Retention rates of new antiepileptic drugs in localization-related epilepsy: a single-center study

OBJECTIVES

We evaluated long-term retention rates of newer antiepileptic drugs (AED) in adults with localization-related epilepsy retrospectively.

METHODS

We estimated retention rates by Kaplan-Meier method in all 222 patients (age > or = 16) with localization-related epilepsy exposed to new AED at the Tampere University Hospital.

RESULTS

There were 141 patients exposed to lamotrigine, 78 to levetiracetam, 97 to topiramate, 68 to gabapentin, and 69 to tiagabine. Three-year retention rate for lamotrigine was 73.5%, levetiracetam 65.4%, topiramate 64.2%, gabapentin 41.7%, and tiagabine 38.2%. The most common cause for withdrawal of these AED was lack of efficacy.

CONCLUSIONS

Our study suggests that there are clinically significant differences among gabapentin, lamotrigine, levetiracetam, tiagabine, and topiramate as treatment for focal epilepsy in everyday practice. Gabapentin and tiagabine seem to be less useful than the other three AED. Furthermore, our study supports the value of retention rate studies in assessing outcome of the drugs in clinical practice.

New antiepileptic drugs in pediatric epilepsy

New antiepileptic drugs (AEDs), introduced since 1993, provide more diverse options in the treatment of epilepsy. Despite the equivalent efficacy and better tolerability of these drugs, more than 25% of patients remain refractory to treatment. Moreover, the issues for pediatric patients are different from those for adults, and have not been addressed in the development and application of the new AEDs. Recently published evidence-based treatment guidelines have helped physicians to choose the most reasonable AED, although they cannot fully endorse new AEDs because of the lack of well-designed, randomized controlled trials. We review the mechanisms of action, pharmacokinetic properties, adverse reactions, efficacy, and tolerability of eight new AEDs (felbamate, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, topiramate, vigabatrin, and zonisamide), focusing on currently available treatment guidelines and expert opinions regarding pediatric epilepsy.

Molecular pharmacodynamics, clinical therapeutics, and pharmacokinetics of topiramate

Topiramate (TPM; TOPAMAX) is a broad-spectrum antiepileptic drug (AED) that is approved in many world markets for preventing or reducing the frequency of epileptic seizures (as monotherapy or adjunctive therapy), and for the prophylaxis of migraine. TPM, a sulfamate derivative of the naturally occurring sugar D-fructose, possesses several pharmacodynamic properties that may contribute to its clinically useful attributes, and to its observed adverse effects. The sulfamate moiety is essential, but not sufficient, for its pharmacodynamic properties. In this review, we discuss the known pharmacodynamic and pharmacokinetic properties of TPM, as well as its various clinically beneficial and adverse effects.

A highly conserved hydrophobic motif in the exofacial vestibule of fructose transporting SLC2A proteins acts as a critical determinant of their substrate selectivity

The substrate specificity of the facilitated hexose transporter, GLUT, family, (gene SLC2A) is highly varied. Some appear to be able to translocate both glucose and fructose, while the ability to handle 2-deoxyglucose and galactose does not necessarily correlate with the other two hexoses. It has become generally accepted that a central substrate binding/translocation site determines which hexoses can be transported. However, a recent study showed that a single point mutation of a hydrophobic residue in GLUTs 2, 5 & 7 removed their ability to transport fructose without affecting the kinetics of glucose permeation. This residue is in the 7th transmembrane helix, facing the aqueous pore and lies close to the opening of the exofacial vestibule. This study expands these observations to include the other class II GLUTs (9 & 11) and shows that a three amino acid motif (NXI/NXV) appears to be critical in determining if fructose can access the translocation mechanism. GLUT11 can also transport fructose, but it has the motif DSV at the same position, which appears to function in the same manner as NXI and when all three residues are replaced with NAV fructose transport lost. These results are discussed in relation to possible roles for hydrophobic residues lining the aqueous pore at the opening of the exofacial vestibule. Finally, the possibility that the translocation binding site may not be the sole determinant of substrate specificity for these proteins is examined.

Lack of Pharmacokinetic Interaction of Levetiracetam on Carbamazepine, Valproic Acid, Topiramate, and Lamotrigine in Children with Epilepsy

PURPOSE

To determine whether levetiracetam (LEV) affects plasma concentrations of carbamazepine, valproic acid, topiramate, and lamotrigine in children with epilepsy.

