[Neuropathic pain in oncology: mechanisms of its occurrence and current approaches to its treatment]

The paper provides evidence for the topicality of therapy for neuropathic pain syndrome (NPS) in cancer patients, describes the mechanisms of its occurrence, the specific features of its clinical manifestations, and presents a complex of currently available etiopathogenetic agents for the therapy of NPS. It also gives the authors' own data on the clinical application of the new anticonvulsant gabapentin (neurontin) in 34 patients with chronic NPS. The findings show the pronounced antineuropathic and analgesic effects of gabapentin in NPS. The side effects of the drug are not hazardous and they are moderately pronounced. These results are in agreement with the presented data of multicenter randomized placebo-controlled studies of the efficacy and tolerance of gabapentin in the treatment of cancer-induced NPS of various genesis.

Profilometric and Microradiographic Studies on the Effects of Toothpaste and Acidic Gel Abrasivity on Sound and Demineralized Bovine Dental Enamel

The objective of this study was to assess the abrasive effects of toothpastes and acidic F gels on sound and demineralized enamel. Pairs of enamel specimens were cut from bovine incisors, embedded in epoxy resin and polished. An artificial subsurface lesion of 80-90 microm depth was created in one specimen from each pair. The samples were covered with adhesive tape, thereby exposing the enamel for abrasivity testing. All samples were divided into six groups of 15 and brushed with a slurry (1:3) of F gel or toothpaste and human saliva. Brushing with water (control) or with slurry was carried out (16,000 strokes) using a medium toothbrush (load 275 g) mounted in a brushing machine. Abrasion was evaluated using laser profilometry, and was about 50% less on sound than on demineralized enamel (p < 0.001). In the latter, brushing with water (0.09 +/- 0.03 microm) or with fluoride-free gel (0.08 +/- 0.03 microm) resulted in negligible wear. With a medium-abrasive paste (1.76 +/- 0.85 microm) and an acidic F gel (2.48 +/- 0.72 microm), brushing abrasion was significantly greater (p < 0.001) than with a low-abrasive paste (0.84 +/- 0.38 microm). The greatest wear (16.6 +/- 10.8 microm) was observed with high-abrasive paste (p < 0.001), and here transversal microradiography revealed a complete loss of the pseudointact surface after brushing. In vitro formed caries-like lesions can be abraded (by toothbrushing) more easily than sound enamel; hence, initial white spot lesions should preferably be brushed with oral hygiene products of low abrasivity.

Meat and meat-mutagen intake and risk of non-Hodgkin lymphoma: results from a NCI-SEER case-control study

Non-Hodgkin Lymphoma (NHL) incidence has risen dramatically over past decades, but the reasons for most of this increase are not known. Meat cooked well-done using high-temperature cooking techniques produces heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs) such as benzo[a]pyrene (B[a]P). This study was conducted as a population-based case-control study in Iowa, Detroit, Seattle and Los Angeles and was designed to determine whether meat, meat-cooking methods, HCAs or PAHs from meat were associated with NHL risk. This study consisted of 458 NHL cases, diagnosed between 1998 and 2000, and 383 controls. Participants completed a 117-item food frequency questionnaire (FFQ), with graphical aids to assess the meat-cooking method and doneness level, which was linked to a HCA and B[a]P database. Logistic regression, comparing the fourth to the first quartile, found no association between red meat or processed meat intake and risk for NHL [odds ratio (OR) and 95% confidence interval (CI): 1.10 (0.67-1.81) and 1.18 (0.74-1.89), respectively]. A marginally significant elevated risk for NHL was associated with broiled meat [OR and 95% CI: 1.32 (0.99-1.77); P trend = 0.09], comparing those who consumed broiled meat with those who did not. The degree to which meat was cooked was not associated with the risk for NHL, although one of the HCAs, DiMeIQx (2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline), was associated with an inverse risk. Fat intake was associated with a significantly elevated risk for NHL [OR and 95% CI: 1.60 (1.05-2.45); P trend = 0.12]; in contrast, animal protein was inversely associated with risk for NHL [OR and 95% CI: 0.39 (0.22-0.70); P trend = 0.004]. Overall, our study suggests that consumption of meat, whether or not it is well-done, does not increase the risk of NHL. Furthermore, neither HCAs nor B[a]P from meat increase the risk of NHL.

