Interaction Checker

Talk to your pharmacist or doctor before changing any medicine. This app can miss things. "Nothing found" is not proof there is no interaction.

Not clinical decision support. Grades come from free graded sources first (CDC MEC, ONC expert lists, DDInter, MED-RT). FDA label text alone never sets a clinical grade; it shows as a label mention. A pharmacist must verify every result in a full reference. No result does not mean no interaction.

Add items

Your list

Add two or more items to check them against each other.

Saved lists

Saved only in this browser on this device. Nothing is sent anywhere.

No saved lists yet.

About and sources

Non-commercial. This app is free and non-commercial because it uses DDInter 2.0 grades, which are licensed for non-commercial use only. It is a reference aid, not clinical decision support. A pharmacist or doctor should check every result.

Your data. Lists are saved only in this browser. Drug names you add are sent to NLM RxNorm, NLM RxClass and openFDA to look them up. Nothing else leaves the device.

How grades are chosen

CDC U.S. Medical Eligibility Criteria for Contraceptive Use, 2024 (sets its own category)

ONC high-priority drug-drug interaction list (Phansalkar et al., JAMIA 2012)

DDInter 2.0 (graded by clinical pharmacists)

VA MED-RT “contraindicated with” relations, via NLM RxClass

FDA's table of CYP inhibitors, inducers and substrates (a prediction, not a clinical grade)

FDA package insert text never sets a grade; those pairs are listed as label mentions. Food, alcohol, supplement and vaccine-timing pairs from CDC and NIH pages carry an app-assigned level marked “No clinical grade”.

Sources

Drug lookups: NLM RxNorm and RxClass (FDA SPL classes, MED-RT).

FDA drug labels via openFDA (DailyMed).

CDC: U.S. MEC 2024 Appendix D; Timing and Spacing of Immunobiologics.

NIH NCCIH, NIH Office of Dietary Supplements, NIH NIAAA.

U.S. FDA: Drugs that interact with CYP enzymes and transporter systems; FDA drug labels for inducers missing from that table (each cited on its card).

ONC high- and low-priority drug-drug interaction lists (Phansalkar et al., JAMIA 2012 and 2013).

DDInter 2.0 (Tian Y, et al. Nucleic Acids Res. 2025;53(D1):D1356-D1362, doi:10.1093/nar/gkae726), licensed CC BY-NC-SA 4.0. Changes: severity levels re-keyed from DDInter drug ids to RxNorm ingredient ids. The re-keyed table is shared under the same license.