Laboratory test results indicate that warfarin anticoagulant therapy is suddenly ineffective in a patient who has been taking the drug for an extended period of time.The nurse suspects an interaction with herbal medications.What type of interaction does she suspect?

A) Antagonistic drug interaction
B) Synergistic drug interaction
C) Idiosyncratic reaction
D) Drug incompatibility

In an antagonistic drug interaction,one drug interferes with the actions of another and decreases the resultant drug effect.In a synergistic drug interaction,there is an additive effect; that is,the effects of both drugs combined are greater than the individual effects.An idiosyncratic reaction is an unexpected,abnormal,or peculiar response to a medication.Drug incompatibilities occur when drugs are physically mixed together,causing a chemical deterioration of one or both drugs.