Prevalence of potentially hazardous drug interactions amongst Australian veterans

Drug-drug interaction among elderly patients in Africa: a systematic review and meta-analysis

BACKGROUND

Elderly patients are at a heightened risk of drug-drug interactions due to their high prevalence of comorbidities, polypharmacy, and age-related physiological changes that alter drug metabolism and excretion. In Africa, these risks are compounded by unique healthcare challenges, including limited access to diagnostic tools, and high burdens of communicable diseases. The aim of this study is to estimate the prevalence of drug-drug interactions and its associated factors among elderly patients in Africa.

METHODS

Relevant research articles were identified from databases such as HINARI, Science Direct, Embase, PubMed/MEDLINE, Google Scholar, and Research Gate. Data were extracted via a Microsoft Excel spreadsheet and analyzed via STATA version 11.0. Egger regression tests and funnel plot analysis were used to check for publication bias, and the I2 statistic was used to evaluate statistical heterogeneity. Sensitivity and subgroup analyses were also conducted to identify potential causes of heterogeneity.

RESULTS

Fifteen articles were analyzed, and a total of 5651 potential drug-drug interactions (pDDIs) were identified in 1952 patients, resulting in an average of 2.89 pDDIs per patient. The overall prevalence of pDDIs among elderly patients was 52.53% (95% confidence interval (CI): 35.40, 69.66). However, the prevalence of pDDIs ranged widely from 2.8 to 90.1%. When the severity of the interactions was considered, the prevalence of pDDIs was 20.59%, 69.4%, 34.32% and 1.59% for major, moderate, minor, and contraindicated DDIs, respectively. Polypharmacy, long hospital stays, hypertension and diabetes mellitus were identified as factors associated with pDDIs among elderly patients in Africa.

CONCLUSION

DDIs are prevalent among elderly patients in Africa and are often associated with polypharmacy, prolonged hospitalizations, and the presence of chronic comorbidities, particularly hypertension and diabetes mellitus. Moderate-severity interactions were the most prevalent DDIs. The study suggests addressing this issue requires targeted interventions, including improved pharmacovigilance, enhanced prescribing practices, and integration of DDI risk assessment into routine clinical care. The study also suggests that the database itself could have modified the DDI prevalence rate. As a result, a single DDI identification database needs to be authorized; otherwise, clinical knowledge should be taken in to account when interpreting the information obtained.

The European Drug-Drug Interaction (EuroDDI) Study Protocol: A Cross-Country Comparison of Drug-Drug Interaction Prevalence in the Older Community-Dwelling Population

BACKGROUND

Drug-drug interactions (DDIs), highly prevalent amongst the elderly, can lead to avoidable medication-related harm. Cardiovascular and central nervous system (CNS) drugs are commonly implicated. To date, there is no consensus on how to measure DDIs, making comparisons across countries challenging.

OBJECTIVE

To (i) establish a common data model (CDM) to measure DDI prevalence in the older (aged ≥ 70 years) community-dwelling population of three European countries and (ii) compare and describe cardiovascular and CNS DDI prevalence rates across these countries.

METHODS

This cross-country study will apply a harmonised method of DDI identification and analysis using the WHO ATC classification system and national pharmacy claims data from three European countries (Ireland, Italy, Spain). Patients aged ≥ 70 years dispensed ≥ 2 medications during 2016 will be identified from each country's national database. 'Severe' cardiovascular and CNS DDIs (i.e., may result in a life-threatening event/permanent detrimental effect) will be identified using the British National Formulary and Stockley's Drug Interactions. Two separate lists of 'severe' DDIs, per medications reimbursed, will be applied to each database: (i) DDIs relevant to each individual country and (ii) DDIs relevant to all three countries. DDIs will be defined as co-dispensed (same day) and concomitantly (±7 days) dispensed.

RESULTS

Descriptive statistics, including DDI prevalence and 95% confidence intervals, will be reported for each country. Prevalence will be pooled and compared across countries using random effects models and meta-regression, where feasible.

CONCLUSION

The EuroDDI study will develop a harmonised method to measure and compare DDI prevalence across health-related databases in Europe.

Prevalence of potential drug‒drug interactions and associated factors among elderly patients in Ethiopia: a systematic review and meta-analysis

BACKGROUND

The occurrence of potential drug‒drug interactions (pDDIs) is a serious global issue that affects all age groups, with the elderly population being the most vulnerable. This is due to their relatively high rates of comorbidity and polypharmacy, as well as physiological changes that can increase the potential for DDIs and the likelihood of adverse drug reactions. The aim of this study was to estimate the prevalence of pDDIs and associated factors among elderly patients in Ethiopia.

METHODS

A comprehensive literature search using the preferred reporting items for systematic review and meta-analysis statement was conducted on HINARI, Science Direct, Embase, PubMed/MEDLINE, Google Scholar, and Research Gate. Data were extracted via a Microsoft Excel spreadsheet and analyzed via STATA version 11.0. Egger regression tests and funnel plot analysis were used to check publication bias, and the I2 statistic was used to evaluate statistical heterogeneity. Sensitivity and subgroup analyses were also conducted to identify potential causes of heterogeneity.

RESULTS

Seven articles were analyzed, and a total of 1897 pDDIs were identified in 970 patients, resulting in an average of 1.97 DDIs per patient. The number of DDIs per patient ranged from 0.18 to 5.86. The overall prevalence of pDDIs among elderly patients was 50.69% (95% CI 18.77-82.63%). However, the prevalence of pDDIs ranged widely from 2.80 to 90.1%. When the severity of the interactions was considered, the prevalence of potential DDIs was found to be 28.74%, 70.68%, and 34.20% for major, moderate, and minor pDDIs, respectively. Polypharmacy and long hospital stays were identified as factors associated with pDDIs among elderly patients in Ethiopia.

CONCLUSIONS

The overall prevalence of pDDIs among elderly patients was high, with a wide range of prevalence rates. Moderate-severity interactions were the most prevalent. Polypharmacy and long hospital stays were identified as factors associated with pDDIs among elderly patients. The study suggests that DDIs identification database itself could have modified the DDIs prevalence rate. As a result, a single DDIs identification database needs to be authorized; otherwise, clinical knowledge should be taken into account when interpreting the information obtained.

Prevalence of Drug-Drug Interactions in Older Community-Dwelling Individuals: A Systematic Review and Meta-analysis

BACKGROUND

Drug-drug interactions (DDIs) can lead to medication-related harm, and the older population is at greatest risk. We conducted a systematic review and meta-analysis to estimate DDI prevalence and identify common DDIs in older community-dwelling adults.

METHODS

PubMed and EMBASE were searched for observational studies published between 01/01/2010 and 10/05/2021 reporting DDI prevalence in community-dwelling individuals aged ≥ 65 years. Nursing home and inpatient hospital studies were excluded. Study quality was assessed using the Joanna Briggs Institute critical appraisal tool. Meta-analysis was performed using a random-effects model with logit transformation. Heterogeneity was evaluated using Cochran's Q and I². DDI prevalence and 95% confidence intervals (CIs) are presented. All analyses were performed in R (version 4.1.2).

