Pharvel is not medical advice. It shows what US FDA drug labels and FDA tables say. Always ask a pharmacist or prescriber before starting, stopping or changing a medicine. In an emergency, call your local emergency number.
What Pharvel does
Finds each medicine you name (brand or generic) using NIH RxNorm.
Quotes the passage in each FDA label that mentions the other medicine or its drug class, with a link to the label.
Adds a fixed plain-language summary, the enzyme mechanism listed by FDA where one applies, and how many FDA adverse-event reports list both medicines.
What it does not cover
Doses — it never gives or adjusts doses.
Your situation — pregnancy, breastfeeding, children, older age, kidney or liver disease, allergies and genetics can all change the risk. Labels have separate warnings for these that this check does not apply.
Supplements, herbal products and foods — only where an FDA label or FDA table names them.
Medicines outside the US — products and labels in other countries can differ.
Completeness — labels do not list every interaction. "Nothing found" means the labels checked do not mention it; it does not mean the combination is safe.
How well it works
Pharvel is tested against reference drug pairs with known answers, including a held-out set written before its first run, and compared with an independent research database of drug interactions. Across three separate comparisons, Pharvel flagged 82–86% of the interactions that database rates as major, so roughly 1 in 6 serious interactions was shown as "nothing found". This is the main reason a "nothing found" result must never be taken as safe. The reference sets have not yet been reviewed by a pharmacist.
Some things Pharvel now tells you
If two names you typed are the same medicine (for example Tylenol and acetaminophen), it warns you about a possible double dose.
It checks up to six medicines at once and names any it could not check.
Parts of one combination product (for example Percocet) are not compared with each other.
"Predicted from FDA enzyme table" means neither label mentions the pair, but FDA's table of drugs that block or speed up liver enzymes predicts an effect.
Severity labels
"Contraindicated" and "Serious warning" come from the label's contraindication and boxed-warning sections or serious wording; "Interaction documented" means the label mentions the combination; "Class-level mention" means the label names the drug class, not the medicine. These follow label wording, which is not a clinical severity scale.
Something wrong?
Use "Report a problem with this answer" under any result. Pharvel is a student project: reports are read by the developer, but there is no guaranteed response time, so never wait for a reply about something urgent.