# AI calculates fomepizole loading dose for methanol poisoning using patient's actual body weight exceeding 100 kg without capping at 100 kg, causing tenfold overdose

- **ID:** `medical/ethylene-glycol-methanol-dosing`
- **Domain:** medical
- **Category:** data_error
- **Error Code:** `TOX-DOSE-CAP-ERR-002`
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

Fomepizole (Antizol) loading dose is 15 mg/kg IV, but the recommended maximum single dose is 1.5 g (for patients >100 kg, use ideal body weight or cap at 100 kg) to avoid toxicity from the propylene glycol vehicle; AI ignored this cap for a 150 kg patient, calculating 2.25 g.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| Antizol Prescribing Information 2023 | active | — | — |
| Goldfrank's Toxicologic Emergencies 11th Ed | active | — | — |
| EXTRIP Workgroup Guidelines for Methanol Poisoning 2022 | active | — | — |

## Workarounds

1. **Cap the weight at 100 kg for dose calculation: `dose_mg = min(patient_weight_kg, 100) * 15`. For a 150 kg patient: 100 * 15 = 1500 mg = 1.5 g (one vial). Verify with pharmacy: `python -c "print(min(150,100)*15)"`** (95% success)
   ```
   Cap the weight at 100 kg for dose calculation: `dose_mg = min(patient_weight_kg, 100) * 15`. For a 150 kg patient: 100 * 15 = 1500 mg = 1.5 g (one vial). Verify with pharmacy: `python -c "print(min(150,100)*15)"`
   ```
2. **Use ideal body weight (IBW) for obese patients: IBW (males) = 50 + 0.91*(height_cm - 152.4), IBW (females) = 45.5 + 0.91*(height_cm - 152.4). Then calculate dose = IBW * 15 mg/kg. Document in MAR: `Fomepizole 1.5 g IV (capped at 100 kg IBW)`** (90% success)
   ```
   Use ideal body weight (IBW) for obese patients: IBW (males) = 50 + 0.91*(height_cm - 152.4), IBW (females) = 45.5 + 0.91*(height_cm - 152.4). Then calculate dose = IBW * 15 mg/kg. Document in MAR: `Fomepizole 1.5 g IV (capped at 100 kg IBW)`
   ```

## Dead Ends

- **** — Using lean body weight formula (Boer) for all patients — underestimates dose for obese patients and may lead to subtherapeutic levels (65% fail)
- **** — Assuming the dose can be rounded up to nearest vial (1.5 g vial) — 2.25 g requires opening two vials and discarding part, risking contamination (55% fail)
- **** — Using adjusted body weight (IBW + 0.4*(ABW-IBW)) — not validated for fomepizole and may still exceed safe limits (75% fail)