METHODS

The potential for interaction of LEV with other antiepileptic drugs (AEDs) was assessed using plasma drug levels obtained in a randomized placebo-controlled phase III trial of adjunctive LEV in children receiving one or two concomitant AEDs. Multiple plasma AED levels at baseline and during adjunctive treatment with LEV or placebo were compared by repeated measures analysis of covariance and mean concentration ratios (treatment/baseline) were estimated with their 90% confidence intervals (CI).

RESULTS

The study population included 187 children receiving any concomitant AED alone or in combination. The geometric mean concentrations at baseline and during LEV treatment were carbamazepine 8.4 microg/ml versus 8.1 microg/ml (coefficient of variation, CV = 30%; n = 35); valproic acid 83.8 versus 82.5 microg/ml (CV = 38%; n = 23); topiramate 7.3 versus 7.2 microg/ml (CV = 82%; n = 28); lamotrigine 8.2 versus 7.7 microg/ml (CV = 62%; n = 22). For each AED, the mean concentration ratios (LEV/baseline) and their 90% CIs showed that AED concentrations were unaffected by concomitant LEV administration. No differences were observed between LEV and placebo.

CONCLUSIONS

LEV does not affect plasma concentrations of carbamazepine, valproic acid, topiramate, or lamotrigine in children with epilepsy.

Fructose malabsorption may be gender dependent and fails to show compensation by colonic adaptation

Fructose malabsorption is linked to gastrointestinal and other unusual symptoms. Polymers of fructose are also recognized prebiotics. While some prebiotics can self-adapt when consumed regularly (resulting in decreased breath hydrogen and symptoms), we wondered whether self-adaptation occurs with basic fructose. We evaluated 90 subjects (61 females). Each completed a diet questionnaire and underwent a fructose challenge. Breath hydrogen and quantified symptom scores were recorded. Group comparisons for sum of breath hydrogen and total symptom scores were evaluated with the Mann-Whitney U test. Spearman's correlation coefficient and chi(2) or Fisher's exact test were used as appropriate. Malabsorption occurred in 29 patients (32.2%) and low-grade symptoms without malabsorption in 30 (33%). Women complained of symptoms more frequently (p = 0.04) and exhibited more fructose malabsorption (p = 0.0527). Breath hydrogen correlated with symptoms (r = 0.516, p = 0.0037). Adaptation with increasing pretest fructose intake was absent. We conclude that gender may influence fructose malabsorption and there is no adaptation to regular consumption.

PET/CT with Gluc-Lys-([(18)F]FP)-TOCA: correlation between uptake, size and arterial perfusion in somatostatin receptor positive lesions

PURPOSE

Somatostatin receptor (sstr) positive tumours vary widely in uptake of radiolabelled somatostatin (sst) analogues. This study determinates variability in lesion uptake of the glycosylated sst analogon N(alpha)-(1-deoxy-D-fructosyl)-N(epsilon)-(2-[(18)F]fluoropropionyl)-Lys(0)-Tyr(3)-octreotate (Gluc-Lys([(18)F]FP)-TOCA) and correlates it with lesion size and arterial perfusion as measured on computed tomography (CT).

METHODS

Ten patients with metastasized neuroendocrine carcinomas were investigated with positron emission tomography PET/CT (Biograph 16, Siemens, Germany). Lesion standardized uptake values (SUVs) were determined at approximately 50 min post tracer injection according to a 60% isocontour volume of interest around each lesion. Lesion size and enhancement in the arterial phase (hounsfield units, HUs) were derived from CT.

RESULTS

114 lesions in the upper abdomen had a correlate on both, PET and CT. Variability in lesion SUVs was high (SUV(mean) 22 +/- 13). Intraindividually, there was a sigmoid positive correlation between lesion SUV and lesion diameter indicating partial volume effects. Residual variability in lesions > or =3 cm (> or =2.5 cm) ranged down to about half (third) of the maximum lesion uptake and remained unexplained by partial volume effects. No correlation with measured HU in the arterial phase was found, neither intraindividually nor interindividually.

CONCLUSION

Partial volume effects were a major source of intraindividual variability in tumour tracer uptake. Lesions below 2.5 to 3 cm should thus be used with caution when performing dose calculations. In larger lesions residual variability in uptake must be considered; it may be due to variable sstr2 expression on the tumours' cell surfaces.

Effects of sucromalt on postprandial responses in human subjects

BACKGROUND/OBJECTIVE

To compare postprandial responses elicited by sucromalt, a nutritive sweetener produced by treating a blend of sucrose and corn syrup with an enzyme from Leuconostoc mesenteroides, with those after 42% of high-fructose corn syrup (HFCS), and to see if the reduced responses after sucromalt could be accounted for by carbohydrate malabsorption.

