Clinical effects of allopurinol on intractable epilepsy

The compelling role of allopurinol in hyperuricemia-induced epilepsy: Unrecognized like tears in rain

Epilepsy is a common neurological disease characterized by the recurrent, paroxysmal, and unprovoked seizures. It has been shown that hyperuricemia enhances and associated with the development and progression of epilepsy through induction of inflammation and oxidative stress. In addition, uric acid is released within the brain and contributes in the development of neuronal hyperexcitability and epileptic seizure. Brain uric acid acts as damage associated molecular pattern (DAMP) activates the immune response and induce the development of neuroinflammation. Therefore, inhibition of xanthine oxidase by allopurinol may reduce hyperuricemia-induced epileptic seizure and associated oxidative stress and inflammation. However, the underlying mechanism of allopurinol in the epilepsy was not fully elucidated. Therefore, this review aims to revise from published articles the link between hyperuricemia and epilepsy, and how allopurinol inhibits the development of epileptic seizure.

Association between pre-diagnostic serum uric acid levels in patients with newly diagnosed epilepsy and conversion rate to drug-resistant epilepsy within 5 years: A common data model analysis

PURPOSE

Drug-resistant epilepsy (DRE) poses a significant challenge in epilepsy management, and reliable biomarkers for identifying patients at risk of DRE are lacking. This study aimed to investigate the association between serum uric acid (UA) levels and the conversion rate to DRE.

METHODS

A retrospective cohort study was conducted using a common data model database. The study included patients newly diagnosed with epilepsy, with prediagnostic serum UA levels within a six-month window. Patients were categorized into hyperUA (≥7.0 mg/dL), normoUA (<7.0 and >2.0 mg/dL), and hypoUA (≤2.0 mg/dL) groups based on their prediagnostic UA levels. The outcome was the conversion rate to DRE within five years of epilepsy diagnosis.

RESULTS

The study included 5,672 patients with epilepsy and overall conversion rate to DRE was 19.4%. The hyperUA group had a lower DRE conversion rate compared to the normoUA group (HR: 0.81 [95% CI: 0.69-0.96]), while the hypoUA group had a higher conversion rate (HR: 1.88 [95% CI: 1.38-2.55]).

CONCLUSIONS

Serum UA levels have the potential to serve as a biomarker for identifying patients at risk of DRE, indicating a potential avenue for novel therapeutic strategies aimed at preventing DRE conversion.

The Possible Role of Nitric Oxide signaling and NMDA Receptors in Allopurinol effect on Maximal Electroshock- and Pentylenetetrazol-Induced Seizures in Mice

Allopurinol, a uric-acid-lowering medication, has shown its efficacy in several studies suggesting that allopurinol can be prescribed as adjunctive cure meant for intractable epilepsy. The exact mechanism of allopurinol is still unknown. This study evaluates allopurinol's effect on seizure threshold, seizure incidence, and mortality rate in mice models. Moreover, the possible involvement of nitric oxide (NO) pathway and N-methyl-D-aspartate (NMDA) receptors are investigated. To evaluate the effect of allopurinol on seizure, we used the pentylenetetrazole (PTZ)-induced seizure along with maximal electroshock (MES)-induced seizure. To assess the underlying mechanism behind the allopurinol activity, we used nitric oxide synthase (NOS) substrate (L-arginine), NOS inhibitors (L-NAME, aminoguanidine, 7-nitroindazole), and NMDA receptor antagonist (MK-801). Intraperitoneal allopurinol administration at a dose of 50 mg/kg in mice showed a significant (p<0.001) anti-convulsant activity in the PTZ-induced seizure. Even though pre-treatment with L-Arginine (60 mg/kg) potentiates allopurinol's anti-convulsant effect in the PTZ-induced seizure, pre-treatment with L-NAME (10 mg/kg), aminoguanidine (100 mg/kg), and 7-nitroindazole (30 mg/kg) reversed the anti-convulsant effect of allopurinol in the PTZ-induced seizure. In addition, pre-treatment with MK-801 also decreased the anti-convulsant effect of allopurinol in the PTZ-induced seizure. While allopurinol at a dose of 50 mg/kg and 100 mg/kg did not induce protection against seizure incidence in the MES-induced seizure, it revealed a remarkable effect in reducing the mortality rate in the MES-induced seizure. Allopurinol increases the seizure threshold in PTZ-induced seizure and enhances the survival rate in MES-induced seizure. Allopurinol exerts its anti-convulsant effect, possibly through targeting NO pathway and NMDA receptors.

