-world use of PPIs over the past decade in an entire national population.

METHODS

This was a nationwide population-based drug-utilization study. Patterns of outpatient PPI use among adults in Iceland between 2003 and 2015 were investigated, including annual incidence and prevalence, duration of use, and dose of tablet used (lower versus higher), as well as the proportion of PPI use attributable to gastroprotection.

RESULTS

We observed 1,372,790 prescription fills over the entire study period, of which 95% were for higher-dose PPIs. Annual incidence remained stable across time (3.3-4.1 per 100 persons per year), while the annual prevalence increased from 8.5 per 100 persons to 15.5 per 100 persons. Prevalence increased with patient age and was higher among women than men. Duration of treatment increased with patients' age (36% of users over 80 years remained on treatment after 1 year compared with 13% of users aged 19-39 years), and was longer among those initiating on a higher dose compared with a lower dose. The proportion of PPI users concurrently using nonsteroidal anti-inflammatory drugs decreased over the study period, while the proportion concurrently using acetylsalicylic acid, oral anticoagulants, or platelet inhibitors increased.

CONCLUSIONS

In this nationwide study, a considerable increase in overall outpatient use of PPIs over a 13-year period was observed, particularly among older adults. Patients were increasingly treated for longer durations than recommended by clinical guidelines and mainly with higher doses.

Use of beta-blockers and risk of serious upper gastrointestinal bleeding: a population-based case-control study

BACKGROUND

Some studies indicate a reduced risk of serious upper gastrointestinal bleeding (UGIB) for users of beta-blockers, but the association remains to be confirmed in larger studies and characterized with respect to differences among beta-blockers. We aimed to assess whether beta-blocker use decreases the risk of UGIB.

METHODS

We conducted a register-based, population-based case-control study in Denmark. We identified cases with a first validated discharge diagnosis of UGIB during the period 1995-2006. Controls were selected by risk-set sampling in a ratio of 10:1. We estimated crude and adjusted odds ratios (ORs) of the association between current beta-blocker use and the risk of UGIB by using conditional logistic regression and further stratified by selective and non-selective beta-blockers, respectively.

RESULTS

We identified 3571 UGIB cases and 35,582 controls. Use of beta-blockers was not found to be associated with a decreased risk of UGIB (adjusted OR 1.10; 95% CI: 1.00-1.21). The association remained neutral after stratification by selective and non-selective beta-blockers, and by single beta-blocker substances. Similarly, we found no association between current beta-blocker use and the risk of UGIB within different subgroups.

CONCLUSIONS

We found no association between beta-blocker use and UGIB.

Prescription duration and treatment episodes in oral glucocorticoid users: application of the parametric waiting time distribution

Purpose

Glucocorticoids are widely used medications. In many pharmacoepidemiological studies, duration of individual prescriptions and definition of treatment episodes are important issues. However, many data sources lack this information. We aimed to estimate duration of individual prescriptions for oral glucocorticoids and to describe continuous treatment episodes using the parametric waiting time distribution.

Methods

We used Danish nationwide registries to identify all prescriptions for oral glucocorticoids during 1996-2014. We applied the parametric waiting time distribution to estimate duration of individual prescriptions each year by estimating the 80th, 90th, 95th and 99th percentiles for the interarrival distribution. These corresponded to the time since last prescription during which 80%, 90%, 95% and 99% of users presented a new prescription for redemption. We used the Kaplan-Meier survival function to estimate length of first continuous treatment episodes by assigning estimated prescription duration to each prescription and thereby create treatment episodes from overlapping prescriptions.

Results

We identified 5,691,985 prescriptions issued to 854,429 individuals of whom 351,202 (41%) only redeemed 1 prescription in the whole study period. The 80th percentile for prescription duration ranged from 87 to 120 days, the 90th percentile from 116 to 150 days, the 95th percentile from 147 to 181 days, and the 99th percentile from 228 to 259 days during 1996-2014. Based on the 80th, 90th, 95th and 99th percentiles of prescription duration, the median length of continuous treatment was 113, 141, 170 and 243 days, respectively.

