Concomitant treatment with topiramate and ketogenic diet in pediatric epilepsy

PURPOSE: Topiramate (TPM) is widely used as add-on therapy for epilepsy. TPM inhibits carbonic anhydrase, which may result in metabolic acidosis from decreased serum bicarbonate. The ketogenic diet (KGD) predisposes patients to metabolic acidosis, especially during induction. In children with refractory epilepsy, cotreatment with TPM and KGD may be considered, but special attention should be paid to the combined risks for metabolic acidosis and nephrolithiasis. We report our experience in 14 children cotreated with TPM and the KGD. METHODS: Medical records of 14 children cotreated with the KGD and TPM for medically refractory epilepsy were reviewed retrospectively. Bicarbonate levels were analyzed and correlated with clinical profiles, including duration of cotreatment, TPM dose, KGD ratio, and seizure control. RESULTS: Nine children had a <20% decrease in bicarbonate levels, from 5.3 to 12.3 mEq/L (mean, 7.6 mEq/L). Cotreatment was continued in all patients for duration of 33 to 544 days (seven had remained on cotreatment at the end of the study period), although two children required bicarbonate supplements to continue the KGD. No patient had nephrolithiasis. CONCLUSIONS: Although a large decrease in bicarbonate level occurred in the majority of children, the decrease appeared mostly at the time of KGD induction when added to prior TPM therapy. Bicarbonate levels should be monitored carefully with TPM and KGD cotreatment, and bicarbonate supplements given when symptomatic.     

Topiramate-induced metabolic acidosis: report of two cases

Two children who presented with symptomatic metabolic acidosis after being put on topiramate (TPM) are reported. The first patient was an 11-year-old male with refractory complex partial epilepsy who was put on TPM for 13 months. He developed hyperventilation 1 week after increasing the dose to 300 mg/day. Arterial blood gas revealed hyperchloraemic metabolic acidosis with partial respiratory compensation: pH 7.36, PCO2 27.2 mmHg, bicarbonate 14.9 mEq/L, base excess -8.9 mmol/L. Hyperventilation and acidosis resolved after administration of sodium bicarbonate and reduction of the dose of TPM. The second patient was a female who developed increasing irritability at age 16 months and 21 months, each time associated with introduction of TPM and resolved promptly upon withdrawal of the drug. Venous blood gas taken during the second episode revealed pH 7.34, PCO2 37.4 mmHg, bicarbonate 20.4 mEq/L, base excess -4.2 mmol/L. The predominant mechanism of TPM-induced hyperventilation involves inhibition of carbonic anhydrase at the proximal renal tubule, resulting in impaired proximal bicarbonate reabsorption. The occurrence of hyperpnoea or mental status change in any patient who is on TPM should prompt an urgent blood gas sampling, with correction of the acid-base disturbances accordingly.     

Topiramate: effect on EEG interictal abnormalities and background activity in patients affected by focal epilepsy

PURPOSE: To evaluate the effects of topiramate (TPM) on interictal epileptiform abnormalities (IEA) and background activity by means of a computerized EEG analysis, in adult patients affected by focal epilepsy, with or without secondarily generalization, treated with TPM as adjunctive therapy or monotherapy. METHODS: Twenty-four patients affected by symptomatic or cryptogenic focal epilepsy underwent long-term video-EEG recording before and after TPM addition (mean dose 175+/-25 mg per day). RESULTS: TPM addition induced a significant reduction of both partial and secondarily generalized tonic-clonic (SGTC) seizures; treatment responder patients (seizure reduction > or = 50%) were 19 out of 24 patients (79.1%), of whom 5 were seizure-free. Quantitative analysis of IEA showed a significant decrease in the mean number of spikes/10 min during TPM therapy ( 4.2+/-4.2 versus 2.2+/-4.4; P<0.003 ). The analysis of spatial distribution of interictal spikes showed that such reduction was more evident at the level of the epileptogenic area rather than on the spreading component. Statistical analysis revealed only a significant decrease of mean relative power of alpha band in the EEG spectral content, recorded at rest in a group of 18 out of 24 epileptic patients during TPM therapy. In addition, during TPM treatment we observed a significant reduction in alpha reactivity without any important changes of alpha indexes (peak frequency and median frequency). CONCLUSION: These findings suggest that TPM has a strong inhibitory effect on IEA, probably acting on the generating processes, and, if used at low dosage and gradually titrated, seems to have only mild interferences with EEG background activity.     

