经皮神经电刺激的镇痛机制及其临床应用

经皮神经电刺激(transcutaneous electrical nerve stimulation,TENS)是一种非侵入式的通过电流脉冲来激活外周神经纤维的镇痛疗法,具有非药理性、安全无创伤、费用低等多方面优点,已用于临床中多种疼痛的缓解。然而,TENS的临床镇痛效果存在较大的差异,这可能是由于不同刺激参数下的TENS涉及不同的镇痛机制。为推进TENS相关的基础研究与临床应用,本文首先综述了不同类型TENS镇痛的神经生理和生化机制,进而从刺激位置、脉冲参数(电流强度、频率与脉宽)以及使用时长和使用频度等多个方面讨论了影响TENS镇痛效果的因素,并总结了TENS在临床镇痛的相关应用,包括术后痛、慢性腰背痛、分娩痛等情况下的应用。最后,为实现更好的临床镇痛效果,本文提出在TENS相关的临床应用中,应充分考虑到不同刺激参数对TENS镇痛效果的影响以及患者个体间差异所导致的TENS镇痛效果的差别,优化TENS参数设置,建立基于患者疼痛评分与TENS刺激输入之间的动态关系模型,自适应地根据患者实时疼痛评分调整TENS刺激模式。     

云南白族、傣族、彝族X染色体STR基因座的遗传多态性及其与中国5个主要民族的遗传关系

应用复合PCR及基因扫描技术, 对云南白族、傣族、彝族人群X染色体3个STR基因座DXS6804、DXS6799、DXS7132的遗传多态性进行研究。白族89个样本中共检出18个等位基因, 38个基因型, 等位基因频率分布在0.0200~0.6400之间, 基因型频率分布在0.0256~0.3333之间; 傣族100个样本中共检出17个等位基因, 24个基因型, 等位基因频率分布在0.0135~0.7500之间, 基因型频率分布在0.0385~0.5769之间; 彝族88个样本中共检出20个等位基因, 35个基因型, 等位基因频率分布在0.0125~0.5875之间, 基因型频率分布在0.0250~0.3500之间。群体遗传多态性指标及法医学应用指标统计结果显示, 3个基因座在云南3个少数民族人群中均具有高度多态性。聚类分析和系统进化关系分析发现, 彝族、白族、傣族与藏族之间的遗传关系较近。     

CYP2C19 基因多态性与冠心病危险因素对氯吡格雷抵抗的影响

目的:观察细胞色素P450系统药物代谢酶CYP2C19基因多态性以及相关临床因素对氯吡格雷抵抗的影响。方法:选择2010年11月至2011年5月我科拟行PCI术治疗的冠心病患者共145例,均给予氯吡格雷300mg负荷剂量,75mg维持剂量。①通过流式细胞仪检测血管舒张因子刺激酸磷蛋白血小板反应性指数VASP PRI(以VASP PRI≥50%,定义为氯吡格雷抵抗)分为氯吡格雷抵抗组和氯吡格雷反应组。②检测入选患者的药物代谢酶CYP2C19的基因型;根据不同等位基因功能缺失,分为快代谢基因型(*1/*1)、中间代谢基因型(*1/*2、*1/*3)和慢代谢基因型(*2/*2、*2/*3、*3/*3)。③观察CYP2C19基因型及相关临床危险因素对氯吡格雷反应性的影响,④观察氯吡格雷抵抗与临床不良终点事件主要临床不良终点事件[心源性死亡、再发心肌梗死、靶病变再次血运重建术(TLR)]和次要临床终点事件(支架内血栓形成、脑血管意外、大出血)之间的相关性。结果:检测出氯吡格雷抵抗的患者31例,其发生率为20.67%;检测出CYP2C19慢代谢基因型携带患者19例,所占比例为12.67%。慢代谢基因型患者与(快代谢基因型+中间代谢基因型患者)之间VASP PRI比为(49.20±8.45)%VS(44.17±5.41)%,P<0.05,氯吡格雷抵抗发生率之比为35.49%(n=11)VS16.81%(n=20),P<0.05。多元回归分析提示CYP2C19慢代谢基因型(OR:4.43;95%CI:3.28-8.37,P<0.05)和2型糖尿病(OR:2.76;95%CI:2.13-6.14;P<0.05)是氯吡格雷抵抗的两种危险因素。临床随访结果显示氯吡格雷抵抗组与氯吡格雷反应组主要临床不良终点事件的发生率比为6.45%(n=2)vs2.63%(n=3),P<0.05。结论:携带CPY2C19慢代谢基因型和患有2型糖尿病是导致氯吡格雷抵抗的两种重要的危险因素,氯吡格雷抵抗的发生增加了临床不良终点事件的风险。     

