Paroxysmal dystonia induced by exercise and acetazolamide

We report a case of a 40-year-old woman with dystonic attacks precipitated by slight exercise. Episodes lasted 2-5 min and were not precipitated by sudden movements or by being startled, drinking alcohol, coffee or tea, or by stress. Secondary dystonia was ruled out and brain magnetic resonance imaging (MRI) was unremarkable. Routine and video electroencephalogram (EEG) during and between attacks were normal. Acetazolamide greatly worsened her condition, whereas gabapentin [1-(aminomethyl) cyclohexaneacetic acid] treatment markedly reduced the frequency and severity of the episodes.

Use of gabapentin in the treatment of childhood reflex sympathetic dystrophy

Reflex sympathetic dystrophy, a painful syndrome involving an extremity after trauma or injury, is increasingly reported in the pediatric population. Although no clear pathophysiologic mechanism for this disorder has been identified, the role of central serotonin activity seems important. Gabapentin, a new antiepileptic medication, has been demonstrated to be effective in adults with reflex sympathetic dystrophy. The first reported case of a child with a diagnosis of reflex sympathetic dystrophy who was treated successfully with gabapentin is presented.

Improved sexual function in three men taking lamotrigine for epilepsy

Little information exists about the effects of newer antiepileptic drugs (AEDs) on sexual function in men with epilepsy. We report a series of three male veterans whose sexual disorders improved with lamotrigine. All three had partial seizures. One patient was taking phenobarbital and gabapentin and complained of decreased potency and anorgasmia. After lamotrigine was added for better seizure control and the dosage of gabapentin was tapered, anorgasmia improved. The second patient complained of impotence after a rash while taking phenytoin and carbamazepine. Impotence persisted with phenobarbital, valproate, and gabapentin. Eight months after gabapentin was replaced with lamotrigine, impotence improved. The third patient complained of long-standing impotence. Treatment with five AEDs had no effect on the dysfunction. Lamotrigine was added to the carbamazepine regimen; impotence improved with decrease in carbamazepine and increase in lamotrigine. The favorable effect of lamotrigine on sexual disorders in these three patients suggests this drug should be considered under appropriate circumstances for men who have sexual dysfunction while taking other antiepileptic agents.

Repeated administration of systemic gabapentin alleviates allodynia-like behaviors in spinally injured rats

The effect of systemic gabapentin, a novel antiepileptic and analgesic, was tested on allodynia-like behaviors in spinal cord injured rats. On the first day of treatment 30 mg/kg intraperitoneal gabapentin did not alleviate hyper-reactivity to mechanical and cold stimulation. The allodynia was significantly reduced by 100 mg/kg gabapentin, which however, produced sedation and motor impairments. Repeated administration of 30 mg/kg gabapentin once a day produced a gradually increasing anti-allodynic effect. Total alleviation of mechanical allodynia was observed in most rats after the third administration of gabapentin. Thus, build-up of the antiallodynic effect of gabapentin may develop through a time dependent mechanism or alternatively through a gradual accumulation of the effective central nervous system concentration of the drug.

Inhibition of K(+)-evoked glutamate release from rat neocortical and hippocampal slices by gabapentin

Gabapentin (Neurontin((R))) has preclinical and clinical efficacy as an anticonvulsant, antihyperalgesic, anxiolytic, and neuroprotective drug. Since L-glutamic acid (GLU) is involved in various CNS (central nervous system) disorders, gabapentin may attenuate the release of this neurotransmitter possibly by interacting with the auxiliary alpha(2)delta subunit of voltage-sensitive calcium channels (VSCC). The effects of gabapentin, pregabalin (S-(+)-3-isobutylgaba) and its enantiomer R-(-)-3-isobutylgaba, and N- and P/Q-type VSCC-targeting peptide ligands (omega-conotoxin MVIIA, omega-conotoxin MVIIC, omega-agatoxin TK) were assessed in vitro on K(+)-evoked (endogenous) GLU release from rat neocortical and hippocampal slices. Gabapentin and pregabalin decreased GLU release by 11-26% with R-(-)-3-isobutylgaba being less effective than pregabalin. The reference N- and P/Q-type VSCC-targeting ligands reduced GLU release by 19-55% to implicate these VSCC in this Ca(2+)-dependent process. The inhibitory effect of gabapentin and related compounds on GLU release may reflect a subtle modulation of VSCC function which normalizes pathological changes in neurotransmitter release.