Topiramate in patients with learning disability and refractory epilepsy

PURPOSE: Management of seizures in learning disabled people is challenging. This prospective study explored the efficacy and tolerability of adjunctive topiramate (TPM) in patients with learning disability and refractory epilepsy attending a single centre. METHODS: Sixty-four patients (36 men, 28 women, aged 16-65 years) were begun on adjunctive TPM after a 3-month prospective baseline on unchanged medication. Efficacy end points were reached when a consistent response was achieved over a 6-month period at optimal TPM dosing. These were seizure freedom or > or =50% seizure reduction (responder). Appetite, behaviour, alertness, and sleep were assessed by caregivers throughout the study. RESULTS: Sixteen (25%) patients became seizure free with adjunctive TPM. There were 29 (45%) responders. A further 10 (16%) patients experiencing a more modest improvement in seizure control continued on treatment at the behest of their family and/or caregivers. TPM was discontinued in the remaining nine (14%) patients, mainly because of side effects. Final TPM doses and plasma concentrations varied widely among the efficacy outcome groups. Many patients responding well to adjunctive TPM did so on < or =200 mg daily. Mean carer scores did not worsen with TPM therapy. CONCLUSIONS: TPM was effective as add-on therapy in learning-disabled people with difficult-to-control epilepsy. Seizure freedom is a realistic goal in this population.     

Postmarketing experience with topiramate and cognition

Ideal antiepileptic drugs (AEDs) are designed to stop seizures with limited central nervous system (CNS) side effects. However, CNS-related treatment-emergent adverse events (TEAEs) often occur in patients receiving AEDs. Topiramate (TPM) is an AED proven to be safe and effective as adjunctive treatment for epilepsy patients with partial seizures. Double-blind, placebo-controlled, multicenter trials demonstrated potential effects on cognition. The P.A.D.S. (post-marketing antiepileptic drug survey) group, a cooperative group of 14 epilepsy centers that collaborate on obtaining data about new AEDs and devices, prospectively collected standardized data forms before and during treatment with TPM for epilepsy, and analyzed the postmarketing experience of CNS TEAEs with TPM. Our results from 701 treated patients show that cognitive complaints were the most common reason to discontinue TPM. The presence of complaints did have predictive value if the patient would discontinue TPM, although was not specific as to when discontinuation would occur. The spectrum of complaints in our open-label prospective multicenter postmarketing study was similar to those observed in controlled clinical trials. We were unable to demonstrate a specific population, dose titration, or concomitant AED that was at risk to discontinue treatment. We conclude that most patients treated with TPM will continue therapy beyond 6 months. Cognitive complaints and not efficacy reflect the primary reason for discontinuing therapy. Psychomotor slowing was the most common complaint, yet most patients elect to continue treatment, with "better" or "much better" ratings of both seizure and global improvement during treatment.     

A double-blind, placebo-controlled study of topiramate in adult patients with refractory partial epilepsy

PURPOSE: The efficacy and safety of topiramate (TPM) as adjunctive therapy in the treatment of adult Chinese patients with refractory partial epilepsy were investigated in a randomized, double-blind, placebo-controlled study. METHODS: A total of 46 patients who had four or more complex partial seizures with or without secondary generalization within an 8-week baseline phase were enrolled. Patients were assigned randomly to receive TPM (n = 23) or placebo (n = 23). TPM or placebo was titrated to target doses of 300 mg/d for 6 weeks and maintained at stabilized levels for another 8 weeks. Concomitant antiepileptic drugs remained at constant previous levels during the trial. RESULTS: In all, 41 patients completed the trial (TPM group, n = 20; placebo group, n = 21). The proportion of patients with a > or =50% reduction from baseline in complex partial seizures was 11 of 23 (47.8%) in the TPM group and 3 of 23 (13.0%) in the placebo group (p = 0.01). In addition, patients treated with TPM had significantly better investigator (p = 0.014) and patient (p = 0.0005) global assessment scores than patients in the placebo group. Adverse events were mostly mild and transient, with no significant differences between treatment groups. Two patients with TPM therapy complained of weight loss. Routine blood cell counts and other laboratory results showed no significant changes from baseline in either treatment group. CONCLUSIONS: TPM 300 mg/d is effective and well tolerated as treatment for refractory partial epilepsy in adults.     

Lack of an effect of topiramate on lamotrigine serum concentrations

PURPOSE: Pharmacokinetic interactions between the older antiepileptic drugs (AEDs) and topiramate (TPM) were assessed during the clinical development of this drug. Lamotrigine (LTG) has become established as an important new drug in treating a wide spectrum of seizure types, but there are no published data on whether LTG serum concentrations change when TPM is added to treatment. METHODS: Escalating doses of TPM were added to stable LTG treatment in 24 young patients (8-21 years) with epilepsy. Blood samples taken before the morning dose were collected for drug-concentration measurement in all patients before starting treatment with TPM and after stabilisation at each dose escalation. Several patients had been maintained on unchanged therapy with drug-concentration monitoring for many months before introducing TPM, and a sequence of baseline LTG serum concentrations were available on these patients. RESULTS: The mean of all baseline LTG concentrations for the group as a whole was 10.4 +/- 4.4 mg/L compared with 9.7 +/- 4.3 mg/L after addition of TPM. A comparison of last baseline LTG concentration with first test LTG concentration (i.e., after 2 weeks' TPM treatment) gave mean values of 10.7 +/- 4.7 and 10.8 +/- 4.6 mg/L, respectively. The mean LTG concentration for patients while taking their highest TPM dose was 9.5 +/- 4.3 mg/L. The analysis-of-variance modeling for the effect of TPM on LTG concentration yielded a mean LTG concentration ratio (with TPM vs. without TPM) of 94.2%, with a 90% confidence interval of 89.5-99.1%. CONCLUSIONS: TPM did not cause a significant change in LTG serum concentration in this group of patients.     