The effect of a dentifrice and mouth rinse combination containing amine fluoride/stannous fluoride on plaque and gingivitis: a 6-month field study

AIM

To examine the effect of amine fluoride/stannous fluoride (AmF/SnF(2))-containing dentifrice and mouth rinse on plaque formation and gingivitis as compared with habitual oral hygiene procedures with a regular sodium fluoride (NaF) dentifrice.

MATERIAL AND METHODS

In total, 22 general practices participated in this research project. The participants (N=281) were randomly assigned into two groups: the test group received an AmF/SnF(2) dentifrice-mouth rinse combination and the control group received a NaF-containing dentifrice. The patients were requested to brush twice daily for approximately 2 min. The subjects of the test group had to rinse additionally in the evening for 30 s with 10 ml of the mouth rinse.

RESULTS

Both groups started with comparable scores of plaque, bleeding and staining. At 6 months, the plaque scores were 0.95 for the AmF/SnF(2) group and 0.99 for the NaF group (decrease of 16% and 10%, respectively). Bleeding scores, although significantly different from baseline, did not show differences between the two regimes. At the end of the experimental period, the overall staining was more pronounced in the AmF/SnF(2) group (41%) than the NaF group (26%). Both plaque reduction and increase in staining seemed to be correlated to the amount of mouth rinse used in the test group.

CONCLUSION

In instruction-resistant patients recruited from dental practices, the combined use of AmF/SnF(2) did not decrease gingivitis at a significant level in comparison with the regular regime of two times daily brushing with an NaF-containing dentifrice. However, the above-mentioned combination resulted in greater plaque reduction than that observed with the use of the conventional dentifrice. When used according to the manufacturer's instructions, this effect on plaque scores was more pronounced.

Gabapentin-Induced Myopathy in 2 Patients on Short Daily Hemodialysis

Gabapentin is an antiepileptic medication that also has been used for restless legs syndrome. The mechanism of action is unknown. The most commonly reported adverse effects of this medication include somnolence, dizziness, ataxia, fatigue, nystagmus, and tremor. Myalgia has been reported in 2% of gabapentin users compared with 1.9% of patients in placebo-controlled add-on trials. Two patients on short daily hemodialysis therapy developed neuromuscular symptoms and an elevation in creatine kinase levels after starting gabapentin therapy. To our knowledge, this is the first case report of an increase in creatine kinase level after the administration of gabapentin.

Gabapentin withdrawal syndrome in the presence of a taper

OBJECTIVE

To report a case report of a geriatric patient with a 5-year history of gabapentin use for enhanced bipolar control, who was tapered off of gabapentin over 1 week. The patient displayed unique withdrawal symptoms after the taper of gabapentin.

METHODS

The patient is an 81-year-old white female with a life-long history of schizoaffective disorder with bipolar type I tendencies who had been prescribed gabapentin for 5 years.

RESULTS

The patient displayed moderate upper respiratory tract infection symptoms and somatic complaints 1 day after termination of gabapentin. These symptoms gradually worsened until 10 days after, at which time she acutely developed severe mental status changes, severe somatic chest pain, and hypertension. Physical examination, electrolytes, electrocardiogram, computerized tomography, magnetic resonance imaging, and magnetic resonance angiography were all normal. Upon reintroduction of gabapentin, the patient returned to baseline within 1-2 days.

CONCLUSIONS

Gabapentin is widely utilized currently for the chronic treatment of recalcitrant migraines, bipolar illness, pain, and epilepsy. It has a wide therapeutic index with few side effects and drug interactions, is not hepatically metabolized, and is excreted by the kidneys. Past reports have suggested that some withdrawal symptoms can present after 1-2 days upon abrupt discontinuation of gabapentin after chronic use within young to middle-aged patients. These symptoms mimic that of alcohol and benzodiazepine withdrawal purportedly due to a similar mechanism of action. Unique to this case is that this geriatric patient developed debilitating withdrawal symptoms after a gradual, week-long taper of gabapentin along with flu-like symptoms. It is proposed herein that a gabapentin taper should follow a course similar to that of a benzodiazepine taper -- slowly and over a period of weeks to months.

