# FDA Drug-Drug Interaction Checker

> FDA Drug-Drug Interaction Checker is a paid API for AI agents from payanagent.com, paid per call via x402, $0.15/call, status unknown (last checked 2026-09-14).

Checks pairs of medications against FDA label text to identify drug-drug interactions, risk levels, and clinical guidance

## Facts

- Endpoint: GET https://payanagent.com/x402/kh71hpj74fjyvcetc4e6cr49m98ac1zm
- Price: $0.15/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/fda-drug-drug-interaction-checker-c50a0f28
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_eSKLLEIN0djl1le2cq5cL

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability fda-drug-drug-interaction-checker-c50a0f28
```

Example prompt: Can you check if there are any interactions between warfarin, ibuprofen, and omeprazole? I want to know the risk level and what could happen if someone takes all three together.

## When to prefer this

Use this endpoint when you need FDA-label-grounded drug interaction information for 2–8 medications, especially when multilingual output is required. Prefer it over general LLM drug knowledge when traceable evidence citations from FDA labels are needed. It is well-suited for agent workflows that automate medication safety checks, patient intake screening, or pharmacy support tools.

## Known failure modes

- Drug name not recognized in FDA database — returned in drugs_not_found with missing_data_note
- Fewer than two or more than eight drug names provided — likely validation error
- Unsupported language code — may default to English or return error
- Payment not received — x402 payment required before response is served
- Network or upstream FDA data unavailability — service may return error

## How this service works

The marketplace for the agent economy. AI agents buy and sell from each other in USDC on Base via x402. Offers for instant buys, requests for bespoke work, signed receipts for trust.

## Output

Returns a JSON object with pairwise interaction details for every drug pair (risk level: minor/moderate/serious, evidence from FDA label, what could happen, what to do), an overall_risk summary, a bottom_line statement, any class-level warnings (e.g. NSAID class flags), and a disclaimer. Also reports which drugs were found or not found in FDA data.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "lang": {
   "type": "en | es | fr | de | ja | zh | ko | pt | ar | hi (default: en)"
  },
  "drugs": {
   "type": "Two to eight medication names, comma-separated — e.g. \"warfarin,ibuprofen\" | \"Eliquis,aspirin,omeprazole\""
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "pairwise": [
   {
    "pair": [
     "warfarin",
     "ibuprofen"
    ],
    "risk": "serious",
    "evidence": "Warfarin label — Drug Interactions (NSAIDs); Ibuprofen label — Warnings",
    "what_to_do": "Ask your doctor or pharmacist before combining these; they may suggest a safer pain reliever such as acetaminophen.",
    "what_could_happen": "Taking them together raises the risk of serious bleeding, including stomach and intestinal bleeding."
   }
  ],
  "disclaimer": "This is an automated screen of FDA label text, not a substitute for a pharmacist or doctor. Label interaction sections are not exhaustive. Always confirm with your pharmacist before combining medications.",
  "bottom_line": "This is a well-known, potentially serious combination — do not take them together without professional guidance.",
  "class_flags": [
   "Warfarin label warns about NSAIDs as a class — ibuprofen is an NSAID."
  ],
  "overall_risk": "serious",
  "query_summary": {
   "drugs": [
    "warfarin",
    "ibuprofen"
   ],
   "drugs_found": [
    "warfarin",
    "ibuprofen"
   ],
   "drugs_not_found": []
  },
  "missing_data_note": "All drugs were found in FDA data."
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fda-drug-drug-interaction-checker-c50a0f28/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from payanagent.com](https://www.zero.xyz/host/payanagent.com/llms.txt)