Effect of a high-protein meal on gabapentin pharmacokinetics

Interactions between antiseizure medications and foods and drinks: A systematic review

Antiseizure medications (ASMs) constitute the principal of treatment for patients with epilepsy, where long-term treatment is usually necessary. The purpose of this systematic review is to provide practical and useful information regarding various aspects of the interactions between ASMs and foods and drinks. MEDLINE and ScienceDirect, from the inception to July 15, 2023, were searched for related publications. In both electronic databases, the following search strategy was applied, and the following keywords were used (in title/abstract): "food OR drink" AND "antiepileptic OR antiseizure." The primary search yielded 738 studies. After implementing our inclusion and exclusion criteria, we could identify 19 studies on the issue of interest for our endeavor. Four studies were identified in the recheck process and not by the primary search. All studies provided low level of evidence. Interactions between foods and ASMs are a common phenomenon. Many factors may play a role for such an interaction to come to play; these include drug properties, administration route, and administration schedule, among others. Drugs-foods (-drinks) interactions may change the drug exposure or plasma levels of drugs (e.g., grapefruit juice increases carbamazepine concentrations and the bioavailability of cannabidiol is increased 4-5 folds with concomitant intake of fat-rich food); this may require dosage adjustments. Interactions between ASMs and foods and drinks may be important. This should be taken seriously into consideration when consulting patients and their caregivers about ASMs. Future well-designed investigations should explore the specific interactions between foods (and drinks) and ASMs to clarify whether they are clinically important. PLAIN LANGUAGE SUMMARY: Interactions between antiseizure medications and foods and drinks may be important. This should be taken into consideration in patients with epilepsy.

Molecular Variability in Levodopa Absorption and Clinical Implications for the Management of Parkinson's Disease

Levodopa is the most widely used medication for the symptomatic treatment of Parkinson's disease and, despite being an "old" drug, is still considered the gold standard for offering symptomatic relief. The pharmacokinetic and pharmacodynamics of levodopa have been studied extensively. Our review explores the molecular mechanisms that affect the absorption of this drug, focusing on the large intra- and interindividual variability of absorption that is commonly encountered in daily clinical practice, and on the interaction with other medications. In addition, we will explore the clinical implications of levodopa absorption variability and address current and future strategies for researchers and clinicians.

Factors in Variability of Serial Gabapentin Concentrations in Elderly Patients with Epilepsy

OBJECTIVES

To characterize and quantify the variability of serial gabapentin concentrations in elderly patients with epilepsy.

METHODS

This study included 83 patients (age ≥ 60 yrs) from an 18-center randomized double-blind double-dummy parallel study from the Veterans Affairs Cooperative 428 Study. All patients were taking 1500 mg/day gabapentin. Within-person coefficient of variation (CV) in gabapentin concentrations, measured weekly to bimonthly for up to 52 weeks, then quarterly, was computed. Impact of patient characteristics on gabapentin concentrations (linear mixed model) and CV (linear regression) were estimated.

RESULTS

A total of 482 gabapentin concentration measurements were available for analysis. Gabapentin concentrations and intrapatient CVs ranged from 0.5 to 22.6 μg/ml (mean 7.9 μg/ml, standard deviation [SD] 4.1 μg/ml) and 2% to 79% (mean 27.9%, SD 15.3%), respectively, across all visits. Intrapatient CV was higher by 7.3% for those with a body mass index of ≥ 30 kg/m² (coefficient = 7.3, p=0.04). CVs were on average 0.5% higher for each 1-unit higher CV in creatinine clearance (coefficient = 0.5, p=0.03) and 1.2% higher for each 1-hour longer mean time after dose (coefficient = 1.2, p=0.04).

CONCLUSIONS

Substantial intrapatient variability in serial gabapentin concentration was noted in elderly patients with epilepsy. Creatinine clearance, time of sampling relative to dose, and obesity were found to be positively associated with variability.