印楝种子提取物对荔枝蝽的毒性及与其等位酶基因型之间的关系

用5.2 mg/mL（LC₅₀）的印楝种子提取物对荔枝蝽1龄若虫进行急性毒性处理,24 h死亡率为51.8%。通过等位酶分析检测了死亡与存活试虫两种酶（PGI和MDH）,两个基因座（Pgi和Mdh）上各基因型及等位基因与印楝种子提取物毒性之间的关系,进行致死性差异比较研究。结果表明,印楝种子提取物对具有不同基因型及等位基因个体的致死性存在差异。在Pgi基因座上,Pgi-bb基因型死亡率最高,为84%,Pgi-aa 和Pgi-cc基因型死亡率较低,分别为0和7%,且与死亡率最高的Pgi-bb基因型存在显著差异（P<0.05）。在基因座Mdh上,Mdh-aa基因型个体死亡率最高（93%）,而具有Mdh-cc基因型的个体全部存活了下来, 另外3个基因型Mdh-ab、Mdh-bb与Mdh-bc死亡率居中,都与Mdh-aa、Mdh-cc基因型死亡率之间存在显著差异。在等位基因上,Pgi-a和Mdh-c个体的死亡率都最低,与各自其他两个等位基因的死亡率之间存在显著差异。结果说明不同基因型个体对印楝提取物具有不同的反应,印楝种子提取物对荔枝蝽等位酶基因型及等位基因存在选择性致死作用。这种荔枝蝽对印楝种子提取物的敏感性与其等位酶基因型及等位基因之间显明的相关关系提示我们,可将荔枝蝽种群中对印楝种子提取物敏感性低的基因型及等位基因作为遗传标记去监测荔枝蝽对印楝种子提取物的抗性状况。     

非侵入性电刺激神经调控技术：镇痛效果与镇痛机制

非侵入性电刺激神经调控技术是一种潜力巨大的非药物镇痛手段,具有经济、易操作、安全性高等优点,已被应用于各类临床疼痛的治疗。然而,目前仍缺乏对不同电刺激神经调控技术镇痛特性的深入理解。本文从镇痛效果和镇痛机制两个方面入手,评述非侵入性外周神经电刺激(经皮神经电刺激、经皮迷走神经电刺激)和中枢神经电刺激(经颅直流电刺激、经颅交流电刺激)在镇痛方面的研究结果,总结各技术在缓解急性疼痛和慢性疼痛中常用的刺激参数和其镇痛效果,探讨可能的镇痛机制。最后,本文对比和总结各技术的镇痛特点,讨论了现有研究的若干局限和未来的研究方向。克服这些局限将促进相关技术的临床应用,最终达到帮助患者缓解疼痛的目的,减轻疼痛对患者、其家庭和整个社会带来的健康和经济负担。     

经皮穴位电刺激治疗术后疼痛的研究进展

术后疼痛是术后常见的一种伤害性疼痛,随着舒适化医疗的倡导,经皮穴位电刺激因其无创、安全等优点受到关注。经皮穴位电刺激是将经皮神经电刺激与针灸穴位理论相结合的一种方法,虽有研究证实其频率、波形、强度、刺激时间的设定及不同穴位的配伍对镇痛效果均可产生较大的影响,但在规范化方面仍有不足。本文总结其使用方法及镇痛疗效,以期对经皮穴位电刺激应用于临床提供最优参数及穴位配伍,使之规范化,从而发挥出最佳镇痛效果。     

