Table 1

Participant, location, duration, comparison and morphine equivalents

StudyLocation of studyPatient/population/problem/method of patient choosingNumber of patients at start of/end of studyDuration of follow-up post-treatment (all treatments≤3 months)Intervention drug administeredMorphine equivalentComparison administeredOutcome measure
Banerjee et al 25 Medical College, Kolkata, IndiaAdult men (46.2%) and women within 35–60 years of age (mean age NR) with mechanical low back pain for longer than 6 weeks and intolerant to NSAIDs were chosen via screening and recruitment which was carried out at the rheumatology and medicine outpatient department of a tertiary care hospital during the period July 2010–June 20112404 weeks poststoppage of treatmentTramadol 50 mg 2×/day5 mgFlupirtine 100 mg 2×/dayPain perception (100 mm VAS, NRS-11, HAQ-DI, PRR)
Buynak et al 16 USA (85 sites), Canada (15 sites), Australia (3 sites)Men (42.3%) and women ≥18 years of age (mean age NR) with a history of non-malignant low back pain and analgesic use for ≥3 months and a baseline pain intensity ≥5 on NRS-11 (method of patient choosing NR)Titration period: NR
Single blind period: 957/451
4 days postend of treatment and poststudy phone callTapentadol 100–250 mg
Oxycodone HCl 20–50 mg
40–100 mg, 30–75 mgPlaceboAverage pain intensity (NRS-11)
% Improvement from baseline
Chu et al 26 Stanford University, Stanford, CaliforniaMen (42.1%) and women within 18–70 years of age (mean age NR) with non-malignant non-radicular low back pain for at least 6 months and a pain level of 40 on the VAS completed a questionnaire online or over the telephone after volunteering139/1031 month poststoppage of treatment and 1-year poststudy participation surveyMorphine 78 mg (average end titration)78 mgWeight-matched placebo pillHyperalgesia (heat pain test, cold pressor test) and pain intensity (100 mm VAS)
Hale et al 15 NRMen (52.9%) and non-pregnant, non-lactating women with a mean age of 45.5–47.5 (18–75) with a confirmed diagnosis of moderate-to-severe low back pain for 15 days a month for 2 months at participating centres were enrolled based on inclusion/exclusion criteria330/139Study end point (N/A)Oxymorphone ER, oxycodone CR titrated at 10–110 mg or 20–220 mg every 12 hours<660 mgPlaceboAverage pain intensity (100 mm VAS)
Hale et al 28 30 multidisciplinary pain centres in the USAMen (55%) and women ≥18 years of age (mean age NR) with moderate-to-severe low back pain that had been present for at least several hours each day for a minimum of 3 months volunteered and were enrolled based on inclusion/exclusion criteriaOpen label period: 250/143
Double-blind period: 142/67
Study end point (N/A)Equianalgesic dose of OPANA ER (oxymorphone extended release)≥60 mgPlaceboAverage pain intensity (100 mm VAS)
Hale et al 27 66 centres in the USAMen (49.6%) and women with a mean age of 48.6 (18–75) with a documented diagnosis of moderate-to-severe chronic low back pain (non-neuropathic classes 1 and 2 and neuropathic classes 3–6 according to QTFCSD) for at least 3 hours/day, 20 days/month for 6 months (method of patient choosing NR)Open-label period: 459/268
Double-blind period: 268/110
Study end point (N/A)OROS hydromorphone ER in doses of 12, 16, 24, 32, 40, 48 or 64 mg≤60, 80, 120, 160, 200, 240, 320 mg, respectivelyPlaceboAverage pain intensity (NRS-11)
Katz et al 29 29 multidisciplinary pain centres in the USAOpioid-naïve men (46.8%) and women ≥18 years of age (mean age NR) with moderate-to-severe low back pain that had been present for ≥3 months and a pain level of 50 on the VAS volunteered and were enrolled based on inclusion/exclusion criteriaOpen-label period: 326/205