Multi-kinetics and site-specific release of gabapentin and flurbiprofen from oral fixed-dose combination: in vitro release and in vivo food effect

In this work, a fixed-dose combination of gabapentin and flurbiprofen formulated as multilayer tablets has been designed, developed and studied in vitro and in vivo. The aim was to construct a single dosage form of the two drugs, able to perform a therapeutic program involving three release kinetics and two delivery sites, i.e., immediate release of gabapentin, intra-gastric prolonged release of gabapentin and intestinal (delayed) release of flurbiprofen. An oblong three-layer tablet was manufactured having as top layer a floating hydrophilic polymeric matrix for gastric release of gabapentin, as middle layer a disintegrating formulation for immediate release of a gabapentin loading dose and as bottom layer, an uncoated hydrophilic polymeric matrix, swellable but insoluble in gastric fluids, for delayed and prolonged release of flurbiprofen in intestinal environment. The formulations were studied in vitro and in vivo in healthy volunteers. The in vitro release rate assessment confirmed the programmed delivery design. A significant higher bioavailability of gabapentin administered 30min after meal, compared to fasting conditions or to dose administration 10min before meal, argued in favor of the gastro-retention of gabapentin prolonged release layer. The two drugs were delivered at different anatomical sites, since the food presence prolonged the gastric absorption of gabapentin from the floating layer and delayed the flurbiprofen absorption. The attainment of a successful delayed release of flurbiprofen was realized by a matrix based on a polymers' combination. The combined use of three hydrophilic polymers with different pH sensitivity provided the dosage form layer containing flurbiprofen with gastro-resistant characteristics without the use of film coating.

A comparative study of the pharmacokinetics of traditional and automated dosing/blood sampling systems using gabapentin

Objective:

The present study was undertaken to investigate the pharmacokinetics (PKs) of gabapentin as determined by traditional manual blood sampling and by using an automated dosing/blood sampling technique in awake and freely moving rats using combined liquid chromatography tandem mass-spectrometry (LC-MS/MS).

Materials and Methods:

PK comparisons were conducted by allocating rats into two groups; an automated dosing/blood sampling (ADI/ABS) group (IV study, n = 6 and intragastric study, n = 6) and a manual group (IV study, n = 6 and oral study, n = 6). A series of blood samples from carotid artery were taken at specified times and analyzed using a validated LC-MS/MS method. Various PK parameters like area under curve (AUC_inf), maximum concentration, time to reach maximum concentration, terminal half life, distribution volume at the steady state, and total clearance were calculated and the two study groups were compared with respect to these parameters.

Results:

Significant differences in PK parameters were observed between the manual group and the ADI/ABS group and respective bioavailability were measured (46.82 ± 19.45% and 61.54 ± 21.23%, respectively) which is 1.31-fold difference (P = 0.0051, P<0.05).

Conclusion:

The described ADI/ABS method was found to be a useful drug development tool for accelerating the pace of preclinical in vivo studies and for obtaining reliable and accurate PK parameters even from single animals as it minimized interanimal and physiological variations.

A comparison of the pharmacokinetics and pharmacodynamics of pregabalin and gabapentin

Pregabalin and gabapentin share a similar mechanism of action, inhibiting calcium influx and subsequent release of excitatory neurotransmitters; however, the compounds differ in their pharmacokinetic and pharmacodynamic characteristics. Gabapentin is absorbed slowly after oral administration, with maximum plasma concentrations attained within 3-4 hours. Orally administered gabapentin exhibits saturable absorption--a nonlinear (zero-order) process--making its pharmacokinetics less predictable. Plasma concentrations of gabapentin do not increase proportionally with increasing dose. In contrast, orally administered pregabalin is absorbed more rapidly, with maximum plasma concentrations attained within 1 hour. Absorption is linear (first order), with plasma concentrations increasing proportionately with increasing dose. The absolute bioavailability of gabapentin drops from 60% to 33% as the dosage increases from 900 to 3600 mg/day, while the absolute bioavailability of pregabalin remains at > or = 90% irrespective of the dosage. Both drugs can be given without regard to meals. Neither drug binds to plasma proteins. Neither drug is metabolized by nor inhibits hepatic enzymes that are responsible for the metabolism of other drugs. Both drugs are excreted renally, with elimination half-lives of approximately 6 hours. Pregabalin and gabapentin both show dose-response relationships in the treatment of postherpetic neuralgia and partial seizures. For neuropathic pain, a pregabalin dosage of 450 mg/day appears to reduce pain comparably to the predicted maximum effect of gabapentin. As an antiepileptic, pregabalin may be more effective than gabapentin, on the basis of the magnitude of the reduction in the seizure frequency. In conclusion, pregabalin appears to have some distinct pharmacokinetic advantages over gabapentin that may translate into an improved pharmacodynamic effect.

