Penthrox - "The Green Whistle"
Methoxyflurane for Acute Pain
Rapid onset inhaled analgesic for moderate to severe pain in out-of-hospital settings.
CHECK FIRST: Screen patient using "A WHISTLER" below. If ANY answer is YES, do NOT give Penthrox.
Patient Screening: "A WHISTLER"
If ANY answer is "YES" → DO NOT give Penthrox
| Letter | Question |
|---|---|
| A | Age < 18 years old? |
| W | Wonky - More than mildly intoxicated? |
| H | History of Malignant Hyperthermia? |
| I | Impaired kidney function (dialysis, diabetes, transplant)? |
| S | Sensitivity/allergy to inhaled anesthetics? |
| T | Trending down - hemodynamically unstable? |
| L | Liver problems (hepatitis, cirrhosis)? |
| E | Expecting - pregnant or breastfeeding? |
| R | Receiving TB medications? |
Additional Contraindications
- Decreased level of consciousness (LOC)
- Can't self-administer the medication
- Provider is pregnant (or suspected) - DO NOT administer
Quick Reference
| Item | Details |
|---|---|
| Dose | 3 ml (can repeat once = 6 ml total) |
| Onset | 6-8 breaths |
| Duration | 30-60 minutes |
| Age | 18+ years only |
| Patient Must Be | Conscious, stable, able to self-administer |
Indications for Use
Use in stable, conscious adults (18+) with moderate to severe acute pain from:
- Musculoskeletal injuries, burns, extensive wounds
- Medical procedures (abscess drainage, joint relocation, splinting)
- Pain during transport (UTV, logging road, sled)
Safety & Dosage Limits
- Patient limit: Max 6 ml over 48 hours
- Patient limit: Max 15 ml per week
- Provider limit: Max 3 doses per 24 hours
- Storage: Stable -20 to 60°C (optimal 5-30°C)
- Shelf life: 3 years
How to Administer
Dose: 3 ml (can repeat once = 6 ml total)
- Complete ABCs, stabilize injury, take vital signs
- Screen patient using "A WHISTLER"
- Open the medication bottle
- Pour 3 ml into the blunt end of the whistle, turning it 360° as you pour
- Replace cap on bottle
- Stay with patient during use
- Dispose of whistle in sealed plastic bag
- Report every use
Caution When Pouring
Very easy to spill! Pour slowly and carefully. Avoid non-ventilated spaces.
Patient Instructions
What to Tell the Patient
"This is a short-acting pain medication you inhale. It works after 6-8 breaths and lasts 30-60 minutes."
How to Use
- Put fabric loop around wrist
- Hold like a whistle, seal lips around it
- Breathe normally through your mouth
- Exhale through the whistle (forces air through filter)
- Cover the diluter hole for more pain relief
- Use continuously until pain is bearable, then as needed
Side Effects
Common (tell patient to expect)
- Dizziness, drowsiness
- Nausea/vomiting
- Headache, dry mouth
Rare (but serious)
- Kidney or liver injury (from overuse)
- Malignant hyperthermia
- Shortness of breath
⚠️ Important: Screen all patients using "A WHISTLER" before administering. Stay with the patient during use. Report all uses. Providers who are pregnant or suspected pregnant must not administer Penthrox.
Source: Purdue Pharma Product Monograph, last revised April 6, 2018
Document Version: 2023-06-21
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