Acute Seizures in a Patient Receiving Divalproex Sodium After Starting Ertapenem Therapy

Ertapenem-Induced Neurotoxicity: A Literature Review of Clinical Characteristics and Treatment Outcomes

Background

Neurotoxicity is a rare adverse event for ertapenem. Given the limited evidence, large patient data are needed to aid in the identification and management of this fatal complication. Aim of the review, we summarize the characteristics, risk factors, and treatment of ertapenem-induced neurotoxicity.

Methods

Pubmed, Web of Science, Embase, Cochrane library, Wanfang, CNKI, China VIP database were searched up from 31 October 2001 to 31 December 2022. All articles concerning neurotoxicity induced by ertapenem were included. The retrieved articles were screened by two experienced clinicians by reading the titles, abstracts, and full texts.

Results

A total of 66 patients were included, with a median age of 71.5 years (range 40-92), of whom 45 (68.2%) were male. Twelve patients (18.2%) received irrational doses (exceeding the recommended dose), and 30 patients (45.5%) had chronic renal insufficiency. The median time to symptom onset was 5 (range 1-14). Epileptiform seizures (42.4%), visual hallucinations (36.4%), altered mental status (25.8%), and confusion (22.7%) were the most common symptoms of ertapenem-induced neurotoxicity. Of the 29 patients with reported albumin levels, 25 had serum albumin <3.5 g/dl. Ertapenem was discontinued in 95.5% of patients, and 90.9% recovered completely. Median time to symptom recovery was 7 days (range 1-42) after intervention including antiepileptic administration, or hemodialysis.

Conclusion

Neurotoxicity is a rare adverse event for ertapenem, especially in patients with advanced age, renal insufficiency, pre-existing neurological disease, and hypoalbuminemia. This adverse reaction usually resolves with medication interruption, or antiepileptic administration and hemodialysis.

A carbapenem antibiotic inhibiting a mammalian serine protease: structure of the acylaminoacyl peptidase-meropenem complex

The structure of porcine AAP (pAAP) in a covalently bound complex with meropenem was determined by cryo-EM to 2.1 Å resolution, showing the mammalian serine-protease inhibited by a carbapenem antibiotic. AAP is a modulator of the ubiquitin-proteasome degradation system and the site of a drug-drug interaction between the widely used antipsychotic, valproate and carbapenems. The active form of pAAP - a toroidal tetramer - binds four meropenem molecules covalently linked to the catalytic Ser587 of the serine-protease triad, in an acyl-enzyme state. AAP is hindered from fully processing the antibiotic by the displacement and protonation of His707 of the catalytic triad. We show that AAP is made susceptible to the association by its unusually sheltered active pockets and flexible catalytic triads, while the carbapenems possess sufficiently small substituents on their β-lactam rings to fit into the shallow substrate-specificity pocket of the enzyme.

Analytical method validation for related substances in sodium valproate oral solution by gas chromatography

Background

Sodium Valproate is the sodium salt of valproic acid (VPA). Valproic acid is mainly used for the treatment of epilepsy. The specific aim of the study is to develop and validate an optimized method for the determination of six related substances such as N,N-dimethyl valpronamide, valeric acid, 2-methyl valeric acid, 2-ethyl valeric acid, 2-isopropyl valeric acid and 2-n-butyl valeric acid in Sodium Valproate Oral Solution by Gas Chromatography. Chromatographic separations of these six related substances were achieved on DB-FFAP fused silica capillary column (30 m × 0.53 mm) bonded with a 0.5-µm layer of macrogol 20,000 2-nitroterephthalate materials used as stationary phase. The six related impurities were extracted using heptane and monitored by Gas Chromatography coupled with flame ionization detector. The performance of the developed method was assessed by evaluating system suitability, method precision, specificity, linearity and range, ruggedness, accuracy, robustness.

