Adults 18 to 90, any sex, with Abdominal Surgery or Respiratory Failure. Patients with the condition only — healthy volunteers not accepted.
Results — posted to ClinicalTrials.gov
Per-arm endpoint measurements with 95% confidence intervals where reported. Source: trial results section.
Serum Concentration of Tramadol and Tramadol Metabolites With Respect to Metabolic PhenotypePrimary· 1, 2, and 4 hours after first dose and immediately before 2nd, 3rd, and 5th dose, up to 24 hours
The plasma concentrations of tramadol, O-desmethyltramadol (ODT) and N-desmethyltramadol (NDT) will be measured 1, 2 and 4 hours after the first dose of 100 mg tramadol i.v., and immediately before the 2nd, 3rd and 5th dose. There will therefore be 6 measurements of tramadol and its metabolites.
1st measurement
Group
Value
95% CI
Tramadol Concentration
372.7
250.6 – 535.7
ODT Concentration in Poor Metabolizers (PM)
7.05
4.52 – 7.05
ODT Concentration in Intermediate Metabolizers (IM)
17.1
6.3 – 38.1
ODT Concentration in Extensive Metabolizers (EM)
40.9
21.9 – 53.9
ODT Concentration in Ultrafast Metabolizers (UM)
13.8
NDT Concentration in Poor Metabolizers (PM)
11.7
7.6 – 11.7
NDT Concentration in Intermediate Metabolizers (IM)
4.5
3.5 – 11.1
NDT Concentration in Extensive Metabolizers (EM)
4.76
3.5 – 19.1
NDT Concentration in Ultrafast Metabolizers (UM)
3.5
2nd measurement
Group
Value
95% CI
Tramadol Concentration
270.6
201.6 – 447.9
ODT Concentration in Poor Metabolizers (PM)
7.6
4.5 – 7.6
ODT Concentration in Intermediate Metabolizers (IM)
15.7
7.3 – 39.6
ODT Concentration in Extensive Metabolizers (EM)
46.7
23.6 – 64.3
ODT Concentration in Ultrafast Metabolizers (UM)
19.4
NDT Concentration in Poor Metabolizers (PM)
15.3
9.2 – 15.3
NDT Concentration in Intermediate Metabolizers (IM)
6.1
3.9 – 12.2
NDT Concentration in Extensive Metabolizers (EM)
5.2
3.5 – 22
NDT Concentration in Ultrafast Metabolizers (UM)
3.5
3rd measurement
Group
Value
95% CI
Tramadol Concentration
232.1
153.5 – 369.8
ODT Concentration in Poor Metabolizers (PM)
10
4.6 – 10
ODT Concentration in Intermediate Metabolizers (IM)
20.2
12.5 – 40.4
ODT Concentration in Extensive Metabolizers (EM)
46.4
31 – 72.6
ODT Concentration in Ultrafast Metabolizers (UM)
26
NDT Concentration in Poor Metabolizers (PM)
28.9
12.3 – 28.9
NDT Concentration in Intermediate Metabolizers (IM)
9.1
5.3 – 14.7
NDT Concentration in Extensive Metabolizers (EM)
8.5
3.6 – 22.9
NDT Concentration in Ultrafast Metabolizers (UM)
3.5
4th measurement
Group
Value
95% CI
Tramadol Concentration
181.2
122.9 – 270.2
ODT Concentration in Poor Metabolizers (PM)
12.4
5.2 – 12.4
ODT Concentration in Intermediate Metabolizers (IM)
19.1
11.4 – 47.8
ODT Concentration in Extensive Metabolizers (EM)
38.1
30.3 – 74.5
ODT Concentration in Ultrafast Metabolizers (UM)
25.1
NDT Concentration in Poor Metabolizers (PM)
31.2
15.7 – 31.2
NDT Concentration in Intermediate Metabolizers (IM)
9.6
5.1 – 20.7
NDT Concentration in Extensive Metabolizers (EM)
9.7
3.5 – 23.9
NDT Concentration in Ultrafast Metabolizers (UM)
3.5
5th measurement
Group
Value
95% CI
Tramadol Concentration
300.1
191.8 – 417.6
ODT Concentration in Poor Metabolizers (PM)
19.1
10.7 – 19.1
ODT Concentration in Intermediate Metabolizers (IM)
36.6
21.2 – 71.4
ODT Concentration in Extensive Metabolizers (EM)
75.1
46.3 – 117.6
ODT Concentration in Ultrafast Metabolizers (UM)
58.2
NDT Concentration in Poor Metabolizers (PM)
71.4
43 – 71.4
NDT Concentration in Intermediate Metabolizers (IM)
20.2
10.5 – 37.2
NDT Concentration in Extensive Metabolizers (EM)
19
7.4 – 45.6
NDT Concentration in Ultrafast Metabolizers (UM)
9.8
6th measurement
Group
Value
95% CI
Tramadol Concentration
408.5
273.8 – 677.8
ODT Concentration in Poor Metabolizers (PM)
29.7
23.9 – 29.7
ODT Concentration in Intermediate Metabolizers (IM)
51.7
25.7 – 93.5
ODT Concentration in Extensive Metabolizers (EM)
97.4
52.6 – 139
ODT Concentration in Ultrafast Metabolizers (UM)
61.9
NDT Concentration in Poor Metabolizers (PM)
180.5
124.9 – 180.5
NDT Concentration in Intermediate Metabolizers (IM)
34.9
18.5 – 69.9
NDT Concentration in Extensive Metabolizers (EM)
34.4
18.6 – 72.5
NDT Concentration in Ultrafast Metabolizers (UM)
18.1
Analgesic Effect of Tramadol Measured by Numeric Rating Scale (NRS)Secondary· Before each dose of tramadol and 30 minutes after tramadol dose, up to 24 hours
The analgesic effect of tramadol will be measured in awake patients with Numeric Rating Scale (NRS, 0 - without pain, 10 - the worst pain) 30 minutes before and 30 minutes after tramadol administration. The NRS value of 3 or less will be considered as adequate analgesia. In case of inadequate analgesia morphine will be used according to the local protocol.
