Epileptic seizures caused by low valproic acid levels from an interaction with meropenem

Effect of a Declined Plasma Concentration of Valproic Acid Induced by Meropenem on the Antiepileptic Efficacy of Valproic Acid

OBJECTIVE

This study aimed to indicate whether a declined plasma concentration of valproic acid (VPA) induced by co-administration of meropenem (MEPM) could affect the antiepileptic efficacy of VPA.

METHODS

We retrospectively reviewed data of hospitalized patients who were diagnosed with status epilepticus or epilepsy between 2010 and 2019. Patients co-administered VPA and MEPM during hospitalization were screened and assigned to the exposure group, while those co-administerd VPA and other broad-spectrum antibiotics were allocated to the control group.

RESULTS

The exposure group and control group included 50 and 11 patients, respectively. With a similar dosage of VPA, the plasma concentration of VPA significantly decreased during co-administration (24.6 ± 4.3 μg/mL) compared with that before co-administration (88.8 ± 13.6 μg/mL, p < 0.0001), and it was partly recovered with the termination of co-administration (39.8 ± 13.2 μg/mL, p = 0.163) in the exposure group. The inverse probability of treatment weighting estimated the treatment efficacy via changes in seizure frequency, seizure duration, and concomitant use of antiepileptic drugs, which were not significantly different between the exposure and control groups. In the exposure group, there was no significant differences in seizure frequency between the periods of before-during and before-after (p = 0.074 and 0.153, respectively). Seizure duration during VPA-MEPM co-administration was not significantly different from that before co-administration (p = 0.291).

CONCLUSIONS

In this study, the reduced plasma concentration of VPA induced by the co-administration of MEPM did not affect the antiepileptic efficacy of VPA. This conclusion should be interpreted with caution, and more research is warranted.

TRIAL REGISTRATION

Chinese Clinical Trial Registry: ChiCTR2000034567. Registered on 10 July 2020.

Clinical impact of carbapenems in critically ill patients with valproic acid therapy: A propensity-matched analysis

Background

Valproic acid (VPA) is one of the most widely used broad-spectrum antiepileptic drugs, and carbapenems (CBPs) remain the drug of choice for severe infection caused by multidrug-resistant bacteria in critically ill patients. The interaction between VPA and CBPs can lead to a rapid depletion of serum VPA level. This may then cause status epilepticus (SE), which is associated with significant mortality. However, the prognostic impact of drug interactions in critically ill patients remains an under-investigated issue.

Objective

The aim of this study was to compare the prognosis of critically ill patients treated with VPA and concomitant CBPs or other broad-spectrum antibiotics.

Methods

Adult patients admitted to a medical center intensive care unit between January 2007 and December 2017 who concomitantly received VPA and antibiotics were enrolled. The risk of reduced VPA serum concentration, seizures and SE, mortality rate, length of hospital stay (LOS), and healthcare expenditure after concomitant administration were analyzed after propensity score matching.

Results

A total of 1,277 patients were included in the study, of whom 264 (20.7%) concomitantly received VPA and CBPs. After matching, the patients who received CBPs were associated with lower VPA serum concentration (15.8 vs. 60.8 mg/L; p &lt; 0.0001), a higher risk of seizures (51.2 vs. 32.4%; adjusted odds ratio [aOR], 2.19; 95% CI, 1.48–3.24; p &lt; 0.0001), higher risk of SE (13.6 vs. 4.7%; aOR, 3.20; 95% CI, 1.51–6.74; p = 0.0014), higher in-hospital mortality rate (33.8 vs. 24.9%; aOR, 1.57; 95% CI, 1.03–2.20; p = 0.036), longer LOS after concomitant therapy (41 vs. 30 days; p &lt; 0.001), and increased healthcare expenditure (US$20,970 vs. US$12,848; p &lt; 0.0001) than those who received other broad-spectrum antibiotics.

Conclusion

The administration of CBPs in epileptic patients under VPA therapy was associated with lower VAP serum concentration, a higher risk of seizures and SE, mortality, longer LOS, and significant utilization of healthcare resources. Healthcare professionals should pay attention to the concomitant use of VPA and CBPs when treating patients with epilepsy. Further studies are warranted to investigate the reason for the poor outcomes and whether avoiding the co-administration of VPA and CBP can improve the outcomes of epileptic patients.