Ellagic acid and allopurinol decrease H2O2 concentrations, epileptiform activity and astrogliosis after status epilepticus in the hippocampus of adult rats

Status epilepticus (SE) can result in an overproduction of hydrogen peroxide (H₂O₂), which contributes to oxidative stress and brain injury during different phases of epileptogenesis and seizures. The purpose of this study was to evaluate the effects of ellagic acid and allopurinol administered after SE on H₂O₂ concentrations, electrical activity and GFAP immunoreactivity in the hippocampus of rats evaluated on Day 18 after SE. H₂O₂ levels were measured using an online technique with high temporal resolution and simultaneous electrical activity recording. For this purpose, the lateral ventricles of male Wistar rats (200-250 g) were injected with pilocarpine (2.4 mg/2 µl) to induce SE. After SE, rats were injected with ellagic acid (50 mg/kg i.p., and two additional doses at 24 and 48 h) or allopurinol (50 mg/kg i.p., single dose). Administration of ellagic acid or allopurinol after SE significantly reduced the H₂O₂ concentrations and decreased the presence of epileptiform activity and GFAP immunoreactivity in the hippocampus 18 days after SE. In conclusion, the administration of antioxidants potentially reduces oxidative stress, which indicates the possible attenuation of the neurobiological consequences after SE.

Allopurinol attenuates postoperative pain and modulates the purinergic system in patients undergoing abdominal hysterectomy: a randomized controlled trial

PURPOSE

Allopurinol is a potent inhibitor of the enzyme xanthine oxidase used primarily in the treatment of hyperuricemia and gout. The aim of this study was to compare the analgesic efficacy of preanesthetic allopurinol versus placebo on postoperative pain and anxiety in patients undergoing abdominal hysterectomy.

METHODS

This is a prospective, double-blinded, placebo-controlled, randomized clinical trial. We investigated 54 patients scheduled to undergo elective abdominal hysterectomy. Patients were randomly assigned to receive either oral allopurinol 300 mg (n = 27) or placebo (n = 27) the night before and 1 h before surgery. Patients were submitted to evaluation of pain and anxiety before the treatment, for 24 h postoperatively, 30 and 90 days after surgery. Cerebrospinal fluid was collected at the time of the spinal anesthesia to perform the measurement of the central levels of purines.

RESULTS

Preoperative administration of allopurinol was effective in reducing postoperative pain 2 h after surgery. Allopurinol caused a reduction of approximately 40% in pain scores measured by the visual analogue pain scale after surgery (p < 0.05). No differences were found between groups in anxiety scores after surgery. There was a significant change in the cerebrospinal fluid concentrations of xanthine and uric acid before surgery (p < 0.01).

CONCLUSION

This study showed a short-term benefit of the use of allopurinol as a preanesthetic medication since it was related to a reduction on pain scores 2 h after surgery. The purinergic system is a potential target for new analgesic drugs. New studies investigating more selective purine derivatives in the management of pain should be performed.

TRIAL NUMBER REGISTRATION

Brazilian Registry of Clinical Trials-ReBEC #RBR-9pw58p.

Allopurinol for fibromyalgia pain in adults: A randomized controlled trial

BACKGROUND

Allopurinol is a potent inhibitor of the enzyme xanthine oxidase used in the treatment of hyperuricemia and gout. Because it is well known that purines exert multiple affects on pain transmission, we hypothesized that the inhibition of xanthine oxidase by allopurinol could be a valid strategy to treat pain in humans. This study aimed to compare the analgesic efficacy of oral allopurinol versus placebo as an adjuvant therapy in patients displaying fibromyalgia.

METHODS

This randomized, double-blinded, placebo-controlled study included 60 women with the diagnosis of fibromyalgia. Patients were randomly assigned to receive either oral allopurinol 300 mg (n = 31) or placebo (n = 29) twice daily during 30 days. The patients were submitted to evaluation for pain sensitivity, anxiety, depression, and functional status before treatment, and 15 and 30 days thereafter.

RESULTS

Oral administration of allopurinol 300 mg twice daily was ineffective in improving pain scores measured by several tools up to 30 days of treatment (P > 0.05). Additionally, no significant effects of allopurinol over anxiety, depressive symptoms, and functional status of fibromyalgia patients were observed in the present study.

CONCLUSIONS

Although previous findings indicated that allopurinol could present intrinsic analgesic effects in both animals and humans, this study showed no benefit of the use of oral allopurinol as an adjuvant strategy during 30 days in women displaying fibromyalgia. However, considering previous promising results, new prospective studies are still valid to further investigate allopurinol and more selective purine derivatives in the management of pain syndromes.

Serum Uric Acid Is Highly Associated with Epilepsy Secondary to Cerebral Infarction

In this study, we examined the association between serum uric acid levels and epilepsy secondary to cerebral infarction. Clinical data including age, gender, epileptic seizure type, imaging, and serum uric acid levels before and after seizures in patients with cerebral infarction that were collected and analyzed. One hundred patients with cerebral infarction but without epilepsy, 147 patients with epilepsy secondary to cerebral infarction, and 55 patients with status epilepticus secondary to cerebral infarction were recruited. Interestingly, epilepsy secondary to cerebral infarction was associated with both reduced uric acid (adjusted OR 2.09; 95% CI 1.07-4.08) and increased uric acid (adjusted OR 4.05; 95% CI 1.99-8.25); however, status epilepsy secondary to cerebral infarction was only associated with increased uric acid (adjusted OR 2.60; 95% CI 1.05-6.45). A U-shaped association between uric acid levels and seizures was observed by using a multivariable logistic regression model with restricted cubic spline. Serum uric acid levels are associated with both epilepsy secondary to cerebral infarction and status epilepticus secondary to cerebral infarction in patients with cerebral infarction. The appropriate intervention of serum uric acid level might be a therapeutic strategy to reduce epileptic seizures or inhibit the development of status epilepticus.