Gabapentin, an antiepileptic drug, improves memory storage in mice

Male CF-1 mice were tested 48 h after training in a one-trial step-through inhibitory avoidance task. Immediately post-training i.p. injections of the antiepileptic drug gabapentin (1-aminomethyl cyclohexaneacetic acid) (GBP; 5, 10, 50, and 100 mg/kg) induced a dose-dependent enhancement of retention performance. Gabapentin did not affect response latencies in mice not given the footshock on the training trial, indicating that the actions of GBP on retention were not due to non-specific proactive effects on response latencies. The effects of GBP (10 mg/kg) were time-dependent, and the administration of GBP (10 mg/kg) 30 min before training also enhanced retention performance. However, the administration of GBP (10 mg/kg) 30 min prior to the retention test did not modify retention latencies of mice that had received either saline or GBP (10 mg/kg) immediately after training. Altogether, the results suggest that GBP influences retention by modulating time-dependent processes involved in memory storage, although the mechanism(s) of this action remain to be established.

Gabapentin-lactam, a close analogue of the anticonvulsant gabapentin, exerts convulsant activity in amygdala kindled rats

The cyclic GABA analogue gabapentin (GBP), which recently has been marketed for treatment of epilepsy, is particularly effective against complex-partial seizures as occurring in temporal lobe epilepsy. In the present study, we compared the effects of GBP and its lactam analogue (GBP-L) in the amygdala kindling model of temporal lobe epilepsy. In fully kindled rats, GBP (50 mg/kg and 100 mg/kg i.p.) dose-dependently increased the threshold for focal seizures and inhibited the progression from focal to generalized seizures. This effect was not associated with any marked adverse effects. In contrast, GBP-L (10-50 mg/kg) induced myoclonic activity and generalized clonic seizures in kindled rats, demonstrating a striking qualitative difference between the two compounds. By comparison with non-kindled rats it was shown that kindling markedly enhanced the sensitivity of rats to the convulsant activity of GBP-L. The finding that the anticonvulsant efficacy of GBP is lost by lactam formation indicates that GBP and GBP-L differ in their mechanism(s) of action.

Synergistic effect between intrathecal non-NMDA antagonist and gabapentin on allodynia induced by spinal nerve ligation in rats

BACKGROUND

Glutamate and non-N-methyl-D-aspartate (NMDA) receptors have been implicated in the development of neuroplasticity in the spinal cord in neuropathic pain. The spinal cord has been identified as one of the sites of the analgesic action of gabapentin. In the current study, the authors determined the antiallodynic effect of intrathecal 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) in a rat model of neuropathic pain. Also tested was a hypothesis that intrathecal injection of CNQX and gabapentin produces a synergistic effect on allodynia in neuropathic rats.

METHODS

Allodynia was produced in rats by ligation of the left L5 and L6 spinal nerves. Allodynia was determined by application of von Frey filaments to the left hind paw. Through an implanted intrathecal catheter, 10-100 microg gabapentin or 0.5-8 microg CNQX disodium (a water-soluble formulation of CNQX) was injected in conscious rats. Isobolographic analysis was performed comparing the interaction of intrathecal gabapentin and CNQX using the ED50 dose ratio of 15:1.

RESULTS

Intrathecal treatment with gabapentin or CNQX produced a dose-dependent increase in the withdrawal threshold to mechanical stimulation. The ED50 for gabapentin and CNQX was 45.9+/-4.65 and 3.4+/-0.22 microg, respectively. Intrathecal injection of a combination of CNQX and gabapentin produced a strong synergistic antiallodynic effect in neuropathic rats.

