Analgesic effects of topical methadone: a report of four cases

Analgesic efficacy of sufentanil in dressings after surgical treatment of burn wounds

BACKGROUND

The aim of this study was to assess the analgesic efficacy of sufentanil in dressings after surgical treatment of burn wounds.

PATIENTS AND METHODS

Twenty adult patients, who underwent surgical treatment of third-degree burn wounds under general anesthesia, were included. Two of the patients underwent surgery twice. During surgery, patients received 50-100 μg fentanyl every 20-30 min and, after surgery, patients received 100 mg ketoprofen twice daily. Additionally, ten patients (group 1) received 50 μg sufentanil added to the burn wound dressings soaked in octenidine and phenoxyethanol while 10 patients (group 2) received 25 μg sufentanil added to the same dressings. The rescue analgesic, which was administered when pain intensified, was 5 mg subcutaneous morphine. Plasma sufentanil concentrations were assayed at 1, 2, 3, and 6 h after surgery completion and when pain was reported, along with pain intensity evaluation.

RESULTS

Sufentanil was not detected in the serum of any patients. Rescue morphine was given during the postoperative period (24 h) in one patient in group 1 (who underwent surgery twice) and three patients in group 2. The mean sufentanil concentration in dressings was higher in group 1 (0.13 ± 0.03) than group 2 (0.06 ± 0.03 μg/mL; p < 0.001). The group 1 patient who received rescue morphine had a sufentanil concentration of 0.10 μg/mL, which was the lowest concentration in group 1. Group 2 patients who received rescue morphine had sufentanil concentrations of at least two-fold lower (0.03-0.05 μg/mL). No adverse effects were observed.

CONCLUSIONS

Sufentanil in dressings after burn wound surgery provides effective and safe analgesia and the sufentanil concentration in dressings should be ≥0.10 μg/mL in a solution of octenidine and phenoxyethanol.

Topical treatment in pain medicine: from ancient remedies to modern usage

Over several millennia, substances have been applied to the skin for treatment of pain. Some ingredients are in current use; others have been discontinued. Mechanisms of action include interactions with nociceptive neural networks and inflammatory processes. Substances must penetrate the stratum corneum barrier and vehicles that enhance penetration have been developed. Topical drugs with links to the past include menthol, capsaicin, some opioids, local anesthetic agents and NSAIDs. Mandragora is also described as an example of a herbal remedy that has been discontinued due to its toxicity. The future for topical drugs is promising, with the advent of new drugs tailored for specific pain mechanisms and the development of both penetration enhancers and sterile preparation methods.

Topical fentanyl stimulates healing of ischemic wounds in diabetic rats

BACKGROUND

Topically applied opioids promote angiogenesis and healing of ischemic wounds in rats. We examined if topical fentanyl stimulates wound healing in diabetic rats by stimulating growth-promoting signaling, angiogenesis, lymphangiogenesis and nerve regeneration.

METHODS

We used Zucker diabetic fatty rats that develop obesity and diabetes on a high fat diet due to a mutation in the Leptin receptor. Fentanyl blended with hydrocream was applied topically on ischemic wounds twice daily, and wound closure was analyzed regularly. Wound histology was analyzed by hematoxylin and eosin staining. Angiogenesis, lymphangiogenesis, nerve fibers and phospho-platelet derived growth factor receptor-β (PDGFR-β) were visualized by CD31-, lymphatic vessel endothelium-1, protein gene product 9.5- and anti-phospho PDGFR-β-immunoreactivity, respectively. Nitric oxide synthase (NOS) and PDGFR-β signaling were analyzed using Western immunoblotting.

RESULTS

Fentanyl significantly promoted wound closure as compared to phosphate-buffered saline (PBS). Histology scores were significantly higher in fentanyl-treated wounds, indicative of increased granulation tissue formation, reduced edema and inflammation, and increased matrix deposition. Fentanyl treatment resulted in increased wound angiogenesis, lymphatic vasculature, nerve fibers, nitric oxide, NOS and PDGFR-β signaling as compared to PBS. Phospho-PDGFR-β co-localized with CD31 co-staining for vasculature.

CONCLUSIONS

Topically applied fentanyl promotes closure of ischemic wounds in diabetic rats. Increased angiogenesis, lymphangiogenesis, peripheral nerve regeneration, NO and PDGFR-β signaling are associated with fentanyl-induced tissue remodeling and wound healing.

Should topical opioid analgesics be regarded as effective and safe when applied to chronic cutaneous lesions?

Objectives

The induction of analgesia for many chronic cutaneous lesions requires treatment with an opioid analgesic. In many patients suffering with these wounds such drugs are either contraindicated or shunned because of their association with death. There are now case reports involving over 100 patients with many different types of chronic superficial wounds, which suggest that the topical application of an opioid in a suitable gel leads to a significant reduction in the level of perceived pain.

