Metronidazole-associated Neurologic Events: A Nested Case-control Study.

BACKGROUND: Case reports have described instances of peripheral and central nervous system toxicity during treatment with metronidazole; however, no large-scale studies have examined this association. METHODS: We conducted a population-based nested case-control study of adults aged 66 years or older living in Ontario, Canada, between 1 April 2003 and 31 March 2017. Cases were individuals who attended hospital for any of cerebellar dysfunction, encephalopathy, or peripheral neuropathy within 100 days of a prescription for either metronidazole or clindamycin. We matched each case patient with up to 10 event-free control subjects who also received metronidazole or clindamycin. We used conditional logistic regression to test the association between metronidazole exposure and neurologic events, with clindamycin as the reference exposure. RESULTS: We identified 1212 cases with recent use of either metronidazole or clindamycin and 12 098 controls. Neurologic adverse events were associated with an increased odds of metronidazole exposure compared to clindamycin (odds ratio [OR], 1.72 [95% confidence interval {CI}, 1.53-1.94]), which persisted after accounting for patient demographics, comorbidities, and other medication exposures (adjusted odds ratio [aOR], 1.43 [95% CI, 1.26-1.63]). We found a consistent association limited to either central (aOR, 1.46 [95% CI, 1.27-1.68]) or peripheral (aOR, 1.34 [95% CI, 1.02-1.76]) nervous system events. Among metronidazole recipients, the overall incidence of neurologic events at 100 days was approximately 0.25%. CONCLUSIONS: Metronidazole is associated with an increased risk of adverse peripheral and central nervous system events relative to clindamycin. Clinicians and patients should be aware of these rare but potentially serious adverse events.

Impact of a Publicly Funded Herpes Zoster Immunization Program on the Burden of Disease in Ontario, Canada: A Population-based Study.

BACKGROUND: In September 2009, a live attenuated herpes zoster vaccine (ZVL) became available in Canada. Beginning in September 2016, ZVL was made available to all Ontario residents aged 65-70 through a publicly funded immunization program. We assessed the impact of ZVL availability and its subsequent public funding on herpes zoster burden in this population. METHODS: A population-based study of Ontario residents aged 65-70 between January 2005 and September 2018. We used interventional autoregressive integrated moving average models to examine the impact of ZVL market availability and the publicly funded ZVL program on monthly incidence rate of medically attended herpes zoster, defined as an outpatient visit for herpes zoster with a prescription for a herpes zoster antiviral dispensed ≤5 days before or after the visit, or a herpes zoster-related emergency department (ED) visit or hospitalization. In secondary analyses, we examined impacts on any herpes zoster-related ED visits and hospitalizations. RESULTS: We found no association between ZVL market availability and monthly incidence of herpes zoster (P = .32) or monthly rates of ED visits and hospitalizations (P = .88). Conversely, the introduction of publicly funded ZVL reduced the monthly rate of medically attended herpes zoster by 19.1% (from 4.8 to 3.8 per 10 000 population; P < .01) and herpes zoster-related ED visits and hospitalizations by 38.2% (from 1.7 to 1.0 per 10 000 population; P < .05). CONCLUSIONS: The introduction of a publicly funded immunization program for herpes zoster was associated with reduced disease burden and related acute healthcare service use.

Initial opioid prescription patterns and the risk of ongoing use and adverse outcomes.