CONCLUSIONS

This study shows that intrathecal administration of CNQX exhibits an antiallodynic effect in this rat model of neuropathic pain. Furthermore, CNQX and gabapentin, when combined intrathecally, produce a potent synergistic antiallodynic effect on neuropathic pain in spinal nerve-ligated rats.

Complex regional pain syndrome (CRPS) with resistance to local anesthetic block: a case report

We present a case of complex regional pain syndrome (CRPS) Type 1 in a 12-year-old girl. The patient did not respond to the usual therapeutic modalities used to treat CRPS, including physical therapy, lumbar sympathetic block, epidural local anesthetic block, intravenous lidocaine infusion, or other oral medications. Of note is the fact that, during epidural block, the patient demonstrated a resistance to local anesthetic neural blockade in the area of the body involved with the pain problem. The mechanism of this resistance could be related to the changes in the dorsal horn cells of the spinal cord, secondary to activation of N-methyl-D-aspartate receptors, which may play a role in the pathophysiology of this pain syndrome.

Gabapentin effect on spasticity in multiple sclerosis: a placebo-controlled, randomized trial

OBJECTIVE

To investigate the effect of gabapentin on subject self-report and physician-administered spasticity scales in individuals with multiple sclerosis.

DESIGN

Prospective, double-masked, placebo-controlled, crossover design.

SETTING

The Multiple Sclerosis Center at the Denver Veterans Affairs Medical Center.

INTERVENTION

Subjects were titrated to either 900 mg gabapentin orally three times a day or placebo over a 6-day period. Subjects underwent a 14-day washout and then were crossed over. No other changes were made to their medication regimen.

MAIN OUTCOME MEASURES

The outcome measures were divided into two categories: subject self-report scales physician-administered scales. Subject self-report scales included the spasm frequency scale, spasm severity scale, interference with function scale, painful spasm scale, and global assessment scale. Physician-administered scales included the Modified Ashworth Scale, clonus scale, deep tendon reflexes, plantar stimulation response, and the Kurtzke Expanded Disability Status (EDSS) Scale. Digit Span and Digit Symbol subtests of the WAIS-R Intelligence Scale were administered to assess for possible impaired concentration. The Fatigue Impact Scale was administered to assess for changes in fatigue. The adjective generation technique was administered to assess for alterations in mood.

RESULTS

A statistically significant reduction in the impairment of spasticity was found in the gabapentin-treated subjects compared with placebo as measured by the self-report scales of the spasm severity scale, interference with function scale, painful spasm scale, and global assessment scale and by the physician-administered scales of the Modified Ashworth and plantar stimulation response. No significant difference was noted in the Digit Span, Digit Symbol, adjective generation technique, and EDSS.

CONCLUSION

Gabapentin reduces the impairment of spasticity, compared with placebo, without the side effects of worsening concentration and fatigue.

Interstitial cystitis and the potential role of gabapentin

Gabapentin, an antiepileptic agent, is a safe and versatile medication also used in the adjunctive treatment of painful disorders. These include neuropathic pain, such as postherpetic neuralgia, diabetic neuropathy, and the pain of reflex sympathetic dystrophy. Interstitial cystitis, a painful disease entity, shares many common features of these chronic pain states, and the use of gabapentin can assist in pain control. Gabapentin, as an adjunctive agent, may reduce use of cotherapeutics such as narcotics. Two patients with interstitial cystitis improved functional capacity within their activities of daily living and received adequate pain control with the addition of gabapentin to their medication regimen.