Starting dose of gabapentin for patients with post-herpetic neuralgia--a dose-response study

BACKGROUND

Gabapentin has been shown to provide pain relief for post-herpetic neuralgia at dosage of 1200 to 2400 mg/day. However, the initial dosing strategy has not been thoroughly investigated. The purpose of this study was to establish the initial dosing strategy in the treatment of the gabapentin-naive patients with post-herpetic neuralgia.

METHODS

This clinical study was an open-label, randomized, time-sequence and controlled trial. Each gabapentin-naive subject was allocated to receive either 200 mg (100 mg, twice daily), 400 mg (100 mg, four times daily), or 600 mg (200 mg, three times daily) of gabapentin for three days. The analgesic effect and occurrence of dizziness, drowsiness, and fatigue were assessed at day 0 and day 3.

RESULTS

A total of 61 subjects (32 male/29 female) were enrolled in this study. The intensity of pain was greatly improved in all three groups after three days of treatment (visual analog scale decreased from 6.5 +/- 1.6 to 4.5 +/- 2.1, P < 0.05). There was no statistically significant difference among subjects taking 200 mg, 400 mg, or 600 mg with respect to dizziness, drowsiness or fatigue.

CONCLUSIONS

This study shows that elderly gabapentin-naive subjects no matter whether receiving 200, 400 or 600 mg/day of gabapentin benefited a moderate pain relief with minimal side effects at the first three days of treatment. Since starting with a minimal dose of 200 mg/day did not offer a better reduction of side effects, we suggest that 600 mg/day gabapentin could be a safe and effective starting dose for patients with post-herpetic neuralgia.

Preoperative gabapentin decreases anxiety and improves early functional recovery from knee surgery

Gabapentin has antihyperalgesic and anxiolytic properties. We thus tested the hypothesis that premedication with gabapentin would decrease preoperative anxiety and improve postoperative analgesia and early postoperative knee mobilization in patients undergoing arthroscopic anterior cruciate ligament repair under general anesthesia. Forty patients were randomly assigned to receive 1200 mg oral gabapentin or placebo 1-2 h before surgery; anesthesia was standardized. Patients received morphine, 0.1 mg/kg, 30 min before the end of surgery and postoperatively via a patient-controlled pump. Pain scores and morphine consumption were recorded over 48 h. Degrees of active and passive knee flexion and extension were recorded during physiotherapy on days 1 and 2. Preoperative anxiety scores were less in the gabapentin than control group (visual analog scale scores of 28 +/- 16 mm versus 66 +/- 15 mm, respectively; P < 0.001). The gabapentin group required less morphine than the control group (29 +/- 22 mg versus 69 +/- 40 mg, respectively; P < 0.001). Visual analog scale pain scores at rest and after mobilization were significantly reduced in the gabapentin group. First and maximal passive and active knee flexions at 24 and 48 h were significantly more extensive in the gabapentin than in the control group. In conclusion, premedication with 1200 mg gabapentin improved preoperative anxiolysis, postoperative analgesia, and early knee mobilization after arthroscopic anterior cruciate ligament repair.

Practice parameter: treatment of postherpetic neuralgia: an evidence-based report of the Quality Standards Subcommittee of the American Academy of Neurology

A systematic review of the literature on postherpetic neuralgia was performed. The authors identified studies using the National Library of Medicine's Medline database and Cochrane Library database. The authors determined absolute reduction rate, number needed to treat (NNT), 95% CI for NNT, and number needed to harm (NNH) for successful therapies of postherpetic neuralgia. Tricyclic antidepressants, gabapentin, pregabalin, opioids, and lidocaine patch were found to be effective in reducing the pain of postherpetic neuralgia.

Formation and Human Risk of Carcinogenic Heterocyclic Amines Formed from Natural Precursors in Meat

A group of heterocyclic amines that are mutagens and rodent carcinogens form when meat is cooked to medium and well-done states. The precursors of these compounds are natural meat components: creatinine, amino acids, and sugars. Defined model systems of dry-heated precursors mimic the amounts and proportions of heterocyclic amines found in meat. Results from model systems and cooking experiments suggest ways to reduce their formation and, thus, reduce human intake. Human cancer epidemiology studies related to the consumption of well-done meat products are listed and compared in this review.