PURPOSE: As clinical practice moves towards more judicious opioid prescribing, physicians require information on how to safely initiate opioids. The objective of this study was to examine the association between initial opioid prescription characteristics and risks of harm and long-term use. METHODS: We conducted a population-based retrospective cohort study among Ontario residents newly dispensed an opioid for pain between July 2013 and March 2016. The primary exposure was the average daily opioid dose dispensed at initiation (in milligram morphine equivalents; MME), with secondary exposures including the initial prescription's duration and formulation. The primary outcome was fatal or non-fatal opioid overdose. A secondary analysis studied continued opioid use for at least 1 year. RESULTS: Among the 2 021 371 individuals meeting our inclusion criteria, 1121 (0.56 per 1000 person-years) experienced an opioid overdose within 1 year and 64 013 (3.17%) continued treatment for at least 1 year. Higher initial daily dose, longer prescription duration, and receipt of a long-acting formulation at initiation were significantly associated with higher hazard of overdose. Compared to daily doses of 20 MME or lower, initial doses exceeding 200 MME daily were associated with a particularly high hazard of overdose (aHR 2.97, 95% confidence interval [CI] 1.62 to 5.44). In the secondary analysis, there were similar associations between initial dose, duration, and formulation and long-term use. CONCLUSIONS: Although the absolute risk of an opioid overdose within the first year of prescription opioid use is low, better alignment of opioid initiation practices with guidelines may reduce opioid-related harm.

Comprehensive Drug-Class Review Framework for improved evidence-based drug policy and formulary modernization.

Formularies are used by payers to optimize access and ensure the appropriate use of medications. Lack of follow-up and re-evaluation can lead to outdated formularies that are not reflective of current evidence. Formulary modernization, an approach to re-align formularies with current evidence has proven successful. The Ontario Drug Policy Research Network (ODPRN) launched a framework for conducting comprehensive drug-class reviews. This commentary describes the individual components of this framework and lessons learned through completion of 12 reviews between 2013 and 2016. We present the ODPRN drug-class review of treatments for chronic hepatitis B as a case example to illustrate the components and impact. The incorporation of foundational health technology assessment components such as economic evaluations and knowledge synthesis with contextualizing evidence such as patient and clinician perspectives (through qualitative studies), real-world evidence (through data analytics), and cross-jurisdictional comparisons (through environmental scans and data analytics), successfully developed jurisdictionally specific policy recommendations grounded in up-to-date evidence. The ODPRN framework for conducting comprehensive drug-class reviews is a robust and feasible approach to conduct formulary modernization. This framework allows for actionable and specific policies which are likely to be considered by decision makers. Adoption of similar frameworks in other jurisdictions may improve uptake of evidence-informed policy recommendations.

Nursing resource team capacity planning using forecasting and optimization methods: A case study.

AIM: To estimate the cost-minimizing size and skill mix of a nursing resource team (NRT). BACKGROUND: Nurse absences can be filled by an NRT at lower hourly cost than staffing agencies or nurses working overtime, but an NRT must be appropriately sized to minimize total cost. METHODS: Using all registered nurse (RN) absences at an academic teaching hospital from 1 October 2014 to 31 March 2018, we developed a generalized additive model (GAM) to forecast the weekly frequency of each of ten types of absence over 52 weeks. We used the forecasts in an optimization model to determine the cost-minimizing NRT composition. RESULTS: The median weekly frequencies for the ten absence types ranged between 12 and 65.5. The root mean squared errors of the GAMs ranged between 4.55 and 9.07 on test data. The NRT dimensioned by the optimization model yields an estimated annual cost reduction of $277,683 (Canadian dollars) (7%). CONCLUSIONS: The frequency of RN absences in a hospital can be forecasted with high accuracy, and the use of forecasting and optimization to dimension an NRT can substantially reduce the cost of filling RN absences. IMPLICATIONS FOR NURSING MANAGEMENT: This methodology can be adapted by any hospital to optimize nurse staffing.

Impact of delisting high-strength opioid formulations from a public drug benefit formulary on opioid utilization in Ontario, Canada.

