A pharmacokinetic study of a topical anesthetic (EMLA® ) in mouse soft tissue laceration

The Pen Is Milder Than the Blade: Identification Marking Mice Using Ink on the Tail Appears More Humane Than Ear-Punching Even with Local Anaesthetic

Simple Summary

Laboratory mice often look identical, so they are commonly marked by cutting the ear via ear-punching, or marking the tail with permanent marker. Ear-punching is permanent but could be painful, and mice could become stressed by weekly tail-marking, so we compared impacts on mice over 5 weeks. We also explored whether local anaesthetic cream could reduce any ear-punching effects. We found that ear-punching, even with anaesthetic, caused mice to be sniffed and groomed by their cagemates for at least 5 min after marking. Mice ear-punched with anaesthetic also groomed themselves and their ears ~5 times more than tail-marked and control mice. Facial grimacing was most common in the unmarked cagemates of tail-marked mice, and possibly in mice ear-punched with anaesthetic. The next day, mice ear-punched with anaesthetic were significantly less likely to eat unfamiliar food in an anxiety test than tail-marked or control mice. Over 5 weeks, ear-punched mice approached the handler significantly less than unmarked mice did, and tail-marked mice showed reduced defecation during re-marking. Other behaviour, bodyweight, and corticosterone showed no treatment effects. This suggests ear-punching caused some signs of pain and anxiety, and anaesthetic did not help. Tail-marking appeared more humane, showing no differences from the controls.

Abstract

Identification marking mice commonly involves ear-punching with or without anaesthetic, or tail-marking with ink. To identify which is most humane, we marked weanling male BALB/c mice using ear-punching (EP), ear-punching with anaesthetic EMLA^TM cream (EP+A), or permanent marker pen (MP). We compared marked mice, unmarked cagemates, and control mice (n = 12–13/group) for 5 weeks, reapplying MP weekly. Treatment-blind observations following marking showed that EP and EP+A mice were allogroomed (p < 0.001) and sniffed (p < 0.001) by their cagemates more than MP and control mice were. EP+A mice groomed themselves (p < 0.001) and their ears (p < 0.001) ~5 times more than most other mice; their cagemates also increased self-grooming (p < 0.001). Unmarked MP cagemates (p = 0.001), and possibly EP+A mice (p = 0.034; a nonsignificant trend), grimaced the most. The following day, half the EP+A mice showed hyponeophagia versus no MP and control mice (p = 0.001). Over the 5 weeks, EP mice approached the handler significantly less than unmarked cagemates did (p < 0.001). Across weeks, defecation during marking of MP mice decreased (p < 0.001). Treatment showed no effects on immediate responses during marking, aggression, bodyweight, plus-maze behaviour or corticosterone. MP mice showed no differences from controls, whilst EP and EP+A mice showed altered behaviour, so ink-marking may be the more humane identification method.

Topical Application of Lidocaine and Bupivacaine to Disbudding Wounds in Dairy Calves: Safety, Toxicology and Wound Healing

Simple Summary

Disbudding is a common, but painful procedure performed on calves to prevent horn growth. Tri-Solfen^® is a combination local anaesthetic and antiseptic formulation which, applied topically to the disbudding wound, is reported to reduce calf pain. Applied in this manner, the local anaesthetics in Tri-Solfen^®, lidocaine and bupivacaine, are reported to be poorly absorbed, resulting in low risk of neurological or cardiotoxic effects. The potential impacts on other blood, urine and tissue parameters and on wound healing when used in this manner, and/or accidental overdose situations are unknown, however. We performed experiments investigating (i) the safety of Tri-Solfen^® (including overdose situations) and (ii) the impact of Tri-Solfen^® on disbudding wound healing under field conditions. No adverse health effects were observed in Tri-Solfen^®-treated animals, even those receiving 5× the recommended dose, with no clinically significant differences in measured parameters between placebo and Tri-Solfen^® groups. No negative impacts on wound healing were noted. Conversely, lower levels of bacterial wound colonisation were evident, and there was reduced incidence of abnormal wounds at days 11–12 in Tri-Solfen^®-treated animals.

Abstract

Tri-Solfen^® is a combination topical anaesthetic and antiseptic solution containing lidocaine, bupivacaine, adrenaline and cetrimide. Applied to wounds, it is reported to reduce the pain experienced by calves following thermocautery disbudding. While lidocaine and bupivacaine are widely used in medicine, conflicting data exist on the impact of these compounds when applied directly to the surgical wound. To investigate the safety of Tri-Solfen^® applied to thermocautery disbudding wounds of calves, experiments were performed to measure (i) the safety of Tri-Solfen^® (including in overdose situations); and (ii) the impact of Tri-Solfen^® application at recommended doses on disbudding wound healing under field conditions. Haematological, biochemical and urinalysis parameters did not show clinically significant differences between placebo and Tri-Solfen^® groups (1×, 3× and 5× dose). No adverse health impacts were reported. Histopathological analysis of wounds noted a reduction in bacterial colonies in Tri-Solfen^®-treated wounds. Under field conditions, no negative impacts on wound healing were noted. Conversely, there was reduced incidence of abnormal wounds, with an associated trend toward improved average daily gain at days 11–12 in Tri-Solfen^®-treated animals. These data are considered to support the safety of topical anaesthesia, as formulated in Tri-Solfen^®, to the thermocautery disbudding wound in calves.