SUBJECT AND METHODS

Three experiments were performed in separate groups of normal subjects studied after overnight fasts using double-blind, randomized, cross-over designs. HFCS was used as the control because it contained a similar amount of fructose as sucromalt. Experiment 1 (n = 10): plasma glucose and insulin were measured after 50 g sucromalt and 50 g HFCS. Experiment 2 (n = 10): metabolic profiles were measured after 80 g HFCS, 80 g sucromalt or 56 g fructose/glucose blend plus 24 g inulin. Experiment 3 (n = 20): the glycaemic indices of sucromalt and HFCS were determined.

RESULTS

Mean glucose and insulin responses after sucromalt were 66 and 62%, respectively, of those after HFCS (P < 0.05). The inulin treatment, used to mimic the effects of carbohydrate malabsorption, elicited higher breath hydrogen (H2), lower glucose and insulin responses, and a significantly earlier rise in serum free fatty acids (FFA) than those of HFCS (all P < 0.05). Sucromalt elicited no rise in breath H2, and delayed falls in glucose and insulin, and a delayed rebound of FFA compared to HFCS (all P < 0.05).

CONCLUSIONS

The reduced glucose and insulin responses elicited by sucromalt are not explained by malabsorption and are more likely related to differences in either rate of digestion and absorption or postabsorptive handling by body.

Truncated AUCs in the assessment of the bioequivalence of topiramate, a long half-life drug

This study was conducted in order to assess the bioequivalence of two tablet formulations containing topiramate (CAS 97240-79-4), 25 mg. Twenty-four healthy volunteers were enrolled in an open-label, randomised, crossover, 2 periods x 2 sequences, with a minimum washout period of 21 days, single dose study. Blood samples were collected prior to study drug administration and 0.167, 0.333, 0.500, 0.667, 1.00, 1.33, 1.67, 2.00, 2.50, 3.00, 4.00, 6.00, 8.00, 12.0, 24.0, 48.0, 96.0, 144, 192, and 264 h post-dose in each period. Plasma levels of topiramate from the 23 subjects who completed the study, were determined by high-pressure liquid chromatography with tandem mass detection, HPLC/MS/MS (lower limit of quantification 9.98 ng/mL). Pharmacokinetic parameters used for bioequivalence assessment (AUC(last), AUC(inf) and C(max)) were determined from the plasma concentration data using non-compartmental analysis. Mean +/- standard deviation elimination half-life for the reference formulation was 84.18 +/- 14.61h whereas for the test formulation it was 80.82 +/- 11.50h. The 90% Confidence Intervals (90 CI) were 98.00-111.35% for C(max), 98.44-103.76% for AUC(last) and 96.61-103.00% for AUC(inf), that is, within the ranges defined in the protocol for acceptance of bioequivalence. The 90 CIs obtained for the truncated AUCs were as follows: 100.27-105.32% for AUC0-48, 99.28-104.62% for AUC0-48, 99.13-104.56% for AUC0-96, 95.67-104.82% for AUC0-144, and 100.04-103.76% for AUC0-192. Both analysed formulations are bioequivalent irrespective of whether the conventional or truncated AUC approach is used. This study demonstrated that topiramate can be viewed as a long half-life drug and that the truncated AUC ap proach could be considered for bioequivalence assessment.

Ability of the normal human small intestine to absorb fructose: evaluation by breath testing

BACKGROUND & AIMS

Fructose consumption is increasing, and its malabsorption causes common gastrointestinal symptoms. Because its absorption capacity is poorly understood, there is no standard method of assessing fructose absorption. We performed a dose-response study of fructose absorption in healthy subjects to develop a breath test to distinguish normal from abnormal fructose absorption capacity.

METHODS

In a double-blind study, 20 healthy subjects received 10% solutions of 15, 25, and 50 g of fructose and 33% solution of 50-g fructose on 4 separate days at weekly intervals. Breath samples were assessed for hydrogen (H2) and methane (CH4) during a period of 5 hours, and symptoms were recorded.

RESULTS

No subject tested positive with 15 g. Two (10%) tested positive with 25 g fructose but were asymptomatic. Sixteen (80%) tested positive with 50 g (10% solution), and 11 (55%) had symptoms. Breath H2 was elevated in 13 (65%), CH4 in 1 (5%), and both in 2 (10%). Twelve (60%) tested positive with 50 g (33% solution), and 9 (45%) experienced symptoms. The area under the curve for H2 and CH4 was higher (P < .01) with 50 g compared with lower doses. There were no gender differences.

