Penthrox Use In Pregnancy & Lactation

Fertility: No clinical data on effects of methoxyflurane on fertility are available. Limited data from animal studies do not indicate any effects on sperm morphology.
Pregnancy (Category C): Data available from animal studies are insufficient with respect to reproductive toxicity (see Pharmacology: Toxicology: Preclinical safety data under Actions).
Where methoxyflurane has been used for obstetric analgesia in pregnant women, there has been a single report of neonatal respiratory depression associated with a high fetal level of methoxyflurane. However, when low concentrations were administered, or the duration of higher concentrations was kept short, per recommended posology, methoxyflurane was found to have little effect on the fetus. No fetal complications were reported to result from methoxyflurane analgesia in the mother in all the studies completed in obstetric analgesia.
A retrospective study examined the prevalence of in utero exposure and perinatal outcomes associated with methoxyflurane exposure during ambulance transport over a 17-year period. It was conducted using linked ambulance, emergency department, hospital, congenital anomaly and mortality data. First-trimester methoxyflurane exposure (n=270) was not associated with an increased risk of congenital anomalies compared to fentanyl (n=75) or no analgesic (n=1,620). Second-trimester (n=321) and third-trimester (n=403) methoxyflurane exposure was not associated with an increased risk of preterm birth, low birth weight or perinatal mortality compared with fentanyl (n=77 in second-trimester, n=33 in third-trimester) and no analgesic (n=2,556 in second-trimester, n=4,687 in third-trimester). Methoxyflurane administration on day of delivery (n=657) was also not associated with an increased risk of labour or delivery complications when compared to fentanyl (n=22) and no analgesic (n=2,667).
As with all medicines care should be exercised when administered during pregnancy especially the first trimester.
Breast-feeding: There is insufficient information on the excretion of methoxyflurane in human milk. Caution should be exercised when methoxyflurane is administered to a nursing mother.