Conclusion

Our method and results may provide an important framework for future pharmacoepidemiological studies. The choice of which percentile of the interarrival distribution to apply as prescription duration has an impact on the level of misclassification. Use of the 80th percentile provides a measure of drug exposure that is specific, while the 99th percentile provides a sensitive measure.

Using probability of drug use as independent variable in a register-based pharmacoepidemiological cause-effect study-An application of the reverse waiting time distribution

BACKGROUND

In register-based pharmacoepidemiological studies, each day of follow-up is usually categorized either as exposed or unexposed. However, there is an underlying continuous probability of exposure, and by insisting on a dichotomy, researchers unwillingly force a nondifferential misclassification into their analyses. We have recently developed a model whereby probability of exposure can be modeled, and we tested this on an empirical case of nonsteroidal anti-inflammatory drug (NSAID)-induced upper gastrointestinal bleeding (UGIB).

METHODS

We used a case-controls data set, consisting of 3568 cases of severe UGIB and 35 552 matched controls. Exposure to NSAID was based on 3 different conventional dichotomous measures. In addition, we tested 3 probabilistic exposure measures, a simple univariate backward-recurrence model, a "full" multivariable model, and a "reduced" multivariable model. Odds ratios (ORs) and 95% confidence intervals for the association between NSAID use and UGIB were calculated by conditional logistic regression, while adjusting for preselected confounders.

RESULTS

Compared to the conventional dichotomous exposure measures, the probabilistic exposure measures generated adjusted ORs in the upper range (4.37-4.75) while at the same time having the most narrow confidence intervals (ratio between upper and lower confidence limit, 1.46-1.50). Some ORs generated by conventional measures were higher than the probabilistic ORs, but only when the assumed period of intake was unrealistically short.

CONCLUSION

The pattern of high ORs and narrow confidence intervals in probabilistic exposure measures is compatible with less nondifferential misclassification of exposure than in a dichotomous exposure model. Probabilistic exposure measures appear to be an attractive alternative to conventional exposure measures.

Hydrochlorothiazide use is strongly associated with risk of lip cancer

BACKGROUND

The diuretic hydrochlorothiazide is amongst the most frequently prescribed drugs in the United States and Western Europe, but there is suggestive evidence that hydrochlorothiazide use increases the risk of lip cancer.

OBJECTIVES

To study the association between use of hydrochlorothiazide and squamous cell carcinoma of the lip.

METHODS

We conducted a case-control study using Danish nationwide registry data. From the Cancer Registry (2004-2012), we identified 633 case patients with squamous cell carcinoma (SCC) of the lip and matched them to 63 067 population controls using a risk-set sampling strategy. Hydrochlorothiazide use (1995-2012) was obtained from the Prescription Registry and defined according to cumulative use. Applying conditional logistic regression, we calculated odds ratios (ORs) for SCC lip cancer associated with hydrochlorothiazide use, adjusting for predefined potential confounders obtained from demographic, prescription and patient registries.

RESULTS

Ever-use of hydrochlorothiazide was associated with an adjusted OR for SCC lip cancer of 2.1 (95% confidence interval (CI): 1.7-2.6), increasing to 3.9 (95%CI: 3.0-4.9) for high use (≥25 000 mg). There was a clear dose-response effect (P < 0.001), with the highest cumulative dose category of hydrochlorothiazide (≥100 000 mg) presenting an OR of 7.7 (95%CI: 5.7-10.5). No association with lip cancer was seen with use of other diuretics or nondiuretic antihypertensives. Assuming causality, we estimated that 11% of the SCC lip cancer cases could be attributed to hydrochlorothiazide use.

CONCLUSIONS

Hydrochlorothiazide use is strongly associated with an increased risk of lip cancer.

