Onset of acetaminophen analgesia: comparison of oral and intravenous routes after third molar surgery

Moller, P. L.
Sindet-Pedersen, S.
Petersen, C. T.
Juhl, G. I.
Dillenschneider, A.
Skoglund, L. A.

¹Department of Oral and Maxillofacial Surgery, Aarhus University Hospital, Denmark.
²Neuroscience Department, Bristol–Myers Squibb, Rueil-Malmaison, France.
³Section of Dental Pharmacology and Pharmacotherapeutics, Faculty of Dentistry, University of Oslo, Norway.
⁴Present address: UCL Analgesia Centre, Eastman Dental Institute, University College London, London, UK

^*Corresponding author: Department of Anaesthesia, University Hospital of Aarhus, Norrebrogade 44, DK-800 Aarhus, Denmark. E-mail: [email protected]

Accepted for publication: December 22, 2004

BJA: British Journal of Anaesthesia 94(5):p 642-648, May 2005.

Background

The purpose of this randomized double-blind study was to compare the efficacy and safety of propacetamol 2 g (an i.v. acetaminophen 1 g formulation) administered as a 2-min bolus injection (n=50) or a 15-min infusion (n=50) with oral acetaminophen 1 g (n=50) or placebo (n=25) for analgesia after third molar surgery in patients with moderate to severe pain after impacted third molar removal.

Methods

All patients were evaluated for efficacy during the initial 6 h period after treatment administration (T₀) and for safety during the entire week after T₀.

Results

The onset of analgesia after propacetamol was shorter (3 min for bolus administration, 5 min for 15-min infusion) than after oral acetaminophen (11 min). Active treatments were significantly better for all parameters (pain relief, pain intensity, patient's global evaluation, duration of analgesia) than placebo (P<0.05). Adverse events were more frequent after propacetamol, especially pain at the injection site. Propacetamol bolus resulted in a much higher incidence of local adverse events than the infusion (propacetamol bolus 90% vs propacetamol infusion 52%) with no clinically significant benefits in terms of analgesic efficacy.

Conclusion

I.V. propacetamol, administered as a 15-min infusion, is a fast-acting analgesic agent. It is more effective in terms of onset of analgesia than a similar dose of oral acetaminophen.