Pharmacokinetic and pharmacodynamic evaluation of oxycodone and naltrexone for the treatment of chronic lower back pain

Naltrexone Transport by a Proton-Coupled Organic Cation Antiporter in hCMEC/D3 Cells, an in Vitro Human Blood-Brain Barrier Model

Naltrexone is a mu-opioid receptor antagonist used in the treatment of opioid and alcohol dependence. The blood-brain barrier (BBB) transport characteristics of naltrexone was investigated by means of hCMEC/D3 cells, a human immortalized brain capillary endothelial cell line. In hCMEC/D3 cells, naltrexone is taken up in a concentration-dependent manner. Furthermore, naltrexone uptake significantly decreased in the presence of H⁺/organic cation (OC) antiporter substrates, during the little alteration exhibited by substrates of well-identified OC transporters classified into SLC22A family. Although naltrexone uptake by hCMEC/D3 cells was partially affected by changes of ionic conditions, it was markedly decreased in the presence of the metabolic inhibitor sodium azide. Furthermore, when treated by ammonium chloride, naltrexone uptake by hCMEC/D3 cells was altered by intracellular acidification and alkalization, suggesting the involvement of oppositely directed proton gradient in naltrexone transport across the BBB. The results obtained in the present in vitro study suggest the active transport of naltrexone from blood to the brain across the BBB by the H⁺/OC antiporter.

Systematic review of guideline-recommended medications prescribed for treatment of low back pain

OBJECTIVE

To identify and descriptively compare medication recommendations among low back pain (LBP) clinical practice guidelines (CPG).

METHODS

We searched PubMed, Cochrane Database of Systematic Review, Index to Chiropractic Literature, AMED, CINAHL, and PEDro to identify CPGs that described the management of mechanical LBP in the prior five years. Two investigators independently screened titles and abstracts and potentially relevant full text were considered for eligibility. Four investigators independently applied the Appraisal of Guidelines for Research and Evaluation (AGREE) II instrument for critical appraisal. Data were extracted for pharmaceutical intervention, the strength of recommendation, and appropriateness for the duration of LBP.

RESULTS

316 citations were identified, 50 full-text articles were assessed, and nine guidelines with global representation met the eligibility criteria. These CPGs addressed pharmacological treatments with or without non-pharmacological treatments. All CPGS focused on the management of acute, chronic, or unspecified duration of LBP. The mean overall AGREE II score was 89.3% (SD 3.5%). The lowest domain mean score was for applicability, 80.4% (SD 5.2%), and the highest was Scope and Purpose, 94.0% (SD 2.4%). There were ten classifications of medications described in the included CPGs: acetaminophen, antibiotics, anticonvulsants, antidepressants, benzodiazepines, non-steroidal anti-inflammatory drugs (NSAIDs), opioids, oral corticosteroids, skeletal muscle relaxants (SMRs), and atypical opioids.

CONCLUSIONS

Nine CPGs, included ten medication classes for the management of LBP. NSAIDs were the most frequently recommended medication for the treatment of both acute and chronic LBP as a first line pharmacological therapy. Acetaminophen and SMRs were inconsistently recommended for acute LBP. Meanwhile, with less consensus among CPGs, acetaminophen and antidepressants were proposed as second-choice therapies for chronic LBP. There was significant heterogeneity of recommendations within many medication classes, although oral corticosteroids, benzodiazepines, anticonvulsants, and antibiotics were not recommended by any CPGs for acute or chronic LBP.

Pharmacokinetics and Bioequivalence Evaluation of a New Oxycodone Tamper-Resistant Tablet Administered with an Opioid Antagonist in Patients with Chronic Pain

BACKGROUND AND OBJECTIVES

Oxycodone tamper resistant (OTR) is a new extended-release abuse-deterrent formulation providing improvements in the tamper resistant characteristics. This study aimed to investigate the pharmacokinetic properties of the new OTR tablets and evaluate the bioequivalence of oxycodone from OTR and the original extended release (ER) formulation tablets administered with an opioid antagonist in patients with chronic pain.

METHODS

In this open-label, randomized, cross-over study, the enrolled patients were randomised to receive a single dose of 40 mg OTR or 40 mg OXYCONTIN^® (OXY) tablet administered with naltrexone blockade under fasting conditions. Serial blood samples for pharmacokinetic analysis were collected. Plasma oxycodone was quantified by a high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method. Tolerability was evaluated by monitoring adverse events, physical examinations, 12-lead ECG and laboratory tests.

RESULTS

A total of 38 patients were enrolled and 33 subjects completed the study. After a single dose of 40 mg tablets, pharmacokinetic results of the new OTR tablet were found to be similar to those of original extended-release oxycodone tablet. OTR 40 mg was bioequivalent to OXY 40 mg and was well tolerated in patients with chronic pain.

CONCLUSIONS

The new OTR formulation could provide a new choice in the treatment of chronic pain and reduce the potential for oxycodone abuse. Chictr.org identifier: ChiCTR1800017253.

CYP2D6 genotype can help to predict effectiveness and safety during opioid treatment for chronic low back pain: results from a retrospective study in an Italian cohort

Background

Opioids are widely used for chronic low back pain (CLBP); however, it is still unclear how to predict their effectiveness and safety. Codeine, tramadol and oxycodone are metabolized by CYP/CYP450 2D6 (CYP2D6), a highly polymorphic enzyme linked to allele-specific related differences in metabolic activity.

Purpose

CYP2D6 genetic polymorphisms could potentially help to predict the effectiveness and safety of opioid-based drugs in clinical practice, especially in the treatment of CLBP.

Patients and methods

A cohort of 224 Italian patients with CLBP treated with codeine or oxycodone was retrospectively evaluated to determine whether adverse reactions and effectiveness were related to CYP2D6 single-nucleotide polymorphisms. CYP2D6 genotyping was performed using the xTAG^® CYP2D6 Kit v3 (Luminex) to determine CYP2D6 metabolizer phenotype (poor, intermediate, rapid and ultrarapid). Subjects from the cohort were categorized into two groups according to the occurrence of side effects (Case) or benefit (Control) after chronic analgesic treatment. The impact of CYP2D6 polymorphism on treatment outcome was tested at the metabolizer phenotype, diplotype and haplotype levels.

Results

CYP2D6 polymorphism was significantly associated with opioid treatment outcome (Omnibus P=0.018, for both global haplotype and diplotype distribution test). CYP2D6*6 and *9 carriers, alleles characterized by a reduced (*9) or absent (*6) enzymatic activity, were significantly (P<0.05) associated with therapeutic failure. CYP2D6 ultrarapid metabolizers (CYP2D6*2N patients) showed an increased risk of side effects, as would be predicted. Despite their low frequency, CYP2D6 *1/*11, *4/*6 and *41/* 2N diplotypes showed significant (P<0.05) associations of efficacy and side effects with chronic opioid treatment.

Conclusion

Our results showed that reduced CYP2D6 activity is correlated with lack of therapeutic effect. We found that the pharmacogenetic analysis of CYP2D6 could be helpful in foreseeing the safety and effectiveness of codeine or oxycodone treatment in CLBP.