PURPOSE: High-strength opioid formulations were delisted (removed) from Ontario's public drug formulary in January 2017, except for palliative patients. We evaluated the impact of this policy on opioid utilization and dosing. METHODS: We conducted a longitudinal study among patients receiving publicly funded, high-strength opioids from August 2016 to July 2017. The primary outcome measure was weekly median daily opioid dose (in milligrams of morphine or equivalent; MME) of (1) publicly funded and (2) all opioid prescriptions irrespective of funding source, evaluated using interrupted time series analyses and stratified by palliative care status. RESULTS: Following policy implementation, the weekly median daily dose of publicly funded opioids decreased immediately among non-palliative patients by 10 MME (95% confidence limit [CL], -16.8 to -3.1) from a pre-intervention dose of 424.5 MME (95% CL, 417.8-431.2) and fell gradually among palliative patients by 3.9 MME per week (95% CL, -5.5 to -2.3) from a pre-intervention dose of 450.1 MME (95% CL, 432.5-467.7). In contrast, among all opioid prescriptions, gradual reductions in weekly median daily doses were observed only for non-palliative patients, which decreased by 0.7 MME per week (95% CL, -1.3 to -0.2) from a pre-intervention dose of 426.2 MME (95% CL, 420.9-431.5). CONCLUSION: The delisting of publicly-funded, high-strength opioids was accompanied by changes in funding source and small reductions in the weekly median daily doses dispensed. Although observed dose reductions of less than 1 MME weekly are likely not clinically relevant, safety implications of these changes require further monitoring.

Fixed-dose combination antihypertensive medications, adherence, and clinical outcomes: A population-based retrospective cohort study.

BACKGROUND: The majority of people with hypertension require more than one medication to achieve blood pressure control. Many patients are prescribed multipill antihypertensive regimens rather than single-pill fixed-dose combination (FDC) treatment. Although FDC use may improve medication adherence, the impact on patient outcomes is unclear. We compared clinical outcomes and medication adherence with FDC therapy versus multipill combination therapy in a real-world setting using linked clinical and administrative databases. METHODS AND FINDINGS: We conducted a population-based retrospective cohort study of 13,350 individuals 66 years and older in Ontario, Canada with up to 5 years of follow-up. We included individuals who were newly initiated on one angiotensin-converting enzyme inhibitor (ACEI) or angiotensin II-receptor blocker (ARB) plus one thiazide diuretic. High-dimensional propensity score matching was used to compare individuals receiving FDC versus multipill therapy. The primary outcome was a composite of death or hospitalization for acute myocardial infarction (AMI), heart failure, or stroke. We conducted 2 analyses to examine the association between adherence and patient outcomes. First, we performed an on-treatment analysis to determine whether outcomes differed between groups while patients were on treatment, censoring patients when they first discontinued treatment, defined as not receiving medications within 150% of the previous days' supply. Second, we conducted an intention-to-treat analysis that followed individuals allowing for breaks in treatment to quantify the difference in drug adherence between groups and assess its impact on clinical outcomes. As expected, there was no significant difference in the primary outcome between groups in the on-treatment analysis (HR 1.06, 95% CI 0.86-1.31, P = 0.60). In the intention-to-treat analysis, the proportion of total follow-up days covered with medications was significantly greater in the FDC group (70%; IQR 19-98) than in the multipill group (42%, IQR 11-91, P < 0.01), and the primary outcome was less frequent in FDC recipients (3.4 versus 3.9 events per 100 person-years; HR 0.89, 95% CI 0.81-0.97, P < 0.01). The main limitations of this study were the lack of data regarding cause of death and blood pressure measurements and the possibility of residual confounding. CONCLUSIONS: Among older adults initiating combination antihypertensive treatment, FDC therapy was associated with a significantly lower risk of composite clinical outcomes, which may be related to better medication adherence.

Real-world health care utilization and effectiveness of omalizumab for the treatment of severe asthma.