Topiramate and phenytoin pharmacokinetics during repetitive monotherapy and combination therapy to epileptic patients

PURPOSE: To evaluate the potential pharmacokinetic interactions between topiramate (TPM) and phenytoin (PHT) in patients with epilepsy by studying their pharmacokinetics (PK) after monotherapy and concomitant TPM/PHT treatment. METHODS: Twelve patients with epilepsy stabilized on PHT monotherapy were enrolled in this study, with 10 and seven patients completing the phases with 400 and 800 mg TPM daily doses, respectively. TPM was added at escalating doses, and after stabilization at the highest tolerated TPM dose, PHT doses were tapered. Serial blood and urine samples were collected for PK analysis during the monotherapy phase or the lowest PHT dose after taper and the concomitant TPM/PHT phase. Potential metabolic interaction between PHT and TPM also was studied in vitro in human liver microsomal preparations. RESULTS: In nine of the 12 patients, PHT plasma concentrations remained stable, with a mean (+/-SD) area under the curve (AUC) ratio (combination therapy/monotherapy) of 1.13 +/- 0.17 (range, 0.89-1.23). Three patients had AUC ratios of 1.25, 1.39, and 1.55, respectively, and with the addition of TPM (800, 400, and 400 mg daily, respectively), their peak PHT plasma concentrations increased from 15 to 21 mg/L, 28 to 36 mg/L, and 27 to 41 mg/L, respectively. Human liver microsomal studies with S-mephenytoin showed that TPM partially inhibited CYP2C19 at very high concentrations of 300 microM (11% inhibition) and 900 microM (29% inhibition). Such high plasma concentrations would correspond to doses in humans that are 5 to 15 times higher than the recommended dose (200-400 mg). TPM clearance was approximately twofold higher during concomitant TPM/PHT therapy CONCLUSIONS: This study provides evidence that the addition of TPM to PHT generally does not cause clinically significant PK interaction. PHT induces the metabolism of TPM, causing increased TPM clearance, which may require TPM dose adjustments when PHT therapy is added or is discontinued. TPM may affect PHT concentrations in a few patients because of inhibition by TPM of the CYP2C19-mediated minor metabolic pathway of PHT.     

妥泰加用治疗成人难治性部分性癫痫的疗效观察

目的：观察妥泰（TPM）加用治疗成人难治性部分性伴或不伴随继发身性发作（GTCS）的疗效,安全性及耐受性。方法：56例在不动原用抗癫痫药（AEDs)的基础上加用TPM治疗20周、前8周为加量期,后12周为维持治疗的稳定期,治疗前（基础期）记录好作频率,用药情况。体重等作为自身对照。TPM自25mg/d开始,逐渐加量,目标剂量为200mg/d,治疗及治疗结束各查基础AEDs血药浓度进行比较,治疗结束行全面疗效分析。结果：TPM加用治疗20周后,与基础期发作频率比较,64．29％患者发作频率降低≥50％;25．00％,患者发生频率降低≥75％＜100％;16．07％完全不发。不良反应轻至中度,但与合AEDs的多少有关。50％患者体重可有不同程度的下降。TPM对止痛民西平及丙戊酸钠血药浓度影响不大。结论：TMP是治疗难治性部分性伴或不伴继发GTCS的表效的药物。     

妥泰与癫痫儿童轻度代谢性酸中毒

目的:观察妥泰治疗儿童癫痫时其体内酸碱平衡的变化。方法:56例分成三组:(1)A组10例(未服药);(2)B组32例(单独服用妥泰);(3)C组14例(妥泰与其他抗癫痫药CBZ、VPA、NZP等联合应用)。观察指标:血气电解质分析(pH,Pco2HCO3-,BE,K+,Ca2+,Cl-,AG)。结果:与A组比较,B组和C组的癫痫患儿血浆HCO3-(mmol/L)分别降低22%(P<0.01)和16%(P<0.01)。BE值(mmol/L)分别降低225%(P<0.01)和154%(P<0.01)。但B组和C组之间上述指标比较,无显著性差异。各组的pH、Pco2和AG相比较,均无显著性差异。B、C两组血CI(mmol/L)均高于A组,差异有显著意义(P<0.01)。结论:妥泰可导致癫痫患儿代偿性AG正常型高氯性代谢性酸中毒(98%为轻度酸中毒)。