In Vivo Effects of Glycyl-Glutamate and Glycyl-Sarcosine on Gabapentin Oral Absorption in Rat

PURPOSE

The objective of this study was to evaluate the in vivo consequences of glycyl-glutamate coadministration on gabapentin oral absorption.

METHODS

Rats were administered gabapentin (10 mg/kg plus radiotracer) by gastric gavage, in the absence and presence of dipeptides, and by intravenous administration. Serial blood samples were obtained over 6 h and the pharmacokinetics of gabapentin were determined by noncompartmental analysis.

RESULTS

Glycyl-glutamate coadministration increased the Cmax of gabapentin by 86% as compared to gabapentin alone. In agreement, the oral absorption of gabapentin, relative to the intravenous dose, was 79% after glycyl-glutamate loading but only 47% when drug was administered alone. However, when glycyl-sarcosine was added to the orally administered admixture of gabapentin plus glycyl-glutamate, values for Cmax and AUC(0-6 h) reverted back to that of control. In contrast, the tmax and terminal half-life of gabapentin did not change after oral dosing for all treatments.

CONCLUSIONS

These findings are unique in demonstrating that under physiologic, in vivo conditions, the luminal presence of glycyl-glutamate could dramatically enhance the Cmax and AUC(0-6 h) of gabapentin. The results are consistent with previous in situ intestinal perfusion studies in rat, and establish a functional interaction between the activities of PEPT1 and amino acid exchangers.

Novel anticonvulsant drugs

Principles of complex mechanisms of action of anticonvulsants including latest reports concerning new antiepileptic drugs (AED) are considered. Different aspects of new anticonvulsant drugs (2nd generation) from preclinical and clinical testing, pharmacokinetics, and mono or combination therapy in children and adults are summarized. In the following condensed synopsis pharmacological and clinical characteristics of gabapentin (GBP), lamotrigine (LTG), levetiracetam (LEV), oxcarbazepine (OXC), pregabalin (PGB) and tiagabine (TGB) as well as topiramate (TPM) and zonisamide (ZNS) are discussed. In addition to the mechanisms of action, pharmacokinetics, interactions, indications and dosages as well as side effects are considered. Important data concerning the effect and tolerability of anticonvulsant drugs can be obtained from controlled studies. In comparison to drugs of the first generation (phenobarbital [PB], primidon [PRD], phenytoin [PHT], carbamazepine [CBZ] and valproic acid [VPA]) the potential for interactions and side effects due to enzyme induction or inhibition is reduced by most of the anticonvulsant drugs of the second generation. New anticonvulsant drugs increase the spectrum of treatment and represent further steps with regard to the optimization of an individual therapy of the epilepsies.

PEPT1 Enhances the Uptake of Gabapentin via Trans-Stimulation of b0,+ Exchange

PURPOSE

The aims of this study were (1) to determine whether amino acid and dipeptide loading can improve the effective permeability of gabapentin and (2) to characterize the underlying mechanism that is responsible for this interaction.

MATERIALS AND METHODS

An in situ single-pass rat intestinal perfusion model was used to assess the effective permeability of gabapentin in rat, in the absence and presence of cellular loading by amino acid and dipeptide mixtures.