Uric acid and allopurinol aggravate absence epileptic activity in Wistar Albino Glaxo Rijswijk rats

Uric acid has a role in several physiological and pathophysiological processes. For example, uric acid may facilitate seizure generalization while reducing uric acid level may evoke anticonvulsant/antiepileptic effects. Allopurinol blocks the activity of xanthine oxidase, by which allopurinol inhibits catabolism of hypoxanthine to xanthine and uric acid and, as a consequence, decreases the level of uric acid. Although the modulation of serum uric acid level is a widely used strategy in the treatment of certain diseases, our knowledge regarding the effects of uric acid on epileptic activity is far from complete. Thus, the main aim of this study was the investigation of the effect of uric acid on absence epileptic seizures (spike-wave discharges: SWDs) in a model of human absence epilepsy, the Wistar Albino Glaxo/Rijswijk (WAG/Rij) rat. We investigated the influence of intraperitoneally (i.p.) injected uric acid (100 mg/kg and 200 mg/kg), allopurinol (50 mg/kg and 100 mg/kg), a cyclooxygenase 1 and 2 (COX-1 and COX-2) inhibitor indomethacin (10 mg/kg) and inosine (500 mg/kg) alone and the combined application of allopurinol (50 mg/kg) with uric acid (100 mg/kg) or inosine (500 mg/kg) as well as indomethacin (10 mg/kg) with uric acid (100 mg/kg) and inosine (500 mg/kg) with uric acid (100 mg/kg) on absence epileptic activity. We demonstrated that both uric acid and allopurinol alone significantly increased the number of SWDs whereas indomethacin abolished the uric acid-evoked increase in SWD number. Our results suggest that uric acid and allopurinol have proepileptic effects in WAG/Rij rats.

Uric acid is released in the brain during seizure activity and increases severity of seizures in a mouse model for acute limbic seizures

Recent evidence points at an important role of endogenous cell-damage induced pro-inflammatory molecules in the generation of epileptic seizures. Uric acid, under the form of monosodium urate crystals, has shown to have pro-inflammatory properties in the body, but less is known about its role in seizure generation. This study aimed to unravel the contribution of uric acid to seizure generation in a mouse model for acute limbic seizures. We measured extracellular levels of uric acid in the brain and modulated them using complementary pharmacological and genetic tools. Local extracellular uric acid levels increased three to four times during acute limbic seizures and peaked between 50 and 100 min after kainic acid infusion. Manipulating uric acid levels through administration of allopurinol or knock-out of urate oxidase significantly altered the number of generalized seizures, decreasing and increasing them by a twofold respectively. Taken together, our results consistently show that uric acid is released during limbic seizures and suggest that uric acid facilitates seizure generalization.

Seizure activity results in calcium- and mitochondria-independent ROS production via NADPH and xanthine oxidase activation

Seizure activity has been proposed to result in the generation of reactive oxygen species (ROS), which then contribute to seizure-induced neuronal damage and eventually cell death. Although the mechanisms of seizure-induced ROS generation are unclear, mitochondria and cellular calcium overload have been proposed to have a crucial role. We aim to determine the sources of seizure-induced ROS and their contribution to seizure-induced cell death. Using live cell imaging techniques in glioneuronal cultures, we show that prolonged seizure-like activity increases ROS production in an NMDA receptor-dependent manner. Unexpectedly, however, mitochondria did not contribute to ROS production during seizure-like activity. ROS were generated primarily by NADPH oxidase and later by xanthine oxidase (XO) activity in a calcium-independent manner. This calcium-independent neuronal ROS production was accompanied by an increase in intracellular [Na(+)] through NMDA receptor activation. Inhibition of NADPH or XO markedly reduced seizure-like activity-induced neuronal apoptosis. These findings demonstrate a critical role for ROS in seizure-induced neuronal cell death and identify novel therapeutic targets.

Treatment of infantile spasms

BACKGROUND

Infantile spasms (West's Syndrome) is a syndrome that includes a peculiar type of epileptic seizure-the spasms-and an electroencephalographic (EEG) abnormality often called hypsarrhythmia. Psychomotor retardation is frequently found at follow-up. Approximately two-thirds of affected infants will have a detectable underlying neurological abnormality, but still little is known about the pathophysiological basis for infantile spasms, and treatment remains problematic.

OBJECTIVES

To compare the effects of single pharmaceutical therapies used to treat infantile spasms in terms of control of the spasms, resolution of the EEG, relapse rates, psychomotor development, subsequent epilepsy, side effects, and mortality.

