Onset of analgesic effect and plasma levels of controlled-release tramadol (Tramadol Contramid once-a-day) 200-mg tablets in patients with acute low back pain

PHARMACOKINETICS OF TRAMADOL AND O-DESMETHYLTRAMADOL IN GIANT TORTOISES (CHELONOIDIS VANDENBURGHI, CHELONOIDIS VICINA)

The objective of this study was to determine the pharmacokinetics of two orally administered doses of tramadol (1 mg/kg and 5 mg/kg) and its metabolite, O-desmethyltramadol (M1) in giant tortoises (Chelonoidis vandenburghi, Chelonoidis vicina). Eleven giant tortoises (C. vandenburghi, C. vicina) received two randomly assigned, oral doses of tramadol (either 1 mg/kg or 5 mg/kg), with a washout period of 3 wk between each dose. The half-life (t½) of orally administered tramadol at 1 mg/kg and 5 mg/kg was 11.9 ± 4.6 h and 13.2 ± 6.1 h, respectively. After oral administration of tramadol at 1 mg/kg and 5 mg/kg, the maximum concentration (Cmax) was 125 ± 69 ng/ml and 518 ± 411 ng/ml, respectively. There were not enough data points to determine pharmacokinetic (PK) parameters for the M1 metabolite from either dose. Tramadol administered orally to giant tortoises at both doses provided measurable plasma concentrations of tramadol for approximately 48 h with occasional transient sedation. Oral tramadol at 5 mg/kg, on average, achieves concentrations of >100 ng/ml, the reported human therapeutic threshold, for 24 h. Based on the low levels of M1 seen in this study, M1 may not be a major metabolite in this taxon.

Population Pharmacokinetic/Pharmacodynamic Modeling of O-Desmethyltramadol in Young and Elderly Healthy Volunteers

BACKGROUND

Age-related changes in the concentration-effect relationship of (+)-O-desmethyl-tramadol [(+)-ODM], tramadol's active metabolite, are not documented in the elderly.

OBJECTIVE

The objective of this study was to characterize, in elderly and young subjects, the (+)-ODM pharmacokinetic and pharmacodynamic relationship to examine the effect of age after single-dose administration of tramadol 200 mg extended-release tablets.

METHODS

A population analysis of a double-blind, randomized, placebo-controlled, two-period cross-over study including 13 elderly (aged ≥75 years) subjects with mild renal insufficiency and 16 young (aged 18-40 years) subjects was conducted. For 48 h post-dose, blood samples were collected and pain tolerance thresholds measured using an electrically stimulated pain model. A pharmacokinetic/pharmacodynamic model incorporating a one-compartment pharmacokinetic model for (+)-ODM parameterized with first-order formation rate, clearance (CL/f_m), volume of distribution (V/f_m) and a sigmoid maximum effect (E_max) model incorporating baseline (E₀) and placebo effect was used.

RESULTS

Maximum plasma concentrations of (+)-ODM occurred later and plasma concentrations declined more slowly in the elderly than in young subjects. In the elderly, V/f_m was 76% larger and CL/f_m 16% slower. Baseline (E₀) and sensitivity (C₅₀) for pain tolerance were similar between young and elderly subjects. However, the E_max parameter was 2.5 times higher in the elderly and maximum possible treatment-related effect was 169 (135-221) in the young and 194 (149-252) in the elderly; that is, 15% higher in the elderly.

CONCLUSIONS

This exploratory analysis suggests that age-related differences exist in the distribution and elimination of (+)-ODM, including a 76% larger distribution outside the central compartment and 16% slower clearance of (+)-ODM. These pharmacokinetic changes are associated with a 15% higher maximum possible treatment-related effect and carry the potential for greater efficacy but also the potential for increased side effects at the same dose in elderly subjects. Clinicaltrials.gov identifier: NCT02329561.

Randomized, double-blind, placebo-controlled study of the efficacy and safety of biphasic immediate-release/extended-release hydrocodone bitartrate/acetaminophen tablets for acute postoperative pain

BACKGROUND

A fixed-dose combination biphasic immediate-release (IR)/extended-release (ER) hydrocodone bitartrate (HB)/acetaminophen (APAP) tablet is being developed for the management of acute pain severe enough to require opioid treatment and for which alternative treatment options are inadequate.

METHODS

This Phase III, randomized, double-blind, placebo-controlled, parallel-group study evaluated the analgesic efficacy and safety of IR/ER HB/APAP (n = 201) versus placebo (n = 202) over a period of 48 hours in patients with acute moderate to severe pain following unilateral bunionectomy. Patients received three tablets of placebo or IR/ER HB/APAP as an initial dose (hour 0) followed by two tablets every 12 hours for a total daily dose of 37.5/1625 mg HB/APAP on day 1 and 30/1300 mg HB/APAP thereafter. The primary efficacy outcome was the summed pain intensity difference (SPID) over the first 48 hours (SPID48) after the first dose.

RESULTS

SPID48 was significantly greater with IR/ER HB/APAP versus placebo (p < 0.001). SPID dosing interval analyses demonstrated consistent, superior pain relief with IR/ER HB/APAP for each dosing interval (all p < 0.001). Mean PID was greater with IR/ER HB/APAP versus placebo beginning 30 minutes after the first dose (p < 0.05), and IR/ER HB/APAP demonstrated faster median time to the onset of perceptible, meaningful, and confirmed pain relief (all p < 0.001). Mean total pain relief scores also indicated greater pain relief with IR/ER HB/APAP versus placebo throughout the 48-hour period (p = 0.012) for all comparisons. A greater proportion of IR/ER HB/APAP versus placebo patients was either "very satisfied" or "satisfied" with their pain relief (69.3% vs 49.4%; p < 0.001). Nausea was the most common treatment-emergent adverse event (TEAE; IR/ER HB/APAP, 25%; placebo, 7.9%). All TEAEs in IR/ER HB/APAP-treated patients were mild or moderate in severity.

