psd-502 and Pruritus

To prevent pain associated with 8% capsaicin application, pretreatment with local anesthetics, such as EMLA (eutectic mixture of lidocaine 2.5% and prilocaine 2.5%), is considered an option. However, there is contradicting evidence regarding the effects of local analgesia on capsaicin-induced desensitization. In session 1, 2 skin areas in each forearm of 24 healthy volunteers were randomized to 2-hour pretreatment with EMLA/placebo cream. After pretreatment, 8% capsaicin patches were applied for 3 hours in 1 placebo and 1 EMLA pretreated area, obtaining the following four areas: Capsaicin + EMLA, Capsaicin + Placebo, EMLA alone, and Placebo. Pain intensity scores were assessed during the 3-hour application of capsaicin. Warmth detection, heat pain sensitivity, and microvascular reactivity were measured after the removal of capsaicin. After 24 hours, in session 2, all tests were repeated followed by histamine application in each area to examine itch intensity and neurogenic flare. Overall, EMLA caused significant reductions in capsaicin-induced pain compared with placebo (P= .007) and enhanced the capsaicin-induced increase in superficial blood perfusion immediately after the 3-hour capsaicin application (P< .01). Regardless of pretreatment, capsaicin induced heat hyperalgesia immediately after the application (P< .001). Twenty-four hours post application, heat pain sensitivity was normalized. However, WDT increased significantly (P< .001). Capsaicin tended to reduce the itch intensity and significantly reduced the neurogenic flare (P< .05) induced by histamine compared with EMLA alone. The findings suggest that pretreatment with topical analgesic cream reduces application site pain without interfering with the 8% topical capsaicin-induced desensitization. PERSPECTIVE: Pretreatment with local anesthetic EMLA cream might be considered a good therapeutic option to reduce the pain associated with 8% capsaicin application currently used for treatment of neuropathic pain syndromes. This study also suggests the existence of a synergistic effect of capsaicin and EMLA on the process of neurogenic inflammation.

Topics: Administration, Topical; Adult; Anesthetics, Local; Capsaicin; Female; Humans; Lidocaine, Prilocaine Drug Combination; Male; Pain; Pain Measurement; Pruritus; Sensory System Agents; Young Adult

Eutectic mixture of local anaesthetic cream and lidocaine iontophoresis are effective in providing analgesia for peripheral venous cannulation with small gauge cannulae in adults and children. The objective of this study was to compare the analgesic efficacy of the two techniques directly in patients using larger cannulae.. In a double-blind, randomized, controlled study we compared the two techniques directly. Twenty-eight patients had the eutectic mixture of local anaesthetic cream applied to the dorsum of one hand for 60 min followed by sham iontophoresis (group EMLA); the other hand had a sham cream applied for 60 min followed by 10 min of 2 mA iontophoresis with lidocaine 4% and epinephrine 1 in 50,000 (group iontophoresis). Within 5 min of completion of iontophoresis an anaesthetist, unaware of treatment allocation, inserted 18-G venous cannulae into veins of both hands. The patient then scored the amount of pain on cannulation using a 10 point verbal rating scale.. Eight patients were excluded from analysis due to failed cannulation (two group EMLA, two group iontophoresis), intolerable burning sensation from iontophoresis (one), protocol violation (one), and changes in surgical schedule (two). Pain scores were lower for the EMLA treated hand than for the iontophoresis side (median (range) 1 (0-7) vs. 3 (0-6); P = 0.023). Erythema and paraesthesia were common but short lived on the iontophoresis side.. Although lidocaine iontophoresis is effective more quickly than the eutectic mixture of local anaesthetic cream, the superior quality of analgesia produced by the eutectic mixture in this study should be borne in mind if these treatments are used electively.

Topics: Adult; Aged; Analgesia; Anesthetics, Combined; Anesthetics, Local; Catheterization, Peripheral; Double-Blind Method; Erythema; Female; Hand; Humans; Iontophoresis; Lidocaine; Lidocaine, Prilocaine Drug Combination; Male; Middle Aged; Ointments; Pain; Pain Measurement; Paresthesia; Placebos; Prilocaine; Pruritus

To evaluate the anesthetic efficacy of EMLA cream for alleviating pain associated with puncture and pressure in areas where venous catheters are normally inserted.. We performed a prospective, double blind study in 38 volunteers between 25 and 36 years of age, after obtaining informed consent. A 1.5 g dose of EMLA cream was applied to three sites on each patient: the back of the hand, the antecubital fossa and the side of the neck. Placebo cream with similar characteristics was applied to contralateral sites. Pain was evaluated on a visual analog scale (VAS, 0-10). Tactile sensitivity was assessed on a four-point scale (0 = no sensation; 1 = slight sensation; 2 = moderate, and 3 = strong). An analysis of variance study was performed to compare baseline scores to results over time, and placebo results to EMLA scores for each test site.. The assessment of response to puncture and pressure gradually decreased over time for the sites where EMLA cream was applied, but not for the areas where placebo was applied.. The efficacy of EMLA cream varies demonstrably depending on type of stimulus, site of application and time since application.

Topics: Adult; Anesthetics, Combined; Anesthetics, Local; Double-Blind Method; Elbow; Emulsions; Erythema; Female; Hand; Humans; Lidocaine; Lidocaine, Prilocaine Drug Combination; Male; Neck; Needles; Ointments; Organ Specificity; Pain; Prilocaine; Proprioception; Prospective Studies; Pruritus; Punctures; Time Factors

The effectiveness of a eutectic mixture of the local anaesthetics lignocaine and prilocaine (EMLA cream) in relieving artificially induced pruritus was examined in 20 volunteers. The study was conducted in two parts. In part one, the effect of EMLA on the threshold concentration of histamine necessary to induce pruritus was assessed by a double-blind placebo controlled method. In part two, the effect of EMLA on the perception of pruritus induced by the artificial pruritogens cowhage and papain was assessed by a single blind method. Some subjects were less sensitive to histamine after placebo cream treatment, but all subjects showed a marked reduction in sensitivity to histamine after EMLA treatment. The difference between EMLA and the placebo treatment was statistically significant. The EMLA preparation was found to be effective in alleviating pruritus induced by cowhage and papain and this effect was also statistically significant. Thus, EMLA cream was found to be effective in reducing experimentally induced pruritus and, therefore, may be useful in some clinical circumstances where persistent itch is a distressing symptom.

Topics: Adult; Double-Blind Method; Drug Combinations; Female; Histamine; Humans; Lidocaine; Lidocaine, Prilocaine Drug Combination; Male; Middle Aged; Papain; Prilocaine; Pruritus

Notalgia paraesthetica is a rare entity which involves the posterior primary rami of thoracic nerves T2-T6. Patients present with a localized discomfort or pruritus on the back. The condition runs a benign course and usually resolves spontaneously. However, whilst present the symptoms can be relentless and disturbing to patients. We report three patients with notalgia paraesthetica, all of whom were helped symptomatically by the topical application of the local anaesthetic cream, EMLA (2.5% lignocaine and 2.5% prilocaine).

Topics: Anesthetics, Local; Back Pain; Drug Combinations; Female; Humans; Hyperesthesia; Lidocaine; Lidocaine, Prilocaine Drug Combination; Male; Middle Aged; Occlusive Dressings; Prilocaine; Pruritus; Shoulder