RESULTS

There were 5144 unique articles identified. Thirty-three studies involving 17,011,291 community-dwelling individuals aged ≥ 65 years met inclusion criteria. Thirty-one studies reported DDI prevalence at the study-participant level, estimates ranged from 0.8% to 90.6%. The pooled DDI prevalence was 28.8% (95% CI 19.3-40.7), with significant heterogeneity (p < 0.10; I² = 100%; tau² = 2.13) largely explained by the different DDI identification methods. Therefore, 26 studies were qualitatively synthesised and seven studies were eligible for separate meta-analyses. In a meta-analysis of three studies (N = 1122) using Micromedex^®, pooled DDI prevalence was 57.8% (95% CI 52.2-63.2; I² = 69.6%, p < 0.01). In a meta-analysis of two studies (N = 809,113) using Lexi-Interact^®, pooled DDI prevalence was 30.3% (95% CI 30.2-30.4; I² = 6.8%). In a meta-analysis of two studies (N = 947) using the 2015 American Geriatrics Society Beers criteria^®, pooled DDI prevalence was 16.6% (95% CI 5.6-40.2; I² = 97.5%, p < 0.01). Common DDIs frequently involved cardiovascular drugs, including ACE inhibitor-potassium-sparing diuretic; amiodarone-digoxin; and amiodarone-warfarin.

CONCLUSIONS

DDIs are prevalent among older community-dwelling individuals; however, the methodology used to estimate these events varies considerably. A standardised methodology is needed to allow meaningful measurement and comparison of DDI prevalence.

Potentially Hazardous Drug-Drug Interactions Associated With Oral Antineoplastic Agents Prescribed in Chinese Tertiary Care Teaching Hospital Settings: A Multicenter Cross-Sectional Study

Background: Oral administration increases the risk of interactions, because most oral antineoplastic agents (OAAs) are taken on a daily basis. Interactions can increase exposure to antitumoral agents or cause treatment failure. Potential drug-drug interactions (DDIs) are commonly observed in patients with cancer, while the extent to which OAAs related hazardous DDIs remains unclear. Methods: We studied the contraindication patterns between oral antineoplastic agents and other medications among cancer patients in two tertiary care teaching hospitals in China. A total of 20 clinically significant hazardous DDI pairs that involved 30 OAAs were identified based on the predetermined criteria. Patient medications were checked for DDIs by using the US Food and Drug Administration approved labeling. Descriptive statistics and uni- and multivariate logistic regression analyses were carried out. Results: In this study, 13,917 patients were included and a total of 297 DDIs were identified. The results revealed that proton pump inhibitors (PPIs), dexamethasone and fluoroquinolones were the most often involved hazardous DDIs with OAAs. The most prevalent contraindication is the simultaneous use of certain molecular targeted agents and PPIs. In the result of the multivariate analysis, younger age (0-20 group), increasing number of drugs and patient treated with targeted therapy had a higher risk for DDIs. Conclusion: The prevalence of OAAs related hazardous DDIs appears to be low in the cancer patients. However, physicians and clinical pharmacologists should be aware of the potential hazardous DDIs when prescribing OAAs, especially certain pH-dependent molecular targeted agents and potential QTc prolonging drugs.

Prevalence and Factors Associated with Potential Drug-Drug Interactions in Older Community-Dwelling Adults: A Prospective Cohort Study

BACKGROUND

Older patients are at increased risk of drug-drug interactions (DDIs) due to polypharmacy. Cardiovascular and central nervous system (CNS) drugs are commonly implicated in serious DDIs.

OBJECTIVES

This study aimed to determine the prevalence and factors associated with potential 'severe' cardiovascular and CNS DDIs among older (≥ 70 years) community-dwellers.

METHODS

This was a prospective cohort study using linked data from a national pharmacy claims database and waves 1 and 2 of The Irish LongituDinal study on Ageing (TILDA). 'Severe' cardiovascular and CNS DDIs were identified using the British National Formulary 77 and Stockley's Drug Interactions. The prevalence of 'severe' DDIs (any DDI vs. none) was calculated. Logistic regression was used to examine the association between sociodemographic, functional ability, and medication-related factors and the risk of DDI exposure between waves 1 and 2.

RESULTS

A total of 1466 patients were included [mean age (standard deviation) = 78 (5.5) years; female n = 795, 54.2%]. In total, 332 community-dwellers aged ≥ 70 years [22.65%, 95% confidence interval (CI) 20.58-24.86] were potentially exposed to at least one 'severe' cardiovascular or CNS DDI, with more than half (54.82%) of this cohort dispensed the same DDI for a prolonged time (≥ 3 consecutive claims). Aspirin-warfarin was the most frequently dispensed (co-prescribed) DDI (n = 34, 10.24%, 95% CI 7.39-14.00), followed by atorvastatin-clarithromycin (n = 19, 5.72%, 95% CI 3.64-8.81). Polypharmacy [≥ 10 vs. < 5 drugs, odds ratio (OR) 13.40, 95% CI 8.22-21.85] and depression (depressed vs. not, OR 2.12, 95% CI 1.34-3.34) were significantly associated with these DDIs, after multivariable adjustment.

CONCLUSION

'Severe' cardiovascular and CNS DDIs are prevalent in older community-dwellers in Ireland, and those with polypharmacy and depression are at a significantly increased risk.

Investigating Potential Drug-Drug Interactions from Greek e-Prescription Data

BACKGROUND

The prevalence of potential drug-drug interactions (pDDIs) is indicative of the prevalence of actual drug-drug interactions and prescription quality. However, they are significantly understudied in Greece.

OBJECTIVE

To determine the prevalence of pDDIs among outpatients and identify factors associated with their occurrence.

METHODS

Anonymous e-prescription data between 2012 and 2017 were obtained from community pharmacies in Thessaloniki, Greece. Patients taking more than one medication for at least three months were included. pDDIs were identified and categorized depending on their clinical significance using Drug Interactions Checker. Crude and adjusted odds ratios (ORs) with accompanying 95% confidence intervals (CIs) of risk factors of pDDIs occurrence were identified using multivariable logistic regression.

RESULTS

During the study period, 6,000 anonymous e-prescriptions (1,000 per year) satisfying the inclusion criteria, were collected. The overall prevalence of major pDDIs was 17.4% (63.0% for moderate pDDIs). The most common major pDDIs were between amlodipine and simvastatin (22.8% of major interactions) followed by clopidogrel and omeprazole (6.4% of major interactions). Polypharmacy (≥5 concomitantly received medications) was associated with an increased risk of major pDDIs (adjusted OR, 5.72; 95% CI, 4.87-6.72); no associations were observed regarding age, sex and number of prescribing physicians.