Effect of drug interactions between carbapenems and valproate on serum valproate concentration: a systematic review and meta-analysis

Background: Concurrent use of valproate and carbapenem antibiotics may decrease serum valproate concentration (SVC). This study evaluated the effects of carbapenem-valproate drug interactions. Research design and methods: We screened PubMed, EMBASE, and Cochrane databases for eligible prospective or retrospective studies that evaluated the effect of concurrent use of carbapenem and valproate compared with valproate alone on SVC. Primary outcomes were the change in SVC from before the addition of the carbapenem to the SVC during the use of carbapenems and after carbapenem discontinuation, and seizure-related outcomes. Secondary outcomes were the influence of valproate or carbapenem dose on SVC and Drug Interaction Probability Scale scores. Results: Twelve studies (633 patients) were included. Compared with valproate alone, combination treatment with carbapenem substantially decreased mean SVC (mean difference, -43.98 mg/L; 95% confidence interval, -48.18 to -39.78). The onset of SVC decreases was within 1-3 days following carbapenem initiation. Seizure frequency increased by 26.3% during combination treatment. No difference was found in mean SVC between the different doses of valproate or carbapenem during combination treatment. Mean SVC increased to similar pre-carbapenem level within 1 to 2 weeks after carbapenem discontinuation. Conclusions: The drug interaction between valproate and carbapenem causes substantial SVC decreases, even to subtherapeutic levels, which may increase the risk of seizures.

Neurological Adverse Effects Attributable to β-Lactam Antibiotics: A Literature Review

β-lactam antibiotics are commonly prescribed antibiotic drugs. To describe the clinical characteristics, risk markers and outcomes of β-lactam antibiotic-induced neurological adverse effects, we performed a general literature review to provide updated clinical data about the most used β-lactam antibiotics. For selected drugs in each class available in France (ticarcillin, piperacillin, temocillin, ceftazidime, cefepime, cefpirome, ceftaroline, ceftobiprole, ceftolozane, ertapenem and aztreonam), a systematic literature review was performed up to April 2016 via an electronic search on PubMed. Articles that reported original data, written in French, Spanish, Portuguese or English, with available individual data for patients with neurological symptoms (such as seizure, disturbed vigilance, confusional state, myoclonia, localising signs, and/or hallucinations) after the introduction of a β-lactam antibiotic were included. The neurological adverse effects of piperacillin and ertapenem are often described as seizures and hallucinations (>50 and 25% of cases, respectively). Antibiotic treatment is often adapted to renal function (>70%), and underlying brain abnormalities are seen in one in four to one in three cases. By contrast, the neurological adverse drug reactions of ceftazidime and cefepime often include abnormal movements but few hallucinations and seizures. These reactions are associated with renal insufficiency (>80%) and doses are rarely adapted to renal function. Otherwise, it appears that monobactams do not have serious neurological adverse drug reactions and that valproic acid and carbapenem combinations should be avoided. The onset of disturbed vigilance, myoclonus, and/or seizure in a patient taking β-lactam antibiotics, especially if associated with renal insufficiency or underlying brain abnormalities, should lead physicians to suspect adverse drug reactions and to consider changes in antibacterial therapy.

The Effect of Different Carbapenem Antibiotics (Ertapenem, Imipenem/Cilastatin, and Meropenem) on Serum Valproic Acid Concentrations

BACKGROUND

Carbapenem antibiotics (CBPMs) may significantly reduce the serum concentration of valproic acid (VPA), but the extent of this effect among various CBPMs is unknown. This study compared the extent and onset of the interactions among ertapenem, imipenem/cilastatin, and meropenem.

METHODS

A 5-year retrospective study was performed. Hospitalized patients over 18 years old who received VPA and a CBPM concurrently were enrolled via the pharmacy computer system. Patients who lacked VPA serum concentration measurements before or during CBPMs' use, had concurrent medication(s) that might interfere with VPA metabolism, or had a history of liver cirrhosis were excluded. Total VPA serum concentrations before and during CBPMs' use and after its discontinuation were recorded, and differences among various CBPMs were analyzed.

RESULTS

Fifty-two patients were included in this analysis. Irrespective of the route of administration, VPA serum concentrations were subtherapeutic in 90% of the subjects during CBPMs' use. There was a significant decrease (P < 0.001) in VPA serum concentrations during the use of CBPMs: 72% ± 17%, 42% ± 22%, and 67% ± 19% in the ertapenem (N = 9), imipenem/cilastatin (N = 17), and meropenem (N = 26) groups, respectively. The effect of ertapenem and meropenem on VPA was significantly more expressed than that of imipenem/cilastatin (P < 0.005). The onset of this drug interaction occurred within 24 hours of CBPMs' administration, and VPA serum concentrations returned to 90% of baseline within 7 days of CBPMs' discontinuation along with a 20% increase in VPA dose. Increasing VPA dose during the use of ertapenem or meropenem did not result in elevating VPA serum concentrations to therapeutic levels during the combined therapy period.