Intrathecally administered gabapentin inhibits formalin-evoked nociception and the expression of Fos-like immunoreactivity in the spinal cord of the rat

In the present study, we investigated the effects of intrathecal gabapentin on nociceptive behaviors and the numbers of spinal Fos-like immunoreactive (Fos-LI) neurons evoked by injection of 0.25 to 2.5% formalin in the hindpaw of the rat. Pretreatment with gabapentin dose dependently decreased flinches and weighted pain scores in phase 2, but not phase 1, at each concentration of formalin. The highest dose of gabapentin (100 microgram) shifted the EC(50) values of formalin for both flinches and weighted pain scores to the right by 2.5-fold, suggesting that formalin was perceived to be significantly less noxious. Gabapentin also decreased phase 2 behaviors when administered after formalin but was only one third as potent. Unlike its inhibition of formalin-evoked nociceptive behaviors, the effect of gabapentin on the expression of Fos-like immunoreactivity in the spinal cord was highly dependent on the concentration of formalin. Intrathecal pretreatment with 100 microgram of gabapentin did not decrease the numbers of Fos-LI neurons evoked by 0.5% formalin, yet this dose decreased the numbers of Fos-LI neurons in laminae I-II and VII-X of rats that received 1.25% formalin and uniformly decreased by 50% the numbers of Fos-LI neurons in all laminae of rats that received 2.5% formalin. These latter findings suggest that gabapentin neither nonselectively decreases the excitability of spinal cord neurons nor uniformly inhibits the release of all neurotransmitters from primary afferent terminals. Rather, its effects may be preferential for those neurotransmitters released by higher, more noxious concentrations of formalin and for conditions in which there is a greater induction of central sensitization.

Effectiveness of gabapentin for the treatment of behavioral disorders in dementia

Twelve patients with moderate to severe dementia and severe behavioral disorders were treated with open-label gabapentin (200-1,200 mg/day) for 8 weeks in a prospective case-series design. Patients were nonresponders to previous trials of neuroleptics. Behaviors were measured at 2-week intervals with the Neuropsychiatric Inventory (NPI), the Cohen-Mansfield Agitation Inventory (CMAI), and the Clinical Global Impression Scale (CGI). Gabapentin was generally well tolerated in this population. Although 42% of patients experienced adverse events such as gait instability and sedation, only two patients discontinued treatment prematurely because of adverse events. Average patient scores for the CMAI and the NPI remained unchanged after gabapentin. On the CGI, two patients were much improved, three were minimally improved, six were unchanged, and one was minimally worse. Gabapentin may have a role in treating a subgroup of dementia patients with severe behavioral disorders who have not responded to neuroleptics.

Mood stabilizers during breastfeeding: a review

BACKGROUND

The postpartum period is an exceptionally high-risk time for recurrence of depression, mania, or psychosis for women with bipolar disorder. Puerperal prophylaxis with mood stabilizers decreases this risk. To allow patients and clinicians to make informed decisions about mood-stabilizer use during breastfeeding, there is a need for a critical review and analysis of the data.

DATA SOURCES

A search of MEDLINE (1966-1998) and the Lithium Database, Madison Institute of Medicine, was conducted to obtain articles about lithium, valproate, carbamazepine, gabapentin, or lamotrigine use during lactation. Search terms used were pregnancy, teratogenesis, breastfeeding, lactation, breast milk levels and lithium, anticonvulsants, mood stabilizers. No other search restrictions were used. Unpublished data on gabapentin and lamotrigine were provided by the manufacturers.

RESULTS

The search revealed 11 cases of lithium use during breastfeeding, 8 of which reported infant serum levels. Two cases reported symptoms consistent with lithium toxicity in the infants. Thirty-nine cases of valproate use during breastfeeding were found, 8 of which reported infant serum levels. There was 1 report of thrombocytopenia and anemia in an infant. Fifty cases of carbamazepine use during breastfeeding were found, 10 of which reported infant serum levels. Two infants experienced hepatic dysfunction. One unpublished study of gabapentin in breast milk was found. Three reports of lamotrigine use during breastfeeding were found.

DISCUSSION

Available information remains limited to uncontrolled studies and case reports. Carbamazepine and valproate, but not lithium, have generally been considered compatible with breastfeeding. The overall paucity of data, data confounded by polypharmacy and infant age differences, and adverse reactions reported with all established mood stabilizers dictate a reassessment of these recommendations. We propose that a woman's historical response to medication and the clinical circumstances be the primary considerations when choosing a mood stabilizer during breastfeeding, rather than strict adherence to categorical assignments.

