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Pharmacokinetics and clinical efficacy of intrarectal solution of acetaminophen

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Acetaminophen is frequently administered orally to children for its analgesic properties, although its potency has never been clearly evaluated in this population. In certain situations (patients vomiting or unconscious), acetaminophen has to be given rectally. However, the rectal absorption of suppositories is frequently erratic. We undertook this study first, to measure the absorption of an aqueous solution of acetaminophen administered rectally. Secondly, we evaluated acetaminophen’s postoperative analgesic effects in children aged 1 to 8 years old undergoing adenoidectomy and/or tonsillectomy and compared its efficacy to meperidine. Twenty children received 20 mg·kg-1 of acetaminophen at the time of induction of anaesthesia while 20 others received 1 mg·kg-1 of meperidine intramuscularly. Thirty-two patients required meperidine in the Recovery Room. There was no statistical difference between the patients who received acetaminophen (18), and those who received meperidine (14). The absorption of acetaminophen was incomplete (peak serum concentration: 70.8 µnol·L1) and delayed. We conclude that the rectal administration of acetaminophen at the induction of anesthesia results in incomplete and delayed absorption and does not prevent the occurrence of immediate postoperative pain in children undergoing adeno-tonsillectomy.


Ľacétaminophène est un médicament fréquemment utilisé en pédiatrie pour ses propriétés analgésiques quoique son efficacité n’est pas été bien étudié dans cette population. Dans certaines situations cliniques, telles les vomissements et ľinconscience, les médicaments doivent être administrés par voie rectale. Toutefois il est bien connnu que ľabsorption des suppositoires est souvent erratique. C’est pourquoi nous avons étudié ľabsorption rectale ďune solution aqueuse ďacétaminophène. De plus, nous avons comparé son effet analgésique à celui de la mépéridine chez 40 enfants agés de un à huit ans admis pour adéno-amygdalectomie. Au moment de ľinduction anesthésique, 20 patients ont reçu 20 mg·kg-1 ďacétaminophène intrarectal alors que les autres ont reçu 1 mg·kg1 de mépéridine intra-musculaire. čanalgésie post-opératoire s’est avérée insuffisante chez 32 patients (acétaminophène: 18, mépéridine: 14). čabsorption de ľacétaminophène a été incomplète (concentration sérique maximale: 70.8 µmol·L1) et retardée. En conclusion, ľadministration intra-rectale ďacétaminophène au moment de ľinduction anesthésique ne procure pas une analgésie post-opératoire adéquate et entraine une absorption incomplète et retardée.


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Correspondence to Pierre Gaudreault or Joanne Guay or Odette Nicol or Claire Dupuis.

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Gaudreault, P., Guay, J., Nicol, O. et al. Pharmacokinetics and clinical efficacy of intrarectal solution of acetaminophen. Can J Anaesth 35, 149–152 (1988). https://doi.org/10.1007/BF03010655

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Key words

  • analgesics: acetaminophen
  • analgesics
  • narcotic: meperidine
  • pharmacokinetics: acetaminophen
  • rectal absorption