Clinical Management of Pain in Rodents

The use of effective regimens for mitigating pain remain underutilized in research rodents despite the general acceptance of both the ethical imperative and regulatory requirements intended to maximize animal welfare. Factors contributing to this gap between the need for and the actual use of analgesia include lack of sufficient evidence-based data on effective regimens, under-dosing due to labor required to dose analgesics at appropriate intervals, concerns that the use of analgesics may impact study outcomes, and beliefs that rodents recover quickly from invasive procedures and as such do not need analgesics. Fundamentally, any discussion of clinical management of pain in rodents must recognize that nociceptive pathways and pain signaling mechanisms are highly conserved across mammalian species, and that central processing of pain is largely equivalent in rodents and other larger research species such as dogs, cats, or primates. Other obstacles to effective pain management in rodents have been the lack of objective, science-driven data on pain assessment, and the availability of appropriate pharmacological tools for pain mitigation. To address this deficit, we have reviewed and summarized the available publications on pain management in rats, mice and guinea pigs. Different drug classes and specific pharmacokinetic profiles, recommended dosages, and routes of administration are discussed, and updated recommendations are provided. Nonpharmacologic tools for increasing the comfort and wellbeing of research animals are also discussed. The potential adverse effects of analgesics are also reviewed. While gaps still exist in our understanding of clinical pain management in rodents, effective pharmacologic and nonpharmacologic strategies are available that can and should be used to provide analgesia while minimizing adverse effects. The key to effective clinical management of pain is thoughtful planning that incorporates study needs and veterinary guidance, knowledge of the pharmacokinetics and mechanisms of action of drugs being considered, careful attention to individual differences, and establishing an institutional culture that commits to pain management for all species as a central component of animal welfare.

Simultaneous quantification of lidocaine and prilocaine in human plasma by LC-MS/MS and its application in a human pharmacokinetic study

OBJECTIVE

The aim of the work was to develop and validate a simple, sensitive and selective Liquid chromatography with Mass spectroscopic method for simultaneous quantification of lidocaine and prilocaine in human plasma.

DESIGN AND METHODS

Analytes and the internal standards from human plasma were extracted by using solid- phase extraction technique using Waters Oasis® HLB 1 ​cc (30 ​mg) cartridges. The reconstituted samples were chromatographed on Phenomenex Kinetex EVO 4.6*100 ​mm 2.6 μ 100A column by using a mixture of acetonitrile and 5 ​mM ammonium acetate buffer (80:20, v/v) as the mobile phase at a flow rate of 0.6 ​mL/min.

RESULTS

The method was validated over the concentration range of 0.10-201.80 ng/mL for lidocaine and 0.10-201.66 ng/mL for prilocaine. The calibration curve obtained was linear.

CONCLUSION

Method validation was performed as per FDA guidelines and the results met the acceptance criteria. A run time of 3.0 min for each sample, make it possible to analyze more than 350 human plasma samples per day. The proposed method was found applicable for pharmacokinetic studies.

Pharmacokinetics of intravenous, subcutaneous, and topical administration of lidocaine hydrochloride and metabolites 3-hydroxylidocaine, monoethylglycinexylidide, and 4-hydroxylidocaine in horse

Intravenous (iv), subcutaneous (sq), and topical (tp) lidocaine was administered to six horses in a cross-over, randomized design study. Samples were collected for up to 72 hr. Compartmental models were used to investigate the pharmacokinetics of (LD) and its metabolites 3-hydroxylidocaine (3-OH), 4-hydroxylidocaine (4-OH), and monoethylglycinexylidide (MEGX). Metabolites 3-OH and 4-OH were present in conjugated forms, whereas LD and metabolite MEXG were present primarily in the un-conjugated form. Plasma concentrations of LD after iv administration (100 mg) were described by three-compartment model with an additional three compartments to describe the elimination of metabolites. Median (range) elimination micro-constants (K_e ) for LD, 3-OH, 4-OH, and MEXG were 4.12 (2.62-6.23), 1.25 (1.10-2.15), 1.79 (1.22-2.39), and 1.69 (1.03-1.99)/hr, respectively. Median (range) values of alpha (t_½α ), beta (t_½β ), and gamma (t_½γ ) half-lives were 0.08 (0.07-0.13), 0.57 (0.15-1.25), and 4.11 (0.52-7.36) hr. Plasma concentrations of LD after sq (200 mg) administration were described by absorption and two-compartment elimination model. The median (range) of the LD absorption half-life (t_½ab ) was 0.47 (0.29-0.61) hr. The K_e for LD, 3-OH, 4-OH, and MEXG was 3.91 (1.48-9.25), 1.00 (0.78-1.08), 1.76 (0.96-2.11), and 1.13 (0.69-1.33)/hr. The median (range) of t_½α and t_½β was 0.15 (0.06-0.27) and 3.04 (2.53-6.39) hr. Plasma concentrations of LD after tp (400 mg) application were described by one-compartment model with a t_½ab of 8.49 (5.16-11.80) hr. The K_e for LD, 3-OH, and MEXG was 0.24 (0.10-0.81), 0.41 (0.08-0.93), and 0.38 (0.26-1.14)/hr.