CONCLUSIONS

Healthy subjects have the capacity to absorb up to 25 g fructose, whereas many exhibit malabsorption and intolerance with 50 g fructose. Hence, we recommend 25 g as the dose for testing subjects with suspected fructose malabsorption. Breath samples measured for H2 and CH4 concentration at 30-minute intervals and for 3 hours will detect most subjects with fructose malabsorption.

Global transcriptional analysis of Streptococcus mutans sugar transporters using microarrays

The transport of carbohydrates by Streptococcus mutans is accomplished by the phosphoenolpyruvate-phosphotransferase system (PTS) and ATP-binding cassette (ABC) transporters. To undertake a global transcriptional analysis of all S. mutans sugar transporters simultaneously, we used a whole-genome expression microarray. Global transcription profiles of S. mutans UA159 were determined for several monosaccharides (glucose, fructose, galactose, and mannose), disaccharides (sucrose, lactose, maltose, and trehalose), a beta-glucoside (cellobiose), oligosaccharides (raffinose, stachyose, and maltotriose), and a sugar alcohol (mannitol). The results revealed that PTSs were responsible for transport of monosaccharides, disaccharides, beta-glucosides, and sugar alcohol. Six PTSs were transcribed only if a specific sugar was present in the growth medium; thus, they were regulated at the transcriptional level. These included transporters for fructose, lactose, cellobiose, and trehalose and two transporters for mannitol. Three PTSs were repressed under all conditions tested. Interestingly, five PTSs were always highly expressed regardless of the sugar source used, presumably suggesting their availability for immediate uptake of most common dietary sugars (glucose, fructose, maltose, and sucrose). The ABC transporters were found to be specific for oligosaccharides, raffinose, stachyose, and isomaltosaccharides. Compared to the PTSs, the ABC transporters showed higher transcription under several tested conditions, suggesting that they might be transporting multiple substrates.

Safety and efficacy of anticonvulsants in elderly patients with psychiatric disorders: oxcarbazepine, topiramate and gabapentin

Few controlled studies are available to guide the clinician in treating potentially assaultive elderly individuals with psychiatric disorders. Safety concerns limit the use of benzodiazepines and antipsychotic medications in the elderly individual, making anticonvulsants an attractive alternative. This paper reviews three specific anticonvulsants for this purpose: gabapentin, oxcarbazepine and topiramate, describing safety and efficacy in elderly patients with severe agitation from psychosis or dementia. Gabapentin, renally excreted, with a half-life of 6.5-10.5 h, may cause ataxia. Oxcarbazapine, hepatically reduced, may cause hyponatremia, and topiramate may cause significant cognitive impairment. Nonetheless, these are important medications to consider in the treatment of agitation.

Potential genetic causes of heterogeneity of treatment effects

Nongenetic biologic and lifestyle-related factors, including age, sex, hepatic/renal function, diet/exercise practices, illness severity, smoking, and alcohol consumption habits can account for the heterogeneity of treatment effects (HTE). However, even when these factors are taken into account, considerable variation remains unexplained and could potentially be attributable to genetic differences between patients. Drug response may be dictated by variation in genes involved in both pharmacokinetic (PK) (absorption, distribution, metabolism, excretion [ADME]) and pharmacodynamic (PD) (receptors, ion channels, enzymes, immune system) pathways. Functional variants of the ADME genes can result in patients being poor, intermediate, efficient, or ultrarapid metabolizers of specific agents, thereby affecting efficacy and/or susceptibility to adverse drug reaction and necessitating individualized dosing. A well-documented example of ADME gene variation is the debrisoquine polymorphism, which is characterized by markedly different metabolism of numerous commonly prescribed drugs based on variants of the cytochrome P450 2D6 gene. Variants of genes regulating PD pathways cause altering of drug target pathways, which may affect efficacy in a more pronounced manner. Examples of gene variants affecting PD pathways include those coding for dopamine metabolism, synthesis, and transport. These gene variants may act independently, in combination with each other, and/or in combination with PK genes to affect drug response, for example to antipsychotic medications. Increased understanding of a patient's genotype and its corresponding effect on drug response would be useful to the practicing clinician in choosing an effective drug and in optimizing the dose in a timely manner.