CONCLUSION

The prevalence of pDDIs in this study was higher than previously reported in other European countries, with polypharmacy being a potential risk factor. Those results argue for a need for improvement in the area of prescribing in Greece.

A Prospective Analysis of Potential and Observed Drug-Drug Interactions, Adverse Events and its Associated Risk Factors in Hospitalized Cardiology Patients in Benin

BACKGROUND & AIMS

The objective is to ascertain the pattern of potential drug-drug interactions (pDDIs) and record any observed DDIs and adverse events (AEs) in hospitalized Beninese cardiology patients from Sub-Saharan Africa and analyze all risk factors associated with DDIs and AEs.

METHODS

It was a prospective study in which data including AEs were assessed from medical files and interview of patients and their relatives. Patients who were treated with more than two drugs and who remained in the hospital for at least 48 hours were included. A computerized database system Pharma IAM- VIDAL version 2011 was used to identify the pattern for potential DDIs.

RESULTS

156 patients were included in this study. The prevalence of potential DDIs was estimated at 93 % (145/156). Forty (5.1%) among 804 potential DDIs identified were observed clinically. The observed DDIs were attributable to low blood pressure (27.5%), hyponatremia (22.5%), hemorrhage (20.0%), hyperkalemia (17.5%) and nephrotoxicity (7.5%). The combination of spironolactone and furosemide resulted in hyponatremia while the combination of enoxaparin and potassium resulted in hyperkalemia. ACE inhibitor (or ARAII) in combination with furosemide resulted in the nephrotoxicity cases observed. Enoxaparin, Acetyl salicylic acid, Acenocoumarol and Clopidogrel were decreasingly involved in the pairs of drugs responsible for observed hemorrhages. 29 patients out of 156 (18.6%) had at least one AE. AEs were mainly (34.2%) of metabolic type. Severe AEs, which represented 18.4% was mostly from nephrotoxicity and metabolic disorders. More than 14 active substances multiplied the risk factor for AEs occurrence by 42, while more than 14 days hospitalization increased this risk by 42.

CONCLUSION

This study highlights the need to optimize treatments by strictly regulating blood pressure, serum sodium and potassium levels, coagulation parameters and looking for clinical signs of hemorrhage. Physician should be aware of certain drug associations that may carry a risk of severe adverse events.

Countrywide prevalence of critical drug interactions in Hungarian outpatients: a retrospective analysis of pharmacy dispensing data

Background

Drug-drug interactions (DDIs) present a significant source of adverse drug reactions. Despite being one of the commonly cited risks to patient safety, prevention of DDIs still poses a challenge to healthcare systems. The prevalence of DDIs can be used as a quality indicator for the safety of prescribing. With the analysis of drug utilization databases, real-world data on critical DDIs can be obtained. The aim of this study was to establish a list of critical DDIs and estimate their prevalence in the Hungarian outpatient population.

Methods

Since there is no conclusive and generally accepted repository of high-risk DDIs, a systematic search of the literature for consensus-based lists was performed. Based on these results and their analysis with 5 interaction compendia, we propose a simple methodology to identify critical combinations. Present study focused on DDIs which are (1) of high clinical importance thus being most likely to cause significant harm if not detected, (2) well-supported by available evidence and (3) affect drugs which are routinely dispensed in the community pharmacy setting. A retrospective analysis of prescriptions filled between 2013 and 2016 was performed. The source of drug utilization data was the IQVIA’s national prescription fill database. The number of interacting drug pairs dispensed at the same time to the same patient was established.

Results

After excluding drugs with low dispensing rates, the analysis covered 39 DDIs. The distribution of risk categories of the analysed DDIs was inconsistent among different drug interaction compendia. The total number of prescriptions filled varied between 173924449 and 176368468 per year. The prevalence of the selected potential DDIs ranged from 0.00 to 355.89 per 100000 prescriptions per year. There was significant variation between how the number of cases had changed for each DDI throughout the study period, no general tendency could have been described.

Conclusions

There were 1.8 million cases of co-dispensing each year, where prescribers’ and community pharmacists’ role in recognizing and managing potentially serious interactions was or would have been critical. The method presented to identify high-risk DDIs can serve as a starting point for the much-needed improvement of routine interaction screening.

Electronic supplementary material

The online version of this article (10.1186/s40360-019-0311-0) contains supplementary material, which is available to authorized users.

Potential and clinical relevant drug-drug interactions among elderly from nursing homes: a multicentre study in Murcia, Spain

This study purposes to determine the prevalence of potential and clinical relevant Drug-Drug-Interactions (pDDIs) in institutionalized older adults and to identify the pertinent factors associated. We conduct an observational, multicenter and cross-sectional study during the last quarter of 2010. We selected a sample of 275 subjects (aged ≥ 65 years) from 10 nursing homes of Murcia (Spain) by a two-stage complex sampling. pDDIs were identified using the College of Pharmacists Database. We only considered pDDIs of clinical relevance, and thereafter the relevant factors were identified through uni-level and multi-level regression analyses. A total of 210 pDDIs were identified, 120 of which were considered clinically relevant (57.1%), affecting a total of 70 elderly (25.8%). Eight pharmacological groups made up 70.2% of the clinically relevant pDDIs. More clinically relevant DDIs were found in people suffering several pathologies (OR = 2.3; 95%CI = 1.4-4.5), and also in people who take ten or more drugs daily (OR = 9.6; 95%CI = 4.8-19.1), and people who take anti-inflammatory drugs (OR = 3.9; 95%CI = 1.4-10.4). This study reveals that clinically relevant pDDIs are very common in institutionalized elderly people, and that caregivers should aim at improving their practice in order to reduce the prevalence of this phenomenon.

Assessment of Drug-Drug Interaction in Ayder Comprehensive Specialized Hospital, Mekelle, Northern Ethiopia: A Retrospective Study

Introduction

Adverse drug interaction is a major cause of morbidity and mortality. Its occurrence is influenced by a multitude of factors. The influences of drug-drug interactions (DDIs) can be minimized through creation of awareness to health care professionals.

Objective

The objective of this study was to assess DDIs in Ayder Comprehensive Specialized Hospital (ACSH).

Methodology

A retrospective study design was employed on patient prescriptions available in the outpatient department of pharmacy and filled from September 2016 to February 2017 in ACSH.

Result

From the 600 prescription records assessed, the average number of drugs on single prescription was 2.73. Regarding the interaction observed 34 (9.63%) prescriptions with major drug-drug interaction, 210 (59.5%) moderate, 87 (24.65%) minor, and 22 (6.22%) unknown were identified. Age category showed significant association to affect the occurrence of DDIs and polypharmacy had statistically significant association with DDIs in bivariate analysis which was lost in adjusted OR.

Conclusion

From the current study it can be concluded that nearly half of the prescription ordered in ACSH contained DDIs and from the prescription with interacting medications majority of them had moderate DDIs.

