{"openapi":"3.1.0","info":{"title":"Interaction Checker API","version":"1.0.0","summary":"Free drug, supplement, food, and alcohol interaction data sourced from FDA prescribing labels.","description":"Every interaction quotes the FDA prescribing label sentence it came from, with a DailyMed link. No API key. 60 requests per minute per IP. Label data exported 2026-09-03. Not medical advice. Please link back to https://interaction-checker.com when you show results.","termsOfService":"https://interaction-checker.com/terms","contact":{"name":"Interaction Checker","url":"https://interaction-checker.com/api"},"license":{"name":"Free to use with attribution","url":"https://interaction-checker.com/terms"}},"externalDocs":{"description":"Developer docs","url":"https://interaction-checker.com/api"},"servers":[{"url":"https://interaction-checker.com/api/v1"}],"tags":[{"name":"Checks","description":"Check every pair in a list of medicines, supplements, foods, and habits."},{"name":"Substances","description":"Search and read the drugs, supplements, foods, and habits the checker knows."}],"paths":{"/":{"get":{"operationId":"getIndex","summary":"API index: endpoints, limits, data dates","responses":{"200":{"description":"Index","content":{"application/json":{"schema":{"type":"object"}}}}}}},"/checks":{"get":{"tags":["Checks"],"operationId":"checkInteractions","summary":"Check interactions among a list of items","description":"Items may be ids, generic names, brand names, aliases, or a plain question (\"can I take advil with lisinopril\"). 2 to 10 items. Every pair among the resolved items is returned, most severe first, each with the verbatim label quotes behind it.","parameters":[{"name":"items","in":"query","required":true,"schema":{"type":"string"},"description":"Comma-separated items. Repeat the parameter or use item= for names that contain commas.","example":"lisinopril,ibuprofen,potassium"}],"responses":{"200":{"description":"Check result","content":{"application/json":{"schema":{"$ref":"#/components/schemas/CheckResult"}}}},"400":{"description":"Fewer than two or more than ten items.","content":{"application/json":{"schema":{"$ref":"#/components/schemas/Error"}}}},"429":{"description":"Rate limited.","content":{"application/json":{"schema":{"$ref":"#/components/schemas/Error"}}}}}},"post":{"tags":["Checks"],"operationId":"checkInteractionsPost","summary":"Check interactions (JSON body)","requestBody":{"required":true,"content":{"application/json":{"schema":{"type":"object","required":["items"],"properties":{"items":{"type":"array","minItems":2,"maxItems":10,"items":{"type":"string","maxLength":80}}}},"example":{"items":["Zoloft","tramadol","St. John's wort"]}}}},"responses":{"200":{"description":"Check result","content":{"application/json":{"schema":{"$ref":"#/components/schemas/CheckResult"}}}},"400":{"description":"Malformed body or bad item count.","content":{"application/json":{"schema":{"$ref":"#/components/schemas/Error"}}}},"429":{"description":"Rate limited.","content":{"application/json":{"schema":{"$ref":"#/components/schemas/Error"}}}}}}},"/interactions/{a}/{b}":{"get":{"tags":["Checks"],"operationId":"getPair","summary":"One pair","parameters":[{"name":"a","in":"path","required":true,"schema":{"type":"string"},"example":"lisinopril"},{"name":"b","in":"path","required":true,"schema":{"type":"string"},"example":"ibuprofen"}],"responses":{"200":{"description":"The pair with its evidence","content":{"application/json":{"schema":{"type":"object","required":["pair"],"properties":{"pair":{"$ref":"#/components/schemas/Pair"},"data":{"type":"object"},"disclaimer":{"type":"string"},"attribution":{"$ref":"#/components/schemas/Attribution"}}}}}},"404":{"description":"One of the two items did not resolve.","content":{"application/json":{"schema":{"$ref":"#/components/schemas/Error"}}}}}}},"/substances":{"get":{"tags":["Substances"],"operationId":"searchSubstances","summary":"Search (typo-tolerant, brands, aliases, plain language) or list every substance","parameters":[{"name":"q","in":"query","schema":{"type":"string","maxLength":100},"description":"Search text. Omit to list everything.","example":"advil"},{"name":"limit","in":"query","schema":{"type":"integer","minimum":1,"maximum":25,"default":8}},{"name":"kind","in":"query","schema":{"type":"string","enum":["drug","other"]},"description":"Filter the full list."