A placebo-controlled randomized clinical trial of perioperative administration of gabapentin, rofecoxib and their combination for spontaneous and movement-evoked pain after abdominal hysterectomy

Current treatments for post-injury movement-evoked pain are inadequate. Non-opioids may complement opioids, which preferentially reduce spontaneous pain, but most have incomplete efficacy as single agents. This trial evaluates efficacy of a gabapentin-rofecoxib combination following hysterectomy. In addition to IV-PCA morphine, 110 patients received either placebo, gabapentin (1800 mg/day), rofecoxib (50 mg/day) or a gabapentin-rofecoxib combination (1800/50 mg/day) starting 1 h pre-operatively for 72 h. Outcomes included pain at rest, evoked by sitting, peak expiration and cough, morphine consumption and peak expiratory flow (PEF). For placebo, gabapentin, rofecoxib and combination, 24 h pain (100 mm VAS) was: at rest-23.6 (P<0.05 vs. all treatments), 13.8, 14.4 and 12.1; during cough-50.7 (P<0.05 vs. all treatments), 41.5, 44.8 and 30.8; 48 h morphine consumption (mg) was: 130.4 (P<0.05 vs. all treatments), 81.7, 75.6 and 57.2 (P<0.05 vs. gabapentin and rofecoxib) and 48 h PEF (% baseline) was: 63.9 (P<0.05 vs. all treatments), 77.2, 76.7 and 87.5 (P<0.05 vs. gabapentin and rofecoxib). Adverse effects were similar in all groups except sedation which was more frequent with gabapentin. Combination and rofecoxib reduced pain interference with movement, mood and sleep (P<0.05) and combination was superior to gabapentin for all these three (P<0.05). These data suggest that a gabapentin-rofecoxib combination is superior to either single agent for postoperative pain. Other benefits include opioid sparing, reduced interference with movement, mood and sleep and increased PEF suggesting accelerated pulmonary recovery. Future research should identify optimal dose-ratios for this and other analgesic combinations.

Potential sources of carcinogenic heterocyclic amines in the Chinese diet: results from a 24-h dietary recall study in Singapore

OBJECTIVE

Heterocyclic amines (HCAs) from high-temperature cooking of meat have been linked to increased cancer incidence in Western populations, but data on the sources of HCAs in Asian diets are scarce. Our aim was to identify potential sources of HCAs in the Chinese diet, and to provide the basis for efforts to quantify dietary exposure to these compounds.

DESIGN AND SETTING

We conducted 24-h dietary recall interviews among 986 Chinese men and women in Singapore, who were a randomly selected subpopulation of participants from the Singapore Chinese Health Study, a population-based cohort. Details of all foods and beverages consumed by each subject in the past 24 h were recorded, and information on meat type, cooking method and portion size were abstracted from all meat-containing dishes, and gram weight equivalents computed.

RESULTS

The mean meat intake per person was 103.0 g/day (standard deviation 74.2), of which 97.2% was fresh meat. Fish (38.0%), pork (30.6%), and poultry (21.0%) accounted for 89.6% of meat consumed. Patterns of meat consumption and cooking methods differed markedly from Western populations. Documented high-temperature cooking methods, combined with stir-frying, accounted for 44.3% of fish, 35.1% of pork and 25.6% of poultry consumed. Specifically, potentially significant sources of HCAs were pan-fried fish and barbecued pork.

CONCLUSIONS

Our results identify the potential sources of HCA in the Chinese diet, highlight aspects which are relevant to HCA formation and intake, and call for novel approaches to estimating individual exposure to dietary HCAs in this and similar populations.