Prevalence and predictors of potential drug-drug interactions in patients of internal medicine wards of a tertiary care hospital in India

Background

Drug-drug interactions are a major source of adverse drug events (ADEs). Polypharmacy, age and the number of comorbid conditions are important predictors of adverse drug interactions. ADEs account for up to 5% of hospital admissions per year and an increase in the length of hospital stay.

Objective

To find the prevalence and predictors of potential drug-drug interactions (pDDIs) in patients admitted to the wards of an internal medicine department of a tertiary care hospital.

Method

Patients admitted to internal medicine wards with prescriptions having more than one drug were selected. Demographic details including age, gender, number of comorbid conditions, number of drugs prescribed and the disease for which the patient was admitted were recorded in a case record form. Interactions were checked using Micromedex DrugReax software.

Results

A total of 939 patients were recruited for this study based on inclusion criteria. 433 prescriptions (46%) had one or more pDDIs, with a range of 1-13 drug interactions per prescription. A total of 1395 drug interactions were found, with 866 moderate drug interactions (62%), 435 major interactions (31.1%) and 89 minor interactions (6.3%). During the study period only three contraindicated drug combinations (0.2%) were recorded. A significant association (p<0.01) was found between the number of pDDIs and predictors, age and number of drugs.

Conclusion

A total of 433 prescriptions (46%) had one or more pDDIs. Older patients and those prescribed >6 drugs are at major risk for occurrence of pDDIs. Moderate severity interactions were the highest number followed by major severity interactions.

Prevalence of Drug Combinations Increasing Bleeding Risk Among Warfarin Users With and Without Alzheimer's Disease

PURPOSE

The aim of this study was to analyse the prevalence and predictors of drug combinations increasing bleeding risk among warfarin users with and without Alzheimer's disease (AD).

METHODS

This retrospective observational study utilised data from the Finnish MEDALZ-2005 cohort. The MEDALZ-2005 study included all community-dwelling persons with a clinically verified diagnosis of AD at the end of 2005, and one comparison person without AD for each case. Data on drug use was collected from the Prescription Register. We included persons who were warfarin users during the study period 2006-2009. Drug combinations increasing bleeding risk with warfarin included selective serotonin reuptake inhibitors (SSRIs), non-steroidal anti-inflammatory agents (NSAIDs), other antithrombotic drugs and tramadol. Factors associated with combination use were investigated with logistic regression.

RESULTS

During the follow-up, 3385 persons with AD and 4830 persons without AD used warfarin. Drug combinations increasing bleeding risk were more common in warfarin users with AD than without AD [35.9 and 30.5%, respectively (p < 0.0001)]. The most common combination was SSRIs and warfarin, which was more common among persons with AD (23.8%) than among persons without AD (10.9%). NSAIDs and warfarin combination was more common among persons without AD. Combination use was associated with AD, female gender, younger age, diabetes mellitus, rheumatoid arthritis and asthma/chronic obstructive pulmonary disease (COPD).

CONCLUSIONS

Use of drug combinations increasing bleeding risk was more common among warfarin users with AD. Special attention should be paid to minimise the duration of concomitant use and to find safer alternatives without increased bleeding risk.

Prevalence of Potential and Clinically Relevant Statin-Drug Interactions in Frail and Robust Older Inpatients

BACKGROUND

A significant proportion of older people are prescribed statins and are also exposed to polypharmacy, placing them at increased risk of statin-drug interactions.

OBJECTIVE

To describe the prevalence rates of potential and clinically relevant statin-drug interactions in older inpatients according to frailty status.

METHODS

A cross-sectional study of patients aged ≥65 years who were prescribed a statin and were admitted to a teaching hospital between 30 July and 10 October 2014 in Sydney, Australia, was conducted. Data on socio-demographics, comorbidities and medications were collected using a standardized questionnaire. Potential statin-drug interactions were defined if listed in the Australian Medicines Handbook and three international drug information sources: the British National Formulary, Drug Interaction Facts and Drug-Reax(®). Clinically relevant statin-drug interactions were defined as interactions with the highest severity rating in at least two of the three international drug information sources. Frailty was assessed using the Reported Edmonton Frail Scale.

RESULTS

A total of 180 participants were recruited (median age 78 years, interquartile range 14), 35.0% frail and 65.0% robust. Potential statin-drug interactions were identified in 10% of participants, 12.7% of frail participants and 8.5% of robust participants. Clinically relevant statin-drug interactions were identified in 7.8% of participants, 9.5% of frail participants and 6.8% of robust participants. Depending on the drug information source used, the prevalence rates of potential and clinically relevant statin-drug interactions ranged between 14.4 and 35.6% and between 14.4 and 20.6%, respectively.

CONCLUSION

In our study of frail and robust older inpatients taking statins, the overall prevalence of potential statin-drug interactions was low and varied significantly according to the drug information source used.

Prevalence of statin-drug interactions in older people: a systematic review

PURPOSE

Statins are among the most frequently prescribed medications internationally. Older people are commonly prescribed multiple medications and are at an increased risk of drug-drug interactions, including statin-drug interactions. The aim of this study was to conduct a systematic review of current evidence on the prevalence of statin-drug interactions in older people.

METHODS

A systematic search of observational studies in Embase, Medline, and PubMed was conducted. Articles were included if they were published in English during the period July 2000-July 2014 and reported on the prevalence of statin-drug interactions in people over 65 years of age. Two reviewers independently assessed the articles for eligibility and extracted the data.

RESULTS

The search returned 1556 eligible articles. A total of 19 articles met the inclusion criteria. In studies (n = 7) that focused on statin users only, the prevalence of potential statin-drug interactions assessed using different measures ranged from 0.19 to 33.0 %. In studies that examined drug interactions across a population of both statin users and non-users (n = 12), the prevalence of potential statin-drug interactions ranged from 0.1 to 7.1 % (n = 8), and the prevalence of clinically relevant statin-drug interactions ranged from 1.5 to 4 % (n = 4).

CONCLUSIONS

Current published evidence suggests substantial variations in the prevalence of statin-drug interactions and their clinical relevance. Further studies are necessary to provide a better understanding of the prevalence of clinically significant statin-drug interactions, the medications most frequently contributing to statin-drug interactions, and impact on relevant clinical outcomes in older people.

[Results of an intervention to reduce potentially inappropriate prescriptions of beta blockers and calcium channel blockers]

OBJECTIVE

To determine the frequency of simultaneous prescription of β-blockers and calcium channel blockers, notify the cardiovascular risk of these patients to the health care professionals in charge of them, and achieve a reduction in the number of those who use them.

METHODS

Quasi-experimental, prospective study by developing an intervention on medical prescriptions of patients older than 65 years treated between January 1 and July 30, 2014, affiliated to the Health System in 101 cities in Colombia. A total of 43,180 patients received a β-blocker each month, and 14,560 receiving a calcium channel blocker were identified. Educational interventions were performed and an evaluation was made, using sociodemographic and pharmacological variables, on the number of patients that stopped taking any of the two drugs in the following three months.

