Targinact is the first prolonged-release (PR) analgesic that combines an opioid agonist with an antagonist. Naloxone is an opioid antagonist that binds to opioid receptors in the gut thereby counteracting the binding of oxycodone and preventing its potential negative effects on bowel function i.e. constipation. At least 97 per cent of the naloxone is eliminated by first-pass elimination in the healthy liver, preventing it from significantly affecting analgesic effects.1
In a study involving 463 patients with moderate to severe lower back pain those treated with oxycodone PR/naloxone PR had a significantly longer time to recurrent pain events compared with those treated with oxycodone PR alone. The appearance of pain events in patients treated with oxycodone PR/naloxone PR was comparable to that in patients treated with oxycodone PR alone, confirming that naloxone did not adversely affect analgesic efficacy of the opioid when used in combination. Laxative use was lower in the oxycodone PR/naloxone PR group than in the oxycodone PR group with patients having a mean of 7.85 per cent of days with laxative intake in the oxycodone PR/naloxone PR group compared with 10.36 per cent in the oxycodone PR group.2
In a double-blind trial involving 322 patients with moderate to severe non-malignant pain a significant improvement in constipation (measured by bowel function index) was observed in the oxycodone PR/naloxone PR group compared with the oxycodone PR group after four weeks of treatment. A significant increase in the number of complete spontaneous bowel movements and a decrease in laxative use were also reported in the combination group. The pain intensity remained constant throughout the study and was comparable between the two treatment groups indicating that the improvement in bowel function did not compromise the analgesic efficacy of the oxycodone component.3
In another study, involving 202 patients with malignant or non-malignant severe pain, patients and investigators assessed the efficacy and tolerability of the addition of naloxone PR to stable treatment with oxycodone PR. Patients were randomised to one of four groups - 10, 20 and 40mg naloxone PR or placebo - all in addition to stable oxycodone PR dose. Patient and investigator assessment of tolerability was similar between the naloxone treatment groups and the placebo group. Efficacy was ranked as ‘good' or ‘very good' by 50.0, 67.4 and 72.5 per cent of patients in the 10mg, 20mg and 40mg naloxone PR groups, respectively, and 43.5 per cent in the placebo group. The investigators mirrored the trend; increased naloxone doses were associated with higher percentages of investigators ranking the efficacy as ‘good' or ‘very good'.4
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1. Targinact, Summary of Product Characteristics.
2. Vondrackova D, Leyendecker P, Hopp M et al. Analgesic efficacy and safety of oxycodone in combination with naloxone as prolonged release tablets in patients with moderate to severe chronic pain. Journal of Pain, 2008: 9; 1144-54.
3. Simpson K, Leyendecker P, Hopp M et al. Fixed-ratio combination oxycodone/naloxone compared with oxycodone alone for the relief of opioid-induced constipation in moderate -to-severe noncancer pain. Curr Med Res Opin 2008: 24; 3503-3512.
4. Nadstawek J, Leyendecker P, Hopp M et al. Patient assessment of a novel therapeutic approach for the treatment of severe, chronic pain. Int J Clin Pract 2008: 62; 1159-1167.
Further information: Napp