Evaluation of the Optimal Preemptive Dose of Gabapentin for Postoperative Pain Relief After Lumbar Diskectomy

We evaluated the optimal preemptive dose of gabapentin for postoperative pain relief after single-level lumbar diskectomy and its effect on fentanyl consumption during the initial 24 hours in a randomized, double-blinded, placebo-controlled study in 100 patients with American Society of Anesthesiologists physical status I and II. Patients were divided into five groups to receive placebo or gabapentin 300, 600, 900, or 1200 mg 2 hours before surgery. After surgery, patients were transferred to the postanesthesia care unit (PACU). A blinded anesthesiologist recorded the pain scores at time points of 6, 12, 18, and 24 hours in the PACU on a Visual Analog Scale (VAS; 0-10 cm) at rest. Patients received patient-controlled analgesia (fentanyl 1.0 mug/kg on each demand with lockout interval of 10 minutes); total fentanyl consumption during initial 24 hours was recorded. Data were entered into the statistical software package SPSS 9.0 for analysis (one-way analysis of variance and Student-Newman-Keuls test). Patients who received gabapentin 300 mg had significantly lower VAS score at all time points. They consumed less fentanyl (patients who received placebo processed 1217.5 +/- 182.0 versus 987.5 +/- 129.6 mug; P < 0.05). Patients who received gabapentin 600, 900, and 1200 mg had lower VAS scores at all time points than patients who received gabapentin 300 mg (P < 0.05). Increasing the dose of gabapentin from 600 to 1200 mg did not decrease the VAS score, nor did the increasing dose of gabapentin significantly decrease fentanyl consumption (702.5, 635, and 626.5 microg). Thus, gabapentin 600 mg is the optimal dose for postoperative pain relief following lumbar diskectomy.

Morphine, gabapentin, or their combination for neuropathic pain

BACKGROUND

The available drugs to treat neuropathic pain have incomplete efficacy and dose-limiting adverse effects. We compared the efficacy of a combination of gabapentin and morphine with that of each as a single agent in patients with painful diabetic neuropathy or postherpetic neuralgia.

METHODS

In this randomized, double-blind, active placebo-controlled, four-period crossover trial, patients received daily active placebo (lorazepam), sustained-release morphine, gabapentin, and a combination of gabapentin and morphine--each given orally for five weeks. The primary outcome measure was mean daily pain intensity in patients receiving a maximal tolerated dose; secondary outcomes included pain (rated according to the Short-Form McGill Pain Questionnaire), adverse effects, maximal tolerated doses, mood, and quality of life.

RESULTS

Of 57 patients who underwent randomization (35 with diabetic neuropathy and 22 with postherpetic neuralgia), 41 completed the trial. Mean daily pain (on a scale from 0 to 10, with higher numbers indicating more severe pain) at a maximal tolerated dose of the study drug was as follows: 5.72 at baseline, 4.49 with placebo, 4.15 with gabapentin, 3.70 with morphine, and 3.06 with the gabapentin-morphine combination (P<0.05 for the combination vs. placebo, gabapentin, and morphine). Total scores on the Short-Form McGill Pain Questionnaire (on a scale from 0 to 45, with higher numbers indicating more severe pain) at a maximal tolerated dose were 14.4 with placebo, 10.7 with gabapentin, 10.7 with morphine, and 7.5 with the gabapentin-morphine combination (P<0.05 for the combination vs. placebo, gabapentin, and morphine). The maximal tolerated doses of morphine and gabapentin were lower (P<0.05) with the combination than for each drug as single agent. At the maximal tolerated dose, the gabapentin-morphine combination resulted in a higher frequency of constipation than gabapentin alone (P<0.05) and a higher frequency of dry mouth than morphine alone (P<0.05).

CONCLUSIONS

Gabapentin and morphine combined achieved better analgesia at lower doses of each drug than either as a single agent, with constipation, sedation, and dry mouth as the most frequent adverse effects.

Antiepileptic medications in multiple sclerosis: adverse effects in a three-year follow-up study

Neuropathic pain and paroxysmal symptoms are common in multiple sclerosis (MS) patients, although no double-blind clinical trial has been conducted to support antiepileptic medications (AED) use in MS. The aim of the study was to evaluate the frequency of AED utilisation and reported adverse events, in a cohort of MS patients. For a period of 3 years the rationale for prescribing AED, adverse effects, treatment duration and reasons for discontinuation were recorded in a database. Carbamazepine (CBZ) was prescribed in 36 patients, with adverse effects reported in 20 cases, of which 12 mimicked a relapse. Gabapentin (GBP) was prescribed in 94 patients, with adverse effects reported in 16 cases and in one case mimicked a relapse. Lamotrigine (LMT) was prescribed in 22 patients, with adverse effects reported in 4 cases, none mimicking a relapse. The present study found a significantly higher incidence of adverse effects in patients treated with CBZ, with a high rate of discontinuation at low dosages and episodes of evident worsening of neurological functioning compared to GBP or LMT.

