This code system http://hl7.org/fhir/interaction-type defines the following codes:

CodeDisplay
drug-drug drug to drug interaction
drug-food drug to food interaction
drug-test drug to laboratory test interaction
other other interaction
<status value="active"/><experimental value="false"/><date value="2021-01-05T10:01:24+11:00"/><publisher value="HL7 (FHIR Project)"/><contact><telecom><system value="url"/><value value="http://hl7.org/fhir"/></telecom><telecom><system value="email"/><value value="fhir@lists.hl7.org"/></telecom></contact><description value="A categorisation for an interaction between two substances."/><jurisdiction><coding><system value="http://unstats.un.org/unsd/methods/m49/m49.htm"/><code value="001"/><display value="World"/></coding></jurisdiction><caseSensitive value="true"/><valueSet value="http://hl7.org/fhir/ValueSet/interaction-type"/><content value="complete"/><concept><code value="drug-drug"/><display value="drug to drug interaction"/></concept><concept><code value="drug-food"/><display value="drug to food interaction"/></concept><concept><code value="drug-test"/><display value="drug to laboratory test interaction"/></concept><concept><code value="other"/><display value="other interaction"/></concept></CodeSystem>