BACKGROUND: Omalizumab is indicated for the treatment of moderate to severe asthma. There is limited observational evidence on the costs and effectiveness of omalizumab. OBJECTIVE: To examine the costs and effectiveness of omalizumab for treatment of severe asthma relative to nonusers. METHODS: We conducted a within-person repeated-measures matched cohort study in Ontario, Canada from April 1, 2012 to March 31, 2014. Continuous users of omalizumab were matched with up to 4 nonusers according to age, sex, recent specialist visits, oral corticosteroid use, asthma severity, and Charlson comorbidity score. The primary outcome was direct health care costs. Secondary outcomes were asthma-related hospitalizations or emergency department visits and oral corticosteroid use. The association between omalizumab use and each outcome was assessed using mixed-effects models adjusting for confounders. RESULTS: Ninety-five omalizumab users and 352 nonusers were matched. Among users, there was a significant increase in health care costs of $1,796 per person owing to the cost of the medication at treatment initiation (P < .0001). Costs did not change significantly among nonusers ($85 increase in average monthly costs per person; P = .59). We found no significant changes in the rates of asthma-related hospitalizations or emergency department visits among omalizumab users (P = .44) or nonusers (P = .99) between pre- and postintervention periods. CONCLUSION: The use of omalizumab was associated with increased costs but no evidence of lower rates of clinically important outcomes. These results suggest omalizumab had limited effectiveness in our study population. Future studies should further explore subsets of patients most likely to benefit from omalizumab therapy.

A population-based study of the risk of osteoporosis and fracture with dutasteride and finasteride.

BACKGROUND: Dutasteride is a potent inhibitor of 5-alpha reductase enzymes that reduces concentrations of dihydrotestosterone to a greater extent than finasteride. Whether this has adverse implications for bone health is unknown. We compared the risk of osteoporosis and fractures in older men treated with dutasteride or finasteride. METHODS: We conducted a population-based retrospective cohort study with high-dimensional propensity score matching of Ontario men aged 66 years or older who started treatment with dutasteride or finasteride between January 1, 2006 and December 31, 2012. The primary outcome was a diagnosis of osteoporosis within 2 years of treatment initiation. A secondary outcome was osteoporotic or fragility fractures. RESULTS: We studied 31,615 men treated with dutasteride and an equal number of men treated with finasteride. Dutasteride-treated patients had a lower incidence of osteoporosis than those receiving finasteride [2.2 versus 2.6 per 100 person years; hazard ratio (HR) 0.82; 95% confidence interval (CI) 0.72 to 0.93]. This effect was no longer statistically significant following adjustment for specialty of prescribing physician (HR 0.90; 95% CI 0.78 to 1.02)]. There was no differential risk of fractures with dutasteride (HR 1.04; 95% 0.86 to 1.25). CONCLUSIONS: Despite differential effects on 5-alpha reductase, dutasteride is not associated with an increased risk of osteoporosis or fractures in older men relative to finasteride. These findings suggest that dutasteride does not adversely affect bone health.

Gabapentin, opioids, and the risk of opioid-related death: A population-based nested case-control study.