Gabapentin as add-on therapy in focal epilepsy: a computerized EEG study

OBJECTIVES

Gabapentin (GBP) possesses a well documented clinical efficacy in those types of focal epilepsy otherwise resistant to conventional antiepileptic drugs (AEDs); on the basis of this, it appears important to investigate the drug effects on the EEG epileptiform and background activity.

METHODS

Twenty-five patients with cryptogenic or symptomatic partial epilepsy resistant to conventional AED treatment were included in the study. All patients underwent long-term video-EEG recordings before and after GBP addition (900-1200 mg/day).

RESULTS

Quantitative analysis of the interictal EEG paroxysms revealed that GBP had no effect on the rate of occurrence of interictal and ictal EEG abnormalities. GBP was active in delimiting the spatial extent of the interictal spiking activity in those patients who displayed a significant reduction (> or =50%) in seizure occurrence (32% of the patients). EEG background activity recorded under rest condition from 18 out of 25 epileptic patients, before GBP therapy, was characterised by a higher content of the slow spectral components (delta and theta) with respect to control subjects. After GBP addition, the increase of theta relative power was also evident during task performance.

CONCLUSIONS

These findings suggest that GBP does not interfere with the generation of interictal EEG spiking while it appears to reduce the susceptibility to seizures concomitantly with a limiting effect on the spiking activity spatial extent. The utilization of GBP in controlling focal seizures is reinforced by the absence of negative influence on cognitive functioning.

Pharmacologic reversal of cortical hyperexcitability in patients with ALS

OBJECTIVE

To reverse the profile of abnormal intracortical excitability in patients with ALS by administering drugs that promote GABAergic transmission.

BACKGROUND

Transcranial magnetic stimulation (TMS) has revealed abnormalities of cortical inhibition in ALS, a reduction of the silent period, and the absence of intracortical inhibition normally occurring in response to paired TMS. Impaired inhibitory transmission could play a role in the physiopathology of this illness.

METHODS

Using paired TMS with conditioning stimuli from 1-to-6-msec-interstimulus intervals, we investigated 16 patients with ALS. The protocol included: (1) the "drug-free" profile of paired TMS; (2) paired TMS 30 minutes after the intake of diazepam (3.5 mg); (3) paired TMS after 3 weeks' treatment with gabapentin (GBP) (600 mg/day) or riluzole (50 mg/twice a day).

RESULTS

Intracortical inhibition is lost in patients with ALS, and this abnormal profile is reversed by diazepam or sustained treatment with GBP. We also noted that motor-evoked potential amplitudes to single stimuli increased (p<0.01) after diazepam and GBP.

CONCLUSIONS

The demonstration of pharmacologic reversal of hyperexcitability in patients with ALS makes a potentially significant contribution toward understanding the pathophysiology of a disease that has so far eluded an effective cure.

Gabapentin treatment in a child with delayed-onset hemichorea/hemiballismus

A 13-year, 6-month-old female was evaluated for subacute onset of left-sided hemichorea/hemiballismus, with an old, right parietal, cortical, and subcortical stroke as the presumed cause. Treatment with gabapentin was initiated, with good results at 6-month follow-up. Discussion of the differential diagnosis and evaluation of delayed-onset movement disorders in children and the mechanism of action of gabapentin is included.

Gabapentin in childhood epilepsy: a prospective evaluation of efficacy and safety

PURPOSE

To evaluate the efficacy and safety of gabapentin (GBP) in partial epilepsy in children.

METHODS

We performed a prospective open label add-on study in 52 children and adolescents (age 1.8-17.5 years, mean 11.1 years) with refractory partial seizures. Gabapentin was added to one other baseline drug and the efficacy was rated according to seizure type and frequency.

RESULTS

The GBP dose ranged from 26 to 78 mg/kg per day (mean 52 mg/kg per day) and was well tolerated in most patients. The seizure frequency remained unchanged in 34 patients (65%). We saw a provocation of seizures in three children (6%). Initially 15 patients (29%) benefited from GBP: five (10%) with a seizure reduction of 50-74%, seven (13%) with a reduction of 75-99% and three (6%) became seizure free. All but three experienced a development of tolerance within the next weeks to months.