Results

The correlation coefficient was within the acceptance criteria in the range of 0.9998. The evaluated concentrations for Sodium Valproate were in the ranges of 5.05–25.27 ppm. The average recovery values were in the range of 92.4–100.4%. Solution Stability experiments were performed to evaluate the degradation behavior of SVS.

Conclusion

A novel, precise and sensitive GC method was developed, validated and optimized for the determination of six related substances in sodium Valproate oral solution. The results obtained from the validation experiments demonstrated that the method is accurate, precise, linear, specific, sensitive and robust. Hence, the proposed method can be an alternative method, for the determination of related substances in sodium valproate oral solution drug substance.

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.

Antibiotic-induced epileptic seizures: mechanisms of action and clinical considerations

In recent years, there has been growing interest in the development of epileptic seizures as an adverse effect of antibiotic therapy. The most commonly accepted mechanisms underlying the development of antibiotic-induced seizures include direct- and indirect gamma-aminobutyric acid (GABA) antagonism, inhibition of GABA synthesis, and glutaminergic N-methyl-D-Aspartate (NMDA) receptor agonistic activity. Inhibitory pathway inhibition leads to increased neuronal excitability and lowered seizure threshold. Blockage of myoneural presynaptic acetylcholine release, mitochondrial dysfunction, interference of neural protein synthesis, and oxidative stress caused by the generation of neurotoxic radicals also contributes to the development of neurotoxicity. Patients with pre-existing risk factors such as renal or hepatic insufficiency, central nervous system pathology, neurological diseases, history of epilepsy or seizures, critical illness, and increased age are more susceptible to seizure development as a consequence of antibiotic therapy. Administration of antibiotics, together with antiseizure drugs, may also lead to enhanced seizure risk due to drug interactions, which predisposes to alterations in drug metabolism and therapeutic efficacy.

Valproate Interaction With Carbapenems: Review and Recommendations

Introduction: Valproic acid is a commonly used antiepileptic drug. Combining valproate derivatives with carbapenem antibiotics is associated with a potential drug interaction that decreases serum concentration of valproate and may expose the patient to uncontrolled seizure risk from valproate subtherapeutic concentration. Raising awareness of this drug interaction among health care providers including emergency department physicians, neurologists, and pharmacists is highly needed. The aim of this article was to review the current literature about the potential drug interaction resulting from combining valproate derivatives with carbapenem antibiotics and to establish therapeutic recommendations regarding their use together. Methods: A review of the literature was conducted using Medline (through PubMed), Ovid, Embase, Cochrane library using the following keywords: valproate, valproic acid, carbapenem, ertapenem, doripenem, meropenem, imipenem, and valproate drug interaction. In addition, a manual search through major journals for articles referenced in PubMed was performed. Related publications from January 1998 till November 2018 were included in the initial search. Relevant publications were reviewed, and data regarding patients, type of carbapenem used, valproic acid dosing and level, interaction severity, and clinical outcome were summarized. Results and Discussion: Few clinical trials and multiple case reports have shown that carbapenem antibiotics including meropenem, ertapenem, imipenem, and doripenem can decrease the serum concentration of valproate derivatives leading to a subtherapeutic serum concentration and seizures in some patients. Valproic acid serum concentration may be significantly decreased with addition of a carbapenem antibiotic but generally return toward normal shortly after discontinuation of the carbapenem antibiotic. Conclusions: Generally, the concurrent use of carbapenem antibiotics with valproate derivatives should be avoided due to the potential of drug-drug interaction that results in subtherapeutic valproate serum concentration. Other antimicrobial agents should be considered as alternatives to carbapenems but if a concurrent carbapenem is necessary, using an additional antiepileptic agent is recommended. Therapeutic drug monitoring of valproate serum concentrations is warranted when a carbapenem-valproic acid combination therapy is unavoidable.