Eucalyptus leaf extract inhibits intestinal fructose absorption, and suppresses adiposity due to dietary sucrose in rats

Sucrose is more lipogenic than starch, and the extreme ingestion of sucrose induces adiposity and obesity. The aim of this study was to examine the effect of the eucalyptus (Eucalyptus globulus) leaf extract (ELE) on adiposity due to dietary sucrose in rats. In addition, in this study, the effect of ELE on intestinal fructose absorption was also examined. Rats were fed a high-sucrose diet (75 % in calorie base) with or without ELE (10 g/kg diet) for 5 weeks. Body weight was lower in the rats receiving ELE than in the controls (342 (sd 37·9)v. 392 (sd 26·0) g (n7);P<0·05). Furthermore, ELE resulted in decreases in the triacylglycerol concentrations in the plasma (1·44 (sd 0·448)v.2·79 (sd 0·677) mmol/l (n7);P<0·05) and liver (19·1 (sd 5·07)v.44·1 (sd 16·28) μmol/g (n7);P<0·05). In contrast, ELE did not show any significant effects in the rats fed a starch diet. When rats were orally given ELE 10 min before fructose administration, the intestinal fructose absorption, which was examined by measuring the elevated concentration of fructose in the portal vein at 30 min after the fructose administration, was significantly inhibited in a dose-dependent manner. Furthermore, in rats fed a high-fructose diet, the plasma and hepatic triacylglycerol concentrations were significantly decreased by ELE. These results indicate that ELE, which inhibits the intestinal fructose absorption, can suppress adiposity in rats that ingest large amounts of sucrose or fructose.

Isobolographic analysis of interaction between drugs with nonparallel dose-response relationship curves: a practical application

The objective of this study was to characterize the anticonvulsant and acute adverse-effect potentials of topiramate (TPM) and gabapentin (GBP)-two second-generation antiepileptic drugs administered alone and in combination in the maximal electroshock (MES)-induced seizures and chimney test in mice. The anticonvulsant and acute adverse effects of the combination of TPM with GBP at the fixed ratio of 1:1 were determined using the type I isobolographic analysis for nonparallel dose-response relationship curves (DRRCs). To ascertain any pharmacokinetic contribution to the observed interaction between TPM and GBP, total brain concentrations of both drugs were determined. The isobolographic analysis of interaction for TPM and GBP, whose DRRCs were not parallel in both MES and chimney tests, was accompanied with a presentation of all required calculations allowing the determination of lower and upper lines of additivity. The isobolographic analysis revealed that TPM combined with GBP at the fixed-ratio combination of 1:1 interacted supraadditively (synergistically) in terms of suppression of MES-induced seizures, and simultaneously, the combination produced additive interaction with respect to motor coordination impairment (adverse effects) in the chimney test. The evaluation of pharmacokinetic characteristics of interaction for the combination of TPM with GBP revealed that neither TPM nor GBP affected their total brain concentrations in experimental animals, and thus, the observed interaction in the MES test was pharmacodynamic in nature. In conclusion, the combination of TPM with GBP, because of supraadditivity in the MES test and additivity in terms of motor coordination impairment in the chimney test as well as lack of pharmacokinetic interactions between drugs, fulfilled the criterion of a favorable combination, worthy of recommendation in further clinical practice.

Sodium, ammonium, calcium, and magnesium forms of zeolite Y for the adsorption of glucose and fructose from aqueous solutions

The kinetics of adsorption by sodium, ammonium, calcium and magnesium forms of zeolite Y from aqueous solutions containing 25% w/v of either one or an equimolar mixture of glucose (G) and fructose (F) have been studied batch-wise at 50 degrees C. The adsorption of aqueous pure G was fast, while that of aqueous pure F depended on the cationic form, approaching that of G on the Mg-Y, and slowing down in the sequence of Mg2+ > NH4+ > Ca2+ > Na+ of the cations. The adsorption behavior from solutions containing both G and F indicated significant hindering effects of F on G on Na-Y. Na-Y and Mg-Y did not exhibit rate-based selectivity, while Ca-Y an NH4-Y adsorbed G faster than F. Addition of CaCl2 to the mixture of Ca-Y and aqueous solution of G and F improved the separation, by hindering the adsorption of F. Addition of NH4Cl to the mixture of the sugar solution and NH4-Y, on the other hand, had a negative effect on the separation. NH4-Y was found to be desorbing about 30% of the adsorbed sugars and this value was found to be around 50% for Ca-Y. Re-adsorption experiments resulted in similar or somewhat higher percentages of amounts adsorbed compared to adsorption on fresh samples. Both NH4-Y and Ca-Y were found to be re-adsorbing around 50% of the sugars they adsorbed on fresh samples.

