Yu Ko

Clinically Significant Drug–Drug Interactions Between Oral Anticancer Agents and Nonanticancer Agents: Profiling and Comparison of Two Drug Compendia

Background: Use of oral anticancer agents is gaining wide acceptance in the treatment of cancer. However, patients receiving oral therapy are at high risk for drug–drug interactions (DDIs). Objective: To create a drug profile for each clinically significant DDI involving selected oral anticancer agents and evaluate the agreement between 2 commonly used DDI compendia: Drug Interaction Facts (DIF) 2008 and Micromedex DRUGDEX. Methods: DDI profiles were developed based on primary and tertiary literature reviews. DIF 2008 and Micromedex DRUGDEX were compared to assess the consistency of listings, severity, and scientific evidence ratings of DDIs involving the oral anticancer agents that were selected. The Spearman correlation test was used to assess the correlation of the severity ratings between the 2 compendia. Results: A total of 184 DDIs were identified. A DDI profile was created for 40 of these that met the predetermined criteria for clinically significant interactions. The comparative assessment showed inconsistency in DDI listings (15.2% of those identified were listed in DIF only and 46.7% were listed in Micromedex only), severity ratings (Spearman correlation coefficient 0.49), and scientific evidence ratings (disagreement 25.8%). Conclusions: The discrepancies in DDI listing and rating systems between the compendia evaluated here reflect the need for more studies to standardize the definitions and classifications of DDIs.

Clinically significant drug—drug interactions between oral anticancer agents and nonanticancer agents: A delphi survey of oncology pharmacists

BACKGROUND Drug-drug interactions (DDIs) can lead to adverse clinical outcomes, particularly in oncology, because of the narrow therapeutic index of chemotherapeutic agents and because patients with cancer are at a high risk due to polypharmacy and age-related organ dysfunction. In a previously published study, drug profiles were developed based on primary and tertiary literature reviews for a list of clinically significant DDIs involving 28 oral anticancer agents (OAAs). OBJECTIVE This study was based on a Delphi survey of oncology pharmacists; the survey results were used to develop a consensus list of clinically significant DDIs involving OAAs and nonanticancer agents. METHODS In this study, the DDI profiles previously developed were updated, and the DDI pairs that were listed both in the 2009 Drug Interaction Facts (DIF) and the Thomson Micromedex DrugDex System compendia and that also met the predetermined criteria for clinical significance were selected for further evaluation. In a 2-round, electronically administered Delphi survey of oncology pharmacists, a 5-point Likert scale (1-5, where 1 = strongly agree and 5 = strongly disagree) was used to evaluate the DDI pairs based on 8 clinical aspects (clinical importance; irreversible morbidity and mortality; quality of data; quantity of data; patients organ functions; comorbid conditions; awareness of interaction; and management burden). International pharmacists who specialized in oncology pharmacy practice and had > or =5 years of practice experience were eligible to participate. RESULTS Nine of the 23 surveyed pharmacists responded, giving a response rate of 39.1%. A total of 37 DDI pairs were selected from DIF and DrugDex and evaluated by the survey respondents, resulting in the identification, via consensus, of 12 clinically significant DDI pairs. The clinical aspects with the most DDIs that reached consensus of agreement were clinical importance (82.9%) and awareness of interaction (73.2%). CONCLUSION An expert panel identified 12 clinically significant DDIs involving OAAs.

Costs and Length of Stay of Drug-Related Hospital Admissions in Cancer Patients

BACKGROUND Most previous studies of the incidence and economic impact of drug-related hospital admissions were not cancer specific, despite the fact that drug-related problems (DRPs) are of particular concern in oncology. OBJECTIVE The goals of this study were to assess the economic impact, particularly the length of stay (LOS) and direct medical costs (DMC), of drug-related hospital admissions and the associated factors in cancer patients in Singapore. METHODS A prospective study was conducted over a 5-month period in 2 oncology wards at the largest acute tertiary hospital in Singapore. Drug-related admissions were identified from all oncology admissions to these wards, and the demographic, clinical, and cost data of these drug-related admissions were collected. The association between LOS and DMC as well as their associations with age, severity, and preventability of DRPs were examined. A nationwide estimation was made to determine the overall DMC of drug-related hospital admissions among cancer patients. RESULTS A total of 151 drug-related admissions that occurred among 137 cancer patients were identified. The mean DMC (in Singapore dollars [SGD]) and LOS per drug-related admission were SGD