CONCLUSIONS

CBPMs reduced VPA serum concentration within 24 hours of administration by approximately 60%. Ertapenem and meropenem had a greater effect on VPA serum concentration than imipenem/cilastatin. Because of the dramatic reduction of VPA serum concentration during CBPMs' use, concomitant use of VPA and CBPMs should be avoided.

Meropenem-induced Valproic Acid Elimination: A Case Report of Clinically Relevant Drug Interaction

We present two case reports of drug interaction between valproic acid and meropenem. In comparison with expected population-kinetic based serum levels, we observed 90.8 and 93.5% decrease in valproic acid serum levels during concomitant administration with meropenem. If carbapenems need to be administered to valproic acid treated patient, other anticonvulsant addition seems to be the appropriate as most probably the valproic acid dose escalation would not be sufficient to achieve therapeutic serum concentration.

Carbapenems and valproate: A consumptive relationship

A clinical case series is presented to characterize the interaction between carbapenem antibiotics and sodium valproate. Six illustrative cases are presented in which carbapenem therapy led to the rapid depletion of serum valproate levels, and one case is presented to demonstrate the difficulty of initiating valproate therapy in patients already on meropenem. The speed of valproate depletion after the initiation of carbapenem therapy, the effect of treatment duration, clinical manifestations, delay in valproate level normalization after carbapenem therapy, the efficacy of supplemental valproate doses, and the usefulness of valproate dose escalation are evaluated. Five out of the 7 patients became acutely symptomatic owing to their subtherapeutic valproate levels. The presented cases also highlight the relatively slow normalization of valproate levels after discontinuation of the antibiotic therapy. Our cases suggest that the interaction is not absorption‐mediated because all of our patients received intravenous valproate. We observed that the introduction of alternative antiepileptic drugs (AEDs) may be preferable to valproate dose escalation, which is ineffective in the presence of concomitant meropenem therapy. The characterization and recognition of this interaction have implications for the management of a particularly vulnerable patient cohort.

Influence of acylpeptide hydrolase polymorphisms on valproic acid level in Chinese epilepsy patients

BACKGROUND

Concomitant use of meropenem (MEPM) can dramatically decrease valproic acid (VPA) plasma level. It is accepted that inhibition in acylpeptide hydrolase (APEH) activity by MEPM coadministration was the trigger of this drug-drug interaction.

AIM

To investigate the influence of APEH genetic polymorphisms on VPA plasma concentration in Chinese epilepsy patients.

PATIENTS & METHODS

Urinary VPA-d6 β-D-glucuronide concentration was determined in 19 patients with VPA treatment alone (n = 10) or concomitant use with MEPM (n = 9). A retrospective study was performed on 149 epilepsy patients to investigate the influence of APEH polymorphisms rs3816877 and rs1131095 on adjusted plasma VPA concentration (C_VPA) at steady-state.

RESULTS

Urinary VPA-d6 β-D-glucuronide (VPA-G) concentration was increased significantly in patients with MEPM coadministration. The C_VPA of patients carrying the APEH rs3816877 C/C genotype was significantly higher than that of C/T carriers, and the difference was still obvious when stratified by UGT2B7 rs7668258 polymorphism.

CONCLUSION

APEH polymorphism has significant influence on VPA pharmacokinetics in Chinese population.

Seizures as adverse events of antibiotic drugs: A systematic review

OBJECTIVE

Antibiotic drugs are commonly associated with seizures. Tailoring antibiotics to the individual risk for seizures is challenged as avoidance of certain antibiotic classes may no longer be possible due to the emergence of resistant bacteria. We performed a systematic review regarding the current evidence for seizures associated with all antibiotic classes, their underlying mechanisms, and predisposing factors.

METHODS

The medical search engine PubMed was systematically screened to identify articles in English published between 1960 and 2013. All study designs were considered and evidence was assessed.

RESULTS

We included 143 articles involving 25,712 patients and 25 different antibiotics. Evidence for antibiotic-related symptomatic seizures is low to very low, mainly deriving from studies regarding β-lactams, especially unsubstituted penicillins and fourth-generation cephalosporins, as well as carbapenems, mainly imipenem, all administered in high doses or in patients with renal dysfunction, brain lesions, or known epilepsy. Evidence regarding symptomatic seizures from fluoroquinolones only relies on case reports and case series with most reports for ciprofloxacin in patients with renal dysfunction, mental disorders, prior seizures, or coadministered theophylline.

CONCLUSIONS

Evidence for an association between antibiotic drugs and symptomatic seizures is low to very low (evidence Class III-IV). Despite this, numerous reports point to an increased risk for symptomatic seizures especially of unsubstituted penicillins, fourth-generation cephalosporins, imipenem, and ciprofloxacin in combination with renal dysfunction, brain lesions, and epilepsy. During administration of such antibiotics in patients with particular predispositions, close monitoring of serum levels is advocated. As most seizures associated with cephalosporins are nonconvulsive, continuous EEG should be considered in patients with altered levels of consciousness.