Pharmacokinetic and pharmacodynamic interactions of aminophylline and topiramate in the mouse maximal electroshock-induced seizure model

The aim of this study was to determine the influence of acute (single) and chronic (twice daily for 14 consecutive days) treatments with aminophylline (theophylline(2).ethylenediamine) on the anticonvulsant potential of topiramate (a broad-spectrum antiepileptic drug) in the mouse maximal electroshock-induced seizure model. Additionally, the effects of acute and chronic administration of aminophylline on the adverse effect potential of topiramate were assessed in the chimney test (motor performance). To evaluate pharmacokinetic characteristics of interaction between topiramate and aminophylline, total brain concentrations of topiramate and theophylline were estimated with fluorescence polarization immunoassay technique. Results indicate that aminophylline in non-convulsive doses of 50 and 100 mg/kg (i.p.), both in acute and chronic experiments, markedly attenuated the anticonvulsant potential of topiramate by raising its ED(50) value against maximal electroconvulsions. Aminophylline at a lower dose of 25 mg/kg did not affect significantly the ED(50) value of topiramate in the acute experiment, but the drug markedly increased the ED(50) value of topiramate during the chronic treatment in mice. Only, aminophylline at 12.5 mg/kg, in both acute and chronic experiments, did not affect the antielectroshock action of topiramate in mice. Moreover, aminophylline at a dose of 100 mg/kg had no impact on the adverse effect potential of topiramate in the chimney test. Pharmacokinetic evaluation of total brain concentrations of topiramate and theophylline revealed that topiramate significantly increased total brain theophylline concentrations following both acute and chronic applications of aminophylline. Conversely, aminophylline did not alter total brain concentrations of topiramate in mice. Based on this preclinical study, one can conclude that aminophylline attenuated the antiseizure action of topiramate in the mouse maximal electroshock-induced seizure model and the observed interaction between drugs was both pharmacokinetic and pharmacodynamic in nature.

[An association between the FABP2 gene polymorphism and efficacy of valproates]

To search for association between the 163G>A polymorphism of the fatty acid binding protein 2 (FABP2) gene and intracellular transport of the valproic acid in the small intestines, 168 patients with different forms of epilepsy, aged from 1 to 89 years, and different illness duration have been studied. The patients received valproates (127 patients) and topiramate (41 patients) as a monotherapy. It has been shown that the 163G>A (Ala54Thr) polymorphism exerts an influence on effective dose of the valproic acid but not of topiramate.

Fructose malabsorption in Thai adult

Fructose malabsorption has not been well-defined in Thai populations but there has been increasing consumption of fructose-fortified drinks.

OBJECTIVES

To assess the incidence of fructose malabsorption and intolerance in Thai normal subjects as well as the facilitating effect of glucose on fructose absorption.

METHODS

Twenty-five gram of fructose was ingested by 77 subjects (37 men, 40 women; mean age 26 and 31 y, range 20-50 y and 21-50 y for men and women, respectively). Measurement of breath-H(2) levels after fructose ingestion in each subject up to 2 h was performed. Those who showed fructose malabsorption were later given 25 g of each glucose and fructose and second tests of breath-H(2) tests were done.

RESULTS

Fructose malabsorption was found in eleven females with a significant rise in average breath-H(2) level at 30, 60, 90, and 120 min (p< 0.001), whereas none of the males had an abnormal breath-H(2) test. Only 1 of the 11 females with increased breath H(2) had gastrointestinal symptoms. In all the fructose malabsorbers, excess breath-H(2) reverted to normal when the fructose solution was mixed and administered with 25 g glucose (p< 0.001).

CONCLUSION

The incidence rate of fructose malabsorption was 11 of 77 subjects but these were female. One of the 11 had gastrointestinal symptoms. It was found that an equal amount of glucose would abolish fructose malabsorption.

A 4-wk high-fructose diet alters lipid metabolism without affecting insulin sensitivity or ectopic lipids in healthy humans

BACKGROUND

High fructose consumption is suspected to be causally linked to the epidemics of obesity and metabolic disorders. In rodents, fructose leads to insulin resistance and ectopic lipid deposition. In humans, the effects of fructose on insulin sensitivity remain debated, whereas its effect on ectopic lipids has never been investigated.