Ophthalmic nepafenac use in the Netherlands and Denmark

Purpose

To describe nepafenac use in the Netherlands and Denmark with reference to its approved indications. For context, we also describe the use of ketorolac and diclofenac.

Methods

We identified users in the PHARMO Database Network (the Netherlands, 2008–2013) and the Danish national health registers (Denmark, 1994–2014). We described prevalence of cataract surgery and duration of use in patients with cataract surgery with and without diabetes.

Results

In the Netherlands, 9530 nepafenac users (mean age, 71 years; 60% women) contributed 12 691 therapy episodes, of which 21% had a recently recorded cataract surgery. Of 2266 episodes in adult non‐diabetic patients with cataract surgery, 60% had one bottle dispensed (treatment duration ≤21 days). Of 441 episodes in adult diabetic patients with cataract surgery, 90% had up to two bottles dispensed (≤60 days).

Denmark had 60 403 nepafenac users (mean age, 72 years; 58% women) and 73 648 episodes (41% had recorded cataract surgery). Of 26 649 nepafenac episodes in adult non‐diabetic patients with cataract surgery, 92% had one bottle dispensed. Of 3801 episodes in adult diabetic patients with cataract surgery, 99.8% had up to two bottles dispensed.

Use patterns of nepafenac, ketorolac and diclofenac were roughly similar in the Netherlands, but not in Denmark.

Conclusion

Less than half of therapy episodes were related to cataract surgery; around 90% of episodes with surgery were within the approved duration. Underrecording of ophthalmic conditions and procedures was a challenge in this study.

External adjustment of unmeasured confounders in a case-control study of benzodiazepine use and cancer risk

AIMS

Previous studies have reported diverging results on the association between benzodiazepine use and cancer risk.

METHODS

We investigated this association in a matched case-control study including incident cancer cases during 2002-2009 in the Danish Cancer Registry (n = 94 923) and age- and sex-matched (1:8) population controls (n = 759 334). Long-term benzodiazepine use was defined as ≥500 defined daily doses 1-5 years prior to the index date. We implemented propensity score (PS) calibration using external information on confounders available from a survey of the Danish population. Two PSs were used: The error-prone PS using register-based confounders and the calibrated PS based on both register- and survey-based confounders, retrieved from the Health Interview Survey.

RESULTS

Register-based data showed that cancer cases had more diagnoses, higher comorbidity score and more co-medication then population controls. Survey-based data showed lower self-rated health, more self-reported diseases, and more smokers as well as subjects with sedentary lifestyle among benzodiazepine users. By PS calibration, the odds ratio for cancer overall associated with benzodiazepine use decreased from 1.16 to 1.09 (95% confidence interval 1.00-1.19) and for smoking-related cancers from 1.20 to 1.10 (95% confidence interval 1.00-1.21).

CONCLUSION

We conclude that the increased risk observed in the solely register-based study could partly be attributed to unmeasured confounding.

Association of Pre-Pregnancy Body Mass Index, Pregnancy-Related Weight Changes, and Parity With the Risk of Developing Degenerative Musculoskeletal Conditions

OBJECTIVE

To examine how pre-pregnancy body mass index (BMI), parity, and pregnancy-related weight changes are associated with long-term risk of degenerative musculoskeletal conditions.

METHODS

A total of 79,687 mothers with singleton births from the Danish National Birth Cohort were included. Information on height and weight prior to pregnancy and 6 months postpartum as well as gestational weight gain (GWG) was obtained from telephone interviews, while parity was derived from the Danish Medical Birth Registry. Diagnoses of musculoskeletal conditions, including osteoarthritis, disc disorders, low back pain, and soft tissue disorders, were obtained from the Danish National Patient Registry. Hazard ratios (HRs) were estimated using a Cox proportional hazards regression model.

