Coumarin anticoagulants liver disease

Although vitamin K deficiency in the adult is uncommon, the risk is increased for fat malabsorption states (bile duct obstruction, cystic fibrosis, and chronic pancreatitis) and liver disease. Risk is also increased by the use of drugs that interfere with vitamin K metabolism, such as the coumarin anticoagulants (e.g., warfarin) and antibiotics containing the N-methylthiotetrazole side chain (e.g., cephalosporin). ... 

A number of early studies showed that the effects of the coumarin oral anticoagulants are unlikely to be changed in those with normal liver function who drink small or moderate amounts of alcoholic beverages such as wine or spirits. An increase in bleeding time may occur in patients with Uver disease who drink to excess. 

Not understood. The interaction between nafcillin and warfarin is possibly due to increases in the metabolism of warfarin by the liver. Dicloxacillin also possibly reduces serum warfarin levels. Other penicillins (ampicillin, benzylpenicillin, carbenicillin, methicillin, ticarcillin ) have caused increased bleeding times when given alone, principally due to platelet inhibition, which might be additive with the effects of oral anticoagulants. Broad-spectrum antibacterials may decrease the gut flora and thereby possibly decrease production of vitamin K. Other factors relating to the disease may be important, see Coumarins -i- Antibacterials p.365. 

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