Pharmacological interaction between valproic acid and carbapenem: what about levels in pediatrics?

Valproic acid (VPA) is the most commonly used antiepileptic drug in pediatric patients, but its major drawback is its multiple pharmacological interactions.

OBJECTIVE

To study children who had been simultaneously treated with carbapenems and valproic acid, considering drug levels, pharmacological interactions and clinical follow-up.

MATERIAL AND METHODS

Retrospective study of children who simultaneously received treatment with VPA and carbapenems between January 2003 and December 2011. Demographic variables, indication of treatment, dose, VPA plasma levels, interactions, clinical manifestations and medical management were analyzed.

RESULTS

28 children with concomitant treatment with both drugs were included in the study. 64.3% were males. 78.6% of the interactions were observed in the Intensive Care Unit. 60.7% of children had been previously treated VPA and its major indication were generalized seizures. Basal plasma levels of VPA were recorded in 53% and at 24 h after admittance in 60%. "40% of basal VPA levels were below therapeutic range prior to the administration of carbapenem. After the introduction of carbapenem 88% of level determinations were below therapeutic range". 54.5% of the patients that were chronically receiving VPA and had good control of epilepsy before admission had seizures during the coadministration. One patient that was on VPA before admission but with bad control of epilepsy worsened, and one patient that acutely received VPA did not achieve seizure freedom. In these cases it was necessary to either increase VPA dose or change to a different antiepileptic drug.

CONCLUSIONS

Little is known about the mechanism of pharmacologic interactions between carbapenems and VPA, but it leads to a reduction in plasma levels that may cause a loss of seizure control, so simultaneous use of both drugs should be avoided when possible. If not, VPA levels should be monitored.

[Effect of modal computer-based alerts on the prescription of valproic acid and meropenem]

OBJECTIVE

To analyze the effect of modal computer-based alerts on the concomitant prescription of valproic acid (VPA) and meropenem.

MATERIAL AND METHOD

Analytical intervention study conducted in a tertiary hospital for eleven months. Hospitalized patients with a diagnosis of epilepsy and treated with VPA and meropenem in concomitant therapy were included. In the computerized prescription order entry software an automatic non-modal alert was reconverted to a modal one. This was triggered when the physician introduced VPA and meropenem together in the same prescription. To measure the effect of this alert the prescription habits were compared with a previous period in which the alert was not modal.

RESULTS

Modal computer-based alert modified the prescription habit by reducing the number of patients with concomitant treatment from 13 to 4 (P=.046). However, it was notable that the number of requests for VPA serum levels decreased, and the average number of concomitant days of treatment rose from 4.7 to 8.75 in those patients in which none of the drugs was suspended.

CONCLUSIONS

The implementation of modal computer-based alerts reduces patient exposure to concomitant treatment with meropenem and VPA.

The multidrug transporter P-glycoprotein in pharmacoresistance to antiepileptic drugs

This review provides an overview of the knowledge on P-glycoprotein (P-gp) and its role as a membrane transporter in drug resistance in epilepsy and drug interactions. Overexpression of P-gp, encoded by the ABCB1 gene, is involved in resistance to antiepileptic drugs (AEDs), limits gastrointestinal absorption and brain access of AEDs. Although several association studies on ABCB1 gene with drug disposition and disease susceptibility are completed to date, the data remain unclear and incongruous. Although the literature describes other multidrug resistance transporters, P-gp is the main extensively studied drug efflux transporter in epilepsy.

Cerebral expression of drug transporters in epilepsy

Over-expression of drug efflux transporters at the level of the blood-brain barrier (BBB) has been proposed as a mechanism responsible for multidrug resistance. Drug transporters in epileptogenic tissue are not only expressed in endothelial cells at the BBB, but also in other brain parenchymal cells, such as astrocytes, microglia and neurons, suggesting a complex cell type-specific regulation under pathological conditions associated with epilepsy. This review focuses on the cerebral expression patterns of several classes of well-known membrane drug transporters such as P-glycoprotein (Pgp), and multidrug resistance-associated proteins (MRPs) in the epileptogenic brain. Both experimental and clinical evidence of epilepsy-associated cerebral drug transporter regulation and the possible mechanisms underlying drug transporter regulation are discussed. Knowledge of the cerebral expression patterns of drug transporters in normal and epileptogenic brain will provide relevant information to guide strategies attempting to overcome drug resistance by targeting specific transporters.