SEARCH METHODS

To identify published data, we searched the Cochrane Epilepsy Group Specialised Register (October 2012), CENTRAL (The Cochrane Library 2012, Issue 9), MEDLINE (1946 to September Week 4, 2012), EMBASE (1980 to March 2003), and the reference lists of all retrieved articles.To identify unpublished data, we searched the ISRCTN Register (www.controlled-trials.com), corresponded with colleagues and drug companies, and made requests at international conferences.

SELECTION CRITERIA

All randomised controlled trials (RCTs) of the administration of drug therapy to patients with infantile spasms.

DATA COLLECTION AND ANALYSIS

Data collection from all relevant publications was independently undertaken by three review authors (before 2010) or by two review authors using a standard proforma. Analysis included assessment of study quality and a search for sources of heterogeneity.

MAIN RESULTS

We found 16 small RCTs (fewer than 100 patients enrolled) and 2 larger RCTs (more than 100 patients enrolled). These 18 studies looked at a total of 916 patients treated with a total of 12 different pharmaceutical agents. Overall methodology of the studies was poor, in part because of ethical dilemmas such as giving placebo injections to children. Two studies showed that placebo was not as good as active treatment in resolving the spasms. The strongest evidence suggested that hormonal treatment (prednisolone or tetracosactide depot) leads to resolution of spasms faster and in more infants than does vigabatrin. Responses without subsequent relapse may be no different. The same study suggests that hormonal treatments might improve the long-term developmental outcome compared with vigabatrin in infants not found to have an underlying cause for their infantile spasms.

AUTHORS' CONCLUSIONS

To date, few well-designed RCTs have considered the treatment of infantile spasms, and the numbers of patients enrolled have been small. In the majority, methodology has been poor, hence it is not clear which treatment is optimal in the treatment of this epilepsy syndrome. Hormonal treatment resolves spasms in more infants than vigabatrin, but this may or may not translate into better long-term outcomes. If prednisolone or vigabatrin is used, high dosage is recommended. Vigabatrin may be the treatment of choice in tuberous sclerosis. Resolution of the EEG features may be important, but this has not been proven. Further research using large studies with robust methodology is required.

Role of oxidative stress in refractory epilepsy: evidence in patients and experimental models

Oxidative stress, a state of imbalance in the production of reactive oxygen species and nitrogen, is induced by a wide variety of factors. This biochemical state is associated with systemic diseases, and diseases affecting the central nervous system. Epilepsy is a chronic neurological disorder with refractoriness to drug therapy at about 30%. Currently, experimental evidence supports the involvement of oxidative stress in seizures, in the process of their generation, and in the mechanisms associated with refractoriness to drug therapy. Hence, the aim of this review is to present information in order to facilitate the handling of this evidence and determine the therapeutic impact of the biochemical status for this pathology.

Influence of allopurinol on evoked cortical afterdischarges during early ontogenesis

The aim of our study was to test the hypothesis, whether repeated allopurinol pre-treatment (in dose of 135 mg/kg s.c.) can influence changes of brain excitability caused by long-term hypoxia exposition in young immature rats. Rat pups were exposed together with their mother in to an intermittent hypobaric hypoxia (simulated altitude of 7 000 m) since the day of birth till the 11th day (youngest experimental group) or 17th day for 8 hours a day. Allopurinol was administered daily immediately before each hypoxia exposition. The duration of evoked afterdischarges (ADs) and the shape of evoked graphoelements were evaluated in 12, 18, 25 and 35-day-old freely moving male pups. Hypobaric hypoxia prolonged the duration of ADs in 12, 18 and 25-day-old rats. The ADs were prolonged in 35-day-old rats only after the first stimulation. Allopurinol shorted the duration of ADs only in 12-day-old pups. In older experimental group the effect of allopurinol treatment was less pronounced.

Anti-nociceptive properties of the xanthine oxidase inhibitor allopurinol in mice: role of A1 adenosine receptors

BACKGROUND AND PURPOSE

Allopurinol is a potent inhibitor of the enzyme xanthine oxidase, used primarily in the treatment of hyperuricemia and gout. It is well known that purines exert multiple effects on pain transmission. We hypothesized that the inhibition of xanthine oxidase by allopurinol, thereby reducing purine degradation, could be a valid strategy to enhance purinergic activity. The aim of this study was to investigate the anti-nociceptive profile of allopurinol on chemical and thermal pain models in mice.

EXPERIMENTAL APPROACH

Mice received an intraperitoneal (i.p.) injection of vehicle (Tween 10%) or allopurinol (10-400 mg kg(-1)). Anti-nociceptive effects were measured with intraplantar capsaicin, intraplantar glutamate, tail-flick or hot-plate tests.

KEY RESULTS

Allopurinol presented dose-dependent anti-nociceptive effects in all models. The opioid antagonist naloxone did not affect these anti-nociceptive effects. The non-selective adenosine-receptor antagonist caffeine and the selective A(1) adenosine-receptor antagonist, DPCPX, but not the selective A(2A) adenosine-receptor antagonist, SCH58261, completely prevented allopurinol-induced anti-nociception. No obvious motor deficits were produced by allopurinol, at doses up to 200 mg kg(-1). Allopurinol also caused an increase in cerebrospinal fluid levels of purines, including the nucleosides adenosine and guanosine, and decreased cerebrospinal fluid concentration of uric acid.