CONCLUSIONS

Although gabapentin seems also to be safe in children, the efficacy in refractory partial seizures was disappointing.

Gabapentin treatment for muscle cramps: an open-label trial

To evaluate the efficacy and safety of gabapentin in the treatment of muscle cramps, we engaged an open-label trial with a group of 30 patients with frequent (> 5 cramps/week), stable, long-lasting cramps, associated with different diseases. Gabapentin was effective in reducing the frequency and severity of muscle cramps and associated sleep disturbances (clinical outcome measures) within the first 2 weeks of medication at 600 mg/d. At the 1 month control (mean dosage, 825 +/- 35 mg), almost every patient had responded to treatment and two thirds experienced a total remission of symptoms. After 3 months of therapy (mean dosage, 892 +/- 180 mg), cramps disappeared in 100% of patients and this benefit persisted as long as 6 months. Additionally, we evaluated in 10 patients the Cramps Threshold Frequency (CTF) (neurophysiological outcome measure) before and during gabapentin treatment. Gabapentin significantly increased the CTF, returning it to normal values. With the limitation of an open-label methodology, our clinical and neurophysiologic experience suggests that a gabapentin dose of 600-1200 mg/d would be helpful in the treatment of muscular cramps.

Gabapentin for drug-resistant partial epilepsy

BACKGROUND

The majority of epileptic patients have a good prognosis and their seizures can be well controlled with the use of a single antiepileptic agent, but up to 30% develop refractory epilepsy, especially those with partial seizures. In this review we summarise the current evidence regarding a new antiepileptic drug, gabapentin, when used as an add-on treatment for drug-resistant partial epilepsy

OBJECTIVES

To evaluate the efficacy and tolerability of gabapentin when used as an add-on treatment for patients with drug-resistant partial epilepsy.

SEARCH STRATEGY

We searched the Cochrane Epilepsy Group trial register, the Cochrane Controlled Trials Register of The Cochrane Library Issue 4, 1998. In addition, we contacted Parke Davis (manufacturers of gabapentin) and experts in the field to seek any ongoing studies or unpublished studies.

SELECTION CRITERIA

Randomized placebo controlled double blind add-on trials of gabapentin in patients with drug-resistant partial epilepsy.

DATA COLLECTION AND ANALYSIS

Two reviewers independently selected trials for inclusion and extracted the relevant data. The following outcomes were assessed: (a) 50% or greater reduction in seizure frequency; (b) treatment withdrawal (any reason); (c) side effects. Primary analyses were intention to treat. Sensitivity best and worst case analyses were also undertaken. Summary odds ratios were estimated for each outcome. Dose response was evaluated in regression models, and Number Needed to Treat (NNTs) were calculated for individual doses.

MAIN RESULTS

Four trials were included representing 750 randomized patients.

EFFICACY

Overall odds ratio (OR) (95% Confidence Interval (CI)) for 50% or greater reduction in seizure frequency compared to placebo 2.22 (1.49 - 3.32). Dose regression analysis shows increasing efficacy with increasing dose, with 28.5% (21.5 - 36.7) of patients responding to 1800mg of gabapentin compared to placebo, NNT 6.7 (3.0 - 10.5). Global effectiveness: treatment withdrawal OR (95% CI) compared to placebo 1.40 (0.76 - 2.55); Side effects: OR (99% CI) compared to placebo. dizziness 2.26 (1.28 - 3.99); fatigue 2.29 (1.11 - 4.74); somnolence 2.04 (1.21 - 3.45) were significanty associated with gabapentin.

REVIEWER'S CONCLUSIONS

Gabapentin has efficacy as an add-on treatment in patients with drug-resistant partial epilepsy. However, trials reviewed were of relatively short duration, and provide no evidence for the long term efficacy of gabapentin. Results cannot be extrapolated to monotherapy or patients with other epilepsy types.