RESULTS

Compared to gabapentin alone, cellular loading with amino acid and dipeptide mixtures significantly improved the effective permeability of gabapentin by 46-79% in jejunum and by 67-72% in ileum (p < or = 0.01). However, coperfusion of glycylsarcosine (i.e., PEPT1 substrate), methionine sulfoximine (i.e., glutamine synthase inhibitor), or lysine and arginine (i.e., b(0,+) substrates) with the amino acid and dipeptide mixtures compromised the intestinal uptake of gabapentin.

CONCLUSIONS

These findings demonstrate, for the first time, a direct relationship between the PEPT1-mediated uptake of a dipeptide and the trans-stimulated uptake of gabapentin (an amino acid-like drug) through the transport system b(0,+).

Gabapentin dosing in the treatment of epilepsy

BACKGROUND

Gabapentin is considered a safe and well-tolerated antipileptic drug (AED) with a favorable pharmacokinetic profile and a broad therapeutic index. However, recent studies have used higher doses and faster titration schedules than those used in the pivotal trials that established the efficacy of gabapentin in the treatment of partial seizures.

OBJECTIVE

The purposes of this review were to assess the gabapentin titration and dosing regimens that have been published in peer-reviewed journals, to develop dosing recommendations to maximize antiseizure efficacy without compromising tolerability, and to formulate guidelines for an adequate therapeutic assessment of gabapentin dosage efficacy.

METHODS

In the absence of sufficient placebo-controlled, double-blind studies, a formal evidence-based assessment could not be performed. However, a MEDLINE search using the search terms gabapentin and epilepsy, spanning back to the year 1986, produced numerous published reports from randomized, placebo-controlled and open-label trials, as well as case reports. These were reviewed to assess the range of dosing and titration schedules reported. Reports that employed gabapentin doses and titration schedules were selected for review.

RESULTS

Our review of this literature suggests improved seizure control at higher gabapentin maintenance dosages (< or =3600 mg/d) than are used today in clinical practice (1800 mg/d) without an increase in the incidence of adverse reactions. Most of the patients who received high dosages (eg, 3600 mg/d) or experienced fast titration rates tolerated gabapentin well. Side effects occurred around the onset of dosing and were reported in some studies to be transient.

CONCLUSIONS

Based in the literature here, in most adult patients, gabapentin may be initiated at a dosage of 900 mg/d and titrated to maintenance dosages > or = 3600 mg/d. Children may be treated with gabapentin 23 to 78 mg/kg per day. Based on controlled and open trials, the majority of patients will tolerate gabapentin well enough for an adequate therapeutic assessment. Titration to effect can be accomplished rapidly, if necessary; however, as with other AEDs, optimal seizure control may take months to achieve.

Single-dose gabapentin pharmacokinetics and safety in healthy infants and children

Gabapentin (Neurontin) is a gamma-aminobutyric acid analogue indicated in adults for adjunctive treatment of partial seizures with or without secondary generalization. Two studies were conducted to determine the single-dose pharmacokinetics of gabapentin in healthy subjects age 1 month to 12 years and to guide dose selection in safety and efficacy trials in pediatric patients. Forty-eight subjects were given single oral doses of gabapentin (10 mg/kg) while fasting. Enrollment was homogeneously distributed throughout the age range. Plasma samples were drawn predose and then serially for 24 hours postdose. Single doses of gabapentin were well tolerated by healthy pediatric subjects. Plots of pharmacokinetic parameters versus age suggested significant differences between younger (1 month to < 5 years) and older (> or =5 to 12 years) subjects. Mean area under the plasma concentration-time curve from zero to infinity (AUC(0-infinity)) was 25.6 microg x h/mL in younger subjects and 36.0 microg x h/mL in older subjects (p < 0.001). Corresponding mean peak plasma concentrations (Cmax) were 3.74 and 4.52 microg/ml (p < 0.05). Oral clearance (normalized for body weight) was 7.40 and 4.41 mL/min/kg in younger subjects and older subjects, respectively (p < 0.001). It was concluded that children between 1 month and < 5 years of age require approximately 30% higher daily doses of gabapentin than those > or =5 to 12 years of age.

