Interactive tool · FDA label data

Drug Interaction Checker

Select two medications below to check for a known interaction. Severity and the interaction text come from the FDA-approved drug labels themselves.

Compiled by PlainMeds, Drug Information Editorial Process

Data updated 2026-05-15

3,919
Interactions tracked: 268
Major (high-severity): 711
Moderate: 682
Medications covered

PlainMeds tracks 3,919 labeled drug-interaction pairs across 682 medications, including 268 major-severity pairs pulled from FDA drug labels.

This checker searches 3,919 interaction pairs derived from FDA-approved drug labels (268 major, 711 moderate) covering 682 medications. Pick two drugs to see severity and the label text when a pair is documented. Absence from the file is not proof that no interaction exists. Educational information only, not medical advice.

Registry boundary: This tool displays compiled FDA-label interaction records and does not provide medical, treatment, or medication-change directions.

Medication 1

Medication 2

Results: Nirmatrelvir/Ritonavir + Simvastatin

Major Interaction between Nirmatrelvir/Ritonavir and Simvastatin

FDA severity

Minor FDA-label category

Moderate FDA-label category

Major FDA-label category

Description

HMG-CoA reductase inhibitors lovastatin, simvastatin ↑ lovastatin ↑ simvastatin Co-administration contraindicated due to potential for myopathy including rhabdomyolysis [see Contraindications (4) ] . If treatment with PAXLOVID is considered medically necessary, discontinue use of lovastatin and simvastatin at least 12 hours prior to initiation of PAXLOVID, during the 5 days of PAXLOVID treatment, and for 5 days after completing PAXLOVID.

Based on interactions documented in FDA drug labeling. Label-documented interactions are not exhaustive, so a pharmacist checking a full clinical interaction database may find more. This is informational, not a clinical decision.

View Nirmatrelvir/Ritonavir details View Simvastatin details Full interaction details

What does "Major" severity mean?

This pair is classified as major in the FDA-label source record. The category does not provide an individual response direction.

Frequently Asked Questions

How does the drug interaction checker work?

Select two medications from the dropdown menus and choose "Check Interaction." The tool retrieves the recorded FDA-label interaction row and its source-record severity. It does not provide an individual response or treatment direction.

What do the interaction severity levels mean?

Minor, moderate, and major are source-record severity categories in the compiled FDA-label data. The category does not provide an individual risk estimate, monitoring plan, or medication-combination direction.

What if no interaction is found?

If no interaction row is found in this database, that does not establish that no interaction exists. The database covers a defined catalogue and is not a complete medication review.

Can I check more than two drugs at once?

This tool checks interactions between two specific drugs at a time. For checking multiple medications simultaneously, visit our full Interaction Checker at /interactions which supports adding multiple drugs.

Is this tool a substitute for medical advice?

No. This tool displays a defined set of FDA-label source records and does not provide medical advice, diagnosis, treatment, or medication-change directions.

Registry boundary: This tool displays sourced FDA-label interaction rows. It does not provide medical advice, diagnosis, treatment, medication-selection, or response directions.

Data source: U.S. Food and Drug Administration (FDA) drug labels via openFDA. The interaction set covers 3,919 documented drug-drug pairs across 682 medications, compiled from FDA Structured Product Labeling and last refreshed May 2026. See our methodology for source dates and how pairs are matched. Spot a pair that looks wrong? Report a correction.

Source: U.S. Food and Drug Administration (FDA): drug labels (Drug Interactions sections), Structured Product Labeling via openFDA.