RESULTS

The cumulative incidence of musculoskeletal conditions during a median follow-up of 12.4 years was 19.7%. The risk of musculoskeletal conditions increased with both increasing pre-pregnancy BMI and increasing parity. Compared to normal-weight first-time mothers, the highest risk was seen in obese women with >2 births (HR 1.61 [95% confidence interval 1.41-1.83]). GWG of 10-15 kg was associated with the lowest risk of musculoskeletal conditions. Compared to women with no change in weight from preconception to 6 months after childbirth (±1 BMI unit), increasing postpartum weight increased the risk of musculoskeletal conditions in normal-weight and overweight women.

CONCLUSION

Our findings indicate that high pre-pregnancy BMI increases the risk of degenerative musculoskeletal conditions. Low and high GWG, higher postpartum weight retention, and especially higher parity are associated with an increased risk. Prevention of being overweight before, during, and after pregnancy may reduce the risk of development of degenerative musculoskeletal conditions among mothers.

Montelukast use-a 19-year nationwide drug utilisation study

PURPOSE

Montelukast is a leukotriene receptor antagonist used in asthma and rhinitis treatment. Despite being marketed nearly two decades ago, little is known about its utilisation pattern.

METHODS

Using the Danish National Prescription Registry, we identified subjects filling a montelukast prescription between 1998 and 2017. Using descriptive statistics, we reported the development in incidence, and prevalence, as well as a measure of treatment duration, and concomitant use of asthma- or anti-allergic therapy.

RESULTS

We identified 147,247 individuals filling 1,327,489 montelukast prescriptions. A total of 54,349 users (37%) filled only one montelukast prescription. The prevalence increased from 0.9/1000 persons in 1998 to 3.3/1000 persons in 2016. The rate of new users reached its maximum of 2.1/1000 person-years in 2009. Among new montelukast users, 28% were still users after 1 year. Among all montelukast initiators, 60% filled at least one prescription of short-acting beta-2-agonists (SABA) up to a year prior to montelukast initiation, and 49% filled a prescription of inhaled corticosteroids (ICS). Only 0.8% (n = 1148) of all individuals initiated montelukast without a redeemed prescription of short- or long-term inhalation therapy, systemic antihistamines, or nasal topical anti-allergic treatment.

CONCLUSIONS

The usage of montelukast has increased over threefold since its market entry in 1998, mainly driven by an increased number of prevalent users. The majority of individuals who initiated montelukast filled a prescription of SABA up to a year prior to montelukast initiation, whereas almost half filled a prescription of ICS.

Population Exposure to Phthalate-containing Drugs

Phthalates are known endocrine disruptors. Not commonly recognized, phthalates are used as excipients in a number of drug formulations. We aimed to describe the sale of phthalate-containing drugs in Denmark from 2004 to 2015. National data on annual sale of medications (tablets only) were accessed from medstat.dk. Data from the Danish Medicines Agency on phthalate content per tablet were merged with data on total sale for each active substance and drug formulation. We used the 'defined daily dose' (DDD) as the unit of sale and calculated the total amount of phthalate (mg) dispensed per 1000 inhabitants. Specific tablet content was compared with the maximum daily exposure limits defined by regulatory agencies for diethyl phthalate (DEP) and dibutyl phthalate (DBP) of 4.0 and 0.01 mg/kg/day, respectively. Use of phthalate-containing drugs in Denmark was common. We found 154 drug products containing five different phthalates. Two low-molecular-weight phthalates and three high-molecular-weight phthalates were identified, with a total sale of 59.4 and 112 DDD per 1000 inhabitants per day during the study period, respectively. The highest amount of DBP was found in multi-enzymes (24.6-32.8 mg per DDD) and mesalazine (12.5-26.4 mg per DDD). Budesonide, lithium and bisacodyl also exceeded the DBP exposure limit of 0.01 mg/kg/day. Other drugs had high levels of DEP, although not exceeding the exposure limit. Sales of phthalate-containing drugs in Denmark from 2004 to 2015 were substantial, and phthalate exposure from several products exceeded the regulatory exposure limit introduced in 2014.