RESULTS

A total of 535 patients, with a mean age 75.8±6.7 years received concomitant β-blockers plus calcium channel blockers. Modification of therapy was achieved in 235 patients (43.9% of users) after 66 educational interventions. In 209 cases (88.9%) one of the two drugs was suspended, and 11.1% changed to other antihypertensive drugs. The variable of being more than 85 years old (OR: 1.93; 95% CI: 1.07-3.50), and receiving concomitant medication with inhibitors of the renin-angiotensin system (OR: 2.16; 95% CI: 1.28-3.65) were associated with increased risk of their doctor changing or stopping the prescription.

CONCLUSIONS

An improved adherence to recommendations for appropriate use of β-blockers and calcium channel blockers by health service providers was achieved. Intervention programs that reduce potentially inappropriate prescriptions for patients treated for cardiovascular disease should be used more frequently.

Assessment of drug-drug interactions in hypertensive patients at a superspeciality hospital

Objective:

The objective of the study was to assess the incidence and pattern of drug-drug interactions (DDIs) in hypertensive patients by using Micromedex and Medscape databases.

Materials and Methods:

A prospective observational study was carried out in a superspeciality hospital setting in South India for period of 9 months. Hypertensive patients who admitted into the hospital with the age more than 18 years, received more than 3 drugs per prescription and length of hospital stay for more than 24 hours were included in the study. An appropriate data was collected and assessed for DDIs with the help of Micromedex and Medscape databases.

Results:

A total of 227 patients were enrolled during the study period. Among the 227 patients, 48 of them developed 53 clinically significant DDIs. Out of 48 patients, most of them were in the age-group of 50–60 years [18 (37.49%)]. The percentage of DDIs were higher in males [30 (62.5%)] compared to females [18 (37.5%)]. The most common drugs responsible for DDIs in the present study were Insulin [18 (33.96%)] followed by Metoprolol [10 (18.86%)], Torsemide [8 (15.09%)], and Hydrochlorothiazide [8 (15.09%)]. The most commonly interacting pairs were Ciprofloxacin-Insulin [6 (11.32%)], followed by Metoprolol-Insulin [4 (7.54%)] and Atenolol-Insulin [4 (7.54%)]. The most common consequences of interacting pairs were reduced serum potassium levels and hyperglycemia.

Conclusion:

The overall incidence rate of DDIs was found to be 21.14% and the increasing number of co-morbidities (P ≤ 0.003) and polypharmacy (P ≤ 0.002) were the risk factor for the development of significant number of DDIs.

Impact of specific Beers Criteria medications on associations between drug exposure and unplanned hospitalisation in elderly patients taking high-risk drugs: a case-time-control study in Western Australia

BACKGROUND

Certain broad medication classes have previously been associated with high rates of hospitalisation due to related adverse events in elderly Western Australians, based on clinical coding recorded on inpatient summaries. Similarly, some medications from the Beers Criteria, considered potentially inappropriate in older people, have been linked with an increased risk of unplanned hospitalisation in this population.

OBJECTIVE

Our objective was to determine whether risk estimates of drug-related hospitalisations are altered in elderly patients taking 'high-risk drugs' (HRDs) when specific Beers potentially inappropriate medications (PIMS) are taken into consideration.

METHODS

Using the pharmaceutical claims of 251,305 Western Australians aged ≥65 years (1993-2005) linked with other health data, we applied a case-time-control design to estimate odds ratios (ORs) for unplanned hospitalisations associated with anticoagulants, antirheumatics, opioids, corticosteroids and four major cardiovascular drug groups, from which attributable fractions (AFs), number and proportion of drug-related admissions were derived. The analysis was repeated, taking into account exposure to eight specific PIMs, and results were compared.

RESULTS

A total of 1,899,699 index hospitalisations were involved. Of index subjects, 12-57 % were exposed to each HRD at the time of admission, although the proportions taking both an HRD and one of the selected PIMs were much lower (generally ≤2 %, but as high as 8 % for combinations involving temazepam and for most PIMs combined with hypertension drugs). Included PIMs (indomethacin, naproxen, temazepam, oxazepam, diazepam, digoxin, amiodarone and ferrous sulphate) all tended to increase ORs, AFs and drug-related hospitalisation estimates in HRD combinations, although this was less evident for opioids and corticosteroids. Indomethacin had the greatest overall impact on HRD ORs/AFs. Indomethacin (OR 1.40; 95 % confidence interval [CI] 1.27-1.54) and naproxen (OR 1.22; 1.14-1.31) were associated with higher risks of unplanned hospitalisation than other antirheumatics (overall OR 1.09; 1.06-1.12). Similarly, among cardiac rhythm regulators, amiodarone (OR 1.22; 1.13-1.32) was riskier than digoxin (OR 1.08; 1.04-1.13). For comparisons of drug-related hospitalisation estimates, temazepam yielded the greatest absolute increases, especially with hypertension drugs.

CONCLUSIONS

Indomethacin and temazepam should be prescribed cautiously in elderly patients, especially in drug combinations. Furthermore, it appears other antirheumatics should be favoured over indomethacin/naproxen and, in situations where both drugs may be appropriate, digoxin over amiodarone. Our methodology may help assess the safety of new medications in drug combinations in preliminary pharmacovigilance investigations.

Australian pharmacies prevent potential adverse reactions in patients taking warfarin requesting over-the-counter analgesia

Objective

The objective of this article was to assess if Australian pharmacy staff prevent potential adverse reactions in warfarin patients requesting over-the-counter (OTC) analgesia.

Methods

Mystery shoppers entered 170 pharmacies across Australia to request OTC analgesia for a hypothetical patient with a wrist injury who currently takes warfarin following a heart valve replacement. The request was made to the first pharmacist or non-pharmacist staff member to approach the mystery shopper. The interaction was audio-taped and assessed by a pharmacist. The OTC analgesic recommended was assessed for the potential to cause an adverse bleeding event. The quality of advice given with the OTC analgesic was assessed against determined criteria. Results were compared with scenarios of similar request type where the hypothetical patient was not taking warfarin.

Key findings

Mystery shoppers enquiring about taking OTC analgesics concomitantly with warfarin had access to the pharmacist in 97.0% of cases. All 170 pharmacies recommended OTC analgesics that were less likely to cause adverse events when taken with warfarin. The advice given and the communication between pharmacy staff and mystery shoppers were of high quality.

Conclusion

Australian pharmacies support the quality use of medicines by patients taking warfarin by providing expeditious access to the pharmacist, appropriate recommendations of OTC analgesics, high standards of quality of advice and they communicate in a way to ensure ease of understanding by the consumer. The protocols used by pharmacy staff help prevent potentially serious adverse drug events.