BACKGROUND: Prescription opioid use is highly associated with risk of opioid-related death, with 1 of every 550 chronic opioid users dying within approximately 2.5 years of their first opioid prescription. Although gabapentin is widely perceived as safe, drug-induced respiratory depression has been described when gabapentin is used alone or in combination with other medications. Because gabapentin and opioids are both commonly prescribed for pain, the likelihood of co-prescription is high. However, no published studies have examined whether concomitant gabapentin therapy is associated with an increased risk of accidental opioid-related death in patients receiving opioids. The objective of this study was to investigate whether co-prescription of opioids and gabapentin is associated with an increased risk of accidental opioid-related mortality. METHODS AND FINDINGS: We conducted a population-based nested case-control study among opioid users who were residents of Ontario, Canada, between August 1, 1997, and December 31, 2013, using administrative databases. Cases, defined as opioid users who died of an opioid-related cause, were matched with up to 4 controls who also used opioids on age, sex, year of index date, history of chronic kidney disease, and a disease risk index. After matching, we included 1,256 cases and 4,619 controls. The primary exposure was concomitant gabapentin use in the 120 days preceding the index date. A secondary analysis characterized gabapentin dose as low (<900 mg daily), moderate (900 to 1,799 mg daily), or high (≥1,800 mg daily). A sensitivity analysis examined the effect of concomitant nonsteroidal anti-inflammatory drug (NSAID) use in the preceding 120 days. Overall, 12.3% of cases (155 of 1,256) and 6.8% of controls (313 of 4,619) were prescribed gabapentin in the prior 120 days. After multivariable adjustment, co-prescription of opioids and gabapentin was associated with a significantly increased odds of opioid-related death (odds ratio [OR] 1.99, 95% CI 1.61 to 2.47, p < 0.001; adjusted OR [aOR] 1.49, 95% CI 1.18 to 1.88, p < 0.001) compared to opioid prescription alone. In the dose-response analysis, moderate-dose (OR 2.05, 95% CI 1.46 to 2.87, p < 0.001; aOR 1.56, 95% CI 1.06 to 2.28, p = 0.024) and high-dose (OR 2.20, 95% CI 1.58 to 3.08, p < 0.001; aOR 1.58, 95% CI 1.09 to 2.27, p = 0.015) gabapentin use was associated with a nearly 60% increase in the odds of opioid-related death relative to no concomitant gabapentin use. As expected, we found no significant association between co-prescription of opioids and NSAIDs and opioid-related death (OR 1.11, 95% CI 0.98 to 1.27, p = 0.113; aOR 1.14, 95% CI 0.98 to 1.32, p = 0.083). In an exploratory analysis of patients at risk of combined opioid and gabapentin use, we found that 46.0% (45,173 of 98,288) of gabapentin users in calendar year 2013 received at least 1 concomitant prescription for an opioid. This study was limited to individuals eligible for public drug coverage in Ontario, we were only able to identify prescriptions reimbursed by the government and dispensed from retail pharmacies, and information on indication for gabapentin use was not available. Furthermore, as with all observational studies, confounding due to unmeasured variables is a potential source of bias. CONCLUSIONS: In this study we found that among patients receiving prescription opioids, concomitant treatment with gabapentin was associated with a substantial increase in the risk of opioid-related death. Clinicians should consider carefully whether to continue prescribing this combination of products and, when the combination is deemed necessary, should closely monitor their patients and adjust opioid dose accordingly. Future research should investigate whether a similar interaction exists between pregabalin and opioids.

The Cardiovascular Safety of Dutasteride.

PURPOSE: Randomized controlled trials suggest an increased risk of heart failure with dutasteride, which inhibits both the type 1 and type 2 isoforms of 5α-reductase. In contrast, no such association has been suggested for finasteride, which selectively inhibits the type 2 isoform. We investigated the risk of cardiovascular events among patients receiving dutasteride relative to finasteride. MATERIALS AND METHODS: We performed a population based cohort study of Ontario men 66 years old or older who commenced treatment with dutasteride or finasteride between October 1, 2005 and March 31, 2015. For each individual treated with dutasteride, we identified 1 treated with finasteride, matching on a propensity score and calendar quarter of treatment initiation to account for temporal changes in prescribing. The primary outcome was hospitalization for heart failure. Secondary analyses were done to examine acute myocardial infarction and stroke. Cox proportional hazards regression was used to adjust for differences between groups. RESULTS: We studied 36,311 men who commenced dutasteride and 36,311 treated with finasteride. In the primary analysis, we found no difference in the risk of heart failure among patients receiving dutasteride relative to those receiving finasteride (adjusted HR 0.98, 95% CI 0.88-1.08). Similarly, we found no difference in the risk of acute myocardial infarction (HR 0.94, 95% CI 0.82-1.08) or stroke (HR 1.03, 95% CI 0.88-1.20). CONCLUSIONS: In this population based cohort study of more than 72,000 older men, dutasteride was not associated with an increased risk of cardiovascular events relative to finasteride.

Second-Generation Antidepressants and Hyponatremia Risk: A Population-Based Cohort Study of Older Adults.