OBJECTIVE

We assessed the effect of moderate fructose supplementation on insulin sensitivity (IS) and ectopic lipids in healthy male volunteers (n = 7).

DESIGN

IS, intrahepatocellular lipids (IHCL), and intramyocellular lipids (IMCL) were measured before and after 1 and 4 wk of a high-fructose diet containing 1.5 g fructose . kg body wt(-1) . d(-1). Adipose tissue IS was evaluated from nonesterified fatty acid suppression, hepatic IS from suppression of hepatic glucose output (6,6-2H2-glucose), and muscle IS from the whole-body glucose disposal rate during a 2-step hyperinsulinemic euglycemic clamp. IHCL and IMCL were measured by 1H magnetic resonance spectroscopy.

RESULTS

Fructose caused significant (P < 0.05) increases in fasting plasma concentrations of triacylglycerol (36%), VLDL-triacylglycerol (72%), lactate (49%), glucose (5.5%), and leptin (48%) without any significant changes in body weight, IHCL, IMCL, or IS. IHCL were negatively correlated with triacylglycerol after 4 wk of the high-fructose diet (r = -0.78, P < 0.05).

CONCLUSION

Moderate fructose supplementation over 4 wk increases plasma triacylglycerol and glucose concentrations without causing ectopic lipid deposition or insulin resistance in healthy humans.

Gabapentin synergistically interacts with topiramate in the mouse maximal electroshock seizure model: an isobolographic analysis

The anticonvulsant effects produced by topiramate (TPM) and gabapentin (GBP)--two second-generation antiepileptic drugs, in numerous fixed-ratio combinations of 8:1, 4:1, 2:1, 1:1, 1:2, 1:4 and 1:8 were examined by isobolographic analysis in the mouse maximal electroshock seizure (MES) model. Results indicate that the combinations of TPM and GBP at the fixed-ratios of 2:1, 1:1, 1:2, 1:4 and 1:8 resulted in supra-additive (synergistic) interaction against MES-induced seizures. Moreover, the combinations of TPM and GBP (at their median effective doses) did not affect motor performance of animals challenged with the chimney test and had no impact on neuromuscular tone in the grip-strength test. Additionally, GBP had no impact on total brain TPM concentrations, and simultaneously, TPM did not alter brain GBP concentrations, indicating that the interaction between drugs was pharmacodynamic in nature. In conclusion, supra-additive interaction of TPM with GBP against MES-induced seizures, lack of motor coordination and neuromuscular tone impairments as well as lack of pharmacokinetic interactions between TPM and GBP in preclinical study, strongly support the combined application of both antiepileptic drugs in patients with refractory partial epilepsy.

Topiramate and its clinical applications in epilepsy

Topiramate, a derivative of the monosaccharide d-fructose, has shown a wide spectrum of antiepileptic efficacy in both animal models and clinical trials. Multiple putative mechanisms of action include voltage-sensitive sodium channel blockade, calcium channel inhibition, increase of potassium conductance, GABA-mediated chloride current increment, glutamate-mediated neurotransmission inhibition and carbonic anhydrase isoenzyme inhibition. In general, the clinical response is maintained in the long-term. The most common side effects include somnolence, fatigue, headache, psychomotor slowing, confusion, difficulty with memory, impaired concentration and attention, speech and language problems and weight loss. If slowly titrated and used at a low-to-medium dosage, it is well tolerated and offers a valid therapeutic option, the relevance of which is comparable to that of the most widely used 'old' antiepileptic drugs. As it is not yet wholly clear which specific epilepsy syndromes may benefit most from topiramate with respect to other drugs, more accurate indications for initial monotherapy would require syndrome-oriented trials and more clinical experience.

Gluc-Lys([18F]FP)-TOCA PET in patients with SSTR-positive tumors: biodistribution and diagnostic evaluation compared with [111In]DTPA-octreotide

A recently developed (18)F-labeled PET tracer for somatostatin receptor (sstr) imaging, N(alpha)-(1-deoxy-D-fructosyl)-N(epsilon)-(2-[(18)F]fluoropropionyl)-Lys(0)-Tyr(3)-octreotate (Gluc-Lys([(18)F]FP)-TOCA), was evaluated in patients with sstr-positive tumors by assessing the pharmacokinetics, biodistribution, and diagnostic performance in comparison with [(111)In]DTPA-octreotide.