The clinical pharmacokinetics of the new antiepileptic drugs

Because pharmacokinetics is a major determinant of the magnitude and duration of pharmacologic response, understanding the kinetic properties of the new antiepileptic drugs (AEDs) is essential for the correct use of these compounds in clinical practice. After oral administration, absorption is rapid and relatively efficient for the new AEDs, the most notable exception being gabapentin, whose bioavailability decreases with increasing dosage. None of the new AEDs is extensively bound to plasma proteins except for tiagabine, which is over 95% protein-bound. The route of elimination differs to an important extent from one compound to another, and elimination half-lives range from over 30 h for zonisamide to 5-7 h for gabapentin. For all drugs that are metabolized, half-life is shortened and clearance is increased when patients receive concomitant enzyme-inducing agents such as barbiturates, phenytoin, and carbamazepine. Lamotrigine metabolism is markedly inhibited by valproic acid, and felbamate may increase the serum levels of most other AEDs. Felbamate, topiramate, and oxcarbazepine may also reduce the efficacy of the contraceptive pill by stimulating its metabolism.

Gabapentin in the management of convulsive disorders

Gabapentin, in clinical use since 1993, is indicated as an adjunctive antiepileptic drug (AED) for treatment of complex partial seizures, with or without secondary generalization, in patients over 12 years of age. Although several cellular actions have been described in the literature, the molecular mechanism(s) of action responsible for the anticonvulsant effect of gabapentin has not been conclusively determined. It is likely that gabapentin has multiple concentration-dependent actions that combine in a unique manner to produce antiepileptic efficacy. The pharmacokinetic properties of this water-soluble, amino-acid AED are generally favorable. Absorption appears to be dependent on transport by the L-system amino acid transporter. Elimination of unmetabolized drug occurs by the renal route. Although its therapeutic range is not well characterized, gabapentin has a broad therapeutic index. This implies that a wide range of doses can be used, based on individual patient needs, without significant limitation due to dose-dependent side effects. Gabapentin has few drug-drug interactions, none of which is clinically limiting. Several studies have demonstrated the long-term efficacy of gabapentin with no systematic evidence of tachyphylaxis. In addition, there is increasing evidence to support the use of gabapentin as monotherapy. Gabapentin is safe and is generally well tolerated. To date, nearly 3 million patients have been treated in studies and in open use without causal relationship to a specific life-threatening organ toxicity. Seizure control superior to that observed in well-controlled trials has been reported at higher doses used in clinical practice and in studies. Therefore, gabapentin dosing must be optimized on an individual basis to achieve an adequate trial of the drug and obtain the best seizure control.