BACKGROUND: Hyponatremia may occur after initiation of a second-generation antidepressant drug. However, the magnitude of this risk among older adults in routine care is not well characterized. STUDY DESIGN: Retrospective, population-based, matched-cohort study. SETTING & PARTICIPANTS: In Ontario, Canada, 2003 to 2012, we compared older adults with a mood or anxiety disorder who were dispensed 1 of 9 second-generation antidepressant drugs with matched adults with comparable indicators of baseline health who were not dispensed an antidepressant drug (n=138,246 per group). A similar comparison was made in a subpopulation with available laboratory data (n=4,186 per group). PREDICTOR: Second-generation antidepressant prescription versus no antidepressant prescription. OUTCOMES: The primary outcome was hospitalization with hyponatremia. A secondary outcome was hospitalization with both hyponatremia and delirium. MEASUREMENTS: We assessed hospitalization with hyponatremia using a diagnosis code and, in the subpopulation, serum sodium values. We assessed hospitalization with hyponatremia and delirium using a combination of diagnosis codes. RESULTS: Second-generation antidepressant use versus nonuse was associated with higher 30-day risk for hospitalization with hyponatremia (450/138,246 [0.33%] vs 84/138,246 [0.06%]; relative risk [RR], 5.46 [95% CI, 4.32-6.91]). This association was consistent in the subpopulation with serum sodium values (73/4,186 [1.74%] vs 18/4,186 [0.43%]; RR, 4.23 [95% CI, 2.50-7.19]; absolute risk increase, 1.31% [95% CI, 0.87%-1.75%]). Second-generation antidepressant use versus nonuse was also associated with higher 30-day risk for hospitalization with both hyponatremia and delirium (28/138,246 [0.02%] vs 7/138,246 [0.005%]; RR, 4.00 [95% CI, 1.75-9.16]). LIMITATIONS: Measures of serum sodium could be ascertained in only a subpopulation. CONCLUSIONS: Use of a second-generation antidepressant in routine care by older adults is associated with an approximate 5-fold increase in 30-day risk for hospitalization with hyponatremia compared to nonuse. However, the absolute increase in 30-day incidence is low.

Association between statin use and ischemic stroke or major hemorrhage in patients taking dabigatran for atrial fibrillation.

BACKGROUND: Dabigatran etexilate is a prodrug whose absorption is opposed by intestinal P-glycoprotein and which is converted by carboxylesterase to its active form, dabigatran. Unlike other statins, simvastatin and lovastatin are potent inhibitors of P-glycoprotein and carboxylesterase, and might either increase the risk of hemorrhage with dabigatran etexilate or decrease its effectiveness. METHODS: We conducted 2 population-based, nested case-control studies involving Ontario residents 66 years of age and older who started dabigatran etexilate between May 1, 2012, and Mar. 31, 2014. In the first study, cases were patients with ischemic stroke; in the second, cases were patients with major hemorrhage. Each case was matched with up to 4 controls by age and sex. All cases and controls received a single statin in the 60 days preceding the index date. We determined the association between each outcome and the use of simvastatin or lovastatin, relative to other statins. RESULTS: Among 45 991 patients taking dabigatran etexilate, we identified 397 cases with ischemic stroke and 1117 cases with major hemorrhage. After multivariable adjustment, use of simvastatin or lovastatin was not associated with an increased risk of stroke (adjusted odds ratio [OR] 1.33, 95% confidence interval [CI] 0.88 to 2.01). In contrast, use of simvastatin and lovastatin were associated with a higher risk of major hemorrhage (adjusted OR 1.46, 95% CI 1.17 to 1.82). INTERPRETATION: In patients receiving dabigatran etexilate, simvastatin and lovastatin were associated with a higher risk of major hemorrhage relative to other statins. Preferential use of the other statins should be considered in these patients.

Pregabalin and heart failure: A population-based study.

PURPOSE: The anticonvulsant pregabalin is increasingly prescribed for pain, seizures, and psychiatric disorders. Although evidence suggests pregabalin can cause edema and heart failure, its cardiac safety profile in clinical practice is unknown. We sought to examine the risk of heart failure among older patients receiving pregabalin compared to those receiving gabapentin. METHODS: We conducted a population-based cohort study of Ontarians aged 66 and older with a history of seizure who received pregabalin or gabapentin between April 2013 and March 2014. We used propensity scores to match patients commencing pregabalin to those commencing gabapentin. The primary outcome was an emergency department visit or hospitalization for heart failure within 90 days. RESULTS: We studied 9855 patients who initiated pregabalin and an equal number treated with gabapentin. In the primary analysis, we found no difference in the risk of heart failure with pregabalin compared to gabapentin (1.2% versus 1.3%, hazard ratio of 0.77; 95% CI 0.58-1.03). Secondary analyses stratified for baseline history of heart failure yielded similar findings. CONCLUSION: In a large cohort of older patients with a seizure disorder, pregabalin was not associated with an increased risk of heart failure relative to gabapentin.

