Some antibiotics, including co-trimoxazole, inhibit warfarin’s metabolism and may be associated with greater risk of hemorrhage in warfarin-treated patients. This thesis examines the risk of upper gastrointestinal (UGI) hemorrhage in older patients receiving warfarin and antibiotics commonly used to treat urinary tract infections, with a focus on co-trimoxazole. This population-based nested case-control study using Ontario healthcare databases, identified residents aged 66 years or older continuously on warfarin (n=134,637). Cases were those hospitalized with UGI hemorrhage (n=2151). Cases were nearly 4 times more likely than controls to have recently received co-trimoxazole (adjusted odds ratio (OR), 3.84; 95% confidence interval (CI) 2.33 – 6.33). Ciprofloxacin was also associated with an increased risk (adjusted OR 1.94; 95% CI 1.28 – 2.95), but no significant association was observed with amoxicillin, ampicillin, nitrofurantoin or norfloxacin. Among older patients receiving warfarin, co-trimoxazole is associated with a significantly higher risk of UGI hemorrhage than other commonly used antibiotics.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OTU.1807/18297 |
| Date | 18 January 2010 |
| Creators | Fischer, Hadas Daisy |
| Contributors | Laupacis, Andreas |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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