Gabapentin for the treatment of itching produced by burns and wound healing in children: a pilot study

We describe the use of gabapentin for the treatment of itching in wound healing in 35 children. All children were already treated with chlorpheniramine and trimeprazine but they remained irritable and were constantly rubbing their wounds. Within 24h of commencing treatment itching had improved significantly in all of the children.

The use of lamotrigine, vigabatrin and gabapentin as add-on therapy in intractable epilepsy of childhood

PURPOSE

Lamotrigine (LTG), vigabatrin (VGB) and gabapentin (GBP) are three anti-epileptic drugs (AEDs) used in the treatment of children with epilepsy for which long-term retention rates are not currently well known. This study examines the efficacy, long-term survival and adverse event profile of these three agents used as add-on therapy in children with refractory epilepsy over a 10-year period.

METHODS

Three separate audits were conducted between February 1996 and September 2000. All children studied had epilepsy refractory to other AEDs. Efficacy was confirmed if a patient became seizure free or achieved >50% reduction in seizure frequency for 6 months or more after starting therapy. Adverse events and patient survival for each drug were recorded at the end of the study period.

RESULTS

Between September 1990 and February 1996, 132 children received LTG, 80 VGB and 39 GBP. At the 10-year follow-up audit, 33% of the children on LTG had a sustained beneficial effect on their seizure frequency in contrast to 19% for VGB and 15% for GBP. No significant difference in efficacy was found in children with partial seizures. Children with epileptic encephalopathy (EE) including myoclonic-astatic epilepsy and Lennox-Gastaut Syndrome (LGS) achieved a more favorable response to LTG. The main reasons for drug withdrawal were lack of efficacy for VGB, apparent worsening of seizures for GBP and the development of a rash for LTG.

CONCLUSIONS

Lamotrigine is a useful add-on therapy in treating children with epilepsy. It has a low adverse event profile and a sustained beneficial effect in children with intractable epilepsy.

Dystonia Induced by Gabapentin

OBJECTIVE:

To report a case of dystonia as an adverse effect of gabapentin.

CASE SUMMARY:

A 72-year-old woman was diagnosed with essential tremor and treated with propranolol 120 mg daily. The drug was withdrawn because of bradycardia, and gabapentin was prescribed 3 times a day at escalating doses to reach 2100 mg daily. The woman developed a dystonic reaction involving muscles of the neck and both arms that resolved rapidly after drug withdrawal. She was restarted on gabapentin with slow titration to 1800 mg daily, but the same dystonic reaction appeared, which led to definitive withdrawal of the drug. An objective causality assessment revealed that this adverse effect was highly probable.

DISCUSSION:

There have been only a few previous reports of gabapentin-induced dystonia. Other movement disorders reported with gabapentin include myoclonus, ataxia, and choreoathetosis. Gabapentin has been used to treat dystonias with variable results.

CONCLUSIONS:

Although gabapentin is widely used and well tolerated, it can cause dystonic reactions, which are reversible after drug withdrawal.

Asterixis Related to Gabapentin as a Cause of Falls

Negative myoclonus, commonly known as asterixis, is often observed in patients with toxic-metabolic encephalopathies or focal brain lesions. It is a movement disorder characterized by postural lapses resulting from brief cessation of tonic muscular contraction. Negative myoclonus has a characteristic appearance on needle electromyography. Lapses in continuous postural muscle activity can lead to falls. This increased risk of falls makes it particularly important to recognize and treat negative myoclonus, especially in patients with multiple medical problems, deconditioning, and gait disturbances. To our knowledge, there have been no published reports implicating negative myoclonus as a cause of falls in adults. We present a case of asterixis as a cause of falls and near falls in a patient with metastatic breast cancer and normal mental status who was receiving gabapentin.