Double-blind period: 205/118
Study end point (N/A)Oxymorphone ER 5 mg (initial dose) every 12 hours15 mgPlaceboPain intensity (100 mm VAS)
Li et al 35 4 hospitals in Beijing, ChinaMen (40.6%) and women with a mean age of 46–46.5 (18–65) with moderate subacute non-malignant non-radicular low back pain that had been present for at least 4 weeks, meeting diagnostic criteria for unspecific low back pain as stated by the American College of Physicians and the American Pain Society, and a pain level of ≥4 on the NRS-11 (method of patient choosing NR)220/209Study end point (N/A)Tramadol 50 mg capsules 3×/day5 mgFlupirtine 100 mg 3x/dayAverage pain intensity (NRS-11)
O’Donnell et al 30 56 and 59 centres in the USAMen (42.4%) and women ≥18 years of age (mean age NR) with a diagnosis of low back pain existing for ≥12 weeks that requires the use of analgesics ≥4 days/week and a pain level of ≥4 on the NRS-11 (method of patient choosing NR)Study 1: 796/614
Study 2: 802/636
Study end point (N/A)Tramadol HCl 50 mg 4×/day5 mgCelecoxib (COX-2 anti-inflammatory) 200 mg 2×/daySeverity of pain (NRS-11)
Rauck et al 31 59 sites in the USAOpioid experienced men (44.7%) and non-pregnant, non-lactating women within 18–75 years of age (mean age NR) with a diagnosis of moderate-to-severe low back pain for at least several hours a day for ≥3 months and an average pain score of ≥4 on the NRS-11 (method of patient choosing NR)Open-label period: 510/302
Double-blind period: 302/183
14 days postend of studyHydrocodone ER 10, 20, 30, 40 and 50 mg10, 20, 30, 40 and 50 mg, respectivelyWeight-matched placebo pillAverage pain intensity (NRS-11)
Schnitzer et al 32 26 investigational centres across the USAMen (50%) and women with a mean age of 47.1 (27–79) (double-blind period) with low back pain severe enough to require daily medication for at least 3 months and a pain score of ≥4 on the VAS volunteered and were enrolled based on inclusion/exclusion criteriaOpen-label period: 380/254
Double-blind period: 254/146
Study end point (N/A)Tramadol 50 mg capsules, up to 400 mg/day5 mg up to 40 mg/dayPlacebo capsulesAverage pain intensity (NRS-11)
Uberall et al 17 31 active investigational sites across GermanyMen (38%) and women with a mean age of 58.5 (18–75) with a history of non-malignant low back pain for ≥3 months and an average pain score of ≥4 on the NRS-11 (method of patient choosing NR)326/2761-week poststudy end pointTramadol ER 200 mg 1×/day20 mgFlupirtine 400 mg 1x/day, placebo tabletAverage pain intensity (NRS-11)
Vorsanger et al 34 30 centres in the USAMen (50%) and women with a mean age between 47 and 49 (19–80) with chronic (≥6 months) low back pain requiring daily treatment of medication for at least 60 of 90 days and a score of ≥40 mm on the 100 mm VAS postwashout period (method of patient choosing NR)Open-label period: 619/386
Double-blind period: 386/241
1-week poststudy end pointTramadol 300 or 200 mg (in 100 mg tablets) 1×/day30 mg or 20 mgPlacebo tabletsPain intensity (100 mm VAS)
Wen et al 33 94 sites in the USAMen (43%) and women with a mean age of 48.6 (≥18) (double-blind period) with low back pain for at least 3 months (method of patient choosing NR)Open-label period: 905/592
Double-blind period: 588/439
5–7 days postfinal double-blind periodHydrocodone 20–120 mg tablets 1×/day20 to 120 mgWeight-matched placebo pillAverage pain experienced (100 mm VAS)
  • CR, controlled release; HAQ-DI, Health Assessment Questionnaire Disability Index; N/A, not available; NR, not reported; NRS, numerical rating scale; NSAID, non-steroidal anti-inflammatory drug; PRR, pain relief rate; VAS, visual analogue scale.