Gabapentin

Gabapentin (GBP) is a antiepileptic drug (AED) indicated as adjunct therapy for treatment of partial seizures, with and without secondary generalization, in patients 12 and older with epilepsy. GBP (1-(aminomethyl) cyclohexaneacetic acid) is structurally related to gamma-aminobutyric acid (GABA), which readily crosses the blood-brain barrier. Radiolabeled GBP binds throughout the central nervous system in anatomic areas important in treatment of seizures. Its precise mechanism of action is unknown. An open-label, dose-ranging study of doses up to 1,800 mg produced > or =50% seizure reductions [responder rate (RR)] in 29% of patients with partial seizures. Three double-blind, placebo-controlled, parallel add-on trials at doses of 300-1,800 mg have produced RR of up to 28%, with a placebo RR of 8-10%. An active controlled, parallel group comparison of 600 mg to 2,400 mg in monotherapy conversion design showed no significant difference among the 600 mg, 1,200 mg, and 2,400 mg groups compared to a placebo group. An inpatient, active-controlled comparison of 300 mg and 3,600 mg in a parallel-design monotherapy trial showed that time to exit from the study was significantly longer for the 3,600-mg group and the completion rate significantly higher (53% vs. 17%) for patients receiving 3,600 mg/day vs. 300 mg/day of GBP. Successful double-blind, placebo-controlled trials in refractory childhood partial seizures and benign childhood epilepsy with centrotemporal spikes have been recently concluded. Absence was not successfully treated in one small double-blind trial. Open-label reports emphasize adjustments of patients to higher doses than those indicated in the package labeling. An open-label trial of GBP therapy in patients with partial seizures (n = 2,216) produced progressively greater seizure freedom rates as patients were titrated from > or =900 mg daily to > or = 1,800 mg daily (15.1% vs. 33.4%), with a similar effect on RR (18.1% vs. 44.9%). An add-on, open-label study treating partial seizures (n = 141) reported an RR of 71%, with 46% seizure-free in the last 8 weeks of treatment and doses up to 2,400 mg daily. A comparison trial of three doses of GBP to 600 mg of carbamazepine showed similar retention rates for 1,800 mg of GBP and 600 mg of CBZ. Another study reported 48% of patients experiencing 50% reduction, nine of whom had doses greater than 2,400 mg. Treatment in children has reported a 34.4% RR in 32 children with refractory partial seizures. A French open-label adjunctive trial documented a 33.9% RR; 13.4% were seizure-free during the evaluation period. Adverse experiences most commonly noted included somnolence, dizziness, and ataxia. Weight gain was sometimes reported with higher doses of GBP, and pediatric reports cite prominent behavioral changes, including hyperactivity, irritability, and agitation. GBP appears best used at doses at and potentially above those suggested in its package labeling. Although efficacy occurs at lower levels, increased GBP doses are associated with additional efficacy. Reports suggest that initiation at 2,400 mg or 3,600 mg may not be associated with increased adverse experiences. Titration to 900 or 1,200 mg on the first day of GBP therapy appear to be well tolerated.

Drug, meal and formulation interactions influencing drug absorption after oral administration. Clinical implications

Drug-drug, drug-formulation and drug-meal interactions are of clinical concern for orally administered drugs that possess a narrow therapeutic index. This review presents the current status of information regarding interactions which may influence the gastrointestinal (GI) absorption of orally administered drugs. Absorption interactions have been classified on the basis of rate-limiting processes. These processes are put in the context of drug and formulation physicochemical properties and oral input influences on variable GI physiology. Interaction categorisation makes use of a biopharmaceutical classification system based on drug aqueous solubility and membrane permeability and their contributions towards absorption variability. Overlaying this classification it is important to be aware of the effect that the magnitudes of drug dosage and volume of fluid administration can have on interactions involving a solubility rate limits. GI regional differences in membrane permeability are fundamental to the rational development of extended release dosage forms as well as to predicting interaction effects on absorption from immediate release dosage forms. The effect of meals on the regional-dependent intestinal elimination of drugs and their involvement in drug absorption interactions is also discussed. Although the clinical significance of such interactions is certainly dependent on the narrowness of the drug therapeutic index, clinical aspects of absorption delays and therapeutic failures resulting from various interactions are also important.

Gabapentin absorption: effect of mixing with foods of varying macronutrient composition

OBJECTIVE

To compare the oral absorption profile of gabapentin following administration of the contents of opened capsules that were mixed with food vehicles of varied macronutrient (protein) composition.

DESIGN

An unblinded, randomized, single-dose, four-way crossover pharmacokinetic study in nine healthy adult men and women volunteers.

METHODS

Following an overnight fast, a single 600-mg dose of gabapentin (2 x 300-mg Neurontin capsules) was given either as an intact capsule swallowed with 120 mL of tap water (control, phase I), or after capsule contents were opened and mixed with; 4 oz. of applesauce (phase II), 120 mL of orange juice (phase III), or 4 oz. of fat-free chocolate pudding (phase IV). Subjects fasted for 4 hours following drug ingestion. Serial venous blood samples were obtained over 24 hours to determine gabapentin serum concentrations. Pharmacokinetic variables including AUC, maximum serum concentration (Cmax), and time to maximum serum concentration (tmax) were calculated by using standard noncompartmental methods. Subjects served as their own controls, and were randomly crossed over following a minimum 7-day washout period. Statistical analysis was performed by using ANOVA and Student's t-test where appropriate.

