Statins Coumarins

The fibrates potentiate the actions of the coumarin anticoagulants, such as warfarin, so care should be taken to reduce the dose of simultaneously administered anticoagulants, and plasma prothrombin should be frequently measured until the level stabilizes. As mentioned earlier, great care should be given to combining a statin with a fibrate, since this combination may increase the risk of myositis and perhaps rhabdomyolysis. Table 23.4 summarizes major interactions of drugs that lower cholesterol. 

Studies have suggested that fluvastatin and rosuvastatin can increase warfarin levels and/or effects. Other studies with atorvas-tatin, lovastatin, pravastatin, and simvastatin suggest that they do not usually significantly alter the effects of warfarin, although cases of bleeding have been seen when these statins were given with coumarins and fluindione. 

Pharmacological studies of the etfeet of statins on warfarin are summarised in Table 12.6 , (p.449), and ease reports of interactions between statins and coumarins are summarised in Table 12.7 , (p.451). An early report, from the first 7 months after lovastatin became available in the USA, notes that the manufacturers had reeeived 10 spontaneous reports of bleeding and/or increased prothrombin times in patients taking warfarin with lovastatin. ... 

Table 12.7 Summary of the case reports of interactions between statins and coumarins...

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