The appropriateness and persistence of testosterone replacement therapy in Ontario.

PURPOSE: To examine the concordance between testosterone replacement therapy (TRT) use and established reimbursement criteria, as well as compare the persistence of use among available formulations (injectable, oral, topical gel, transdermal patch) among elderly men in Ontario, Canada. METHODS: We conducted a retrospective cohort study of men aged 66 years or older in Ontario newly treated with testosterone between 1 January 2009 and 31 December 2012 using linked health administrative data. Continuous use was defined on the basis of prescription refills issued within 180 days of the preceding prescription. We studied men who received at least two consecutive TRT prescriptions. We estimated the prevalence of hypogonadism, human immunodeficiency virus, specialist visits and lab tests for serum testosterone prior to initiation of TRT to investigate concordance with prescribing criteria. We also performed a Kaplan-Meier analysis to test for differences in the median time to discontinuation among formulations. RESULTS: Among the 4797 men who received at least two TRT prescriptions, only 38.7% met the reimbursement criteria for use prior to initiating therapy. The median time to discontinuation differed significantly among formulations and was longest among recipients of oral TRT products (383 days), and lower for recipients of topical gels (319 days), injectable (283 days) and transdermal patches (160 days; Log-rank test p < 0.001). CONCLUSIONS: A large proportion of older men in Ontario do not appear to meet reimbursement criteria prior to commencing therapy, and many discontinue TRT within a year of initiation. Copyright © 2016 John Wiley & Sons, Ltd.

Off-label use of inhaled tobramycin in Ontario, Canada.

Inhaled tobramycin solution is indicated for use in the management of Pseudomonas aeruginosa in patients with cystic fibrosis (CF). Concerns have been raised regarding increasing off-label use of inhaled tobramycin, particularly for the management of COPD. We conducted an 8-year repeated cross-sectional study examining the indication for prescription claims for inhaled tobramycin in Ontario paid for by the Public Drug Benefit Program, which covers all Ontario residents with financial needs or aged 65 and older. Inhaled tobramycin prescription claims increased approximately 3 times greater from 86 prescriptions in the second quarter of 2007 to 261 prescriptions in the first quarter of 2015. Approximately half of all prescriptions (range: 46-65%) per quarter were dispensed to patients with CF. A large proportion of prescriptions (range: 31-36%) were dispensed to individuals who did not have a diagnosis of CF but had a diagnosis of COPD. In 2014, there were 324 unique users of inhaled tobramycin solution in the Ontario Public Drug Program (OPDP). Only half of users (54%; n=163) had a diagnosis of CF. Our study found increasing prescriptions of inhaled tobramycin from 2007 to 2015 in the OPDP with approximately half of these claims being for off-label use, mostly among patients with COPD.

Antiepileptic drugs and hyponatremia in older adults: Two population-based cohort studies.