}],"responses":{"200":{"description":"Matches","content":{"application/json":{"schema":{"type":"object","properties":{"query":{"type":"string"},"count":{"type":"integer"},"results":{"type":"array","items":{"allOf":[{"$ref":"#/components/schemas/SubstanceRef"},{"type":"object","properties":{"brands":{"type":"array","items":{"type":"string"}},"matchedOn":{"type":"string"}}}]}}}}}}}}}},"/substances/{id}":{"get":{"tags":["Substances"],"operationId":"getSubstance","summary":"One substance: names, classes, label source, interaction counts","parameters":[{"name":"id","in":"path","required":true,"schema":{"type":"string"},"description":"Substance id (slug). Find it with GET /substances?q=.","example":"lisinopril"}],"responses":{"200":{"description":"Substance","content":{"application/json":{"schema":{"allOf":[{"$ref":"#/components/schemas/SubstanceRef"},{"type":"object","properties":{"brands":{"type":"array","items":{"type":"string"}},"aliases":{"type":"array","items":{"type":"string"}},"classes":{"type":"array","items":{"type":"object","properties":{"key":{"type":"string"},"name":{"type":"string"}}}},"components":{"type":"array","items":{"type":"string"}},"source":{"type":"object","description":"The FDA label this drug's evidence is read from (drugs only)."},"interactions":{"type":"object","properties":{"total":{"type":"integer"},"bySeverity":{"type":"object"},"url":{"type":"string","format":"uri"}}},"links":{"type":"object","properties":{"pills":{"type":"string","format":"uri"},"facts":{"type":"string","format":"uri"}}}}}]}}}},"404":{"description":"Unknown id.","content":{"application/json":{"schema":{"$ref":"#/components/schemas/Error"}}}}}}},"/substances/{id}/interactions":{"get":{"tags":["Substances"],"operationId":"getSubstanceInteractions","summary":"Everything a substance has documented evidence with, most severe first","parameters":[{"name":"id","in":"path","required":true,"schema":{"type":"string"},"description":"Substance id (slug). Find it with GET /substances?q=.","example":"lisinopril"},{"name":"severity","in":"query","schema":{"type":"string","enum":["major","moderate","minor","none","unknown"]}}],"responses":{"200":{"description":"Interaction list","content":{"application/json":{"schema":{"type":"object","properties":{"substance":{"$ref":"#/components/schemas/SubstanceRef"},"interactions":{"type":"array","items":{"allOf":[{"$ref":"#/components/schemas/SubstanceRef"},{"type":"object","properties":{"severity":{"type":"string","enum":["major","moderate","minor","none","unknown"]},"severityLabel":{"type":"string"},"page":{"type":"string","format":"uri"}}}]}}}}}}},"404":{"description":"Unknown id.","content":{"application/json":{"schema":{"$ref":"#/components/schemas/Error"}}}}}}},"/substances/{id}/pills":{"get":{"tags":["Substances"],"operationId":"getPillAppearances","summary":"Every tablet and capsule version in the drug's FDA labels, with rendered images where available","parameters":[{"name":"id","in":"path","required":true,"schema":{"type":"string"},"description":"Substance id (slug). Find it with GET /substances?q=.","example":"lisinopril"}],"responses":{"200":{"description":"Appearances","content":{"application/json":{"schema":{"type":"object","properties":{"substance":{"$ref":"#/components/schemas/SubstanceRef"},"fetchedAt":{"type":"string"},"forms":{"type":"array","items":{"type":"object","properties":{"form":{"type":"string"},"n":{"type":"integer"}}}},"appearances":{"type":"array","items":{"type":"object","properties":{"key":{"type":"string"},"kind":{"type":"string","enum":["tablet","capsule"]},"form":{"type":"string"},"productName":{"type":"string"},"strengths":{"type":"array","items":{"type":"string"}},"imprint":{"type":"string"},"imprintSides":{"type":"array","items":{"type":"string"}},"colors":{"type":"array","items":{"type":"string"}},"shape":{"type":"string"},"sizeMm":{"type":["number","null"]},"score":{"type":"integer"},"coating":{"type":"string"},"labelers":{"type":"array","items":{"type":"string"}},"ndc":{"type":"string"},"setIds":{"type":"array","items":{"type":"string"}},"description":{"type":"string","description":"One sentence, e.g. 'Lisinopril 10 mg tablet: pink, round, 8 mm, imprinted ...'"},"image":{"type":"object","description":"A rendering generated from the label's appearance fields (not a photograph). Reuse with a link back.","properties":{"id":{"type":"string"},"url":{"type":"string","format":"uri"},"thumbnailUrl":{"type":"string","format":"uri"}}}}}},"page":{"type":"string","format":"uri"},"attribution":{"$ref":"#/components/schemas/Attribution"}}}}}},"404":{"description":"Unknown id, or no solid oral form.","content":{"application/json":{"schema":{"$ref":"#/components/schemas/Error"}}}}}}},"/substances/{id}/facts":{"get":{"tags":["Substances"],"operationId":"getDrugFacts","summary":"Sourced facts, community claims with evidence status, misconceptions, and FAQ","parameters":[{"name":"id","in":"path","required":true,"schema":{"type":"string"},"description":"Substance id (slug). Find