Pharmacokinetic drug interactions of antimicrobial drugs: a systematic review on oxazolidinones, rifamycines, macrolides, fluoroquinolones, and Beta-lactams

Like any other drug, antimicrobial drugs are prone to pharmacokinetic drug interactions. These drug interactions are a major concern in clinical practice as they may have an effect on efficacy and toxicity. This article provides an overview of all published pharmacokinetic studies on drug interactions of the commonly prescribed antimicrobial drugs oxazolidinones, rifamycines, macrolides, fluoroquinolones, and beta-lactams, focusing on systematic research. We describe drug-food and drug-drug interaction studies in humans, affecting antimicrobial drugs as well as concomitantly administered drugs. Since knowledge about mechanisms is of paramount importance for adequate management of drug interactions, the most plausible underlying mechanism of the drug interaction is provided when available. This overview can be used in daily practice to support the management of pharmacokinetic drug interactions of antimicrobial drugs.

Levetiracetam compared to valproic acid: plasma concentration levels, adverse effects and interactions in aneurysmal subarachnoid hemorrhage

OBJECTIVE

Both valproic acid and levetiracetam are anti-epileptic drugs, often used either alone or in combination. The present study compares valproate (VPA) with levetiracetam (LEV) as an intravenous (i.v.) anticonvulsant treatment in intensive care patients suffering from aneurysmal subarachnoid hemorrhage (aSAH) with a high risk of seizures.

PATIENTS AND METHODS

A prospective, single-center patient registry of 35 intensive care unit (ICU) patients with onset seizure and/or high risk of seizures underwent an anticonvulsive, first-line single treatment regimen either with VPA or LEV. Plasma concentrations (pc), interactions between drugs in the ICU context, adverse effects and seizure occurrences were observed and recorded.

RESULTS

A significant decrease in the pc in patients treated with LEV was observed after changing from intravenous (160±51μmol/l) to enteral liquid application (113±58μmol/l), corresponding to a 70.3% bioavailability for enteral liquid applications. The pc in VPA patients decreased significantly, from (491±138μmol/l) to (141±50μmol/l), after adding meropenem to the therapy (p<0.05). Three epileptic seizures occurred during anticonvulsive therapy in the LEV group, and two in the VPA group, including one non-convulsive status epilepticus (NCSE).

CONCLUSION

Though this finding needs further verification, the enteral liquid application of levetiracetam seems to be associated with lower bioavailability than the common oral application of levetiracetam. The use of the antibiotic drug meropenem together with valproic acid leads to lower pc levels in patients treated with of valproic acid. For clinical practice, this indicates the need to monitor the levels of valproic acid in combination with meropenem.

[Analysis of the valproic acid-meropenem interaction in hospitalised patients]

INTRODUCTION

Published data demonstrate a serious interaction between valproic acid and meropenem. However, recommendations about the management of concomitant treatment are contradictory; some experts recommend closer monitoring of valproic acid serum concentrations and others recommend avoiding concurrent therapy. The purpose of this study is to critically analyse the interaction and to evaluate the impact of pharmaceutical intervention in the use of these drugs in hospitalised patients.

MATERIAL AND METHODS

Study of the concomitant prescription of valproic acid and meropenem in a general hospital of 1,080 beds divided in to two periods; the first period was retrospective and observational and it was followed by a prospective period involving pharmaceutical intervention. The prescription habits between both periods were compared.

RESULTS

A total of 26 patients received concurrent treatment with valproic acid and meropenem (13 per period) and none of them maintained therapeutic serum levels of the antiepileptic drug. Pharmaceutical intervention modified prescription habits, reducing by half the number of days of concomitant treatment, changing the antibiotherapy and/or monitoring serum concentrations more often.

CONCLUSIONS

The interaction between valproic acid and meropenem is serious, especially because of the dramatic decrease in the antiepileptic serum concentrations. The concomitant use of both drugs should be avoided, replacing the antibiotherapy empirically, or according to the resistance profiles of the microorganism and maintaining the same the anti-epileptic treatment.

Drug interaction between carbapenems and extended-release divalproex sodium in a patient with schizoaffective disorder

BACKGROUND

Clinicians prescribing divalproex sodium (DVX) are well aware of its potential to cause a drug-drug interaction. One specific interaction occurs between the carbapenem antibiotics and DVX resulting in decreased valproic acid (VPA) levels immediately following the initiation of this antibiotic class.

OBJECTIVE/METHOD

We describe a case of a 46 year-old Caucasian male who had an undetectable VPA level following treatment with carbapenems.

RESULTS

On admission the patient's VPA level was 115 μg/ml; however, a routine VPA level on day 19 of his hospitalization returned a value of 16 μg/ml. At this point, he had received a total of 15 days of carbapenem antibiotics for treatment of lower leg cellulitis. His DVX dose was increased to a maximum of 6g daily, twice his home dose, but it did not produce a therapeutic VPA concentration. The patient was lost to follow-up before an outpatient VPA level was drawn.