1st pain assessment
Group
Value
95% CI
Median NRS Score Before Tramadol Administration
7
3 – 9
Median NRS Score After Tramadol Administration
5
3.5 – 6
2nd pain assessment
Group
Value
95% CI
Median NRS Score Before Tramadol Administration
5
3 – 6.75
Median NRS Score After Tramadol Administration
3
1 – 4.75
3rd pain assessment
Group
Value
95% CI
Median NRS Score Before Tramadol Administration
3.5
2.25 – 5
Median NRS Score After Tramadol Administration
2
1 – 3
4th pain assessment
Group
Value
95% CI
Median NRS Score Before Tramadol Administration
4
2 – 5
Median NRS Score After Tramadol Administration
2
1 – 4
5th pain assessment
Group
Value
95% CI
Median NRS Score Before Tramadol Administration
3
2 – 5
Median NRS Score After Tramadol Administration
2
1 – 3
Analgesic Effect of Tramadol Measured by Critical Care Pain Observation Tool (CPOT)Secondary· Pain was assessed before and 30 minutes after each tramadol dose, up to 24 hours.
In unconsciousness patents, the analgesic effect of tramadol will be tested by Critical Care Pain Observation Tool (CPOT). Highest score on a scale is 8 (worst pain) and lowest is 0 (no pain). The CPOT value of less than 2 will be considered as adequate analgesia.
1st assessment point
Group
Value
95% CI
Median CPOT Score Before Tramadol Administration
0
0 – 0
Median CPOT Score After Tramadol Administration
0
0 – 0
2nd assessment point
Group
Value
95% CI
Median CPOT Score Before Tramadol Administration
0
0 – 0
Median CPOT Score After Tramadol Administration
0
0 – 0
3rd assessment point
Group
Value
95% CI
Median CPOT Score Before Tramadol Administration
0
0 – 0
Median CPOT Score After Tramadol Administration
0
0 – 0
4th assessment point
Group
Value
95% CI
Median CPOT Score Before Tramadol Administration
0
0 – 0
Median CPOT Score After Tramadol Administration
0
0 – 0
5th assessment point
Group
Value
95% CI
Median CPOT Score Before Tramadol Administration
0
0 – 0
Median CPOT Score After Tramadol Administration
0
0 – 0
Number of Participants With Nausea and Vomiting After TramadolSecondary· Nausea and vomiting was assessed during first 30 minutes after tramadol administration
Nausea and/or vomiting during treatment with tramadol in ICU will be recorded.
Group
Value
95% CI
PONV in EM
12
PONV in IM
4
Number of Patients With Respiratory Depression After TramadolSecondary· Respiratory depression was observed up to 30 minutes after tramadol administration
Respiratory depression after tramadol is considered to be any drop in saturation below 90% or drop in respiratory rate below 10/min.
Group
Value
95% CI
Number of Patients With Postoperative Respiratory Depression
0
Length of ICU StaySecondary· Up to 6 months
Length of stay in ICU will be recorded and correlated with standard laboratory values and tramadol and metabolites concentration.
Group
Value
95% CI
Low Plasma Cholinesterase Activity
1.5
1 – 6
Normal Plasma Cholinesterase Activity
1
1 – 1
Adverse events — posted to ClinicalTrials.gov
Time frame: 24 hours.
Reporting threshold: 5%.
Adverse-event reports describe events observed during the trial — not all are caused by the drug.
Tramadol is opioid analgesic widely used to treat moderate to severe pain. It is metabolized by cytochrome CYP2D6 into two major metabolites: pharmacologically active metabolite O-desmethyltramadol (M1) and inactive N-desmethyltramadol (M2), respectively. Tramadol kinetics in a population of patients undergoing major abdominal surgical procedures, and in patients with a greater or lesser degree of organic failure, is still not well researched. The investigators will measure plasma concentrations of tramadol and its metabolites after usual tramadol doses in ICU patients after major abdominal surgery. Also analgesic affect and side effect of tramadol will be recorded.
Publications & conference data
1 peer-reviewed publication reference this trial (live from Europe PMC):
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· active not recruiting
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Publications: Europe PMC API search by NCT ID, retrieved 10 June 2026
Drug + disease cross-links: matched in real time against Drug Landscape's normalised drug + company + condition tables
Sponsor: as reported to ClinicalTrials.gov by Osijek University Hospital
Last refreshed: 9 July 2021
Drug Landscape aggregates and links these public records for informational use only. Always verify against the primary source before clinical or regulatory decisions. Canonical URL: https://druglandscape.com/trial/NCT04004481.