曲马多、吗啡术后自控镇痛对食管癌患者细胞免疫功能的影响

目的：比较曲马多、吗啡对食管癌术后患者的镇痛疗效以及对机体免疫功能的影响。方法：将本院50 例行食管癌手术患者随 机分成对A 组和B 组,A 组接受硬膜外吗啡镇痛,B 组接受硬膜外曲马多镇痛,常规监测心电图（ECG）、无创血压（BP）、心率 （HR）、血氧饱和度（SPO2）、呼气末二氧化碳分压(PETCO2）。记录两组患者不同时间点视觉模拟疼痛（VAS）评分、不良反应发生 率、外周血T 淋巴细胞亚群(CD3+、CD4+、CD8+)、NK 细胞的变化。结果：两组患者均得到满意的术后镇痛效果,术后1d,A、B两组 患者外周血T淋巴细胞亚群、NK 细胞的水平较术前降低（P<0.05）,且A 组降低幅度明显大于B 组（P<0.05）;术后2d,A 组外周 血T 淋巴细胞亚群、NK 细胞的水平虽有所升高,但仍较术前降低（P<0.05）,B 组CD3+、CD4+、CD8+及NK细胞水平恢复至术前水 平;术后3d,A 组上述指标恢复至麻醉前水平。结论：曲马多在镇痛的同时对机体外周血T 淋巴细胞亚群和NK细胞水平影响较 小,减轻了麻醉对细胞免疫功能的抑制效应。     

辣椒素的镇痛作用

辣椒素是从辣椒中提取出来的一种具有镇痛作用的物质。通过激活感觉神经纤维上的瞬时感受器电位香草酸受体1(transient receptor potential vanilloid 1,TRPV1),释放并消耗大量神经肽物质,使神经细胞对伤害性刺激产生脱敏化反应,进而发挥持久的镇痛作用而不影响运动功能。因而在难治性疼痛类疾病中,辣椒素具有独特的治疗价值。以辣椒素为主要成分的制剂已经在临床治疗中开展应用。特定位点注射辣椒素或其类似物resiniferatoxin可以减轻癌痛患者的疼痛症状。但由于辣椒素的治疗剂量与毒性剂量存在部分重叠,使得其在临床应用中受到一定程度的限制。不同的给药方式和作用部位所产生的作用效果可能不同。为深入了解辣椒素的镇痛作用及作用机制,充分发挥其治疗价值,现从不同给药途径总结近几年来辣椒素镇痛作用的研究成果。     

中国汉族人群肿瘤坏死因子-α（TNF-α）基因-238G/A和-308G/A多态性与强迫症的关联分析（英文）

目的：探讨在中国汉族人群中强迫症与TNF-a基因-238G/A和-308G/A多态性之间的关联。方法：我们的研究所招募的161例强迫症患者和325名健康对照中,应用PCR-RFLP比较了OCD组和对照组之间的TNF-α基因在-238G/A（rs361525）和-308G/A（rs1800629）位点的基因型和等位基因频率多态性。结果：在中国大陆汉族人群TNF-α基因的OCD组与对照组之间-308 G/A等位基因频率及-238G/A的基因型频率和等位基因频率无显着差异,而-308G/A基因型频率有显著不同。在-308G/A位点,女性强迫症患者和对照组之间的基因型频率关联分析有增高的趋势。结论：我们的研究结果表明,肿瘤坏死因子-α在-308G/A点位多态性可能会影响在中国大陆汉族人群强迫症的发展。     

