Skin pretreatments for shortening onset of dermal patch anesthesia with 3% GA MHPh 2Na-10% lidocaine gel mixture

Onset Mechanism and Pharmaceutical Management of Dry Skin

Dry skin is a common symptom of various conditions, and elderly individuals commonly exhibit this physiological symptom. Dry skin develops owing to sebum deficiency; however, the use of moisturizers can typically overcome this issue, particularly in patients in whom there are no other skin problems. If dry skin is left untreated, itching and eczema can occur, resulting in skin damage. Additionally, hemodialysis patients exhibit reduced barrier function and can experience pain associated with repeated needle insertion; the repeated use of lidocaine tape to manage the pain can cause further skin damage. To reduce the occurrence of dry skin, the skin is hydrated using moisturizers. Dry skin is also prominent in patients with varicose veins in the lower extremities, and many biochemical studies have shown that skin immunity is altered in patients with dry skin. Moreover, the incidences of dry skin and pruritus differ in male and female patients. Furthermore, in elderly patients, zinc deficiency is likely to cause dry skin, and zinc supplementation may maintain skin hydration. To date, few reports have described dry skin from a clinical point of view. In this review, research on dry skin is presented, and the findings of basic research studies are integrated.

From Physical Pharmacy to Clinical Pharmacology

Research works on molecular interactions in solutions were carried out at School of Pharmacy, the University of Wisconsin under the direction of Prof. T. Higuchi and at Faculty of Pharmaceutical Sciences, Kyoto University under the direction of Prof. H. Sezaki. Studies on permeation of drugs through polymer membranes were carried out at Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Canada and at Pharmaceutical Chemistry Research Laboratories at Food and Drug Directorate, Department of Health and Welfare, Canada. Studies on modification of delivery patterns by means of pharmaceutical approaches were carried out at Faculty of Pharmaceutical Sciences, Hokkaido University. Topics related to modification of drug delivery patterns include employment of amorphous forms such as ground mixture with micro-crystalline cellulose and coprecipitate with polyvinylpyrrolidone, use of biodegradable polymers such as polylactic acid and polycarbonates, gel-forming materials such as konjac, agar and hydroxypropylcellulose, and physicochemical systems such as complexation. Works related to drug delivery and disposition of drugs in humans were carried out at Department of Pharmacy, Kumamoto University Hospital. Topics related to drug delivery in humans include injections containing anticancer drugs for intra-arterial administration, lidocaine gels for dermal anesthesia, glucagon solution for nasal administration. Topics related to disposition of drugs in humans include clinical pharmacokinetic studies in infants and elderly and medical uses of adsorbents.

Warm Steaming Enhances the Topical Anesthetic Effect of Lidocaine

Warm steaming has been used for hydrating the skin, thereby increasing its permeability. We studied whether skin pretreatment with a steamed towel (at 45 degrees C) for 5 min could enhance the anesthetic effect of a topical lidocaine tape in 14 female volunteers. After each volunteer received the skin pretreatment on one of the forearms, lidocaine tape was applied for 30 min on both the treated and the untreated forearms. Superficial anesthesia was scored by recording the number of painful experience during 5 pinpricks delivered with a 27-gauge needle. To assess anesthesia of the deeper layer, single insertion of a 27-gauge needle to a depth of 3 mm was made and pain was scored by a visual analog scale (VAS). There were significant reductions in the scores of superficial anesthesia (median [range]: treated arm, 2 [0-5], versus untreated arm, 4 [1-5]; P < 0.01) and the VAS scores of deeper insertion (median [range]: treated arm, 4.5 [0-8], versus untreated arm, 8 [2-10]; P < 0.01). In conclusion, the application of a warm steamed towel enhanced the anesthetic effect of a topical lidocaine tape.

IMPLICATIONS

We showed that the skin pretreatment with a steamed towel (at 45 degrees C) enhanced the anesthetic effect of a topical lidocaine tape in female volunteers.

