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Open Access Research article

Pharmacokinetics of tramadol after subcutaneous administration in a critically ill population and in a healthy cohort

Neil M Dooney1, Krishnaswamy Sundararajan24, Tharapriya Ramkumar1*, Andrew A Somogyi3, Richard N Upton145, Jennifer Ong4, Stephanie N O’Connor24, Marianne J Chapman24 and Guy L Ludbrook14

Author Affiliations

1 Department of Anaesthesia, Pain Medicine and Hyperbaric Medicine, Royal Adelaide Hospital, Adelaide, SA 5000, Australia

2 Intensive Care Unit, Royal Adelaide Hospital, Adelaide, Australia

3 Discipline of Pharmacology, Faculty of Health Sciences, University of Adelaide, Adelaide, Australia

4 Discipline of Acute Care Medicine, University of Adelaide, Adelaide, Australia

5 Discipline of Pharmacometrics, Division of Health Sciences, University of South Australia, Adelaide, Australia

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BMC Anesthesiology 2014, 14:33  doi:10.1186/1471-2253-14-33

Published: 12 May 2014

Abstract

Background

Tramadol is an atypical centrally acting analgesic agent available as both oral and parenteral preparations. For patients who are unable to take tramadol orally, the subcutaneous route of administration offers an easy alternative to intravenous or intramuscular routes. This study aimed to characterise the absorption pharmacokinetics of a single subcutaneous dose of tramadol in severely ill patients and in healthy subjects.

Methods/design

Blood samples (5 ml) taken at intervals from 2 minutes to 24 hours after a subcutaneous dose of tramadol (50 mg) in 15 patients (13 male, two female) and eight healthy male subjects were assayed using high performance liquid chromatography. Pharmacokinetic parameters were derived using a non-compartmental approach.

Results

There were no statistically significant differences between the two groups in the following parameters (mean ± SD): maximum venous concentration 0.44 ± 0.18 (patients) vs. 0.47 ± 0.13 (healthy volunteers) mcg/ml (p = 0.67); area under the plasma concentration-time curve 177 ± 109 (patients) vs. 175 ± 75 (healthy volunteers) mcg/ml*min (p = 0.96); time to maximum venous concentration 23.3 ± 2 (patients) vs. 20.6 ± 18.8 (healthy volunteers) minutes (p = 0.73) and mean residence time 463 ± 233 (patients) vs. 466 ± 224 (healthy volunteers) minutes (p = 0.97).

Conclusions

The similar time to maximum venous concentration and mean residence time suggest similar absorption rates between the two groups. These results indicate that the same dosing regimens for subcutaneous tramadol administration may therefore be used in both healthy subjects and severely ill patients.

Trial registration

ACTRN12611001018909

Keywords:
Tramadol; Subcutaneous; Pharmacokinetics; Severely ill; Healthy subjects