癫痫患儿SCN1A、MDR1 G2677TA、ABCB1 C3435T基因多态性与左乙拉西坦治疗效果的关系及疗效的影响因素分析

摘要 目的：探讨癫痫患儿SCN1A、MDR1 G2677TA、ABCB1 C3435T基因多态性与左乙拉西坦（LEV）治疗效果的关系及疗效的影响因素。方法：选择2019年6月至2021年7月在本院接受LEV治疗的癫痫患儿226例为研究对象,分析所有患儿基因型和等位基因分布情况;治疗3个月后根据治疗效果分为有效组和无效组,分析两组患儿SCN1A、MDR1 G2677TA、ABCB1 C3435T基因型及等位基因频率分布;采用单因素及多因素Logistic回归分析法分析影响临床疗效的因素。结果：癫痫患儿SCN1A rs4667869、SCN1A rs10497275、MDR1 G2677TA、ABCB1 C3435T基因型及等位基因分布频率有统计学差异（P＜0.05）。有效组SCN1A rs4667869的基因型GG、GC及等位基因G分布频率高于无效组（P＜0.05）,基因型CC及等位基因C分布频率低于无效组（P＜0.05）;有效组SCN1A rs10497275的基因型GA及等位基因G高于无效组（P＜0.05）,基因型AA及等位基因A分布频率低于无效组（P＜0.05）;有效组MDR1 G2677TA的基因型GT、TT及等位基因T高于无效组（P＜0.05）,基因型GG、AA及等位基因G分布频率低于无效组（P＜0.05）;有效组ABCB1 C3435T的基因型CC、CT及等位基因C分布频率高于无效组（P＜0.05）,基因型TT及等位基因T分布频率低于无效组（P＜0.05）。单因素分析显示,月发作频率和出生窒息史与LEV治疗癫痫患儿疗效有关。多因素Logistic回归分析显示,SCN1A rs4667869、SCN1A rs10497275、MDR1 G2677TA和ABCB1 C3435T基因型及等位基因、出生窒息史是LEV治疗癫痫患儿疗效的影响因素。结论：癫痫患儿SCN1A、MDR1 G2677TA和ABCB1 C3435T基因多态性与LEV治疗效果有关,其多种基因型是LEV治疗效果的影响因素。     

Tramadol and Propentofylline Coadministration Exerted Synergistic Effects on Rat Spinal Nerve Ligation-Induced Neuropathic Pain

Neuropathic pain is an intractable clinical problem. Drug treatments such as tramadol have been reported to effectively decrease neuropathic pain by inhibiting the activity of nociceptive neurons. It has also been reported that modulating glial activation could also prevent or reverse neuropathic pain via the administration of a glial modulator or inhibitor, such as propentofylline. Thus far, there has been no clinical strategy incorporating both neuronal and glial participation for treating neuropathic pain. Therefore, the present research study was designed to assess whether coadministration of tramadol and propentofylline, as neuronal and glial activation inhibitors, respectively, would exert a synergistic effect on the reduction of rat spinal nerve ligation (SNL)-induced neuropathic pain. Rats underwent SNL surgery to induce neuropathic pain. Pain behavioral tests were conducted to ascertain the effect of drugs on SNL-induced mechanical allodynia with von-Frey hairs. Proinflammatory factor interleukin-1β (IL-1β) expression was also detected by Real-time RT-PCR. Intrathecal tramadol and propentofylline administered alone relieved SNL-induced mechanical allodynia in a dose-dependent manner. Tramadol and propentofylline coadministration exerted a more potent effect in a synergistic and dose dependent manner than the intrathecal administration of either drug alone. Real-time RT-PCR demonstrated IL-1β up-expression in the ipsilateral spinal dorsal horn after the lesion, which was significantly decreased by tramadol and propentofylline coadministration. Inhibiting proinflammatory factor IL-1β contributed to the synergistic effects of tramadol and propentofylline coadministration on rat peripheral nerve injury-induced neuropathic pain. Thus, our study provided a rationale for utilizing a novel strategy for treating neuropathic pain by blocking the proinflammatory factor related pathways in the central nervous system.     