CONCLUSION

Our case report is the first to document this drug-drug interaction in a patient diagnosed with schizoaffective disorder, bipolar type.

[Therapeutic drug monitoring of valproate]

Valproic acid is an anticonvulsant drug available in France since 1967. It is a broad spectrum molecule indicated in various forms of epilepsy of the adult and the child, but it is also prescribed in the treatment of different other pathologies of nervous system. The divalproate sodium is indicated in the treatment of bipolar disorders. The valproic acid is marketed under various pharmaceutical forms, with different corresponding tmax values. But, whatever the administered preparation, the circulating active molecule is the ion valproate. Elimination half-life is from 11 to 20 h. Metabolization of valproate is important and represents its main route of elimination. Valpromide is comparable to a prodrug which metabolizes in valproate. The inter and intraindividual variability of the plasma concentrations are important. Several studies show a concentration-effect relationship, but two interventional trials ended in the lack of interest of the Therapeutic Drug Monitoring (TDM), although it is of current practice. However, numerous drug interactions may modify the plasma concentrations of valproate. The therapeutic range is from 50 to 100 mg/L (346-693 micromol/L). The level of proof of the interest of the TDM for this molecule was estimated in: recommended.

Identification of valproic acid glucuronide hydrolase as a key enzyme for the interaction of valproic acid with carbapenem antibiotics

Plasma levels of valproic acid (VPA) are decreased by concomitant use with carbapenem antibiotics, such as panipenem (PAPM). One of the plausible mechanisms of this interaction is the inhibition of VPA glucuronide (VPA-G) hydrolysis by carbapenems in the liver. To elucidate this interaction mechanism, we purified VPA-G hydrolase from human liver cytosol, in which the hydrolytic activity was mainly located. After chromatographic purification, the VPA-G hydrolase was identified as acylpeptide hydrolase (APEH). APEH-depleted cytosol, prepared by an immunodepletion method, completely lacked the hydrolytic activity. These results demonstrate that APEH is a single enzyme involved in PAPM-sensitive VPA-G hydrolysis in cytosol. In addition, the hydrolytic activity of recombinant human APEH was inhibited by PAPM and the inhibition profile by typical esterase inhibitors (diisopropyl fluorophosphate, 5,5'-dithiobis(2-nitrobenzoic acid), p-chloromercuribenzoic acid, and d-saccharic acid 1,4-lactone) was similar to that of human liver cytosol. Cytosolic VPA-G hydrolase activity was slightly inhibited by cholinesterase and carboxylesterase inhibitors. beta-Glucuronidase activity remained in APEH-depleted cytosol, whereas VPA-G hydrolase activity was completely abolished. Thus, either cholinesterase, carboxylesterase, or beta-glucuronidase in cytosol would not be involved in VPA-G hydrolysis. Taken together, APEH plays a major role in the PAPM-sensitive VPA-G hydrolysis in the liver. These findings suggest that APEH could be a key enzyme for the drug interaction of VPA with carbapenems via VPA-G hydrolysis.

Investigation of low levels of plasma valproic acid concentration following simultaneous administration of sodium valproate and rizatriptan benzoate

Drug interaction between rizatriptan benzoate, an anti-migraine agent, and sodium valproate (VPA-Na), an anticonvulsant, was studied in rats. When rizatriptan benzoate was administered orally immediately after VPA-Na oral administration, the pharmacokinetic parameters, such as plasma valproic acid (VPA) and area under the plasma concentration-time curve up to 3 h (AUC0–3), were significantly decreased compared with those in the control group. However, when rizatriptan benzoate was administered intraperitoneally immediately after VPA-Na orally, these parameters were not changed. In addition, when benzoic acid was administered orally immediately after VPA-Na orally, these were significantly lower compared with the control values. Therefore, it might be possible that VPA transport by monocarboxylate transporter was competitively inhibited by rizatriptan benzoate and thus absorption of VPA was decreased.

The Effect of Carbapenem Antibiotics on Plasma Concentrations of Valproic Acid

Objective:

To critically evaluate the mechanisms of the interaction between valproic acid and carbapenem antibiotics.

Data Sources:

A PubMed search (January 1971–June 2009) was performed to identify literature on the interaction between valproic acid and carbapenem antibiotics. Additional references were identified through review of bibliographies of identified articles.

Study Selection and Data Extraction:

Data on the mechanisms of the interaction between valproic acid and carbapenem antibiotics were extracted from identified references that were published in English.

