Table 1 Summary of recent studies reporting drug-drug interactions involving rifampicin and warfarin in humans
Study | Country | Type of study | Number of patients | Sex | Age (years) | Warfarin administration | Comments | ||
|---|---|---|---|---|---|---|---|---|---|
Chronic dose | Titration | Plasma levels | |||||||
Lee & Thrasher, 2001 [16] | USA | Case report | 1 | Male | 58 | Yes | Yes | No | A 233% increase in the warfarin dose over four months could not attain a therapeutic INR* during the use of rifampicin. A therapeutic INR* was obtained after a 70% reduction in the warfarin dose over four to five weeks after rifampicin discontinuation. |
Kim et al., 2007 [18] | USA | Case report | 1 | Male | 79 | Yes | Yes | No | Increases of 500-600% in the warfarin dose were insufficient to maintain an INR* in the therapeutic range. After rifampicin was discontinued, the warfarin dose was gradually reduced over two months to achieve a therapeutic INR*. |
Krajewski, 2010 [17] | USA | Case report | 1 | Male | 71 | Yes | Yes | No | The warfarin dose was sequentially increased by up to 500%, from a starting point of 35–40 mg/week to an endpoint of 175 mg/week over two months, with no achievement of a therapeutic INR*. After rifampicin discontinuation, the warfarin dose was gradually reduced to the initial regimen over three to four months to attain a therapeutic INR*. |