Rofecoxib and tramadol do not attenuate delayed-onset muscle soreness or ischaemic pain in human volunteers

We assessed the effect of rofecoxib, a cyclo-oxygenase-2 inhibitor, and tramadol, a centrally acting analgesic, on both delayed-onset muscle soreness (DOMS) and experimentally induced ischaemic pain. We induced DOMS in 10 male and 5 female healthy volunteers by downhill running for 30 min at a 12% decline and a speed of 9 km x h(-1). We also induced ischaemic pain by finger movements with an arterial tourniquet around the arm. In a randomized, double-blind crossover format, we administered rofecoxib (50 mg, daily), tramadol (50 mg, 3 times per day), and a placebo (orally for 3 days), starting immediately after exercise. A 100 mm visual analogue scale (VAS) and McGill pain questionnaire were used to describe muscle soreness and ischaemic forearm pain 24 h after the exercise. The pressure pain threshold (PPT) in the thigh and ischaemic pain tolerance in the forearm were measured before exercise and 24 and 72 h after exercise. PPT decreased 24 h after exercise, compared with pre-exercise values (ANOVA, p < 0.05), but neither drug had any significant effect on the PPT. Neither rofecoxib nor tramadol had any effect on time of ischaemia tolerated or amount of finger activity during ischaemia. The VAS and pain-rating index, for both muscle soreness and experimental ischaemic pain, were not affected significantly by either drug. Both DOMS and ischaemic pain share peripheral and central mechanisms, yet neither are attenuated by rofecoxib or tramadol.     

The antinociceptive effect of tramadol on a model of neuropathic pain in rats

The antinociceptive activity of tramadol was investigated on the vocalization threshold to paw pressure in a rat model of unilateral mononeuropathy produced by loose ligatures around the common sciatic nerve. Despite the analgesic activity of tramadol was clearly established in motor and sensory responses of the nociceptive system in rats, the effect of this atypical opioid on experimental neuropathic pain models is not investigated. The intraperitoneally injected tramadol (2.5, 5 and 10 mg/kg) produced a potent and dose-dependent antinociceptive effect on both lesioned and non-lesioned hind paws. However, the analgesic effect on the lesioned paw was significantly more potent than the non-lesioned paw. This effect was partially antagonized by intraperitoneally administered naloxone (0.1 mg/kg) suggesting an additional non-opioid mechanism. Our results suggest that tramadol may be useful for the alleviation of some symptoms in peripheral neuropathic conditions     

Gender differences in the antinociceptive effect of tramadol,alone or in combination with gabapentin,in mice

Gender difference in the antinociceptive effect of tramadol and gabapentin (alone or in combination) were investigated in mice. For investigation of acute antinociceptive effect, tramadol and gabapentin were administered to mice by intraperitoneal injection and per os, respectively, and antinociceptive activity was measured by the tail-flick test 30 min after drug administration. For investigation of the development of antinociceptive tolerance to analgesics, mice were injected with tramadol (60 mg/kg), alone or in combination with gabapentin (75 mg/kg), twice daily for seven consecutive days and the tail-flicks were tested on experimental days 1, 3, 5 and 7. Results showed there was a lower ED₅₀ value of tramadol antinociception in males than in females, indicating that females were less sensitive to the drug. Gabapentin produces a limited antinociception in both males and females. The combination of gabapentin and tramadol produced synergistic effect without gender difference. Repeated administration of tramadol produced antinociceptive tolerance in both genders. Gabapentin produced synergistic effect in tramadol-tolerant mice and repeated administration of gabapentin did not alter the synergistic effect in tramadol-tolerant mice. Because females show a higher overall prevalence of pain and less sensitivity to opioids, our finding may suggest a clinical significance of combined use of the two drugs.     

Systems properties of the Haemophilus influenzae Rd metabolic genotype.

