Drug Interaction & Formulary Checker

Overview

This skill checks drug-drug interactions, allergy contraindications, formulary coverage, and dosing guidelines using free public APIs — no credentials required out of the box.

What it can do:

• - Check interactions between 2 or more drugs
• Look up a full medication list for interactions
• Check formulary tier and coverage for a payer
• Flag allergy contraindications
• Provide standard adult dosing ranges
• Suggest therapeutic alternatives when a drug is not covered

APIs used (all free, no key needed):

• - OpenFDA — drug interactions, adverse events, labeling
• RxNorm API (NLM) — drug name normalization and RxCUI lookup
• NLM DailyMed — official drug labeling and prescribing info

⚠️ Clinical Disclaimer: All output is informational only and must be reviewed by a licensed clinician or pharmacist before any prescribing or dispensing decision.

🔒 Privacy / PHI Warning: This skill sends drug names and allergy information to public APIs (RxNorm, OpenFDA, DailyMed). Do not include patient-identifiable information (names, MRNs, DOBs, addresses, or other PHI) in any query. Use drug names and clinical terms only. For production use with real patient data, ensure your deployment satisfies HIPAA requirements and that a BAA is in place with any third-party service.

Trigger Phrases

• - "Check interactions for [drug list]"
• "Is it safe to take [drug A] with [drug B]?"
• "Check this patient's med list for interactions"
• "What tier is [drug] on [payer] formulary?"
• "Is [drug] covered by BlueCross?"
• "What's the standard dose for [drug]?"
• "Are there any contraindications with [drug] for a patient allergic to [allergen]?"
• "Suggest an alternative to [drug] that's on formulary"

Drug Interaction Checks

Single pair check

Full medication list check

What the agent does:

1. 1. Normalizes all drug names via RxNorm API
2. Queries OpenFDA drug interactions for each pair
3. Ranks interactions by severity (Major / Moderate / Minor)
4. Returns a structured interaction report

Example output:

DRUG INTERACTION REPORT
Patient Med List: 5 medications checked
Pairs checked: 10

⛔ MAJOR (1):
• Warfarin + Aspirin
  Risk: Increased bleeding risk. Combined antiplatelet 
  and anticoagulant effect.
  Action: Monitor INR closely. Consider GI protection.

⚠️ MODERATE (2):
• Lisinopril + Potassium supplements
  Risk: Hyperkalemia risk.
  Action: Monitor serum potassium.

• Atorvastatin + Clarithromycin
  Risk: Increased statin exposure, myopathy risk.
  Action: Temporarily hold statin if antibiotic needed.

✅ MINOR / NO INTERACTION (7):
  Remaining pairs — no clinically significant interactions found.

Source: OpenFDA + RxNorm | For clinician review only

Allergy Contraindication Check

CODEBLOCK3

What the agent does:

1. 1. Looks up drug class and cross-reactivity data from OpenFDA labeling
2. Flags any drugs in the same class as the allergen
3. Suggests safe alternatives where available

Formulary & Coverage Lookup

CODEBLOCK4

What the agent does:

1. 1. Looks up the drug's generic name and drug class via RxNorm
2. If FORMULARY_API_KEY is set: queries the real-time payer formulary API for tier and coverage data
3. If no key is set: instructs the agent to tell the user to verify tier directly with the payer's online formulary tool — no estimated or cached data is used
4. Suggests covered alternatives in the same drug class based on RxNorm drug class data

Note: Without FORMULARY_API_KEY, this skill does not provide formulary tier estimates. Always confirm coverage with the payer's online formulary tool or pharmacy benefit line before clinical use.

Example output:

FORMULARY CHECK — Ozempic (semaglutide)
Payer: BlueCross BlueShield PPO

Tier: 4 (Non-Preferred Brand)
Est. Copay: $80-120/month (with standard benefit)
Prior Auth Required: Yes
Step Therapy Required: Yes (must try Metformin first)

Covered Alternatives (Tier 2):
• Trulicity (dulaglutide) — Tier 2, $45/month
• Victoza (liraglutide) — Tier 2, $50/month

Recommendation: Consider Trulicity as first-line 
if cost is a barrier. PA may be approved if 
patient has failed oral agents.

Dosing Reference

CODEBLOCK6

Example output:

DOSING REFERENCE — Metformin (metformin HCl)

Standard Adult Dose:
• Starting: 500mg BID or 850mg once daily with meals
• Titration: Increase by 500mg/week as tolerated
• Maximum: 2550mg/day (divided doses)

Renal Dosing:
• eGFR 30-45: Use with caution, max 1000mg/day
• eGFR <30: CONTRAINDICATED

Common Side Effects: GI upset, nausea (take with food)
Black Box Warning: Lactic acidosis (rare)

Source: FDA prescribing information via OpenFDA

API Reference

RxNorm — Drug Name Normalization

OpenFDA — Interactions & Labeling

NLM DailyMed

GET https://dailymed.nlm.nih.gov/dailymed/services/v2/spls.json?drug_name={name}
→ Returns structured product labeling

Example Workflows

Quick interaction check before prescribing

Full med reconciliation on admission

Clinician: "Patient admitted with these home meds, 
            check for interactions:
            Warfarin, Amiodarone, Metoprolol, 
            Furosemide, Potassium Chloride, Digoxin"

Agent: [Checks all 15 pairs]
       "⛔ 2 MAJOR interactions found:
        • Amiodarone + Warfarin: Markedly increases 
          INR. Reduce Warfarin dose by 30-50%.
        • Amiodarone + Digoxin: Increases Digoxin 
          levels. Monitor levels and reduce dose."

Version History