Clinical utility of topiramate extended-release capsules (USL255): Bioequivalence of USL255 sprinkled and intact capsule in healthy adults and an in vitro evaluation of sprinkle delivery via enteral feeding tubes

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.

A Clinician's Guide to Oral Extended-Release Drug Delivery Systems in Epilepsy

Epilepsy is one of the most common chronic neurologic disorders that affects individuals of all ages. It is primarily managed with antiepileptic drugs (AEDs), with the goal of maintaining complete seizure control combined with minimal or no adverse effects. Oral administration is the mainstay of AED delivery for patients with chronic epilepsy and consists essentially of immediate-release (IR) and modified-release (delayed-release and extended-release [ER]) dosage formulations. Extended-release formulations (hydrophilic or hydrophobic matrix systems, reservoir systems, and osmotic-release systems) release a drug in a controlled manner during an extended period of time following administration. Extended-release formulations have many advantages compared with IR formulations, including simplification of dosing regimens, reduction in pill burden, and reduction in the peak-to-trough fluctuations in serum drug concentration that may be associated with a decreased risk of adverse effects and of seizures. These advantages have the potential to increase adherence to antiepileptic therapy, improve the quality of life of patients, and reduce health care costs. This article, which is intended as a practical guide for clinicians, reviews the properties of the different ER AED formulations currently available and discusses the advantages of ER over IR formulations. Subsequently, an explanation of the technologic basis of the different oral ER formulations, the critical attributes that differentiate ER products, and their individual strengths and weaknesses is provided. Specific recommendations to practitioners on treating patients with ER formulations are included.

Going down the tubes! Impact on seizure control of antiepileptic medication given via percutaneous feeding tubes

BACKGROUND

Long-term feeding by percutaneous endoscopic gastrostomy tube (PEG) is uncommon but can present significant issues when both nutrition and medication have to be fed down the same tube. This is especially important in people with epilepsy where the dose and bioavailability of antiepileptic drugs are critical to maintain adequate seizure control. This group with long-term PEG tubes is particularly vulnerable and dependent on their carers to provide high standard of care. Indeed, approximately half of the people with long-term feeding tubes suffer from severe intellectual disability which requires careful coordination of all members of the multidisciplinary team. It is all the more important when consideration is given that around 50% of people with severe ID have seizures, mostly treatment resistant.

METHOD

A detailed literature review was conducted with the focus on the numerous factors that can affect medication delivery and absorption with the potential to destabilize seizure control in people with PEG. Issues concerning the site of drug absorption, excipients and dilution, interaction between antiepileptic drugs and the nutritional feed, bioavailability, and problems with the PEG tube are considered.

RESULTS

There is limited research in this area and the studies are often based on small numbers, healthy volunteers or in vitro findings.

CONCLUSION

In the absence of sound research data, seizure control in each patient with a PEG needs to be considered on an individual basis. Establishing a baseline by measuring the serum levels prior to the tube insertion may be helpful, followed by checking the levels after PEG insertion.

The application of half-life in clinical decision making: Comparison of the pharmacokinetics of extended-release topiramate (USL255) and immediate-release topiramate

OBJECTIVE

For extended-release drugs with multi-compartment kinetics, such as topiramate, effective half-life (t_1/2eff) may be a more clinically relevant parameter than elimination half-life (t_1/2z). Using topiramate as a real-life example, the objective was to compare these half-life values for immediate- and extended-release topiramate (TPM-IR and USL255, respectively) to understand how drug pharmacokinetics may impact drug dosing recommendations.

METHODS

The t_1/2z and t_1/2eff for USL255 and TPM-IR were compared using data from a phase I study (N=36) of 200mg USL255 administered once daily (QD) or TPM-IR twice daily (BID); effect of sampling duration on t_1/2z was investigated. To further explore the relationship between half-life and dosing, steady-state PK was simulated for USL255 and TPM-IR.