Haemophilus influenzae Rd was the first free-living organism for which the complete genomic sequence was established. The annotated sequence and known biochemical information was used to define the H. influenzae Rd metabolic genotype. This genotype contains 488 metabolic reactions operating on 343 metabolites. The stoichiometric matrix was used to determine the systems characteristics of the metabolic genotype and to assess the metabolic capabilities of H. influenzae. The need to balance cofactor and biosynthetic precursor production during growth on mixed substrates led to the definition of six different optimal metabolic phenotypes arising from the same metabolic genotype, each with different constraining features. The effects of variations in the metabolic genotype were also studied, and it was shown that the H. influenzae Rd metabolic genotype contains redundant functions under defined conditions. We thus show that the synthesis of in silico metabolic genotypes from annotated genome sequences is possible and that systems analysis methods are available that can be used to analyze and interpret phenotypic behavior of such genotypes.     

Modelling the pharmacokinetics of tramadol: on the difference between CYP2D6 extensive and poor metabolizers

In this work we propose a mathematical model for the kinetics of tramadol, a synthetic opioid commonly used for treating moderate to severe pain. This novel theoretical framework could result in an objective criterion on how to adjust the assigned dose, depending on the genetic polymorphisms of CYP2D6. The model describes the coupled dynamics of tramadol and the metabolite O-desmethyltramadol. The effect of diffusion of the drug in the blood is here accounted for and we further hypothesize the existence of a time delay in the process of chemical translation from tramadol into metabolites. The system of coupled differential equations is solved numerically and the free parameters adjusted so to interpolate the experimental time series for the intravenous injection setting. Theoretical curves are shown to reproduce correctly the experimental profiles obtained from clinical trials. This enables in turn to extract an estimate of the metabolization rate. A difference in metabolization rate between CYP2D6 poor and extensive metabolizers is also found, and the stereoselectivity in the O-demethylation of tramadol highlighted. Our results allow one to quantify the dose of (+)-tramadol (resp. (-)-tramadol) administered to poor or extensive metabolizers, if the same effect is sought. The latter is here quantified through the blood concentration of (+)-metabolites (resp. (-)-metabolites).     

Antinociceptive efficacy of lacosamide in the monosodium iodoacetate rat model for osteoarthritis pain

The etiology of osteoarthritis is multifactorial, with inflammatory, metabolic, and mechanical causes. Pain in osteoarthritis is initiated by mild intra-articular inflammation and degeneration of articular cartilage and subchondral bone. The principle of treatment with acetaminophen or non-steroidal anti-inflammatory drugs is to reduce pain and improve joint function. Recently, animal models for osteoarthritic pain behavior have been established. The most frequently used rat model for analyzing properties of drugs on the pathology of osteoarthritis is the injection of the metabolic inhibitor monosodium iodoacetate into the joint, which inhibits the activity of glyceraldehyde-3-phosphate dehydrogenase in chondrocytes. Here, we characterize the effect on pain behavior of lacosamide, a member of a family of functionalized amino acids that are analogues of endogenous amino acids and D-serine, in the monosodium iodoacetate rat model for osteoarthritis in comparison to diclofenac and morphine. Lacosamide (3, 10, and 30 mg/kg) was able to reduce secondary mechanical allodynia and hyperalgesia similarly to morphine (3 mg/kg). In contrast, diclofenac (30 mg/kg) was only effective in reducing secondary mechanical hyperalgesia. During the first week, pain is induced mainly by inflammation in the iodoacetate model, but afterwards inflammation plays only a minor role in pain. Lacosamide was able to inhibit pain at days 3, 7 and 14 after induction of arthritis. This shows that lacosamide is able to reduce pain behavior induced by multiple mechanisms in animals.     