Drug Interactions in Neurocritical Care

Drug-drug interactions (DDIs) are common and avoidable complications that are associated with poor patient outcomes. Neurocritical care patients may be at particular risk for DDIs due to alterations in pharmacokinetic profiles and exposure to medications with a high DDI risk. This review describes the principles of DDI pharmacology, common and severe DDIs in Neurocritical care, and recommendations to minimize adverse outcomes. A review of published literature was performed using PubMed by searching for 'Drug Interaction' and several high DDI risk and common neurocritical care medications. Key medication classes included anticoagulants, antimicrobials, antiepileptics, antihypertensives, sedatives, and selective serotonin reuptake inhibitors. Additional literature was also reviewed to determine the risk in neurocritical care and potential therapeutic alternatives. Clinicians should be aware of interactions in this setting, the long-term complications, and therapeutic alternatives.

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.

Reliable GC Method for Related Substances in Divalproex Sodium Drug

A specific GC method has been developed, optimized and validated for the determination of seven related substances namely N,N-dimethyl valpronamide, valeric acid, 2-methyl valeric acid, 2-ethyl valeric acid, 2-isopropyl valeric acid, 2-n-butyl valeric acid and 2-propyl-2-pentenoic acid in divalproex sodium (DPS) drug substance. Chromatographic separations of these seven impurities were achieved on DB-FFAP column (30 m × 0.53 mm, 1.0 μm), which consists nitroterephthalic acid modified polyethylene glycol material as stationary phase. DPS is a coordination complex of the sodium valproate and valproic acid (VPA). Nonanoic acid is used as internal standard. All the seven related substances, VPA and nonanoic acid were extracted into dichloromethane and monitored by GC with flame ionization detector. The performance of the developed method was assessed by evaluating specificity, linearity, sensitivity, precision, accuracy and robustness. Forced degradation experiments were conducted to evaluate the degradation behavior of DPS. The established limits of detection (LODs) and limits of quantification (LOQs) values for the related substances were in the ranges of 4-5 and 12-15 μg mL-1, respectively. Further, for VPA, LOD and LOQ values were 4 and 12 μg mL-1, respectively. The correction factors of these related substances with respect to VPA and lie between 0.92 and 1.44. The average recoveries were in the range of 92.4-108.4%.

Risk factors associated with the development of seizures among adult patients treated with ertapenem: A matched case-control study

Objective

The purpose of this study is to compare the characteristics of those ertapenem-treated adult patients with and without development of seizures, and identify the associated factors for the development of seizures.

Methods

This retrospective study was conducted at Chia-Yi Christian Hospital from January 2012 to December 2014. Patients developing seizures during their ertapenem treatment course were identified as case patients. Those without seizures who had received ertapenem for at least five days were considered as the pool of control patients. For each case patient, four matched patients from the control pool were randomly selected as the final control group, based on age, gender, and the date of ertapenem prescription.

Results

A total of 1706 ertapenem-treated patients were identified, 33 (1.9%) individuals developed seizures with the enrollment of 132 matched control patients. Among these 33 patients, the average age was 79.3 ± 7.5 years, and 20 (60.6%) were male. The mean Charlson co-morbidity score was 4.5 ± 2.4, and the first episode of seizure happened 3.3 ± 2.6 days after receiving ertapenem. In multivariate logistic regression analysis, the independent predictors associated with the development of ertapenem-associated seizures were old stroke (OR, 14.36; 95% CI, 4.38–47.02; p < 0.0001), undergoing brain images within one year prior to the admission (OR, 5.73; 95% CI, 1.78–18.43; p = 0.0034), low hemoglobin level (OR, 3.88; 95% CI, 1.28–12.75; p = 0.0165) and low platelet count (OR, 4,94; 95% CI, 1.56–15.68; p = 0.0067) at presentations, and protective factors against the development of seizures were heart failure (OR, 0.04; 95% CI, 0.00–0.63; p = 0.0222), concomitant use of steroids (OR, 0.19; 95% CI, 0.05–0.77; p = 0.0201), or antiplatelet agents (OR, 0.12; 95% CI, 0.02–0.63, p = 0.0123) with ertapenem.

