The efficacy of locally applied morphine in post-operative pain after bilateral third molar surgery

Topic delivery of analgesics in oral surgery

Introduction: Following any oral surgery procedure, postoperative pain is an inevitable outcome and can be described as moderate to severe. The pain management is essential for the comfort and the well-being of the patients. Topical delivery and more specifically transmucosal delivery systems seem to be of great value for the development of new pain management strategies. Method: A systematic literature review was performed using PubMedCentral database. Only PubMedCentral indexed publications were selected and included if they described i) a human clinical study with pharmacokinetic and/or pain relief assessment a biomaterial for topic delivery, ii) the delivery of analgesics or NSAIDs for analgesic purpose and iii) a biomaterial for topic delivery. Results: Ten articles were selected among which 4 pharmacokinetic studies and 8 studies describing pain relief. Six of the selected articles were well defined with a good scientific level of evidence (level 2) and 4 of them with a low level of evidence. Discussion: The clinical investigations demonstrated a good analgesia, a rapid pain relief with a decrease of the administered doses compared to the oral administration. Moreover, these topic analgesics were well tolerated by the patients. Number of devices was developed for the topical delivery after oral surgery procedures. Excepting a gelatin sponge and a hydro alcoholic gel, most of the devices were made of cellulose and its derivatives. Authors reported that the materials showed a good maintenance at the site of application and the release of the analgesic was well controlled over the time. Conclusion: However, well conducted large clinical trials are still missing in order to validate the absence of side effects.

Peripherally applied opioids for postoperative pain: evidence of an analgesic effect? A systematic review and meta-analysis

BACKGROUND

Opioids applied peripherally at the site of surgery may produce postoperative analgesia with few side effects. We performed this systematic review to evaluate the analgesic effect of peripherally applied opioids for acute postoperative pain.

METHODS

We searched PubMed (1966 to June 2013), Embase (1980 to June 2013), and the Cochrane Central Register of Controlled Trials (The Cochrane Library 2013, Issue 6). Randomized controlled trials investigating the postoperative analgesic effect of peripherally applied opioids vs. systemic opioids or placebo, measured by pain intensity scores, consumption of supplemental analgesics and time to first analgesic were included. Trials with sample sizes of fewer than 10 patients per treatment group or trials with opioids administered intra-articularly or as peripheral nerve blocks were excluded.

RESULTS

Data from 26 studies, including 1531 patients and 13 different surgical interventions were included. Clinical heterogeneity of the studies was substantial. Meta-analysis indicated statistically significant, but not clinically relevant, reductions in VAS score at 6-8 h (mean difference -4 mm, 95% CI: -6 to -2) and 12 h postoperatively (mean difference -5 mm, 95% CI: -7 to -3) for peripherally applied opioids vs. placebo and statistically significant increased time to first analgesic (mean difference 153 min, 95% CI: 41-265). When preoperative inflammation was reported (five studies), peripherally applied opioids significantly improved postoperative analgesia.

CONCLUSION

Evidence of a clinically relevant analgesic effect of peripherally applied opioids for acute postoperative pain is lacking. The analgesic effect of peripherally applied opioids may depend on the presence of preoperative inflammation.

Topical analgesics

Historically, analgesics were applied by the topical route of administration. With the advent of oral formulations of drugs, topical application became less popular among physicians, although patients still rated this method of drug delivery as efficacious and practical. We now appreciate that peripheral mechanisms of actions of a variety of preparations rationalizes their topical application and gives further opportunity to target peripheral receptors and neural pathways that previously required systemic administration to achieve therapeutic effect. Therefore, a peripheral effect can be generated by using locally applied drug and, consequently, systemic concentrations of that drug may not reach the level at which systemic side effects can occur.

Topical analgesics

Our knowledge and understanding of the pathophysiology and treatment of pain is increasing; however, we should not lose sight of the simple opportunities that exist for intercepting pain at peripheral targets. Although systemic medication often has peripheral and central modes of action, the appeal for provision of medication close to where these peripheral targets exist should be high. If these sites can be attacked with relatively high concentrations of active drug while keeping systemic levels of that drug below the level at which systemic side effects become apparent, then this should lead to desirable outcomes. Even though the number of true topical agents with an indication for this use is small, a number of other topical agents are available that evidence suggests have the possibility of being effective. Given the increased understanding of pain, the likelihood of further topical agents becoming available is high.

Assessment of the effectiveness of peripheral administration of morphine with local articaine anaesthesia for surgery in inflamed oral and maxillofacial tissues

The controversy surrounding clinical trials of peripherally applied morphine with local anaesthetic and the attendant ambiguous results led to a study of our own clinical material. The aim of the study was to assess the effectiveness of peripheral administration of morphine with local articaine anaesthesia in inflamed oral and maxillofacial tissues. Sixty patients who qualified for the randomized, double-blinded study were randomly divided into two groups. Group 'LA' received a standard local anaesthetic solution (articaine plus epinephrine) while group 'LA-Mo' received the standard solution with an addition of 1 mg of morphine. Pain intensity was assessed using the Visual Analogue Scale, before and directly after surgery as well as at 1, 2, 6, 12, 24 and 48 h after completion of surgery. Furthermore, supplemental consumption of the prescribed analgesic was recorded. Despite a very similar average level of initial pain, there was a marked difference between the groups in the pain level during surgery. Moreover, during the next 12 h, there were significant differences observed in the level of pain between both groups. There was also considerable difference between both groups in the time of first analgesic intake and the total amount of analgesic. Our results show that modified local anaesthesia may be of benefit for the relief of operative and post-operative pain and may also help reduce analgesic intake after oral surgery.