CONCLUSIONS AND IMPLICATIONS

Allopurinol-induced anti-nociception may be related to adenosine accumulation. Allopurinol is an old and extensively used compound and seems to be well tolerated with no obvious central nervous system toxic effects at high doses. This drug may be useful to treat pain syndromes in humans.

Treatment of infantile spasms

BACKGROUND

Infantile spasms (West's Syndrome) is a syndrome which includes a peculiar type of epileptic seizure, the spasms, and an electroencephalogram (EEG) abnormality often called hypsarrhythmia. Psychomotor retardation is frequently found at follow up. Approximately two thirds of affected infants will have a detectable underlying neurological abnormality, but still little is known about the pathophysiological basis for infantile spasms and treatment remains problematic.

OBJECTIVES

To compare the effects of single pharmaceutical therapies used to treat infantile spasms in terms of control of the spasms, resolution of the EEG, relapse rates, psychomotor development, subsequent epilepsy, side effects, and mortality.

SEARCH STRATEGY

Published data: Cochrane Epilepsy Group Specialised Register, CENTRAL (The Cochrane Library 2007, Issue 4), MEDLINE, EMBASE, and the reference lists of all retrieved articles.Unpublished data: ISRCTN Register (www.controlled-trials.com), correspondence with colleagues and drug companies, and requests at international conferences.

SELECTION CRITERIA

All randomised controlled trials of the administration of drug therapy to patients with infantile spasms.

DATA COLLECTION AND ANALYSIS

Data collection from all relevant publications was independently undertaken by three review authors using a standard proforma. Analysis included assessment of study quality and looking for sources of heterogeneity.

MAIN RESULTS

We found 12 small RCTs (less than 60 patients enrolled) and two larger RCT (more than 100 patients enrolled). These 14 studies looked at a total of 681 patients treated with a total of nine different pharmaceutical agents. Overall methodology of the studies was poor, partly because of ethical dilemmas such as giving placebo injections to children. Two studies showed that placebo was not as good as active treatment in resolving the spasms. The strongest evidence suggested that hormonal treatment leads to resolution of spasms faster and in more infants than does vigabatrin. Responses without subsequent relapse may be no different. The same study suggests that hormonal treatments (prednisolone or tetracosactide) might improve the long-term developmental outcome compared with vigabatrin in infants not found to have an underlying cause for their infantile spasms.

AUTHORS' CONCLUSIONS

To date, there have been few well-designed RCTs that considered the treatment of infantile spasms, and the numbers of patients enrolled have been small. Overall methodology has been poor, hence it is not clear which treatment is optimal in the treatment of this epilepsy syndrome. Hormonal treatment resolves spasms in more infants than vigabatrin but this may or may not translate into a better long-term outcome. If prednisone or vigabatrin are used then high dosage is recommended. Vigabatrin may be the treatment of choice in tuberous sclerosis. Resolution of the EEG features may be important but this has not been proven. Further research using large studies with robust methodology is still required.

Allopurinol as Adjunctive Therapy in Intractable Epilepsy: A Double-blind and Placebo-controlled Trial

BACKGROUND

Adenosine has been proposed to be an endogenous anticonvulsant agent. It inhibits glutamate release from excitatory neurons and neuronal firing. Therefore, adenosine agonists have potential clinical application as antiepileptics. In this double-blind randomized, placebo-controlled trial, we assessed the antiepileptic effect of allopurinol as an adjuvant agent in 38 patients with refractory epilepsy.

METHODS

Thirty eight patients were randomly allocated equally to allopurinol+preexisting antiepileptic (Group A) or placebo+preexisting antiepileptic (Group B) for a 6-month, double-blind, placebo-controlled study. The dose of allopurinol was titrated up to 300 mg/day (100 mg TDS). The dose of preexisting medications was maintained without change over the trial. The effect of allopurinol was evaluated by a reduction in the total number of seizures per month and duration of seizure attacks.

RESULTS

Of 38 participants, 32 patients completed the study. There were significant differences between the two groups in terms of reduction in the total number of seizure over the trial. Seizures reduction of >30% in 66%, >50% in 55%, and >60% in 44% of cases in the allopurinol group was achieved after 2 months and persisted during the study. Nevertheless, only during month 4 was there a significant difference between the two groups regarding reduction in seizure duration. In the allopurinol group, two patients had transient rashes, two patients had mild nausea, and two experienced dizziness, but only one patient discontinued the drug due to dizziness. In the placebo group, one patient had rash and one patient had nausea. In addition, no significant hematological or hepatic changes were found during the trial in both groups.

CONCLUSIONS

The results suggest allopurinol as a safe and effective adjuvant agent in refractory epilepsy. Based on this study, we suggest that purine metabolism pathways and the specific use of allopurinol should be further investigated with regards to neurobiology and treatment of refractory epilepsy.