Behavioral control of the efficiency of pharmacological anesthesia in fish

An original behavioral test was used to study the effect of opioid substances on the thresholds of nociceptive responses to pain stimuli—a series of electric impulses applied to nerve endings of the caudal fin—in the common carp (Cyprinus carpio). The substances tested included tramadol (μ-agonist of opioid receptors), DADLE (δ-agonist), and U-50488 (κ-agonist) injected intramuscularly in concentrations 10–100 nmol/g of body weight. Raised thresholds of sensitivity to the pain stimulus were observed in the studied fish 5 to 15 min after the injection. The degree of analgesia and the rate of its increase varied depending on the dose. The total duration of analgesia was 40 to 90 min and depended on the concentration of the injected substance. It was observed in some experiments that the analgesic effect of tramadol (the most efficient of the analgesics used) could last longer than 4 h. The analgesic effect of opioids was not detected in experiments where they were applied together with naloxone, an antagonist of opioids. Decreased motor response to pain stimuli after injections of analgesics was not caused by the immobilization of the animal, because the tested fish individuals released into an aquarium demonstrated normal swimming and their usual behavior. We concluded that the systems of opioid nociceptive regulation function similarly in fish and land vertebrates. This regulation can play an important role in defense behavior and in other behaviors in fish.     

Effect of rectal or intravenous tramadol on the incidence of pain-related behaviour after disbudding calves with caustic paste

To evaluate the efficacy of tramadol (suppositories or intravenous) in alleviating pain after caustic paste disbudding, two behaviour-assessing methods were used during the first hour post-disbudding: the objective recording of four pain-related behaviours and the subjective scoring pain on a scale of 0-10 (Numerical Rating Scale, NRS). Sixty dairy calves were allocated to five groups: disbudded with no treatment (C); disbudded after rectal tramadol (TR-r); disbudded after i.v. tramadol (TR-iv); sham-disbudded after i.v. tramadol (TR-SD); sham-disbudded with no treatment (SD). All disbudded groups showed more head shakes, head rubs and transitions for the first 15 min when compared with sham-disbudded calves. Animals treated with rectal tramadol showed more head shakes, head rubs and transitions than all other groups from 15 to 30 min after disbudding. Ear flicks were more frequent in disbudded calves than in sham-disbudded ones at the end of the observation period (45-60 min). NRS showed a higher score at all moments for all disbudded groups when compared with sham-disbudded. Sham-disbudded animals with i.v. tramadol had a higher score than sham-disbudded with no treatment at the first observation period (15 min). We concluded that caustic paste disbudding causes severe pain for the first 30 min after applying the paste and that tramadol is not efficient in controlling this pain but when given i.v. it may help in reducing post-operative nociception. We also showed that tramadol can be used safely in young calves although after i.v. administration it may cause some sham-disbudded animals to shake their heads and ears during the first minutes after injection. NRS showed to be a reliable method of evaluating the acute pain in caustic paste disbudded calves.     

Miotic action of tramadol is determined by CYP2D6 genotype

Polymorphic CYP2D6 is the enzyme that activates the opioid analgesic tramadol by O-demethylation to its active metabolite O-demethyltramadol (M1). Our objective was to determine the opioid effects measured by pupillary response to tramadol of CYP2D6 genotyped volunteers in relation to the disposition of tramadol and M1 in plasma. Tramadol displayed phenotypic pharmacokinetics and it was possible to identify poor metabolizers (PM) with >99% confidence from the metabolic ratio (MR) in a single blood sample taken between 2.5 and 24 h post-dose. Homozygous extensive metabolizers (EM) differed from PM subjects by an almost threefold greater (P=0.0014) maximal pupillary constriction (Emax). Significant correlations between the AUC and Cmax values of M1 versus pupillary constriction were found. The corresponding correlations of pharmacokinetic parameters for tramadol itself were weaker and negative. The strongest correlations were for the single-point metabolic ratios at all sampling intervals versus the effects, with rs ranging from 0.85 to 0.89 (p<0.01). It is concluded that the concept of dual opioid/non-opioid action of the drug, though considerably stronger in EMs, is valid for both EM and PM subjects. This is the theoretical basis for the frequent use and satisfactory efficacy of tramadol in clinical practice when given to genetically non-selected population.