Gabapentin-induced Myoclonus in End-stage Renal Disease

PURPOSE

We analyzed the occurrence and clinical features of myoclonus in patients with end-stage renal disease (ESRD) who were treated with gabapentin (GBP).

METHODS

We reviewed the medical records of patients with ESRD who were treated with GBP and hospitalized during an 18-month period and analyzed clinical details such as type of myoclonus, doses of GBP, electroencephalographic (EEG) findings, and relation of symptoms to GBP exposure and dosage.

RESULTS

Three of 71 patients had myoclonus with GBP doses ranging from 9 mg/kg to 20 mg/kg and within 4 months of treatment onset. Myoclonus was characterized as multifocal, involving all extremities in the three patients. EEG did not show epileptiform discharges with the myoclonus. Myoclonus resolved in the three individuals within 4-15 days after GBP was discontinued.

CONCLUSIONS

GBP increases the risk of myoclonus in ESRD. Myoclonus in these individuals was more disabling than that in patients with normal renal function, and discontinuation of GBP is required to restore normal function.

Occipital neuralgia secondary to respiratory tract infection

Occipital neuralgia is an extracranial pain that may be confused with other headaches. It can be attributed to multiple causes. The authors report the case of a 55-year-old woman suffering from right occipital neuralgia secondary to respiratory tract infection that began 6 days before the pain started. The patient suffered from a sharp and burning pain with paroxysms in the right occipital region and at the top of the right ear. Sensation was decreased in the affected area, and hypersensitivity to touch and cold water was also noted. Tinel's sign was present, and local anesthetic block produced pain relief. The combination of gabapentin and amitriptyline did not provide significant pain relief but led to marked adverse effects. Carbamazepine (300 mg/d) was required for pain control. A month later the patient appeared totally pain-free. The treatment was continued for 3 months, and the patient remained pain-free over a subsequent follow-up period of more than 6 months. Thus, in the case of occipital pain, a careful assessment of symptoms and a thorough history are necessary to obtain the correct diagnosis and to choose the appropriate treatment plan.

Chronic Oral Gabapentin Reduces Elements of Central Sensitization in Human Experimental Hyperalgesia

Background

In chronic pain, increased activity from intact or damaged peripheral nerve endings results in an enhanced response in central pain transmission systems, a mechanism known as central sensitization. Central sensitization can also be invoked in human experimental models. Therefore, these models may be useful to characterize novel analgesics in humans. The anticonvulsant gabapentin has demonstrated efficacy in patients with neuropathic pain, but its mode of action remains unclear. This study examined the effects of gabapentin on signs of central sensitization (brush and pinprick hyperalgesia) in a human model of capsaicin-evoked pain, using a gabapentin dosing regimen similar to that used in the clinic. The aims were to determine whether gabapentin, dosed in a manner similar to that used in the clinic, affected the various components of central sensitization and to assess the utility of this model for characterizing novel analgesics.

Methods

Intradermal capsaicin (100 microg/20 microl) was administered in the volar forearm of 41 male human volunteers to induce pain and clinical signs of central sensitization. Gabapentin (titrated to 2,400 mg daily) or placebo was given orally for 15 days in a randomized, double-blind, parallel-group design. The capsaicin test was conducted at baseline and after gabapentin or placebo. Endpoints were the size of areas of brush-evoked allodynia (with cotton gauze) and pinprick hyperalgesia (with von Frey filament), and the intensity of ongoing brush- and pinprick-evoked pain.

Results

Gabapentin significantly reduced the area of brush allodynia compared with placebo (P &lt;/= 0.05) and insignificantly attenuated the area of pinprick hyperalgesia. Gabapentin had no significant effect on spontaneous and evoked pain intensity.

Conclusion

Oral gabapentin, administered to healthy volunteers in a regimen similar to that used in treating chronic neuropathic pain, reduces measures of central sensitization evoked by intradermal capsaicin. This suggests that the pain-relieving effect in chronic neuropathic pain condition is linked to the effect of gabapentin on central sensitization. The ability of the capsaicin model to detect the efficacy of this standard treatment of neuropathic pain suggests that it may have a predictive value for detection of efficacy in human subjects.