Pharmacokinetic considerations in the treatment of childhood epilepsy

Organogenesis throughout childhood affects almost every aspect of pediatric pharmacotherapy. The antiepileptic drugs (AEDs) are particularly impacted since most elimination rates are diminished for the first 6 months of infancy, but quickly attain and supersede adult values. When children enter a hypermetabolic stage, large doses of AEDs may be necessary to maintain effective serum concentrations. Medication noncompliance is frequently confused as hypermetabolism, since both present with low serum drug concentrations. Amazingly, noncompliance among children with chronic illness approaches a similar incidence to that reported in the adult population. It is obviously important to include this in the differential diagnosis of the etiology of subtherapeutic serum AED concentrations. Maturational differences also affect gastrointestinal drug absorption. Intestinal transit time and absorptive surface area are both diminished in young children. Drug delivery systems suitable in adults may not deliver the total dosage in children. Differences in the composition of body compartments and protein binding can alter the volume of drug distribution and, consequently, serum concentrations. In addition to pathophysiologic changes, there is evidence to suggest differences between a mature and immature brain. These differences include quantitative and qualitative responses to neurotransmitters. Hence, it is understandable why seizure semiology is different in children compared with adults. This constellation of factors contributes to the challenges of caring for children with epilepsy.

Allopurinol for the treatment of aggressive behaviour in patients with dementia

Aggressive behaviour is commonly observed in patients with dementia, and current pharmacological treatments are still deficient in terms of efficacy and tolerability. Allopurinol is an inhibitor of the enzyme xanthine oxidase, with previously suggested anti-aggressive effects. After successful treatment of aggression in two patients, we performed a case-series study with allopurinol 300 mg a day orally for 6 weeks (increasing 300 mg every 2 weeks if the response was less than 50%) in six patients with dementia associated with prominent aggressive behaviour who failed to respond to two previous treatment strategies. Five patients were considerably responsive to allopurinol (four with 300 mg within 2 weeks and one with 600 mg), apparently without side-effects, which is in accordance with its well-established safety and tolerability profile. The observed therapeutic effect of allopurinol might be due to the inhibition of the enzyme xanthine oxidase, possibly decreasing production of oxygen-free radicals or promoting the accumulation of purines. Controlled studies are warranted to confirm these preliminary observations.

Treatment of infantile spasms

BACKGROUND

Infantile spasms (West's Syndrome) is a syndrome which includes a peculiar type of epileptic seizure, usually hypsarrhythmia and in the majority of people, psychomotor retardation. It remains poorly understood and despite modern imaging techniques an underlying cause is often not found. Little is known about their pathophysiological basis and treatment remains problematic.

OBJECTIVES

To compare the effects of single drugs used to treat infantile spasms in terms of long-term psychomotor development, subsequent epilepsy, control of the spasms and adverse effects.

SEARCH STRATEGY

Our search included the Cochrane Epilepsy Group trials register, MEDLINE (1966 to 2003) and EMBASE (1981 to 2003), contacting pharmaceutical companies and appeals at international conferences.

SELECTION CRITERIA

All randomised controlled trials (RCTs) of the administration of drugs to people with infantile spasms.

DATA COLLECTION AND ANALYSIS

Three reviewers independently selected trials for inclusion and extracted data. Outcomes included cessation of spasms, time to cessation of spasms, participants with cessation of spasms remaining spasm free, reduction in spasms, resolution of hypsarrhythmia, subsequent epilepsy rates and adverse effects.

MAIN RESULTS

Eleven RCTs were included, who in total recruited just 514 participants and tested eight different drugs. Overall, methodology of the studies was poor. No study assessed long-term psychomotor development or onset of other seizure types. One small study found vigabatrin to be more efficacious than hydrocortisone in stopping infantile spasms in a group of people with tuberous sclerosis. One underpowered study showed a trend for vigabatrin to be more efficacious than placebo in stopping infantile spasms. Two small studies when combined showed ACTH to be more efficacious than low-dose prednisone (2 mg/kg). One study also suggested that control of spasms occurred more frequently with high dose vigabatrin as compared to low dose vigabatrin. It was not possible to compare reduction in the number of spasms between the different treatments because of differences in methods of analysis. Overall, only 18 individuals were reported to have been withdrawn from the trial treatments due to adverse effects and 4 deaths were reported.

REVIEWER'S CONCLUSIONS

We found no single treatment to be proven to be more efficacious in treating infantile spasms than any of the others (other than vigabatrin in the treatment of infantile spasms in tuberous sclerosis in one underpowered study). Few studies considered psychomotor development or subsequent seizure rates as outcomes and none had long-term follow-up. Further trials with larger numbers of participants, and longer follow-up are required.

Purinergic dysfunction in mania: an integrative model

The purinergic system, which includes the anticonvulsant and antikindling neuromodulator adenosine and the neurotransmitter ATP, modulates second messenger systems, neurotransmitters, energy metabolism and different behaviors, such as sleep, motor activity, cognition, memory, aggressive behavior and social interaction. At the same time, mania is characterized by similar behavioral changes and a molecular basis to explain the pathological activation observed during manic episodes has been also associated with second messenger systems dysfunction and kindling. This hypothesis put forward an integrative model of neuronal communication, associating a reduced adenosinergic activity, mostly at A1 receptors, with the complex network of changes on neurotransmitters pathways related to manic behavior.