Data Synthesis:

Valproic acid plasma concentrations fall markedly during concomitant administration with carbapenem antibiotics due to a combination of absorption, distribution, and metabolism mechanisms. Carbapenems appear to inhibit the intestinal transporter of valproic acid, thereby reducing absorption of orally administered valproic acid. In vivo experiments in rats demonstrate a 57% reduction in absorption of orally administered valproic acid in the presence of imipenem. Followup studies in Caco-2 cells suggest that the inhibition probably occurs at the basolateral membrane. In addition, enterohepatic recycling of valproic acid may be diminished due to carbapenem activity against gut flora producing β-glucuronidase. When rabbits and rats were given intravenous valproic acid-glucuronide, the glucuronide metabolite of valproic acid, 50–90% of the conversion back into valproic acid was inhibited in the presence of a carbapenem. An increase in erythrocyte distribution of valproic acid has also been observed in the presence of carbapenems. After intravenous administration of a carbapenem and valproic acid, valproic acid plasma concentrations fell in the presence of a carbapenem, yet whole blood concentrations of valproic acid did not change significantly. Follow-up studies suggest that the mechanism of this distribution shift is that multidrug resistance proteins on adenosine triphosphate–binding cassette transporters on erythrocyte membranes are inhibited by carbapenems. Thus, valproic acid is not effluxed out of the erythrocytes. Finally, carbapenems may enhance glucuronidation of valproic acid by increasing UDP-glucuronic acid levels. In rats, UDP-glucuronic acid levels increased by 1,7-fold in the presence of panipenem, which was proportionate to the increase in valproic acid-glucuronide formation.

Conclusions:

Published data demonstrate a serious and complex interaction between valproic acid and carbapenem antibiotics. Coadministration should be avoided, but if no other antibiotic therapies exist, it is imperative to monitor valproic acid concentrations more frequently. Clinicians should anticipate higher doses of valproic acid to maintain therapeutic serum concentrations during coadministration and subsequent dose reductions upon discontinuation of the carbapenem antibiotic.

Effect of concomitant administration of meropenem and valproic acid in an elderly Chinese patient

BACKGROUND

Meropenem is a carbapenem with a broad spectrum of activity against beta-lactamase-producing organisms. Valproic acid is widely used in the treatment of generalized tonic-clonic and partial seizures. Concomitant administration of meropenem and valproic acid reportedly leads to a rapid decline in serum concentrations of valproic acid, which is sometimes associated with seizures.

CASE SUMMARY

This report describes an 85-year-old Chinese male inpatient who twice received concomitant administration of meropenem and valproic acid for the treatment of pneumonia and poststroke epilepsy, respectively. Rapid declines in valproic acid concentrations were observed both times after meropenem administration. No seizures occurred in the first treatment period; however, when the patient suffered pneumonia again 3 months later, the same concomitant therapy was prescribed, and seizures occurred. It is difficult to identify a single etiology of the seizures. Based on a score of 7 on the Naranjo adverse drug reaction probability scale, the seizures were considered to be probably related to the concomitant administration of meropenem and valproic acid.

CONCLUSIONS

Various factors make the effect of concomitant administration of meropenem and valproic acid unpredictable, even in the same patient. Caution should be used when administering meropenem and valproic acid concomitantly, especially in elderly patients with central nervous system disorders, even if the patient has had a successful prior experience with these 2 drugs. If concomitant administration is essential, very close serum concentration monitoring and clinical observation are necessary.

Interaction between valproic acid and carbapenem antibiotics

The serum concentration of valproic acid (VPA) in epilepsy patients decreased by the administration of carbapenem antibiotics, such as meropenem, panipenem or imipenem, to a sub-therapeutic level. This review summarized several case reports of this interaction between VPA (1-4 g dose) and carbapenem antibiotics to elucidate the possible mechanisms decreasing VPA concentration by carbapenem antibiotics. Studies to explain the decrease were carried out using rats by the following sites: absorption of VPA in the intestine, glucuronidation in the liver, disposition in blood and renal excretion. In the intestinal absorption site, there are two possible mechanisms: inhibition of the intestinal transporter for VPA absorption by carbapenem antibiotics, and the decrease of beta-glucuronidase supplied from enteric bacteria, which were killed by antibiotics. This is consistent with a view that the decrease of VPA originated from VPA-Glu, relating to entero-hepatic circulation. The second key site is in the liver, because of no decreased in VPA level by carbapenem antibiotics in hepatectomized rats. There are three possible mechanisms in the liver to explain the decreased phenomenon: first, decrease of the UDPGA level by carbapenem antibiotics. UDPGA is a co-factor for UDP-glucuronosyltransferase (UGT)-mediated glucuronidation of VPA. Second, the direct activation of UGT by carbapenem antibiotics. This activation was observed after pre-incubation of human liver microsomes with carbapenem antibiotics. Third, the inhibition of beta-glucuronidase in liver by carbapenem antibiotics and the decreased VPA amount liberated from VPA-Glu. The third site is the distribution of VPA in blood (erythrocytes and plasma). Plasma VPA distributed to erythrocytes by the inhibition of transporters (Mrp4), which efflux VPA from erythrocytes to plasma, by carbapenem antibiotics. The increase of renal excretion of VPA as VPA-Glu depends on the increase of VPA-Glu level by UGT. One or a combination of some factors in these mechanisms might relate to the carbapenem-mediated decrease of the plasma VPA level.