RESULTS

No statistically significant differences in any kinetic variable were found between any study arm. A trend was noted for a modest increase in both Cmax and AUC in phase IV (chocolate pudding) compared with control (+18.6% and +13.2%, respectively). In a comparison of protein (phase IV) versus nonprotein phases (phases I-III), gabapentin AUC was 26% greater (47.28+/-14.65 vs. 37.43+/-9.78 microg/mL x h; p = 0.03), and Cmax was 32% higher (4.72+/-1.04 vs. 3.56+/-0.92 microg/mL; p = 0.003).

CONCLUSIONS

Opening and mixing the contents of gabapentin capsules does not significantly impair drug absorption. This may be a viable administration option for patients who are unable to swallow intact capsules. Dietary macronutrient composition (i.e., protein) may favorably influence gabapentin oral absorption.

Oral gabapentin disposition in patients with epilepsy after a high-protein meal

PURPOSE

To study the interaction between gabapentin (GBP) and high-protein meals, 12 patients with epilepsy were administered this drug both while in a fasting state and after a high-protein meal.

METHODS

After having acquired their informed consent, the patients (suffering from partial complex seizures resistant to other anticonvulsants) were randomly assigned to 2 groups of 6 subjects. Each subject was treated in a fasting state with a single 400 (group A) or 800 (group B) mg GBP oral dose. After 24 h, the GBP dose regimen was repeated, but was given after a high-protein meal. Serum GBP concentrations were measured by LC-Mass at baseline and 0.5, 1, 2, 3, 5, 7, 9, 12, and 24 h. Saliva GBP concentrations were determined at baseline and 2, 4.8, and 12 h. GBP urinary excretion was determined at 0-4, 4-8, and 8-12 h intervals. The following kinetic parameters were calculated: area under the concentration time curve from zero time to 24 h after the dose, AUC 0-24 h; maximal serum concentration, Cmax; time to the maximal serum concentration, Tmax; absorption rate constant, ka; elimination rate constant, beta; elimination half-time, t1/2beta. Student's t test for paired data, with significance assigned at P < 0.05, was used.

RESULTS

No statistically significant differences were seen in GBP serum or saliva concentrations or in its urinary excretion (both in A or B group) between fasting and after the high-protein meal.

CONCLUSIONS

High-protein meals do not seem to interfere with oral disposition of GBP.

Contrasting nutrient effects on the plasma levels of an amino acid-like antiepileptic agent from jejunal administration in dogs

The absorption of gabapentin was investigated by monitoring drug plasma levels as a function of time following midjejunal administration in mongrel dogs. From previous work, dose-dependent absorption had been postulated to be a consequence of carrier-mediated transport and a paracellular pathway had been postulated to contribute to the passive absorption component in mammalian small intestine. The potential for amino acid inhibition of the carrier-mediated absorption component was investigated by drug coinfusion with leucine and phenylalanine. The potential for monosaccharide-enhanced increases in drug absorption was studied by drug coinfusion with D-glucose and 3-O-methylglucose. While lower drug plasma levels were observed with amino acid coinfusion versus controls in each of the dogs studied, mean area under the plasma level time curves (AUC) were not statistically significantly different (p < or = 0.07). Monosaccharide coinfusion significantly increased gabapentin AUC over control studies (p < or = 0.014) and over coinfusion with L-system amino acids (p < or = 0.0025). Implications for the mechanisms of intestinal absorption of this amino acid-like antiepileptic drug in this canine model are discussed.

Current developments in neurology, Part I: Advances in the pharmacotherapy of headache, epilepsy, and multiple sclerosis

When caring for patients with disorders of the central nervous system such as migraine headaches, epilepsy, or MS, clinicians are faced with increasingly complex pharmacotherapeutic options. Pharmacotherapeutic strategies directed toward prevention, reversal, or cure of these diseases are hampered by an incomplete understanding of the underlying pathophysiology. In this decade of the brain, basic science research combined with difficult but necessary clinical trials may answer some seemingly overwhelming questions for these devastating illnesses.