METHODS

Twenty-five patients with different sstr-positive tumors were included in the study and were injected with 105 +/- 50 MBq Gluc-Lys([(18)F]FP)-TOCA. PET was performed up to 120 min with 2 different dynamic imaging protocols. Tracer kinetics in tumors and nontumor tissues and tumor-to-background ratios were described by region-of-interest analysis and standardized uptake values (SUVs). In 16 patients, sstr scintigraphy with [(111)In]DTPA-octreotide was performed (whole-body scans and SPECT). Two independent experts on PET and gamma- camera scans performed lesion counts.

RESULTS

Gluc-Lys([(18)F]FP)-TOCA showed a fast and intense tumor accumulation as well as a rapid clearance from blood serum (biexponential elimination, with the half-lives of the initial and the terminal elimination phase calculated as t(1/2)(1) = 2.3 +/- 1.3 min and t(1/2)(2) = 26.4 +/- 14.6 min, respectively). Tumor-to-background ratios at 16 +/- 9 min and 34 +/- 12 min were as high as 80% and 90% (% of maximum ratios), respectively. Tumors showed high SUVs ranging from 13.7 +/- 2.3 (tumors in lung) up to 26.9 +/- 15.4 (abdominal tumors). Tracer distribution within tumor and nontumor tissues was stable up to 120 min (except spleen). No significant bowel activity was observed. Comparison of 29 tumors located in the liver showed a mean tumor-to-background ratio of 5.3 +/- 2.6 for Gluc-Lys([(18)F]FP)-TOCA vs. 4.6 +/- 3.3 for [(111)In]DTPA-octreotide (P = 0.24). Visual image analysis revealed a significantly higher number of lesions (factor of 2.4) and improved interobserver correlation (r = 0.99 vs. 0.86) for PET.

CONCLUSION

Gluc-Lys([(18)F]FP)-TOCA PET allows a fast, high- contrast imaging of sstr-positive tumors. The biokinetics and diagnostic performance of Gluc-Lys([(18)F]FP)-TOCA are superior to [(111)In]DTPA-octreotide and-as far as can be derived from the literature-comparable with [(68)Ga]-DOTA-d Phe(1)-Tyr(3)-octreotide ([(68)Ga]DOTATOC).

Brain Homocarnosine and Seizure Control of Patients Taking Gabapentin or Topiramate

PURPOSE

To assess the relation between seizure control and brain homocarnosine and gamma-aminobutyric acid (GABA) levels of patients with complex partial seizures taking gabapentin (GBP) or topiramate (TPM) as adjunctive therapy.

METHODS

In vivo measurements of GABA and homocarnosine were made of a 14-cc volume in the occipital cortex by using (1)H spectroscopy with a 2.1-Tesla magnetic resonance spectrometer and an 8-cm surface coil. Poor seizure control was defined as more recent seizures than the median for the two groups of patients studied.

RESULTS

Homocarnosine levels were higher in patients with better seizure control than in those with poor control. No differences were found in the intracellular GABA levels between the patients who responded to GBP or TPM compared with those who did not.

CONCLUSIONS

In the visual neocortex, which is remote from the presumed seizure-onset zone, higher homocarnosine levels were associated with better seizure control in the patients taking GBP or TPM as adjunctive therapy; elevated intracellular GABA levels appeared to offer no additional protection.

Clinical experience with topiramate dosing and serum levels in patients with epilepsy

OBJECTIVE

To investigate the relevance of serum topiramate (TPM) levels (SL) monitoring in the clinical management of epileptic patients.

METHODS

Twenty-seven patients with different epileptic syndromes on TPM therapy were studied. TPM was used as add-on in 26 patients, only in one as monotherapy de novo; one case changed from TPM as add-on to TPM monotherapy. The mean follow-up time was 11 months. TPM SL were measured by fluorescence polarization immunoassay.

RESULTS

We analyzed the TPM SL in 43 samples from 27 patients. Mean TPM dose was 3.9mg/kg, mean TPM SL 13.43mumol/l. The mean level to dose ratio (LDR) was 3.63mumol/l/mg/kg. Four patients became seizure-free, all with TPM dosages lower than the mean. Eleven patients had at least 50% seizure reduction. The comedication with enzyme-inducing AED significantly reduced TPM SL and LDR. On the other hand, the influence of valproic acid (VPA) on TPM LDR was not univocal. Indeed, patients younger than 15 years showed SL values lower than the adults did, although not significant.

CONCLUSION

We could not detect a direct relationship between high TPM SL and efficacy neither between high TPM SL and tolerability. However, the data we collected seem to favour the hypothesis that high TPM dosage and SL might be associated to a greater probability to reduce seizure severity.