Safety profile of meropenem: an updated review of over 6,000 patients treated with meropenem

Meropenem is a broad-spectrum carbapenem antibacterial with potent antimicrobial activity against a broad range of Gram-negative, Gram-positive and anaerobic bacteria. The second parenteral carbapenem to be introduced worldwide, meropenem has been in clinical use since 1994. Two previous safety reviews have established that meropenem has a favourable and acceptable safety profile. This new review was conducted after the approval of meropenem in the US in 2005 for the treatment of patients with complicated skin and skin-structure infections, in addition to the previously approved indications of intra-abdominal infections and paediatric bacterial meningitis. The analysis includes the clinical trial data from the previous safety reviews, updated with expanded experience across a number of serious bacterial infections, including a large international study in patients with skin or skin-structure infections and further experience in patients with intra-abdominal infections and bacterial meningitis. A total of 6154 patients with 6308 meropenem exposures were compared with 4483 patients treated with comparator agents (4593 exposures), and the paediatric population base for which safety data are available has doubled to over 1000 patients. The data presented reinforce the favourable safety profile of meropenem. In general, the incidence and pattern of adverse events occurring with meropenem were similar to those of the first carbapenem, imipenem/cilastatin, and to those of the cephalosporin- and clindamycin-based regimens to which it had been compared. The most common adverse events reported for meropenem were diarrhoea (2.5%), rash (1.4%) and nausea/vomiting (1.2%). No adverse event occurred in more than 3% of patient exposures to meropenem, indicating a low overall frequency of adverse events as well as excellent gastrointestinal tolerability. Furthermore, no unexpected adverse events were identified, and the very low incidence of seizures in patients with meningitis was not considered to be drug related. In infections other than meningitis, the incidence of seizures considered by investigators to be related to meropenem treatment was 0.07%. In the new studies that updated the earlier safety data, no new cases of drug-related seizure were reported for any treatment or patient group (meningitis/non-meningitis infections). In conclusion, meropenem is well tolerated and has good CNS and gastrointestinal tolerability when used for the treatment of serious bacterial infections in a wide range of adult and paediatric patient populations.

Interaction between valproate and meropenem: a retrospective study

BACKGROUND

Valproate and meropenem are frequently used in the intensive care unit to treat seizures and serious infections, respectively. Several case reports have described a remarkable interaction between the drugs when administered concurrently. The interaction leads to a significant drop in plasma concentrations of valproate within 24 hours and relapse of seizures in some patients.

OBJECTIVE

To evaluate a consecutive population of hospitalized patients who were simultaneously treated with meropenem and valproate and assess the effect on epileptic activity.

METHODS

A retrospective study of an 18 month period was performed to assess the extent and clinical impact of this interaction. To assess the relevance of the interaction, the time-relationship between the drop in plasma concentrations and relapse in seizure activity and/or deterioration of electroencephalogram recordings was determined. We investigated other contributing proconvulsive cofactors and concomitant antiepileptic treatment. Drug interaction probability scale (DIPS) scores were calculated.

RESULTS

Thirty-nine patients were treated simultaneously with valproate and meropenem. The pharmacokinetic interaction was observed in all 39 patients, with an average drop in valproate plasma concentrations of 66%. The decrease occurred within 24 hours, as shown in 19 patients who had daily plasma concentration monitoring. The clinical impact of the interaction could not be assessed in 19 (49%) patients due to death (n = 13) or incomplete charts (n = 6). In the remaining 20 (51%) patients, DIPS scores were calculated and clinical relevance was assessed. The interaction was considered to be probable in 16 patients and possible in 4, as calculated by the DIPS. The interaction contributed to electroclinical deterioration in 11 patients.

CONCLUSIONS

The pharmacokinetic interaction between valproate and meropenem was present in all patients and led to a drop of valproate concentrations with an average of 66% within 24 hours. This interaction was clinically relevant with electroclinical deterioration in 55% of patients. To avoid patients' possible neurologic deterioration, meropenem and valproate should not be administered together.