OBJECTIVE: To examine the 30-day risk of hospitalization with hyponatremia associated with carbamazepine, valproic acid (V), phenytoin (P), or topiramate (T) use compared to nonuse in the outpatient setting among older adults. METHODS: We conducted two population-based, retrospective cohort studies in Ontario, Canada, between 2003 and 2015 using administrative health care databases of older adults. The first study compared carbamazepine users to a propensity-score matched group of antiepileptic drug nonusers, whereas the second compared V-P-T users to a propensity-score matched group of antiepileptic nonusers. The primary outcome was hospitalization with hyponatremia within 30 days of an antiepileptic prescription. RESULTS: The baseline characteristics between matched groups were similar in both cohorts. Carbamazepine use versus nonuse was associated with a higher 30-day risk of hospitalization with hyponatremia (82/21,191 [0.39%] versus 30/63,573 [0.05%]; relative risk [RR] 8.20, 95% confidence interval [CI] 5.40-12.46). Similarly, V-P-T use versus nonuse was associated with a higher 30-day risk of hospitalization with hyponatremia (34/20,155 [0.17%] versus 26/40,310 [0.06%]; RR 2.62, 95% CI 1.57-4.36). SIGNIFICANCE: Older adults prescribed carbamazepine and V-P-T have a higher risk of being hospitalized with hyponatremia compared to other adults with similar indicators of baseline health who were not prescribed antiepileptic drugs. Physicians should be mindful of this risk; when a patient presents to a hospital with symptomatic hyponatremia these drugs should be considered as potential causes.

Interprovincial Variation in Antipsychotic and Antidepressant Prescriptions Dispensed in the Canadian Pediatric Population.

OBJECTIVE: Although antidepressants and antipsychotics are valuable medications in the treatment of select psychiatric disorders, there is increasing focus on the balance of risks and benefits of these drugs as prescribed, particularly in the pediatric population. We examined recent national trends and interprovincial variation in dispensing of antipsychotic and antidepressant prescriptions to the Canadian pediatric population. METHOD: We conducted a population-based cross-sectional study of antidepressant and antipsychotic prescriptions dispensed by Canadian pharmacies to the pediatric population (≤18 years) between 2010 and 2013. Prescription volumes were obtained from IMS Health. Analysis was stratified by drug, year, quarter, and province and population-standardized using age-adjusted population estimates. RESULTS: From the first quarter of 2010 to the fourth quarter of 2013, dispensing of antipsychotics to the pediatric population increased 33% (from 34 to 45 prescriptions per 1000) and dispensing of antidepressants increased 63% (from 34 to 55 per 1000). We observed a 1.5-fold interprovincial difference in dispensing rates for antidepressants (range: 189 per 1000 to 275 per 1000) and a 3.0-fold difference for antipsychotics (range: 85 per 1000 to 253 per 1000) in 2013. Among antidepressants, selective serotonin reuptake inhibitors were the most dispensed (76%), with fluoxetine being the leading agent. Among antipsychotics, atypical antipsychotics were the most dispensed (97%), with risperidone being the leading agent. CONCLUSIONS: Antipsychotic and antidepressant dispensing to the Canadian pediatric population increased from 2010 to 2013, with considerable interprovincial variation. Future research is required to explore reasons for observed patterns to optimize care for the Canadian pediatric population.

Rates of ischemic stroke during warfarin treatment for atrial fibrillation.

BACKGROUND AND PURPOSE: Recent evidence suggests that there may be an increased risk of ischemic stroke immediately after warfarin initiation. We examined the rate of ischemic stroke among patients with atrial fibrillation newly started on warfarin therapy. METHODS: We conducted a population-based cohort study among Ontario residents aged ≥66 years with atrial fibrillation who received warfarin between April 1, 1997, and March 31, 2010. Each patient was followed up for ≤5 years in 30-day intervals. For each interval, we determined the rate of ischemic stroke. RESULTS: After 5 years, the cumulative incidence of ischemic stroke among new users of warfarin (n=148,446) was 4.0% (n=6006). The risk was highest during the first 30 days after initiation (6.0% per person-year; 95% confidence interval, 5.5%-6.4%) compared with the remainder of follow-up (1.6% per person-year; 95% confidence interval, 1.5%-1.6%), and increased with higher baseline CHADS2 (congestive heart failure, hypertension, age ≥75 years, diabetes, previous stroke) scores. Less frequent monitoring may have contributed. CONCLUSIONS: In a large cohort of older patients with atrial fibrillation, we observed the highest rate of ischemic stroke in the first 30 days after warfarin initiation. Although causation cannot be established given the observational nature of this study, our findings highlight the need for future research in this population.