Refractory grand mal seizures with onset during infancy including severe myoclonic epilepsy in infancy

In 1978, Dravet proposed a clinical entity called severe myoclonic epilepsy in infancy (SMEI). In the same year, a patient group, which was later called high voltage slow wave-grand mal syndrome (HVSW-GM), is reported in Japan. Both syndromes are very similar, except for seizure manifestation: generalized tonic-clonic convulsions (GTC) with myoclonic and other polymorphic seizures in SMEI vs. GTC only in HVSW-GM. To study the pathophysiology of these refractory epilepsies, the author formulated new clinical diagnostic criteria common to both syndromes as follows: GTC with onset before the age of 1 year as the principal seizure type; an epilepsy entity unclassifiable either as partial or generalized by all the clinical data including EEG findings; mental and motor dysfunction absent prior to seizure onset but appearing later; absence of epileptiform activities on EEG in the initial stage; stubborn refractoriness to conventional antiepileptic medication. Twenty-two patients meeting all of five clinical criteria above mentioned were recruited in the study. Detailed analysis of clinico-electrical features and long-term follow-up of these patients led the author to the conclusion that GTC in combination with seizures of other types will contribute to an unfavorable pathophysiological or prognostic conditions, and, especially when GTC exists in combination with myoclonic seizures, the severity of epilepsy will increase. The author claimed that the three clinical entities, SMEI, HVSW-GM, and their variant form, share certain characteristics in common and may constitute a unique epilepsy syndrome for which a new name of infantile refractory grand mal syndrome (IRGMS) was offered. This is a more basic concept with broader spectrum than SMEI, encompassing not only SMEI but also related borderlands like HVSW-GM. More recently, the author observed that early zonisamide medication within 1 year after seizure onset may improve seizure prognosis in IRGMS, by preventing the development of myoclonic seizures.

The treatment of West syndrome: a Cochrane review of the literature to December 2000

BACKGROUND

West syndrome is an age dependent syndrome, which includes a peculiar type of epileptic seizure (infantile spasms), usually hypsarrhythmia and in the majority psychomotor retardation. Despite huge advances in medicine it still remains a poorly understood entity and although with newer imaging techniques we are more often able to elicit the underlying 'causes' of these spasms, still little is known about their pathophysiological basis and treatment remains problematic.

OBJECTIVES

To compare the effects of single pharmaceutical therapies used to treat infantile spasms in terms of long-term psychomotor development, subsequent epilepsy, control of the spasms and side effects.

METHODS

A search of the central trials register of the Cochrane Epilepsy Group, medline database, embase database and the reference lists of all retrieved articles was undertaken. Correspondence with colleagues and drug companies and appeals at international conferences were also undertaken to try and discover unpublished data. All randomised controlled trials (RCTs) on the medical treatment of infantile spasms were included. Data was then extracted independently by the three reviewers and analysed using the RevMan software package.

MAIN RESULTS

We found ten small RCTs on the pharmacological treatment of infantile spasms. No unpublished trials were discovered. These ten studies looked at just 335 patients treated with a total of eight different pharmaceutical agents. Overall methodology of the studies was poor, partly because of ethical dilemmas such as giving placebo injections to children. No study considered the effects of treatment on long-term psychomotor development or onset of other seizure types. One small study found vigabatrin to be more efficacious in stopping infantile spasms in a group of patients with tuberous sclerosis than hydrocortisone. One underpowered study showed a trend for vigabatrin to be more efficacious than placebo in stopping infantile spasms, another two equally underpowered studies suggested adrenocorticotrophic hormone (ACTH) to be more efficacious than low-dose prednisone. It was not possible to compare reduction in the number of spasms between the different treatments because of differences in methods of analysis. Overall, only nine patients were reported to have been withdrawn from the trial treatments due to side effects and two deaths were reported.

CONCLUSIONS

There is still little evidence available on the optimum treatment for infantile spasms. Further trials with larger number of patients, and longer follow-up are required.

Allopurinol for refractory aggression and self-inflicted behaviour

The impairment of the purinergic system, characterized by reduced adenosinergic activity, has been implicated in the neurobiology of aggressive behaviour. Since there are no direct adenosine agonists available for human use, inhibition of purine degradation by allopurinol was conceived as a possible strategy. We report two cases of adults with refractory aggressive behaviour due to a neurological condition (one mainly with self-inflicted behaviour) with dramatic response to therapy with allopurinol, 300 mg/day p.o. These preliminary results reinforce the involvement of the purinergic system in the neurobiology of aggression, warranting further testing of allopurinol as a new treatment for aggressive and self-inflicted behaviours.

Epilepsias

Este é um artigo de revisão no qual os autores fazem uma abordagem geral dos principais tratamentos alternativos atualmente utilizados para as epilepsias, dentre eles: acelazolamida, brometos, alopurinol, piracelam, leviracetam, imunoglobulina, dieta cetogénica e corticostertides.

