How to work the Data to get your Drug to Drug Interactions

WENO DB has the drug to drug interactions from ONCHigh source only. The WENO DB comes with no warranties and we recommend if you are going to alert the prescriber for drug interactions that you use the government’s free API to make sure it is as current and accurate as possible.

Free drug to drug API is found at this url:

It’s important to understand the results will provide:

Remember not all RXCUI #s are of “prescribable drug”….it may be an ingredient of a drug instead.

Here is one of other ways to show the prescriber a drug to drug interaction alert:
  1. Get the RXCUIs the source drug interacts with.
  2. Compare the drug interaction RXCUIs with the patient’s current medication ingredient RXCUI & any drug’s RXCUI and ingredient RXCUI you know that is not yet in the patient’s current medication list. (see “BEWARE” note below).
  3. If any match then show drug to drug interaction alert.
Here is an example:
Source Drug RXCUI # is 123. (This is the drug the prescriber wants to prescribe)

You discovered with API or Weno Drug Database look up that it interacts with RXCUI# 333 and RXCUI# 444.

Your database knows this patient is on a current medication with RXCUI 555 & you store the RXCUI 555’s’s ingredients in your database:


Now you can look for drug interaction RXCUIs for all drugs and ingredient RXCUIs in the patient’s current medication list.

In this example, you should show a drug to drug interaction alert to the prescriber because RXCUI 123 interacts with RXCUI # 444, which is an ingredient of RXCUI 555 that the patient is current taking as a medication.

Beware: Besides a patient’s current medication, you should also run this same look up on any drug he has approved but has not made it to the patient’s current medication list in your database. This can happen when a prescriber is writing multiple drugs in the same patient visit.

Let’s say the patient is seen by the doctor and the doctor wants to prescribe 2 drugs. On the first prescription he signs, he finds no drug to drug interaction alert. But on the 2nd prescription he finds no drug to drug interaction alert with the patient’s known current medications, but the drug may interact with an ingredient in the 1st prescription he wrote.