PROBABLE ACENOCOUMAROL-AMOXICILLIN INTERACTION

We present the case of a woman undergoing treatment with acenocoumarol for deep vein thrombosis, who maintained an international normalized ratio (INR) of between 2.5 and 4 for 2 months. Seven days after the in troduction of amoxycillin (500 mg/8 h) for a probable respiratory infe ction, the patient developed spontaneous bruising, with an INR of 7.1. Treatment with amoxycillin was discontinued, and 3 weeks later the IN R had returned to previous values. In this case, the increase in the I NR value with associated bruising after the addition of amoxycillin su ggests a drug interaction between acenocoumarol and amoxycillin, other possible causes having been eliminated.