Key findings

Some work has been undertaken to elucidate the mechanisms by which such a reduction is achieved. To date there have been no proven deleterious effects of such an analgesic system upon wound healing. Although morphine is not absorbed through the intact epidermis, an open wound provides no such barrier and for large wounds drug absorption can be problematic. However, for most chronic cutaneous lesions, where data has been gathered, the blood levels of the drug applied ranges from undetectable to below that required for a systemic effect.

Summary

If proven, the use of opioids in this way would provide adequate analgesia for a collection of wounds, which are difficult to treat in patients who are often vulnerable. Proof of this concept is now urgently required.

Topical methadone and meperidine analgesic synergy in the mouse

Topical analgesics have many potential advantages over systemic administration. Prior work has shown potent analgesic activity of a number of topical opioids in the radiant heat tail-flick assay. The current study confirms the analgesic activity of morphine and extends it to two other mu opioids, methadone and meperidine. Combinations of topical morphine and lidocaine are synergistic. Similarly, the combination of methadone and lidocaine is synergistic. While there appeared to be some potentiation with the combination of meperidine and lidocaine, it did not achieve significance. Systemically, prior studies have shown that co-administration of morphine and methadone was synergistic. The combination of morphine and methadone was also synergistic when given topically. In contrast, the combination of morphine and meperidine was not synergistic systemically and it was not synergistic topically. Thus, the pharmacology of topical opioids mimics that seen with systemic administration. Their activity in the topical model supports their potential utility while the local limitation of their actions offers the possibility of a reduced side-effect profile.

The role of methadone in cancer pain treatment--a review

BACKGROUND

Methadone is an opioid analgesic of step 3 of the World Health Organization (WHO) analgesic ladder.

AIM AND METHODS

To outline pharmacodynamics, pharmacokinetics, drug interactions, equianalgesic dose ratio with other opioids, dosing rules, adverse effects and methadone clinical studies in patients with cancer pain. A review of relevant literature on methadone use in cancer pain was conducted.

RESULTS

Methadone is used in opioid rotation and administered to patients with cancer pain not responsive to morphine or other strong opioids when intractable opioid adverse effects appear. Methadone is considered as the first strong opioid analgesic and in patients with renal impairment. Methadone possesses different pharmacodynamics and pharmacokinetics in comparison to other opioids. The advantages of methadone include multimode analgesic activity, high oral and rectal bioavailability, long lasting analgesia, lack of active metabolites, excretion mainly with faeces, low cost and a weak immunosuppressive effect. The disadvantages include long and changeable plasma half-life, high bound to serum proteins, metabolism through P450 system, numerous drug interactions, lack of clear equianalgesic dose ratio to other opioids, QT interval prolongation, local reactions when administered subcutaneously.

CONCLUSIONS

Methadone is an important opioid analgesic at step 3 of the WHO analgesic ladder. Future controlled studies may focus on establishment of methadone equianalgesic dose ratio with other opioids and its role as the first strong opioid in comparative studies with analgesia, adverse effects and quality of life taken into consideration.

Effectiveness of topical administration of opioids in palliative care: a systematic review

The discovery of peripheral opioid receptors has become the scientific basis for topical use of opioids in malignant and nonmalignant ulcers and oropharyngeal mucositis. This systematic review aimed to assess the quality of published literature and to examine whether topical opioids are effective in controlling pain in palliative care settings. After a systematic literature review, 19 studies (six randomized controlled trials [RCTs] and 13 case reports) met the inclusion criteria for the review. Eighteen studies favored topical opioids in pain relief, as evidenced by reductions in post-treatment pain scores, but time to onset and duration of analgesia varied widely. Because of the heterogeneity of the studies, meta-analysis was not possible. Despite clear clinical benefits described in small RCTs, there is a deficiency of higher-quality evidence on the role of topical opioids, and more robust primary studies are required to inform practice recommendations. N-of-1 trials should be encouraged for specific clinical circumstances.

Analgesic synergy between topical opioids and topical non-steroidal anti-inflammatory drugs in the mouse model of thermal pain