Implementation of a shared medication list: physicians' views on availability, accuracy and confidentiality

BACKGROUND

Physicians, patients and others involved need to have accurate information on patients' current drug prescriptions available, and have that information protected from unauthorized access. During the past decade, many counties in Sweden have implemented regionally shared medication lists within health care.

OBJECTIVE

The aim of this study was to describe physicians' views on changes in accuracy, availability and confidentiality in the transition from local medication lists to a regionally shared medication list.

SETTING

Health care units in four different counties of Sweden after the transition from local medication lists to a regionally shared medication list. The shared medication list was an integrated part of the electronic health record system in the respective counties, but the system and implementation process varied.

METHODS

Physicians (n = 7) with experience of transition from local medication lists to a regionally shared medication list were interviewed in a semi-structured manner.

MAIN OUTCOME MEASURE

Physicians' views on changes in information risks, focusing on accuracy, availability and confidentiality. Results The transition from local medication lists to a shared medication list increased the availability of information: from being time consuming or not possible to access from other care givers to most information being available in one place. A regionally shared medication list was perceived as having the potential to provide a greater accuracy of information, but not always: the shared medication list was perceived as more complete but with more non-current drugs. On the other hand, a shared medication list implied an increased risk of violating patient privacy, placing greater demands on IT security in order to protect the confidentiality of information.

CONCLUSION

Physicians perceived a regionally shared medication list to increase the availability of information about current prescriptions and potentially the accuracy but may decrease the confidentiality of information. To implement a shared medication list, we recommend providing clear description of responsibilities and routines for normal activities as well as back-up routines, consider IT-security and data protection early, involve patients to improve the accuracy of the list as well as to monitor and evaluate the implementation.

Potential drug related problems detected by electronic expert support system in patients with multi-dose drug dispensing

Background Drug related problems (DRPs) are frequent and cause suffering for patients and substantial costs for society. Multi-dose drug dispensing (MDDD) is a service by which patients receive their medication packed in bags with one unit for each dose occasion. The clinical decision support system (CDSS) electronic expert support (EES) analyses patients' prescriptions in the Swedish national e-prescription repository and provides alerts if potential DRPs are detected, i.e. drug-drug interactions, duplicate therapy, drug-disease contraindications, high dose, gender warnings, geriatric, and paediatric alerts. Objective To analyse potential DRPs in patients with MDDD, detected by means of EES. Setting A register study of all electronically stored prescriptions for patients with MDDD in Sweden (n = 180,059) March 5-June 5, 2013. Method Drug use and potential DRPs detected in the study population during the 3 month study period by EES were analysed. The potential DRPs were analysed in relation to patients' age, gender, number of drugs, and type of medication. Main outcome measure Prevalence of potential DRPs measured as EES alerts. Results The study population was on average 75.8 years of age (± 17.5, range 1-110) and had 10.0 different medications (± 4.7, range 1-53). EES alerted for potential DRPs in 76 % of the population with a mean of 2.2 alerts per patient (± 2.4, range 0-27). The older patients received a lower number of alerts compared to younger patients despite having a higher number of drugs. The most frequent alert categories were drug-drug interactions (37 % of all alerts), duplicate therapy (30 %), and geriatric warnings for high dose or inappropriate drugs (23 %). Psycholeptics, psychoanaleptics, antithrombotic agents, anti-epileptics, renin-angiotensin system agents, and analgesics represented 71 % of all drugs involved in alerts. Conclusions EES detected potential DRPs in the majority of patients with MDDD. The number of potential DRPs was associated with the number of drugs, age, gender, and type of medication. A CDSS such as EES might be a useful tool for physicians and pharmacists to assist in the important task of monitoring patients with MDDD for potential DRPs.

The prevalence of co-prescription of clinically relevant CYP enzyme inhibitor and substrate drugs in community-dwelling elderly Australians

WHAT IS KNOWN AND OBJECTIVE

The elderly are at increased risk of adverse effects resulting from drug interactions due to decreased drug clearance and polypharmacy. This study examines the prevalence of the co-administration of clinically relevant cytochrome P450 (CYP) enzyme inhibitors with drugs that are substrates for these enzymes, in the community-dwelling elderly in Australia.

METHODS

Participants aged 75 years or older (n = 1045) were recruited via their general practitioners at four Australian sites (Newcastle, Sydney, Melbourne and Adelaide). A research nurse visited the home of each patient to compile a list of all prescription medications (including doses) currently used by the patient, and to complete assessments for depression, quality of life and cognitive status. The medication data were searched for the co-prescription of clinically relevant CYP inhibitor and corresponding substrate drugs.

RESULTS AND DISCUSSION

Potentially inappropriate CYP inhibitor-substrate combinations were found in 6·2% (65/1045) of patients. These patients were on significantly more medications (6·1 ± 3·0 vs. 3·9 ± 2·5; P = 0·001) and had a significantly lower physical quality of life (P = 0·047) than those who were not on any CYP inhibitor-substrate combinations. The most commonly prescribed inhibitor-substrate combinations involved the CYP 3A4 inhibitors, diltiazem and verapamil, with the substrates simvastatin or atorvastatin. Only 1 of 41 patients on a CYP3A4 inhibitor and a statin was prescribed a non-CYP 3A4 metabolized statin. Metoprolol was another substrate commonly co-prescribed with a CYP2D6 inhibitor. In many cases, the risks and benefits of potential interactions may have been considered by the GP as the prescribed doses of both the inhibitor and substrate were relatively low. There were, however, some notable exceptions, also involving the substrates simvastatin, atorvastatin and metoprolol. There were no GP factors that were associated with co-prescription of CYP inhibitors and substrates.

WHAT IS NEW AND CONCLUSION

There is not a particular GP demographic that should be targeted for education regarding CYP interactions, but a focus on particular medications such as the statins may reduce the potential for clinically significant drug-drug interactions. As CYP drug-drug interactions are more common in patients on higher number of medications, particular vigilance is required at the time of prescribing and dispensing medications for elderly patients with multiple conditions.

Drug-drug interactions and their predictors: Results from Indian elderly inpatients

Background

In view of the multiple co-morbidities, the elderly patients receiving drugs are prone to suffer with drug interactions since they receive a greater number of drugs.

Objective

The study was undertaken to determine the prevalence of drug interactions, as well as their predictors.

Methods

The prescriptions of a total of 1510 inpatients were collected prospectively for 1.5 years from inpatients wards of public tertiary care teaching hospital. All the prescriptions were checked for drug interactions using the Micromedex® Drug-Reax database-2010 and Stockley’s Drug Interactions. Regression analyses sought to determine predictors for the drug interaction.

Results

The patients, with the average age of 67.2 ±0.2 years, were prescribed an average of 9.15 ±0.03 medications. It was found that out of 1510 prescriptions of inpatients, 126 (8.3%) prescriptions had one or more than one drug interaction. All the identified interactions were severe in nature. The top most interacting drugs were acetylsalicylic acid and anticoagulant (n=59). The second top most interacting drug combination was clopidogrel and proton pump inhibitors (n=51). The most commonly involved drugs in interactions were C (cardiovascular system) and A (alimentary tract and metabolism). Using multivariate binary logistic regression, multiple drugs (Odds Ratio=4.5; 95% Confidence Interval: - 2.38 -9.47) and multiple diagnoses (Odds Ratio=2.6; 95%CI: -1.40 -5.57) were found to be significant predictors for drug interaction.