RESULTS

As previously reported, mean t_1/2z was similar between USL255 (80.2h) and TPM-IR (82.8h); TPM-IR t_1/2z was ∼4 times longer than reported in the Topamax label (21h). In contrast, USL255 displayed a 1.5 fold longer t_1/2eff (55.7 vs 37.1h for TPM-IR). When t_1/2z was calculated from 48 to 336h, values ranged from 28.8 to 82.8h. Simulated steady-state PK profiles of USL255 QD exhibited reduced plasma fluctuations during a dosing interval vs TPM-IR QD or BID.

SIGNIFICANCE

As expected for the same moiety, t_1/2z of USL255 and TPM-IR were similar; however, the longer t_1/2eff for USL255 better approximates differences in recommend dosing (QD USL255 vs BID TPM-IR). Further, sampling duration impacted t_1/2z, diminishing its predictive value for determining dose regimens; sampling-time differences may also explain t_1/2z discrepancy between TPM-IR here versus Topamax label. As expected, steady-state simulations confirm that although TPM-IR has a long t_1/2z, taking TPM-IR QD would lead to large plasma fluctuations. These data demonstrate that t_1/2z may be less clinically meaningful than t_1/2eff, and using t_1/2z for some drugs may lead to erroneous conclusions regarding dosing regimens.

Randomized Pharmacokinetic Crossover Study Comparing 2 Curcumin Preparations in Plasma and Rectal Tissue of Healthy Human Volunteers

Curcumin is poorly absorbed, which is interest in new preparations. However, little is known about variations in its pharmacokinetics and tissue bioavailability between formulations. In this randomized, crossover study we evaluated the relationship between steady-state plasma and rectal tissue curcuminoid concentrations using standard and phosphatidylcholine curcumin extracts. There was no difference in the geometric mean plasma AUCs when adjusted for the 10-fold difference in curcumin dose between the 2 formulations. Phosphatidylcholine curcumin extract yielded only 20% to 30% plasma demethoxycurcumin and bisdemethoxycurcumin conjugates compared to standard extract, yet yielded 20-fold greater hexahydrocurcumin. When adjusting for curcumin dose, tissue curcumin concentrations were 5-fold greater for the phosphatidylcholine extract. Improvements in curcuminoid absorption due to phosphatidylcholine are not uniform across the curcuminoids. Furthermore, curcuminoid exposures in the intestinal mucosa are most likely due to luminal exposure rather than to plasma disposition. Finally, once-daily dosing is sufficient to maintain detectable curcuminoids at steady state in both plasma and rectal tissues.

Topiramate Extended Release: A Review in Epilepsy

Once-daily oral topiramate extended release (USL255; hereafter referred to as topiramate XR) [QUDEXY(®) XR] is approved in the USA for use as initial monotherapy and adjunctive therapy in patients aged ≥2 years with partial-onset seizures (POS) or primary generalized tonic-clonic seizures and as adjunctive therapy in patients aged ≥2 years with seizures associated with Lennox-Gastaut syndrome. Compared with twice-daily topiramate immediate release at the same total daily dose, topiramate XR provided bioequivalent exposure, an extended absorption rate (permitting convenient once-daily dosing) and more constant therapeutic plasma concentrations (potentially minimizing topiramate-associated adverse events). Switching between the two formulations did not affect the maintenance of topiramate concentrations. Moreover, the contents of a topiramate XR capsule may be sprinkled on to soft food for patients who have difficulty swallowing. In a multinational phase III study in adults with refractory POS, adjunctive topiramate XR was associated with significantly greater improvements from baseline in weekly median seizure frequency and the proportion of patients achieving a ≥50 % reduction in seizure frequency compared with placebo. These benefits were sustained during a 55-week open-label extension study. Adjunctive topiramate XR was generally well tolerated in these studies, with the majority of treatment-emergent adverse events being mild or moderate in intensity. In conclusion, current evidence suggests once-daily topiramate XR extends the treatment options currently available for patients aged ≥2 years with epilepsy, with its dosing regimen potentially delivering tolerability and adherence advantages over AEDs that require more frequent administration.