Statin use and mortality among ovarian cancer patients: A population-based cohort study

Statin use has been suggested to improve prognosis in cancer patients, however, for ovarian cancer, the evidence is sparse. From the Danish Cancer Registry, we identified patients aged 30-84 years with a histologically verified first diagnosis of epithelial ovarian cancer between 2000 and 2013. Data on filled prescriptions, death, and potential confounding factors were obtained from nationwide registers. Cox proportional hazard regression models were used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between post-diagnostic statin use and all-cause or ovarian cancer-specific mortality. Among 4,419 patients with epithelial ovarian cancer, post-diagnostic statin use was not statistically significantly associated with all-cause (HR: 0.90, 95% CI: 0.78-1.04) or ovarian cancer-specific mortality (HR: 0.90, 95% CI: 0.76-1.08). There was little evidence of a dose-response relationship and the neutral associations persisted in sensitivity analyses. In women with endometrioid or clear cell tumour histology, cancer-specific mortality was reduced by 30-40% among statin users compared to non-users, however the analyses were limited by small numbers. Significantly reduced mortality with statin use was observed in subcohorts of new users of statins and of patients not using low-dose aspirin. In conclusion, we found no strong evidence of an association between post-diagnostic statin use and reduced mortality in ovarian cancer patients. However, our finding of potential differential susceptibility to statins among patients with different histologic types of ovarian cancer warrants further evaluation.

Refining estimates of prescription durations by using observed covariates in pharmacoepidemiological databases: an application of the reverse waiting time distribution

PURPOSE

The study aimed to develop an automated method to estimate prescription durations in pharmacoepidemiological studies that may depend on patient and redemption characteristics.

METHODS

We developed an estimation algorithm based on maximum likelihood estimation for the reverse waiting time distribution (WTD), which is the distribution of time from the last prescription of each patient within a time window to the end of the time window. The reverse WTD consists of two distinctly different components: one component for prevalent users and one for patients stopping treatment. We extended the model to allow parameters of the reverse WTD to depend on linear combinations of covariates to obtain estimates and confidence intervals for percentiles of the inter-arrival density (time from one prescription to the subsequent). We applied the method to redemptions of warfarin, using the amount of drug filled, patient sex and patient age as covariates.

RESULTS

The estimated prescription durations increased with redeemed amount and age. Women generally had longer prescription durations, which increased more with age than men. For 70-year-old women redeeming 300+ pills, we predicted a 95th percentile of the inter-arrival density of 225 (95%CI: 201, 249) days. For 50-year-old men redeeming 100 pills, the corresponding prediction was 97 (88, 106) days.

CONCLUSIONS

The algorithm allows estimation of prescription durations based on the reverse WTD, which can depend upon observed covariates. Statistical uncertainty intervals and tests allow statistical inference on the influence of observed patient and prescription characteristics. The method may replace ad hoc decision rules. Copyright © 2017 John Wiley & Sons, Ltd.

Odense Pharmacoepidemiological Database: A Review of Use and Content

The Odense University Pharmacoepidemiological Database (OPED) is a prescription database established in 1990 by the University of Southern Denmark, covering reimbursed prescriptions from the county of Funen in Denmark and the region of Southern Denmark (1.2 million inhabitants). It is still active and thereby has more than 25 years of continuous coverage. In this MiniReview, we review its history, content, quality, coverage, governance and some of its uses. OPED's data include the Danish Civil Registration Number (CPR), which enables unambiguous linkage with virtually all other health-related registers in Denmark. Among its research uses, we review record linkage studies of drug effects, advanced drug utilization studies, some examples of method development and use of OPED as sampling frame to recruit patients for field studies or clinical trials. With the advent of other, more comprehensive sources of prescription data in Denmark, OPED may still play a role as in certain data-intensive regional studies.

