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. 2014 May 12:14:33.
doi: 10.1186/1471-2253-14-33. eCollection 2014.

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

Neil M Dooney  1 , Krishnaswamy Sundararajan  2 , Tharapriya Ramkumar  1 , Andrew A Somogyi  3 , Richard N Upton  4 , Jennifer Ong  5 , Stephanie N O'Connor  2 , Marianne J Chapman  2 , Guy L Ludbrook  6
Affiliations

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

Neil M Dooney et al. BMC Anesthesiol. .

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

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Figures

Figure 1
Figure 1
Individual plasma tramadol concentrations in the healthy subjects and patients. All patients and healthy subjects received a 50 mg subcutaneous bolus dose of tramadol. The median for each subject group is shown by the solid line. Graphs are truncated at 1200 minutes and 1440 minutes respectively, as plasma concentrations were less than the lower limit of quantification of the assay.
Figure 2
Figure 2
Mean plasma concentration times in healthy subjects (formula image) and patients (formula image). All patients and healthy subjects received a 50 mg subcutaneous bolus dose of tramadol. Data are shown as mean and standard deviation. The time scale is reduced compared to Figure  1 to emphasise the absorption phase.
See this image and copyright information in PMC

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