The main aim of the study was to examine analgesic effects of the topical opioids and non-steroidal anti-inflammatory drugs (NSAIDs) in a radiant heat tail-flick nociception model. Also, we have tested whether the addition of lauric acid to propylene glycol improves skin permeation for the opioids and NSAIDs. We found that the addition of lauric acid to propylene glycol dramatically improves the penetration of the drugs, measured by the drug's ED(50). We observed a significant dose response shift to the left for all tested drugs. So, morphine's ED(50) was decreased by 19-fold. The duration of the analgesic activity of morphine dissolved in a combination of propylene glycol and lauric acid was much longer compared with the same dose of the drug dissolved in propylene glycol only. Methadone and hydrocodone also produced analgesic activity in this experimental paradigm. We then assessed potential interactions between opioids, ibuprofen and diclofenac using a fixed, low dose of each. The inclusion of either S-ibuprofen or diclofenac to a fixed, low dose of morphine raised the analgesic response from around 20% to 50% and 80%, respectively. Topical methadone and diclofenac alone produced analgesia in 30% of mice. The combination produced analgesia in 100% of mice (100% versus 60%, P<0.001) and the analgesic effect was observed for 90 min. Alone, topical methadone and S-ibuprofen produced analgesia in 25% and 30% of mice, respectively. The combination elicited analgesia in 100% of mice (100% versus 55%, P<0.001) and this analgesic effect lasted for 120 min. Our current findings support the supra-additive interaction of topical mu opioids, S-ibuprofen and diclofenac in a model of moderate to severe pain, radiant heat tail-flick assay.

A randomised controlled trial to test the analgesic efficacy of topical morphine on minor superficial and partial thickness burns in accident and emergency departments

OBJECTIVES

To test the analgesic efficacy of topical morphine on superficial burns within the emergency department by comparing pain scores, comfort ratings and analgesia taken by participants.

METHOD

A placebo-controlled three-treatment randomised controlled trial was undertaken. 59 participants were randomly allocated to receive a dressing containing Intrasite gel and morphine sulphate, Intrasite gel and water or the conventional Jelonet dressing. The study design enabled double-blinding between the two Intrasite gel treatments.

RESULTS

49 participants were included in the final analysis as 10 were lost to follow-up. No significant differences were observed between the pain scores or comfort ratings of the three treatments. Participants receiving Jelonet and the placebo reduced their pain scores by the greatest amount overall. However, participants receiving morphine were the only group to reduce pain scores by >20 mm on two consecutive time intervals (2 and 6 h). At 12 h the morphine group reported the highest pain scores. Only 4/15 participants receiving topical morphine administered additional analgesia compared with 12/17 receiving the Jelonet dressing and 6/17 receiving Intrasite and water (p = 0.055). However, when all analgesia was taken into account, the morphine group was administered the greatest amount. Overall, the placebo group reported their dressings to be the most comfortable and took the least amount of analgesia. Minor adverse reactions included itching, burning and a rash. No serious adverse reactions were reported.

CONCLUSIONS

Topical morphine sulphate does not seem to be as effective when used for the pain associated with superficial burns as when used for the pain associated with chronic inflammatory wounds. (The European Clinical Trials Database number for this study is 2005-003285-42.).

Topical agents for the management of musculoskeletal pain

The recent recognition of the magnitude of cardiovascular risk of both nonselective nonsteroidal anti-inflammatory drugs and COX-2 selective inhibitors, in addition to the persistent concerns about the use of opioids, has brought increased attention to nonsystemic, topical analgesics. These agents have a favorable safety profile and there is increasing evidence indicating their efficacy for a variety of pain disorders. The use of topical analgesics in the treatment of the most prevalent musculoskeletal pain syndromes is described, with a focus on mechanisms for drug delivery and clinical trials data.

Efficacy of a skin-protection powder for use as a dressing for intractable ulcers

OBJECTIVE

Stomahesive skin-protection powder has been reported to be useful as a skin-care and skin-barrier product for the management of stomas. This study aimed to evaluate its efficacy, in terms of wound healing, moisture retention and pain management, as an alternative to conventional dressing materials. Both clinical and animal studies were undertaken.

METHOD

The efficacy of the Stomahesive powder was tested by measuring the thickness of granulation tissue formed in a total skin defect in a db/db mouse model. We then compared the healing process using either the skin-protection powder or a conventional film dressing material. In the clinical study 17 patients with various intractable ulcers were treated with Stomahesive powder, and healing was evaluated.

RESULTS

In the mouse model, granulation tissue in the wounds treated with the powder was 2.86 times thicker than that of the wounds treated with the film dressing. In the clinical study, 16 out of 17 wounds healed completely.

CONCLUSION

The Stomahesive powder could be an effective treatment modality for contact ulceration, superficial ulcers with complex contours and morphology, and superficial ulcers contaminated by liquid faeces or vaginal discharge that have not responded to conventional dressings.

DECLARATION OF INTEREST

None.

Topical agents for the treatment of chronic pain

Unlike systemic analgesics, topical analgesics exert their analgesic activity locally and without significant systemic absorption. This is in contrast to transdermal analgesics, which require systemic absorption for clinical benefit. The mechanism of action of a particular topical analgesic is unique to the specific medication being used as a topical analgesic. Topical analgesics have been studied in an increasing number of painful clinical conditions, and the results of some of these studies are summarized in this article. The potential role of topical analgesics acting peripherally in affecting the central processing of pain as well as painful states considered to be "central," not "peripheral," also are reviewed.