Switching, Adverse Effects and Use of Over-the-Counter Analgesics among Users of Oral Anticoagulants: A Pharmacy-based Survey

Oral anticoagulants are widely used but information on important aspects in that respect is not available from medical registers or clinical databases. Therefore, we conducted a survey including patients filling a prescription for oral anticoagulants at two large Danish community pharmacies. We collected information concerning the patients' knowledge of their anticoagulant treatment including prior drug switching. Further, patients were asked about use of over-the-counter analgesics, adverse effects and how the treatment affected their everyday life. Among 335 eligible patients, 301 (90%) agreed to participate. Atrial fibrillation was the most common indication (65%), and most patients filled a prescription for a non-vitamin K antagonist oral anticoagulant (NOAC) (58%). Among the 12% (n = 35) of participants who had switched oral anticoagulant treatment, 69% had switched from a vitamin K antagonist (VKA) to a NOAC. Switching was most frequently caused by inconvenience (34%) and adverse effects (23%). Although half of all patients had recently bought over-the-counter analgesics, purchase of ibuprofen and aspirin was rare (6%). More VKA users than NOAC users felt limited in their everyday life because of anticoagulant treatment (18% versus 9%). Among non-incident NOAC users, 21% had experienced adverse effects during their current treatment. Based on first-hand information from a large sample of anticoagulant users, we conclude that the main drug-related issues leading to anticoagulant switching and perceived limitations in everyday life were inconvenience and adverse effects. This varied between drug groups. Further, use of NSAIDs obtained over the counter was rare.

Association of Antithrombotic Drug Use With Subdural Hematoma Risk

IMPORTANCE

Incidence of subdural hematoma has been reported to be increasing. To what extent this is related to increasing use of antithrombotic drugs is unknown.

OBJECTIVES

To estimate the association between use of antithrombotic drugs and subdural hematoma risk and determine trends in subdural hematoma incidence and antithrombotic drug use in the general population.

DESIGN, SETTING, AND PARTICIPANTS

Case-control study of 10 010 patients aged 20 to 89 years with a first-ever subdural hematoma principal discharge diagnosis from 2000 to 2015 matched by age, sex, and calendar year to 400 380 individuals from the general population (controls). Subdural hematoma incidence and antithrombotic drug use was identified using population-based regional data (population: 484 346) and national data (population: 5.2 million) from Denmark. Conditional logistic regression models were used to estimate odds ratios (ORs) that were adjusted for comorbidity, education level, and income level.

EXPOSURES

Use of low-dose aspirin, clopidogrel, a vitamin K antagonist (VKA), a direct oral anticoagulant, and combined antithrombotic drug treatment.

MAIN OUTCOMES AND MEASURES

Association of subdural hematoma with antithrombotic drug use, subdural hematoma incidence rate, and annual prevalence of treatment with antithrombotic drugs.

RESULTS

Among 10 010 patients with subdural hematoma (mean age, 69.2 years; 3462 women [34.6%]), 47.3% were taking antithrombotic medications. Current use of low-dose aspirin (cases: 26.7%, controls: 22.4%; adjusted OR, 1.24 [95% CI, 1.15-1.33]), clopidogrel (cases: 5.0%, controls: 2.2%; adjusted OR, 1.87 [95% CI, 1.57-2.24]), a direct oral anticoagulant (cases: 1.0%, controls: 0.6%; adjusted OR, 1.73 [95% CI, 1.31-2.28]), and a VKA (cases: 14.3%, controls: 4.9%; adjusted OR, 3.69 [95% CI, 3.38-4.03]) were associated with higher risk of subdural hematoma. The risk of subdural hematoma was highest when a VKA was used concurrently with an antiplatelet drug (low-dose aspirin and a VKA: 3.6% of cases and 1.1% of controls; adjusted OR, 4.00 [95% CI, 3.40-4.70]; clopidogrel and a VKA: 0.3% of cases and 0.04% of controls; adjusted OR, 7.93 [95% CI, 4.49-14.02]). The prevalence of antithrombotic drug use increased from 31.0 per 1000 individuals from the general population in 2000 to 76.9 per 1000 individuals in 2015 (P < .001 for trend). The overall subdural hematoma incidence rate increased from 10.9 per 100 000 person-years in 2000 to 19.0 per 100 000 person-years in 2015 (P < .001 for trend). The largest increase was among older patients (>75 years; n = 4441) who experienced an increase from 55.1 per 100 000 person-years to 99.7 per 100 000 person-years (P < .001 for trend).