Conclusions

The results of this study substantiate the occurrence of severe drug interactions among Indian elderly inpatients. In order to provide safer pharmaceutical care, the active involvement of clinical pharmacists is a potential option.

Elevation of blood ciclosporin levels by voriconazole leading to leukoencephalopathy

We report that one 18-year-old female patient with no epilepsia history developed severe epileptiform seizures while she was receiving “ciclosporin A (CsA)-mycophenolate-methylprednisolone” antirejection therapy after combining one week's voriconazole administration following allogeneic hematopoietic stem cell transplantation (allo-HSCT) for myelodysplastic syndromes (MDS). Her blood concentration of CsA was 378 ng/ml (elevated ↑64%, contrasted with the level before the addition of voriconazole) on the second day of admission, and the MRI of head showed leukoencephalopathy in bilateral occipital and left frontal lobe on the 4^th day of admission. The most likely mechanism is that because of voriconazole's enzyme inhibition and CsA as the substrate of hepatic enzymes, voriconazole elevated the blood concentration of CsA and enhanced its toxicity. This case highlights the importance of clinical pharmacists joining the medical team and optimizing the patients’ treatment protocols by performing a systematic literature research, accumulating the knowledge of the potential drug interaction and examining prescriptions.

Adverse drug events as a cause of hospitalization in older adults

Older adults are about four to seven times more likely than younger persons to experience adverse drug events (ADEs) that cause hospitalization, especially if they are women and take multiple medications. The prevalence of drug-related hospitalizations has been reported to be as high as 31%, with large heterogeneity between different studies, depending on study setting (all hospital admissions or only acute hospital admissions), study population (entire hospital, specific wards, selected population and/or age groups), type of drug-related problem measured (adverse drug reaction or ADE), method of data collection (chart review, spontaneous reporting or database research) and method and definition used to detect ADEs. The higher risk of drug-related hospitalizations in older adults is mainly caused by age-related pharmacokinetic and pharmacodynamic changes, a higher number of chronic conditions and polypharmacy, which is often associated with the use of potentially inappropriate drugs. Other factors that have been involved are errors related to prescription or administration of drugs, medication non-adherence and inadequate monitoring of pharmacological therapies. A few commonly used drugs are responsible for the majority of emergency hospitalizations in older subjects, i.e. warfarin, oral antiplatelet agents, insulin and oral hypoglycaemic agents, central nervous system agents. The aims of the present review are to summarize recent evidence concerning drug-related hospitalization in older adults, to assess the contribution of specific medications, and to identify potential interventions able to reduce the occurrence of these drug-related events, as they are, at least partly, potentially preventable.

[Prevalence of Avoidable Potential Interactions Between Antidepressants and Other Drugs in Colombian Patients]

OBJECTIVES

To determine the possible drugs interactions with antidepressive agents in data bases of patients in the Health Insurance System of Colombia.

METHODS

From data bases of about 4 million users in Colombia, a systematic review of drugs dispensation statistics was made to identify drug interactions between antidepressive agents, cholinergic antagonists and tramadol in 2010.

RESULTS

We identified 114,465 monthly users of antidepressive agents. Of these, 5776 (5.0%) received two, and 178 (0.2%) received three antidepressive agents simultaneously. The most frequent combination was fluoxetine+trazodone (n=3235; 56.9% of cases). About 1127 (1.0%) patients were prescribed a cholinergic antagonist simultaneously; 2523 (2.1%) users were dispensed tramadol at the same time, while raising the risk of serotonin syndrome.

CONCLUSIONS

Drug interactions represent a potential risk that is often underestimated by physicians. Pharmacovigilance is a useful tool to optimize resources and prevent negative outcomes associated with medication. It is recommended that systematic search is made to enhance surveillance programs for the rational use of medicines in this country.

Herb-drug interaction of Fucus vesiculosus extract and amiodarone in rats: a potential risk for reduced bioavailability of amiodarone in clinical practice

Fucus vesiculosus is a seaweed claimed to be useful for obesity management. Therefore, considering the relationship between obesity and cardiovascular diseases, this work aimed to assess the potential for an herb-drug interaction among a standardized F. vesiculosus extract (GMP certificate) and amiodarone (a narrow therapeutic index drug) in rats. In a first pharmacokinetic study, rats were simultaneously co-administered with a single-dose of F. vesiculosus (575 mg/kg, p.o.) and amiodarone (50 mg/kg, p.o.); in a second study, rats were pre-treated during 14 days with F. vesiculosus (575 mg/kg/day, p.o.) and received amiodarone (50 mg/kg, p.o.) on the 15th day. Rats of the control groups received the corresponding volume of vehicle. After analysis of the pharmacokinetic data it deserves to be highlighted the significant decrease in the peak plasma concentration of amiodarone (55.4%) as well as the reduction of systemic exposure to the parent drug (~30%) following the simultaneous co-administration of F. vesiculosus extract and amiodarone. This paper reports, for the first time, the herb-drug interaction between F. vesiculosus and amiodarone, which determined a considerable decrease on amiodarone bioavailability in rats. Therefore, the therapeutic efficacy of amiodarone may be compromised by the concurrent administration of herbal slimming medicines/dietary supplements containing F. vesiculosus.

Herb-Drug Interaction of Paullinia cupana (Guarana) Seed Extract on the Pharmacokinetics of Amiodarone in Rats

Paullinia cupana is used in weight-loss programs as a constituent of medicinal/dietary supplements. This study aimed to assess a potential herb-drug interaction among a standardized (certified) Paullinia cupana extract and amiodarone (narrow therapeutic index drug) in rats. In a first pharmacokinetic study rats were simultaneously coadministered with a single dose of Paullinia cupana (821 mg/kg, p.o.) and amiodarone (50 mg/kg, p.o.), and in a second study rats were pretreated during 14 days with Paullinia cupana (821 mg/kg/day, p.o.) receiving amiodarone (50 mg/kg, p.o.) on the 15th day. Rats of the control groups received the corresponding volume of vehicle. Blood samples were collected at several time points after amiodarone dosing, and several tissues were harvested at the end of the experiments (24 h after dose). Plasma and tissue concentrations of amiodarone and its major metabolite (mono-N-desethylamiodarone) were measured and analysed. A significant reduction in the peak plasma concentration (73.2%) and in the extent of systemic exposure (57.8%) to amiodarone was found in rats simultaneously treated with Paullinia cupana and amiodarone; a decrease in tissue concentrations was also observed. This paper reports for the first time an herb-drug interaction between Paullinia cupana extract and amiodarone, which determined a great decrease on amiodarone bioavailability in rats.