Economic Evaluation of Anastrozole Versus Tamoxifen for Early Stage Breast Cancer in Singapore

4747 and 6.1 days, respectively. A nationwide extrapolation estimated an annual total DMC of SGD

Clinical Impact of Drug-Drug Interaction Between Aspirin and Prednisolone at a Cancer Center

16.2 million. Longer LOS was found to be correlated with higher DMC (rs = 0.86, P < 0.001) and preventable DRPs (P = 0.02). CONCLUSIONS Drug-related hospitalization among cancer patients is costly; therefore, more attention is warranted to develop and improve strategies for preventing drug-related morbidity and mortality in cancer patients.

Identification and evaluation of pharmacists' commonly used drug information sources.

OBJECTIVES In Singapore, breast cancer is the leading female malignancy and its incidence has increased threefold over the past decades. For treatment of postmenopausal, hormone receptor positive early stage breast cancer, tamoxifen or aromatase inhibitors such as anastrozole are prescribed either as first-line therapy or sequentially. Currently, anastrozole is patented with a higher drug cost compared with tamoxifen. Hence, the aim of this study was to conduct an economic evaluation of anastrozole versus tamoxifen in early stage breast cancer. METHODS A Markov model with a lifetime horizon was developed by using results from the Arimidex, Tamoxifen, Alone or in Combination trial. Direct medical costs were estimated by billing data obtained via financial electronic databases. Utility scores were elicited from 20 experienced oncology nurses using the visual analogue scale. Cost per quality-adjusted life-years was calculated by using the societal perspective. A discount rate of 3% for both charges (expressed in 2010 Singapore dollars) and benefits was used. RESULTS At an additional cost of S

Characteristics of unplanned hospital admissions due to drug-related problems in cancer patients

17,597, anastrozole treatment resulted in a gain of 0.085 life-year survival and 0.154 quality-adjusted life-year. The incremental cost-effectiveness ratio of anastrozole was S

Prevalence of the Coprescription of Clinically Important Interacting Drug Combinations Involving Oral Anticancer Agents in Singapore: A Retrospective Database Study

207,402 per life-year gained and S

Patient Needs and Sources of Drug Information in Singapore: Is the Internet Replacing Former Sources?:

114,061 per quality-adjusted life-year gained compared with tamoxifen. CONCLUSION This is the first economic evaluation that used 10-year results from the Arimidex, Tamoxifen, Alone or in Combination trial and utility elicited from the local population. If the World Health Organizations recommendation of 1 to 3 gross domestic product range is an acceptable threshold, anastrozole is deemed cost-effective compared with tamoxifen in the treatment of early stage breast cancer.

Health State Utility Assessment for Breast Cancer

BACKGROUND Adverse gastrointestinal (GI) events are complications in aspirin and prednisolone cotherapy. The prevalence of adverse GI events would be expected to be increased with cotherapy due to the overlapping toxicities of the 2 drugs. However, there is a dearth of literature investigating how often this interaction causes clinically important adverse GI events. OBJECTIVES This retrospective study aimed to determine the prevalence of adverse GI events associated with the coadministration of aspirin and prednisolone. The use of gastroprotectant agents was also studied. METHODS The medical records of patients with cancer prescribed aspirin and prednisolone therapy between January 2007 and June 2011 were analyzed. The duration of aspirin-prednisolone overlap, prevalence of adverse GI events, and details on the concurrent use of other medications were evaluated. RESULTS The study included data from 142 patients (male, 64.8%; mean [SD] age, 67.4 [11.0] years). A total of 78.9% of the patients were on some form of gastroprotectant, the most common class of which was proton pump inhibitors. The prevalence of adverse GI events was 4.2% (6 patients). Four patients had presented with GI symptoms (abdominal pain, diarrhea, dysphagia, and vomiting); 3 patients had signs of GI injury (duodenal ulcers, iron deficiency anemia, and a Mallory-Weiss tear). The Naranjo algorithm classified 5 patients experienced possible adverse drug reactions (ADRs), and 1 as a probable ADR. CONCLUSION Our study found that the prevalence of adverse GI events was low and managed to establish a weak association between the occurrence of events and the coadministration of aspirin and prednisolone. This finding, together with the concurrent prescription of gastroprotectants, suggests that the clinical impact of the aspirin and prednisolone DDI is minimal.