Valproate Intoxication in a Patient With Blood Valproate Levels Within Therapeutic Range

A 5-Year Study of Antiseizure Medications (ASMs) Monitoring in Patients with Neuropsychiatric Disorders in an Italian Clinical Center

Despite receiving appropriate antiseizure medications (ASMs), a relevant percentage of neuropsychiatric patients do not benefit from this approach, and one reason is subtherapeutic ASMs plasma concentration (C(p)) due to improper drug adherence, interindividual pharmacokinetic differences, or metabolic interactions among different drugs. For these reasons, therapeutic drug monitoring (TDM) by measuring ASMs C(p) is an effective tool that improves pharmacological therapies in clinical practice. Based on these premises, in the present real-world study, we analyzed the C(p) of the most used ASMs in diverse medical conditions, which were assayed during the years 2018-2022 at the University Hospital of Pisa, including about 24,000 samples. This population was largely heterogeneous, and our database did not contain clinical information about the patients. The most used ASMs were Valproate (VPA: 54.5%) and Levetiracetam (LEV: 18.6%), followed by Oxcarbazepine (OxCBZ: 8.3%) and Carbamazepine (CBZ: 7.2%), whereas the associations LEV/VPA, Ethosuximide (ESM)/VPA, and CBZ/VPA were the most frequently proposed. In about 2/3 of assays, ASMs C(p) was in range, except for VPA, which was underdosed in almost half of the samples. Importantly, toxic levels of ASMs C(p) were found very rarely. For VPA, there was a decrease of mean C(p) across ages, from adolescents to older patients, while the C(p) of LEV, CBZ, OxCBZ, and Topiramate (TPM) showed a slight tendency to increase. When we compared females and males, we found that for VPA, the average age was higher for females, whereas women taking Lamotrigine (LTG) and OxCBZ were younger than men. Then, comparing ASMs used in neurologic and psychiatric disorders, based on the request form, it emerged that the mean C(p) of CBZ, OxCBZ, and LTG on samples collected in the Psychiatric Unit was lower compared to the Neurology and Child Neuropsychiatry Units. Finally, the ASMs subjected to multiple dosing starting from an initial subtherapeutic C(p) increased their level at different time points within a year, reaching the reference range for some of them. In conclusion, the present study suggests that TDM is widely applied to monitor ASMs C(p), finding many of them within the reference range, as a demonstration of its utility in clinical practice.

A Retrospective Case Series of Concomitant Carbapenem and Valproic Acid Use: Are Best Practice Advisories Working?

Background: A Best Practice Advisory (BPA) warns clinicians of an interaction between carbapenems and valproic acid (VPA) that can cause significant declines in VPA levels leading to serious consequences for patients treated for seizure disorder and unknown implications for alternative indications. Objective: The goal of this study was to assess BPA efficacy in avoiding concomitant VPA/carbapenems, and to characterize use of these agents, clinical implications, and potential alternative therapeutic options. Methods: Retrospective chart review was performed on all patients over the course of 1 year who were concomitantly prescribed a carbapenem and VPA at Hartford Hospital, Hartford, CT. Data collected included: level of care, duration of concomitant therapy, indications, VPA levels during or surrounding overlap, documentation of the interaction, and therapeutic implications. Results: Carbapenems and VPA were administered to 591 and 625 patients, respectively; the BPA fired 126 times in 24 patients, and 15 patients were initiated on these agents concomitantly. Eight (53%) patients received VPA for seizures. The remaining seven (47%) received VPA for alternative indications. Eight of nine VPA levels were sub-therapeutic during carbapenem therapy and polypharmacy was administered in all patients receiving VPA for non-convulsive indications. Conclusion: Co-prescribing of these drugs was rare; however, the BPA was ineffective in 63% of instances. Reductions in VPA efficacy for any indication should be expected with concomitant carbapenem administration. Antibiotics other than carbapenems should be considered when coverage of multidrug resistant Gram-negative pathogens is required in patients whose VPA treatment cannot be interrupted or switched to a therapeutic alternative.