Medication Interaction Checker
Check for clinically significant drug-drug interactions across common medications. Enter two or more drugs to see interaction severity, mechanism, and management recommendations. For reference use only — always verify with a pharmacist.
⚠️ Check Drug Interactions
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Understanding Drug-Drug Interactions
A drug-drug interaction occurs when one medication affects the activity, metabolism, or toxicity of another. Interactions can increase or decrease drug levels, enhance or reduce therapeutic effects, or produce new adverse effects not seen with either drug alone. Polypharmacy — the use of five or more medications — significantly increases interaction risk.
Interaction Severity Classification
- Contraindicated: The combination should never be used. Risk of severe harm or death.
- Major: Potentially life-threatening or capable of causing permanent damage. Avoid if possible; use only if no alternative exists with close monitoring.
- Moderate: May result in worsening of condition or significant side effects. Usually manageable with dose adjustment or monitoring.
- Minor: Limited clinical significance. Minimal risk with standard management.
Pharmacokinetic vs Pharmacodynamic Interactions
- Pharmacokinetic (PK): One drug affects the absorption, distribution, metabolism, or excretion of another. Most commonly involves CYP450 enzyme inhibition or induction.
- Pharmacodynamic (PD): Two drugs have additive, synergistic, or antagonistic effects at the same target — e.g. additive bleeding risk with warfarin + aspirin, or additive sedation with opioids + benzodiazepines.
For dosing adjustments based on renal function, use our GFR calculator. For calculating doses of individual medications, see our drug dosage calculator and pediatric dose calculator. Explore all tools in our Medical tools hub and our Pharmaceuticals tools.
⚠️ This tool covers a curated set of common interactions and is for educational reference only. It does not replace a comprehensive drug interaction database (e.g. Lexicomp, Micromedex) or the clinical judgment of a licensed pharmacist. Always verify interactions with a qualified pharmacist before prescribing or dispensing.