CONCLUSION

IR/ER HB/APAP provided rapid, significant, and consistent analgesic efficacy over a period of 48 hours in an established model of acute pain and was tolerated with a safety profile similar to other low-dose opioids.

Opioids compared to placebo or other treatments for chronic low-back pain

BACKGROUND

The use of opioids in the long-term management of chronic low-back pain (CLBP) has increased dramatically. Despite this trend, the benefits and risks of these medications remain unclear. This review is an update of a Cochrane review first published in 2007.

OBJECTIVES

To determine the efficacy of opioids in adults with CLBP.

SEARCH METHODS

We electronically searched the Cochrane Back Review Group's Specialized Register, CENTRAL, CINAHL and PsycINFO, MEDLINE, and EMBASE from January 2006 to October 2012. We checked the reference lists of these trials and other relevant systematic reviews for potential trials for inclusion.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) that assessed the use of opioids (as monotherapy or in combination with other therapies) in adults with CLBP that were at least four weeks in duration. We included trials that compared non-injectable opioids to placebo or other treatments. We excluded trials that compared different opioids only.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the risk of bias and extracted data onto a pre-designed form. We pooled results using Review Manager (RevMan) 5.2. We reported on pain and function outcomes using standardized mean difference (SMD) or risk ratios with 95% confidence intervals (95% CI). We used absolute risk difference (RD) with 95% CI to report adverse effects.

MAIN RESULTS

We included 15 trials (5540 participants). Tramadol was examined in five trials (1378 participants); it was found to be better than placebo for pain (SMD -0.55, 95% CI -0.66 to -0.44; low quality evidence) and function (SMD -0.18, 95% CI -0.29 to -0.07; moderate quality evidence). Transdermal buprenorphine (two trials, 653 participants) may make little difference for pain (SMD -2.47, 95%CI -2.69 to -2.25; very low quality evidence), but no difference compared to placebo for function (SMD -0.14, 95%CI -0.53 to 0.25; very low quality evidence). Strong opioids (morphine, hydromorphone, oxycodone, oxymorphone, and tapentadol), examined in six trials (1887 participants), were better than placebo for pain (SMD -0.43, 95%CI -0.52 to -0.33; moderate quality evidence) and function (SMD -0.26, 95% CI -0.37 to -0.15; moderate quality evidence). One trial (1583 participants) demonstrated that tramadol may make little difference compared to celecoxib (RR 0.82, 95% CI 0.76 to 0.90; very low quality evidence) for pain relief. Two trials (272 participants) found no difference between opioids and antidepressants for either pain (SMD 0.21, 95% CI -0.03 to 0.45; very low quality evidence), or function (SMD -0.11, 95% -0.63 to 0.42; very low quality evidence). The included trials in this review had high drop-out rates, were of short duration, and had limited interpretability of functional improvement. They did not report any serious adverse effects, risks (addiction or overdose), or complications (sleep apnea, opioid-induced hyperalgesia, hypogonadism). In general, the effect sizes were medium for pain and small for function.

AUTHORS' CONCLUSIONS

There is some evidence (very low to moderate quality) for short-term efficacy (for both pain and function) of opioids to treat CLBP compared to placebo. The very few trials that compared opioids to non-steroidal anti-inflammatory drugs (NSAIDs) or antidepressants did not show any differences regarding pain and function. The initiation of a trial of opioids for long-term management should be done with extreme caution, especially after a comprehensive assessment of potential risks. There are no placebo-RCTs supporting the effectiveness and safety of long-term opioid therapy for treatment of CLBP.

Acute back pain: benefits and risks of current treatments

OBJECTIVE

To review the efficacy and safety of current treatments for acute low back pain.

RESEARCH DESIGN AND METHODS

PubMed was searched for clinical trials in which the words, acute, back, and pain all appeared in the study summary. The search was from the earliest references included in this database (1949) until 1 May 2009. This resulted in retrieval of 129 papers. Review of study summaries indicated that 36 provided information about either a topical treatment or oral therapy for acute low back pain. In addition, studies included as part of the evidence base for the Evidence Review of American Pain Society/American Academy of Pain Medicine Evidence Review for Evaluation and Management of Low Back Pain were reviewed.

RESULTS

Recommended topical and systemic pharmacologic treatments for acute low back pain include application of superficial heat, acetaminophen, nonsteroidal anti-inflammatory drugs (NSAIDs), skeletal muscle relaxants/benzodiazepines, and opioids including tramadol. Only a small number of studies compared different approaches to treatment of acute back pain and most failed to demonstrate significant differences among treatments. Available results support the view that both NSAIDs and low-level continuous heat treatment are more effective than acetaminophen and that heat treatment is also significantly more effective than ibuprofen. A potential limitation of this study is that information from trials published in journals not included in PubMed or reported only at meetings and not yet published was not included.

CONCLUSIONS

A wide range of treatments is currently recommended for the management of patients with acute back pain and all are supported by results from controlled clinical trials.