Quantitative and selective evaluation of differential sensory nerve block after transdermal lidocaine

We evaluated the effect of transdermal lidocaine on differential sensory nerve block in 15 healthy volunteers. Lidocaine 10% gel was applied topically to a forearm and covered with a plastic film. Three types of sensory nerve fibers (Abeta, Adelta, and C fibers) were evaluated with a series of 2000-, 250-, and 5-Hz stimuli using current perception threshold (CPT) testing. Sensations of touch, pinprick, cold, and warmth were also measured. These measurements were made before the topical lidocaine (baseline), 60 min after the draping (T0), and at 1-h intervals until 5 h after T0 (T1 to T5). A significant increase in CPT compared with baseline was observed until T2 at 5 Hz and T4 at 250 Hz, whereas the increase in CPT at 2000 Hz continued throughout the study period. All subjects experienced the disappearance of pinprick and cold sensations, whereas touch and warmth sensations were detectable during the study period. We conclude that when lidocaine is applied transdermally, the sensitivity of nerves to local anesthetics is proportional to the axon diameters. However, pinprick and cold sensation are affected more strongly than other sensations at receptor sites.

IMPLICATIONS

We evaluated the effect of transdermal lidocaine on differential sensory nerve block in healthy volunteers. Our results show that the sensitivity of nerves to local anesthetics is proportional to the axon diameter.

Laser assisted delivery of topical anesthesia for intramuscular needle insertion in adults

BACKGROUND AND OBJECTIVES

Currently there is no safe, effective, and rapid means to eliminate the pain associated with a needle insertion through the skin. It is hypothesized that ablation of the stratum corneum layer using a low energy Erbium(Er):YAG laser would allow rapid local anesthesia from a lidocaine product.

STUDY DESIGN/MATERIALS AND METHODS

Eighty volunteers participated in a placebo-controlled, double blind, cross-over study employing the Norwood-Abbey (Chelsea Heights, Victoria, Australia) laser anesthesia device (LAD) and two lidocaine preparations. Upper-arm skin ablation was followed by a 5-minute application of study treatment. Pain scores were registered immediately following a needle insertion.

RESULTS

Comparing the combined lidocaine preparations to placebo, there was a statistically significant reduction in pain when the LAD was employed (P < 0.001). The median pain reduction for lidocaine was 51.3% (95% CI = [40.9, 76.1]).

CONCLUSIONS

Use of the low energy Er:YAG LAD device in combination with a 5-minute application of lidocaine significantly reduced the pain associated with a needle insertion.

Dermal patch anaesthesia: comparison of 10% lignocaine gel with absorption promoter and EMLA cream

The analgesic effects of transdermally applied 10% lignocaine aquagel containing 3% glycyrrhetinic acid monohemiphthalate disodium (as an absorption enhancer) and EMLA cream were compared on the forearms of 34 adult volunteers in a double-blind fashion. The mean pinprick pain scores (graded by noting the number of painful pinpricks out of five) at 30, 60 and 90 min after application and 30 min after removal of the anaesthetics were 3.3 (0.3) (mean SE), 1.2 (0.3), 0.3 (0.1) and 0.3 (0.1) respectively, in the lignocaine gel group. Corresponding scores were 3.5 (0.3), 1.5 (0.3), 0.7 (0.2) and 0.1 (0.1) respectively, in the EMLA group. Insertion of a 26-gauge needle into the treated skin to a depth of 1 mm at 90 min after application was not painful in 91% of the volunteers in the lignocaine gel group and 88% of those in the EMLA group. There was no significant difference in any of the corresponding pain scores between the two groups.

Evaluation of the penetration depth of transdermally applied 3% GA MHPh 2Na-10% lidocaine gel in man

In order to estimate the penetration depth of transdermal 3% GA MHPh 2Na-10% lidocaine gel mixture, the following physiological functions of the skin were examined before and after a 60 min occulusive application of the gel in 16 adult volunteers. Thermal sweat expulsins ceased completely on the gel-treated ventral surface of one forearm in all the firs 5 subjects, though it continued on the untreated contrast area of the other forearm. Sympathetic skin response (SSR) was also no longer induced on the gel-treated middle finger in 1 of another 3 subjects and was severely depressed in the other 2 subjects, while the SSR on the untreated index finger appeared constantly. Vasomotion of the skin circulation on another 3 subjects, remained unaffected on both the gel-treated and the untreated fingers. Extraction of a leg-hair in the treated area did not induce pain sensation in all the last 5 subjects. In addition to the transcellular main roots, some of the transcutaneously applied gel seems to penetrate deeply into the skin through the appendageal roots such as the eccrine sweat glands and the pilosebaceous glands.