it with GET /substances?q=.","example":"lisinopril"}],"responses":{"200":{"description":"Facts","content":{"application/json":{"schema":{"type":"object","properties":{"substance":{"$ref":"#/components/schemas/SubstanceRef"},"generatedAt":{"type":"string"},"overview":{"type":"string"},"facts":{"type":"array","items":{"type":"object","properties":{"text":{"type":"string"},"source":{"type":"object"}}}},"claims":{"type":"array","description":"Things people say online, each with a status: unproven, partly-supported, disputed, or debunked. Not facts.","items":{"type":"object"}},"misconceptions":{"type":"array","items":{"type":"object"}},"faq":{"type":"array","items":{"type":"object","properties":{"q":{"type":"string"},"a":{"type":"string"},"source":{"type":"object"}}}},"page":{"type":"string","format":"uri"},"disclaimer":{"type":"string"},"attribution":{"$ref":"#/components/schemas/Attribution"}}}}}},"404":{"description":"Unknown id, or no facts page yet.","content":{"application/json":{"schema":{"$ref":"#/components/schemas/Error"}}}}}}}},"components":{"schemas":{"SubstanceRef":{"type":"object","required":["id","name","kind","url"],"properties":{"id":{"type":"string","description":"Stable slug, e.g. lisinopril or st-johns-wort."},"name":{"type":"string"},"kind":{"type":"string","enum":["drug","other"],"description":"other = supplement, vitamin, mineral, food, drink, or habit."},"group":{"type":"string","description":"Display group for non-drugs."},"url":{"type":"string","format":"uri","description":"The substance's page on the site."}}},"Evidence":{"type":"object","required":["from","about","section","sectionLabel","severity","quote","matchedTerm","matchKind","source"],"properties":{"from":{"type":"string","description":"Id of the entity whose label (or curated rule) the quote comes from."},"about":{"type":"string","description":"Id of the entity the quote is about."},"section":{"type":"string","enum":["boxed_warning","contraindications","warnings_and_cautions","warnings","drug_interactions","precautions","overlay"]},"sectionLabel":{"type":"string"},"severity":{"type":"string","enum":["major","moderate","minor","none"]},"quote":{"type":"string","description":"Verbatim label sentence (or the curated rule's summary)."},"matchedTerm":{"type":"string"},"matchKind":{"type":"string","enum":["name","class","overlay"]},"source":{"type":"object","required":["type","name","url"],"properties":{"type":{"type":"string","enum":["fda_label","curated"]},"name":{"type":"string"},"url":{"type":"string","format":"uri","description":"DailyMed label, or the NIH/FDA page behind a curated rule."},"effectiveDate":{"type":"string","format":"date"}}}}},"Pair":{"type":"object","required":["a","b","severity","severityLabel","url","evidence"],"properties":{"a":{"$ref":"#/components/schemas/SubstanceRef"},"b":{"$ref":"#/components/schemas/SubstanceRef"},"severity":{"type":"string","enum":["major","moderate","minor","none","unknown"]},"severityLabel":{"type":"string"},"url":{"type":"string","format":"uri","description":"Checker deep link for this pair."},"page":{"type":"string","format":"uri","description":"Prerendered pair page, when one exists."},"evidence":{"type":"array","items":{"$ref":"#/components/schemas/Evidence"}}}},"CheckResult":{"type":"object","required":["items","unresolved","pairs","summary","data","disclaimer","attribution"],"properties":{"items":{"type":"array","items":{"allOf":[{"$ref":"#/components/schemas/SubstanceRef"},{"type":"object","required":["query"],"properties":{"query":{"type":"string"},"matchedOn":{"type":"string"}}}]}},"unresolved":{"type":"array","items":{"type":"object","required":["query","suggestions"],"properties":{"query":{"type":"string"},"suggestions":{"type":"array","items":{"$ref":"#/components/schemas/SubstanceRef"}}}}},"pairs":{"type":"array","items":{"$ref":"#/components/schemas/Pair"},"description":"Every pair among the resolved items, most severe first."},"summary":{"type":"object","additionalProperties":{"type":"integer"},"description":"Pair counts by severity."},"data":{"type":"object","properties":{"labelExportDate":{"type":"string","format":"date"},"generatedAt":{"type":"string","format":"date"}}},"disclaimer":{"type":"string"},"attribution":{"$ref":"#/components/schemas/Attribution"}}},"Attribution":{"type":"object","properties":{"text":{"type":"string"},"url":{"type":"string","format":"uri"},"license":{"type":"string"}}},"Error":{"type":"object","required":["error"],"properties":{"error":{"type":"object","required":["code","message"],"properties":{"code":{"type":"string","enum":["invalid_request","not_found","method_not_allowed","rate_limited","unavailable"]},"message":{"type":"string"}}}}}}}}