Topische Applikation von Lokalanästhetika und Opioiden nach elektiver Zahnextraktion

The aim of this study was to provide evidence for the peripheral effect of opioids in oromaxillary procedures and to investigate whether postoperative morphine sulfate plus lidocaine administered as a local spray achieve better analgesic efficacy than lidocaine applied alone. The double-blind randomized study included 60 patients. The patients exhibited neither preoperative pain nor inflammation (tooth extractions) and when pain occurred received as alternative medication diclofenac retard 50 mg or tramadol. Side effects were documented. No differences between the two groups were observed in the demographic data, visual and numeric analog scale in the first 24 h, or in the consumption of analgesics. Since the patients presented in a pain-free state at the time of surgery, apparently no activation of the peripheral opioid receptors occurs. Thus, a peripheral effect of opioids could not be demonstrated in this model.

Potential utility of the peripheral analgesic properties of morphine in stomatitis-related pain: a pilot study

To determine the potential clinical utility of peripheral opioid action using a clinical model of cancer treatment-induced inflammation and pain that allowed for topical application of morphine in the damaged tissue (oral mucosa). This pilot study followed a two blocks design. Ten patients with painful oral mucositis were enrolled in the first block (dose-response relationship finding) and randomized in two groups to receive oral rinses with 15 ml of either 1 per thousand or 2 per thousand morphine solution. Twenty-two patients were enrolled into the second block (efficacy and safety determination). Additionally, serum concentrations of morphine were measured in five representative patients. In the first block (n=10) a dose-response relationship for topical morphine was found. Rinses with 2 per thousand -morphine solution showed better pain relief (median 80%, range 70-80%) than those with 1 per thousand (median 60%, range 55-70%; P=0.0238). Therefore, subsequent patients enrolled for the second block (n=22) received oral rinses with 2 per thousand -morphine solution. In these patients the time to good (>or=50%) or to complete (100%) pain relief was 28 (+/-12)min after the first mouthwash, and the duration of relief was on average 216 (+/-25)min. Twenty patients (90%) received the successive mouthwashes every 3 h and 10% of them every 2 h. The duration of severe pain at the moment of swallowing was 5.17 (+/-1.47) days. Only six patients needed supplementary analgesia, and the time elapsed before the first supplemental analgesic was 1.18 (+/-0.8) days. The duration of severe functional impairment was 1.52 (+/-1.31) days, thus allowing us to feed the patient by mouth with liquid-food supplementation. During our experiment no systemically active detectable concentrations of morphine were found (GC-MS analysis). The most important side effect attributable to morphine mouthwashes was burning/itching sensation (very mild to mild intensity). Patients with painful chemoradiotherapy-induced stomatitis could be alleviated using topical morphine mouthwashes.

Efficacy of peripheral morphine analgesia in inflamed, non-inflamed and perineural tissue of dental surgery patients

In a clinical model of dental pain, the analgesic efficacy of local morphine treatment was examined under three different conditions. Patients undergoing dental surgery were randomly assigned to an injection of local anesthetic (articaine) plus 1 mg morphine either into inflamed (n = 14; trial 1) or non-inflamed (n = 24; trial 2) submucous tissue or perineurally n = 19; trial 3). Patients in the control group for each condition (n = 13, trial 1; n = 26, trial 2; n = 16, trial 3) received articaine plus saline. Postoperative pain intensity was assessed by the visual analog scale (VAS) and numeric rating scale (NRS) at 0, 2, 4, 6, 8, 10, 12, 16, 20, and 24 h. In addition, patients recorded the occurrence of side effects and the supplemental consumption of diclofenac. Immediately after the operation, pain scores were reduced to a similar extent in all groups, most likely due to the local anesthetic effect. Thereafter, pain scores and supplemental consumption of diclofenac were significantly lower in patients receiving 1 mg morphine into inflamed submucous tissue than in the control group for up to 24 h. Patients receiving 1 mg morphine into non-inflamed tissue or perineurally did not show any further reduction in pain scores compared to each control group. Our results show in patients undergoing dental surgery that injection of 1 mg of morphine into inflamed tissue results in significant and prolonged postoperative analgesia, whereas administration into non-inflamed tissue or perineurally is not effective. Thus, consistent with experimental studies, the requirement of an inflammatory process for the occurrence of peripheral opioid effects is also found in the clinical setting.

Effects of peripherally and centrally acting analgesics on somato-sensory evoked potentials

1. The effects of aspirin 1000 mg, paracetamol 1000 mg, codeine 60 mg on somatosensory evoked potentials (SEPs) were measured in a four-way cross-over study. 2. SEPs were elicited by electrical stimulation of the skin overlying the digital nerve at intensities close to pain threshold. 3. Amplitudes and latencies of both early and late SEPs were recorded, as well as first sensory threshold and subjective pain threshold. 4. None of the study medications affected the amplitude or latency of the late SEP components (100-250 ms post-stimulus). The amplitude of early components (15-30 ms post-stimulus) was also unaffected, but aspirin shortened the latency 30 min after ingestion. 5. Sensory detection and pain threshold to electrical skin stimulation were also unaffected by any of the study medications despite subjective central effects with codeine.