Antiepileptic effects of allopurinol on EL mice are associated with changes in SOD isoenzyme activities

We have investigated the potential antiepileptic action of superoxide dismutase (SOD) activities in the brain of the epileptic mutant EL mouse. EL mice which experienced frequent seizures (EL[s]) had abnormally low levels of SOD isoenzyme activity in the hippocampal area. Once epileptogenicity was established in these animals, activity of cyanide-sensitive Cu,Zn-SOD was maintained at significantly lower levels than in control mice. However, cyanide-insensitive Mn-SOD activity was not different from non-epileptic controls. In EL mice which had not experienced seizure provoking stimulations and exhibited no seizures (EL[ns]) there was moderately lower levels of SOD isoenzyme activities compared to controls. In spite of the low level of Cu,Zn-SOD activity in EL[s] mice, the Cu,Zn-SOD protein content was high in the hippocampus of these animals, suggesting that inactive Cu,Zn-SOD might be induced during development. After allopurinol (ALP) was given orally to EL[s] mice, Cu,Zn-SOD activities increased dramatically in the hippocampus and seizure activity was decreased. Even after 48 h, when antiepileptic action of ALP was lost, the SOD activity was maintained at the high level associated with initial ALP administration. EL[s] mice also showed DNA fragmentation in the hippocampal CA1 region and the parietal cortex, detected with in situ terminal transferase-mediated dUTP nick labeling with the aid of alkaliphosphatase or peroxidase. The degree of DNA fragmentation was less severe in EL[ns] mice. We propose that abnormalities in region specific Cu,Zn-SOD isoenzyme activity might produce free radicals, leading to DNA fragmentations and cell loss. This might contribute to hippocampal epileptogenesis in EL mice.

Double-blind, placebo-controlled, cross-over trial of allopurinol as add-on therapy in childhood refractory epilepsy

We report the results of a double-blind, placebo-controlled cross-over trial with allopurinol as add-on therapy in childhood refractory epilepsy. Seventeen patients received allopurinol and matched placebo for 12 weeks in 2 doses (10 mg/kg/day during the first week and 15 mg/kg/day thereafter with a washout period of 2 weeks between treatment phases. The total number of seizures was reduced by 50-98% in 4 patients (23.5%) and by 25-49% in another 4 (23.5%). However, the number of seizures remained unchanged in 5 patients (29.4%) and worsened in 4 (23.5%). Adverse side effects (17.6%) were generally mild and transient, suggesting that allopurinol is well-tolerated. A mean follow-up of 10 months of the responders did not show any relevant efficacy of allopurinol as an adjuvant therapy for refractory epilepsy, even at high doses.

Allopurinol as add-on therapy in refractory epilepsy: a double-blind placebo-controlled randomized study

The antiepileptic effect of allopurinol was assessed in a double-blind, randomized, placebo-controlled, cross-over trial in 84 patients with epileptic seizures refractory to standard antiepileptic drugs (AEDs). During a retrospective baseline period, patients experienced at least four seizures of any type per month. The effects of allopurinol and matching placebo were examined for 4-month periods. Allopurinol dosage was 150 mg daily for children weighing < 20 kg and 300 mg daily for other patients. Efficacy analysis based on the Wilcoxon rank-sum test was conducted for the 80 patients who completed the study. No significant period effect or treatment-period interaction was noted. Allopurinol significantly reduced total seizures (p = 0.005), and secondarily generalized seizures (p = 0.0015). Median seizure reduction for total seizures was 10.5 and 27.9% for secondarily generalized seizures. Subjective preferences by clinicians evaluated blindly significantly favored allopurinol. No significant change occurred in the plasma concentration of concomitant AEDs between treatment periods, but serum urate decreased by 32% during allopurinol treatment. No clinically relevant side effects or changes in routine laboratory clinical chemistry or hematology were ascribed to allopurinol.

Anticonvulsant effect of allopurinol on hippocampal-kindled seizures

This study assessed the anticonvulsant effect of allopurinol (5 and 50 mg/kg, IP) on seizures kindled from the feline hippocampus. Allopurinol at a higher dose significantly reduced the behavioral seizures stage, but not afterdischarge duration, without producing any behavioral toxicity. The present results lend experimental support to the contention that allopurinol possesses anticonvulsant efficacy in the treatment of human epilepsy.

Antagonists of the NMDA receptor and allopurinol protect the olfactory cortex but not the striatum after intra-cerebral injection of kainic acid

Overstimulation of the NMDA receptor, as well as generation of excessive amounts of free radicals, has been implicated in excitotoxic brain injuries. We report here that two antagonists of the NMDA receptor and an inhibitor of the free radical-generating enzyme, xanthine oxidase, protect the olfactory cortex but not the striatum after intrastriatal injection of kainic acid. Our results suggest the existence of a precise link between excitotoxic activation of the NMDA receptor and neuropathology related to excessive amounts of free radicals. The focal point of this link may be the entry of Ca2+ through the NMDA receptor and the consequent activation of proteases and free radical-generating systems.