Blinded withdrawal of regular co-medication with paracetamol in chronic pain patients under strong opioids on pain control.
Chronic pain patients receiving a strong opioid in combination with paracetamol in a minimum dose of 1.5 g/day will be randomized to receive either paracetamol in the dose already prescribed (group "paracetamol") or an identically looking placebo (group "placebo") using the same schedule during the first study phase (days 1-7). In the second study phase (days 8-14) paracetamol or placebo will be stopped in both arms to assess the effect of pill withdrawal on pain control. Next to baseline the patients will be instructed to use a pain diary to rate their pain during the study and also document the required opioid rescue doses. Further assessments will include adverse events, subjective ratings of quality of sleep, overall feeling of functioning and quality of life. At the screening visit, patients will also be asked to rate their expected changes in pain relief as a result of co-treatment with paracetamol. At the completion of the study, patients will be asked about their preference and whether, overall, they felt their pain was more poorly controlled during the study. Adherence will be checked by pill count and measurement of paracetamol blood concentrations. Genotyping of OPRM1, COMT and relevant CYP enzymes and opioid blood concentrations will be assessed as co-variates for pain control.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
DOUBLE
Enrollment
7
Blinded withdrawal of regular co-medication with paracetamol
Paracetamol in the dose already used
Kantonsspital Baden
Baden, Switzerland
Inselspital, Bern University Hospital
Bern, Switzerland
VAS score (average pain intensity)
Time frame: Study day 7
Average pain using the Brief Pain Inventory (BPI)
Time frame: On each study day, up to 14 days
Minimum pain using the Brief Pain Inventory (BPI)
Time frame: On each study day, up to 14 days
Worst pain using the Brief Pain Inventory (BPI)
Time frame: On each study day, up to 14 days
Current pain using the Brief Pain Inventory (BPI)
Time frame: On each study day, up to 14 days
Average pain using the Brief Pain Inventory (BPI)
Time frame: During the last four days of each study phase (days 4-7 und 11-14)
Minimum pain using the Brief Pain Inventory (BPI)
Time frame: During the last four days of each study phase(days 4-7 und 11-14)
Worst pain using the Brief Pain Inventory (BPI)
Time frame: During the last four days of each study phase (days 4-7 und 11-14)
Current pain using the Brief Pain Inventory (BPI)
Time frame: During the last four days of each study phase (days 4-7 und 11-14)
Cumulative dose of rescue medication used
Time frame: On each study day, up to 14 days
Cumulative dose of rescue medication used
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Time frame: During the last four days of each study phase (days 4-7 und 11-14)
Number of rescue medication used
Time frame: On each study day, up to 14 days
Number of rescue medication used
Time frame: During the last four days of each study phase (days 4-7 und 11-14)
Percentage increase in pain compared to baseline
Time frame: During each study phase (days 1-7 and days 8-14)
Percentage of patients meeting the predefined pain threshold
Time frame: During each study phase (days 1-7 and days 8-14)
Subjective ratings of quality of sleep using the Brief Pain Inventory (BPI)
Time frame: At baseline and during each study phase (days 1-7 and days 8-14)
Subjective ratings of quality of life using the EQ-5D-5L questionnaire
Time frame: At baseline and during each study phase (days 1-7 and days 8-14)
Subjective ratings of functioning using the Brief Pain Inventory (BPI) and the EQ-5D-5L questionnaire
Time frame: At baseline and during each study phase (days 1-7 and days 8-14)
Patients' expectation regarding pain relief from paracetamol prior to study treatment paracetamol using the Expectation for Treatment Scale (ETS)
Five-item ETS with each item rated on a 4-point scale ranging from 1 to 4 (partially disagree, partially agree, agree and definitely agree)
Time frame: Prior to study treatment
Question about participant's preference
Study vs. baseline
Time frame: At day 7 and 14
Participant's impression of change
11-point scale tool between -5 ="very much worse" and +5 ="completely recovered"
Time frame: At day 7 and 14
Participants' guess regarding their assigned group (verum or placebo)
Time frame: At day 7 and 14
Assessment of serious adverse events
Time frame: During each study phase (days 1-7 and days 8-14)
Assessment of specific adverse events: nausea/vomiting
Time frame: During each study phase (days 1-7 and days 8-14)
Assessment of specific adverse events: drowsiness
Time frame: During each study phase (days 1-7 and days 8-14)
Assessment of specific adverse events: appetite
Time frame: During each study phase (days 1-7 and days 8-14)
Assessment of specific adverse events: constipation
Time frame: During each study phase (days 1-7 and days 8-14)
Assessment of other adverse events
Time frame: During each study phase (days 1-7 and days 8-14)
Number of withdrawals from study or treatment
Time frame: During each study phase (days 1-7 and days 8-14)
Time (days) of stable pain control
Time frame: During whole study (days 1-14)
Patients' potential to develop hepatotoxicity (investigation of risk factors)
Time frame: During whole study (days 1-14)
% hours with pain/24h
Time frame: On each study day, up to 14 days