Stability of Methoxyflurane Loaded Penthrox Inhaler

Abstract

ABSTRACTBackgroundMethoxyflurane (MEOF), a non‐narcotic inhalational anaesthetic, administered with the Penthrox Inhaler is effective in managing acute pain. Despite widespread use by ambulance services, its use in emergency departments and hospital wards has been limited. MEOF storage to minimise evaporation would facilitate pre‐filling inhalers for multiple treatment use.AimTo ascertain if Penthrox Inhalers loaded with MEOF can be stored for extended periods without appreciable loss of MEOF.Method18 Penthrox Inhalers were loaded with MEOF 3 mL and weighed over 87 hours. 6 inhalers were left in the open, 6 inhalers stored in the packing boxes and 6 inhalers sealed in low‐density polyethylene bags inside the packing boxes.ResultsPenthrox Inhalers in the polyethylene bags retained over 95% of the MEOF after 25 hours and over 80% after 87 hours. Inhalers stored in the packing boxes retained 15% of the MEOF after 25 hours while inhalers left in the open lost 50% of the MEOF after 5 hours with less than 1% remaining after 25 hours.ConclusionPenthrox Inhalers loaded with MEOF and stored in low‐density polyethylene bags inside the packing boxes can be effective for over 3 days without appreciable loss of MEOF.