The effect of a lidocaine/prilocaine topical anesthetic on pain and discomfort associated with orthodontic elastomeric separator placement

Background

The initial placement of orthodontic elastomeric separators can be uncomfortable and painful. Therefore, it is important to relieve this disturbing sensation to create a discomfort or pain-free orthodontic visit. The purpose of this study was to investigate the effect of a lidocaine/prilocaine topical anesthetic on pain and discomfort associated with the placement of orthodontic elastomeric separators.

Methods

Fifty subjects aging between 20–35 years were included in this study. In the maxillary arch, a lidocaine/prilocaine topical anesthetic was placed around the ginigval margins of the premolar and molar on side. On the other side, a placebo agent was placed around the ginigval margins of the premolar and molar. After two minutes, an elastomeric separator was placed between the premolar and molar on both sides. The subjects were then asked to report their findings on a Verbal Scale and a Visual Analogue Scale every second minute for a period of 10 min. The subjects were also given a questionnaire to evaluate the overall impression on the topical anesthetic use.

Results

The overall mean discomfort/pain score was found to be significantly lower (p < 0.001) with the topical anesthetic than with the placebo. Repeated measures ANOVA with a Greenhouse-Geisser correction determined that mean pain scores were statistically significantly low with the 10-min time duration (F_(1.54,42.2) = 40.7, p = 0.001), with an estimated grand mean (8.37, 95% CI 6.75–9.98). The questionnaire responses revealed that 87% of the subjects reported an overall satisfaction and agreement with the topical anesthetic than with the placebo or no difference (13%) after the initial separator placement.

Conclusions

The discomfort and pain resulting from the initial placement of orthodontic elastomeric separators can be significantly reduced with the lidocaine/prilocaine topical anesthetic.

Blood concentration of prilocaine and lidocaine after the use of topical anesthesia (Oraqix® ) in lacerated wounds

BACKGROUND/AIM

Soft tissue injuries have been reported as being sutured using only topical anesthesia applied in the laceration wound. The objective of this study was to assess the pharmacokinetic profile of components of Oraqix^® (2.5% prilocaine and 2.5% lidocaine) when applied in a laceration as compared to intact skin application in the mouse.

MATERIALS AND METHODS

A total of 200 BALB/c male mice were used in this study. The mice were divided into three groups: group A: shaved and laceration group (80 mice); B: shaved and intact skin group (80 mice); and C: control group (shaved, no treatment; 40 mice) which underwent the same procedures but without application of Oraqix^® . Blood samples were collected over 90 min. Plasma sample analysis employing liquid chromatography coupled with the tandem mass spectrometric (LC-MS/MS) method was used to determine plasma concentrations of lidocaine and prilocaine. Pharmacokinetic analysis of mouse plasma concentrations was carried out by standard non-compartmental methods.

RESULTS

Absorption of both lidocaine and prilocaine was rapid. C_max and AUC values of lidocaine were significantly increased by fourfold and twofold, respectively, in lacerated mouse skin compared to intact skin. Similarly, prilocaine's C_max and AUC values were also increased by 2.5-fold and fourfold, respectively, in lacerated skin compared to intact skin.

CONCLUSION

When Oraqix^® was applied directly into the skin laceration, the plasma concentration of lidocaine and prilocaine was significantly increased as compared to when applied on intact skin. The present study, albeit in mice, indicates that the plasma levels of lidocaine and prilocaine can reach very high levels when the thermosetting gel Oraqix^® is placed directly in wounds.

A critical review of microextraction by packed sorbent as a sample preparation approach in drug bioanalysis

Sample preparation is widely accepted as the most labor-intensive and error-prone part of the bioanalytical process. The recent advances in this field have been focused on the miniaturization and integration of sample preparation online with analytical instrumentation, in order to reduce laboratory workload and increase analytical performance. From this perspective, microextraction by packed sorbent (MEPS) has emerged in the last few years as a powerful sample preparation approach suitable to be easily automated with liquid and gas chromatographic systems applied in a variety of bioanalytical areas (pharmaceutical, clinical, toxicological, environmental and food research). This paper aims to provide an overview and a critical discussion of recent bioanalytical methods reported in literature based on MEPS, with special emphasis on those developed for the quantification of therapeutic drugs and/or metabolites in biological samples. The advantages and some limitations of MEPS, as well as its comparison with other extraction techniques, are also addressed herein.