Drug–drug interactions Coumarin anticoagulants A 68-year-old woman taking long-term warfarin for atrial fibrillation had an acute left hemiparesis after taking oral flucloxacillin 500 mg qds and oral phenoxymethylpenicillin 999 mg qds for a soft tissue infection for 17 days [51 A]. The International Normalized Ratio (INR) was 1.4, having been 3.5 before 19 days. Interactions of warfarin with. Drugs.com provides accurate and independent information on more than 24,000 prescription drugs, over-the-counter medicines and natural products. This material is provided for educational purposes only and is not intended for medical advice, diagnosis or treatment. Data sources include IBM Watson Micromedex (updated 4 May 2020), Cerner Multum™ (updated 4 May 2020), Wolters Kluwer™ (updated. Drug Interaction Checker. Use the search field above to look up prescription or OTC drugs, and herbal supplements; Add a full drug regimen and view interactions Drug interactions may lead to an increase or decrease in the beneficial or the adverse effects of the given drugs. When a drug interaction increases the benefit of the administered drugs without increasing side effects, both drugs may be combined to increase the control of the condition that is being treated. For example, drugs that reduce blood pressure by different mechanisms may be combined. Drug-drug interactions occur when two or more drugs react with each other. This drug-drug interaction may cause you to experience an unexpected side effect. For example, mixing a drug you take to. Use WebMD’s Drug Interaction Checker tool to find and identify potentially harmful and unsafe combinations of prescription medications by entering two or more drugs in question. Drug-drug interactions - These are the most common type of drug interaction. The more medications you take, the greater the chance for your drug interacting with another medicine. Drug-drug interactions can decrease how well your medications work, may increase minor or serious unexpected side effects, or even increase the blood level and possible toxicity of a certain drug. For example, if you.