[Drug-drug interactions in antirheumatic treatment]

Clinically relevant drug-drug interactions contribute considerably to potentially dangerous drug side-effects and are frequently the reason for hospitalization. Nevertheless they are often overlooked in daily practice. For most antirheumatic drugs a vast number of interactions have been described but only a minority with clinical relevance. Several potentially important drug interactions exist for non-steroidal anti-inflammatory drugs (NSAIDs), methotrexate, azathioprine, mycophenolate-mofetil and especially for cyclosporin A. Most importantly co-medication with methotrexate and sulfmethoxazole trimethoprim as well as azathioprine and allopurinol carries the risk of severe, sometimes life-threatening consequences. Nevertheless, besides these well-known high-risk combinations in each case of polypharmacy with antirheumatic drugs it is necessary to bear in mind the possibility of drug interactions. As polypharmacy is a common therapeutic practice in older patients with rheumatic diseases, they are at special risk.

Prevalence of the coprescription of clinically important interacting drug combinations involving oral anticancer agents in Singapore: a retrospective database study

BACKGROUND

There has been a recent increase in the availability and use of oral anticancer agents (OAAs). Drug-drug interactions (DDIs) involving OAAs pose a major concern in oncology practice due to these drugs' narrow therapeutic indices and potential for compromised efficacy and fatal adverse events.

OBJECTIVE

To assess the prevalence of the coprescription of potentially interacting drug combinations involving OAAs in Singapore.

METHODS

A retrospective review of physicians' electronic prescription records between the years 2007 and 2009 was performed in the largest cancer center in Singapore. An overall prevalence rate of potential DDIs and a prevalence rate for each individual DDI pair were calculated. Logistic regression was used to identify risk factors for potential DDIs.

RESULTS

Fifty-eight clinically significant DDIs were selected for evaluation from Drug Interaction Facts and Micromedex DrugDex. A total of 39,772 OAA prescriptions prescribed to 8837 patients were reviewed. Potential DDI coprescription was found in 5.4% of the patients on OAAs and in 4.7% of the OAA prescriptions. The drug pair prescribed to the largest number of patients was prednisolone and aspirin. About half (53.3%) of the observed DDIs were found on the same prescription. On multivariate analysis, older patients, males, and those taking prednisolone had a higher risk for potential DDIs.

CONCLUSION

Although limited by the data available, the analysis of prescription records found that ∼5% of patients taking OAAs in Singapore were exposed to ≥1 potentially interacting drug combination.

[Potential interactions of rheumatologic medications in the elderly]

Improving the safety of prescriptions for elderly patients is of substantial interest for physicians of all specialities as well as for general health policy and health services. Owing to the increase in drug prescriptions with age and various drug-drug interactions, the number of adverse drug event-related hospital admissions needs to be minimized as far as possible. Therefore, the present overview focuses on the most important potential drug-drug interactions with a specific focus on antirheumatic medications prescribed for elderly patients.

Analysis of potential interactions between warfarin and prescriptions in Estonian outpatients aged 50 years or more

In Estonia, warfarin is widely prescribed by general practitioners to prevent and treat thromboembolic diseases. To date, there has been no systematic analysis of the potential risk of warfarin interactions with other drugs in the outpatient population.

Objective

The aim of the study was to analyze the incidence of potential interactions in prescription schemes in Estonia in a cohort of outpatients receiving warfarin treatment.

Methods

The retrospective study population included 203,646 outpatients aged 50 years or older of whom 7,175 received warfarin therapy. Patients who had used at least one prescription drug for a minimum period of 7 days concomitantly with warfarin were analyzed. Potential drug interactions were analyzed using Epocrates online, Stockley's Drug Interactions and domestic drug interaction databases.

Results

The average number of drugs used concomitantly with warfarin was 4.8 (SD=1.9) (males: 4.7 SD=2.0, females: 4.9 SD=2.0). No potential interactions in treatment regimens were found in 38% of patients, one potential interaction was observed in 29% and two or more potential interactions were observed in 33% of patients. The mean number of all potential interactions was 1.2 per patient and about the same in men and women. Potential interactions were associated with the number of drugs. Warfarin-related interactions were detected in 57% of patients, and the number of interactions related to warfarin per patient varied from 1 to 5. Most frequent were use of warfarin with NSAIDs (14%), followed by simvastatin (9%) and amiodarone (7%).

Conclusions

This study shows that 57% of outpatients in Estonia receiving warfarin have drugs potentially interacting with warfarin in their treatment schemes. Most interactions (14%) with warfarin are associated with the prescription of NSAIDs.

Drug metabolism in older people--a key consideration in achieving optimal outcomes with medicines

Hepatic clearance plays a key role in determining the systemic exposure of drugs and metabolites, which in turn has a major effect on variability in the beneficial and adverse effects of medicines. Aging results in a number of significant changes in the human liver including reductions in liver blood flow, size, drug-metabolizing enzyme content, and pseudocapillarization. Drug metabolism is also influenced by comorbid disease, frailty, concomitant medicines, and (epi)genetics. These changes have the potential to alter the hepatic clearance of drugs but need to be interpreted in the context of the pharmacokinetic (and pharmacodynamic) characteristics of the drug of interest. There is growing evidence that the age-related changes in the liver not only result in a decrease in the hepatic clearance of unbound drug but also influence variability in response to medicines in older people.

[Analysis of the drug interactions associated to domiciliary drug therapy in elderly hospitalized patients]

OBJECTIVE

To determine the prevalence of potentially relevant drug-drug interactions associated with chronic treatment of elderly patients over 64-years of age on hospital admission and the factors associated with an increased presence of these.

SUBJECTS AND METHODS

Cross-sectional observational study in a hospital referral area. All patients aged 65 or over admitted to the hospital in the last three months in 2009 were included. Based on the drug database of the General Council of Colleges of Pharmacy (BOT), drug-drug interactions and their potential clinical relevance were identified. To identify the variables associated with a higher prevalence of drug-drug interactions, analyses of correlation and of univariable linear regression and uni-and multivariable logistic regression analyses were performed using the SPSS, version 15.0.

RESULTS

We analyzed the drug prescription data of 382 patients, whose mean age was 7.7 years. A total of 45.3% of patients had comorbidities and 78.8% had taken 5 or more drugs. We identified 272 clinically relevant drug-drug interactions that involved 159 patients (41.6%). Seven pharmacological groups accounted for 80.6% of the drug-drug interactions. The variables that had a statistically significant association to a higher prevalence of relevant interactions were polypharmacy, respiratory insufficiency, and treatment with proton-pump inhibitors, vitamin K antagonists, diuretics or anti-platelet drugs.

CONCLUSIONS

A high prevalence of relevant drug-drug interactions was found in elderly hospitalized patients. Our findings suggest that prevention strategies should be implemented to avoid their associated adverse events, especially in high risk populations.