Inhaled methoxyflurane (Penthrox) sedation for third molar extraction: a comparison to nitrous oxide sedation

Aust Dent J. 2011 Sep;56(3):296-301. doi: 10.1111/j.1834-7819.2011.01350.x.


Background: The aim of this study was to evaluate the use of inhaled methoxyflurane (Penthrox) in the reduction of dental anxiety in patients undergoing mandibular third molar removal in a specialist surgical suite and compare it to the conventional nitrous oxide sedation.

Methods: A prospective randomized, non-blinded crossover design study of 20 patients receiving two types of sedation for their third molar extraction who participated in 40 treatment sessions. At first appointment, a patient was randomly assigned to receive either nitrous oxide sedation or intermittent Penthrox inhaler sedation, with the alternate regimen administered during the second appointment. Peri-procedural vital signs (heart rate and blood pressure) were recorded and any deviations from 20% from the baseline values, as well as any drop in oxygen saturation below 92% were documented. The Ramsay Sedation Scale (RSS) score was recorded every five minutes. Patient cooperation during the procedure, patients' general opinion about the sedation technique, surgeon satisfaction and the occurrence of side effects were all recorded. After the second procedure, the patient was also asked if he or she had any preference of one sedation technique over the other.

Results: Levels of sedation were comparable in nitrous oxide and Penthrox sedation sessions. However, at 15 minutes of sedation it was significantly lighter (p < 0.05) in Penthrox. No patient in both regimens reached a RSS deeper than a score of 4. Parameters measured for assessment of sedation (patient cooperation, surgeon satisfaction and patient general opinion about sedation technique) were all similarly comparable for both nitrous oxide and Penthrox. In both sedation sessions, the odour of the inhalational agent was accepted by the patients; half of the patients (10 patients) who received methoxyflurane thought its odour was pleasant. Patients preferred methoxyflurane (Penthrox) inhalation over nitrous oxide sedation (Fisher's Exact test, p < 0.05). Adverse events were minimal. No patient was either deeply sedated or agitated. Blood pressure was within ± 20% from the baseline values. No patient had oxygen saturation less than 92%. Dizziness was the most frequently encountered side effect in both regimens (four patients each). Two patients had bradycardia (HR < 60 beats/minute) when nitrous oxide was used in comparison to one patient with Penthrox sedation. Paraesthesia of fingers and heaviness of the chest was encountered only with nitrous oxide sedation (four patients). Mild self-limited shivering occurred in one patient with Penthrox sedation.

Conclusions: The Penthrox Inhaler can produce a comparable sedation to that of nitrous oxide for the surgical extraction of third molars under local anaesthesia.

Publication types

  • Comparative Study
  • Randomized Controlled Trial

MeSH terms

  • Adolescent
  • Adult
  • Anesthesia, Dental / methods
  • Anesthetics, Inhalation / administration & dosage*
  • Anesthetics, Inhalation / adverse effects
  • Blood Pressure / physiology
  • Bradycardia / chemically induced
  • Conscious Sedation / methods*
  • Cooperative Behavior
  • Cross-Over Studies
  • Dental Anxiety / prevention & control
  • Dizziness / chemically induced
  • Female
  • Fingers
  • Heart Rate / physiology
  • Humans
  • Male
  • Methoxyflurane / administration & dosage*
  • Methoxyflurane / adverse effects
  • Molar, Third / surgery*
  • Nausea / chemically induced
  • Nitrous Oxide / administration & dosage*
  • Nitrous Oxide / adverse effects
  • Oxygen / blood
  • Paresthesia / chemically induced
  • Patient Satisfaction
  • Prospective Studies
  • Thorax / drug effects
  • Tooth Extraction*
  • Treatment Outcome
  • Young Adult


  • Anesthetics, Inhalation
  • Methoxyflurane
  • Nitrous Oxide
  • Oxygen