CONCLUSIONS AND RELEVANCE

In Denmark, antithrombotic drug use was associated with higher risk of subdural hematoma; and the highest odds of subdural hematoma was associated with combined use of a VKA and an antiplatelet drug. The increased incidence of subdural hematoma from 2000 to 2015 appears to be associated with the increased use of antithrombotic drugs, particularly use of a VKA among older patients.

Use of antibiotics in childhood and risk of Type 1 diabetes: a population-based case-control study

AIMS

To investigate whether the use of antibiotics from infancy to adolescence influences the risk of Type 1 diabetes.

METHODS

We conducted a population-based case-control study, including all Type 1 diabetes cases in Denmark among children born between 1997 and 2012 (n = 1578). Odds ratios associating Type 1 diabetes with use of antibiotics were calculated using conditional logistic regression.

RESULTS

Overall, we found no association between the use of antibiotics and risk of Type 1 diabetes. Furthermore, no associations were seen specifically for broad-spectrum, narrow-spectrum, bactericidal or bacteriostatic types of antibiotics or for the most frequently used individual classes of antibiotics. No differences were observed in subgroups defined by sex or by age at time of diagnosis. However, filling five or more antibiotic prescriptions in the first 2 years of life specifically was associated with a higher odds ratio of 1.35 (95% CI 1.10-1.64). This association appeared to be driven by exposure to broad-spectrum antibiotics within the second year of life.

CONCLUSION

Antibiotic exposure in childhood is generally not associated with the risk of developing Type 1 diabetes. Future studies should investigate the effects of multiple exposures to broad-spectrum antibiotics during the second year of life.

Utilization of Stimulants and Atomoxetine for Attention-Deficit/Hyperactivity Disorder among 5.4 Million Children Using Population-Based Longitudinal Data

Use of stimulants to treat attention-deficit/hyperactivity disorder (ADHD) has increased over the past two decades and varies substantially between countries. The objective of this multinational population-based study was to examine utilization of ADHD drugs (stimulants and atomoxetine) including comedication with other psychotropic drugs in the entire child population in the five Nordic countries. We included longitudinal data on dispensed ADHD drugs from five Nordic prescription registers during 2008-2012, which in 2012 comprised 48,296 individuals among 5.42 million inhabitants aged 0-17 years. Prevalence of filling ≥1 prescriptions of ADHD drugs among children aged 6-17 years increased during 2008-2012 from 5.9 to 11.2 and 19.4 to 31.0 per 1000 girls and boys, respectively. Prevalence by country showed that Iceland, Finland and Sweden had a steady increase during the study period, while in Norway the prevalence was quite stable and in Denmark it levelled off from 2010. Use in preschoolers (aged 0-5 years) was rare. Iceland had much higher prevalence and incidence than the other Nordic countries. The incidence of ADHD drug use increased during the study period, from 4.0 to 4.9 and from 1.5 to 2.3 per 1000 boys and girls, respectively. The increasing number of new users levelled off somewhat after 2010. Comedication with other psychotropic drugs was more common among girls (33.9%) than boys (27.0%) and was mainly melatonin, followed by antidepressants and antipsychotics. Overall prevalence of ADHD drug use increased among Nordic girls and boys aged 6-17 years, whereas the incidence increased slightly during 2008-2010 but levelled off through 2012. The substantial differences in ADHD drug use across the Nordic countries and high degree of comedication with other psychotropic drugs underscore the importance of close monitoring of treatment for ADHD among children.