Conclusions

The development of ertapenem-associated seizures may occur more frequently and much earlier due to its widespread use in treating drug-resistant pathogens, especially when these pathogens emerged worldwide.Our study would help physician to estimate the risk of developing seizure among patients receiving ertapenem.

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.

In vivo inhibition of acylpeptide hydrolase by carbapenem antibiotics causes the decrease of plasma concentration of valproic acid in dogs

1. Our previous in vitro studies suggest that inhibition of the acylpeptide hydrolase (APEH) activity as valproic acid glucuronide (VPA-G) hydrolase by carbapenems in human liver cytosol is a key process for clinical drug-drug interaction (DDI) of valproic acid (VPA) with carbapenems. Here, we investigated whether in vivo DDI of VPA with meropenem (MEPM) was caused via inhibition of APEH in dogs. 2. More rapid decrease of plasma VPA levels and increased urinary excretion of VPA-G were observed after co-administration with MEPM compared with those after without co-administration, whereas the plasma level and bile excretion of VPA-G showed no change. 3. Dog VPA-G hydrolase activity, inhibited by carbapenems, was mainly located in cytosol from both the liver and kidney. APEH-immunodepleted cytosols lacked VPA-G hydrolase activity. Hepatic and renal APEH activity was negligible even at 24 h after dosing of MEPM to a dog. 4. In conclusion, DDI of VPA with carbapenems in dogs is caused by long-lasting inhibition of APEH-mediated VPA-G hydrolysis by carbapenems, which could explain the delayed recovery of plasma VPA levels to the therapeutic window even after discontinuation of carbapenems in humans.

Drug interaction between tacrolimus and ertapenem in renal transplantation recipients

To show drug interactions between tacrolimus and ertapenem, we retrospectively evaluated 13 renal transplant recipients who had been treated with ertapenem for urinary tract infections during prescription of a constant dose. The mean dose of tacrolimus to achieve desired therapeutic concentrations decreased significantly after beginning ertapenem. The decrease from 0.079 mg/kg to 0.043 mg/kg occurred 2 days after initiation of ertapenem (P < .005). These results suggest that ertapenem, which is not metabolized through the cytochrome (CYP) P450 3A metabolic pathway, interacts with tacrolimus by an unknown mechanism. This report recommends tacrolimus concentration monitoring and dose reductions when the two drugs are administered in combination.

Comparative pharmacokinetics, pharmacodynamics, and tolerability of ertapenem 1 gram/day administered as a rapid 5-minute infusion versus the standard 30-minute infusion in healthy adult volunteers

STUDY OBJECTIVE

To compare ertapenem pharmacokinetics, pharmacodynamics, and tolerability when administered as a rapid 5-minute infusion to the standard 30-minute infusion.

DESIGN

Prospective, randomized, crossover pharmacokinetic study.

SETTING

Clinical research center.

SUBJECTS

Twelve healthy adult volunteers.

INTERVENTION

Each subject received ertapenem 1 g intravenously, administered either as a rapid 5-minute infusion or the standard 30-minute infusion, every 24 hours for 3 days (first phase); after a 4-day washout period, each subject then received the other infusion every 24 hours for 3 days (second phase).

MEASUREMENTS AND MAIN RESULTS

Plasma samples were collected after the first and third (steady-state) doses of each study phase, and protein binding was assessed by use of ultrafiltration. Pharmacokinetic analyses were conducted using noncompartmental and compartmental methods. A 5000-subject Monte Carlo simulation was used to assess the probability of target attainment for free drug concentration remaining above the minimum inhibitory concentration (MIC) for 40% or greater of the dosing interval (40% fT > MIC) over an MIC range. Ertapenem was well tolerated and adverse events were similar for both infusions. The ertapenem steady-state mean ± SD maximum concentrations were 193.3 ± 43.3 and 165.7 ± 20.4 mg/L for the 5- and 30-minute infusions, respectively; the mean ± SD areas under the concentration-time curves from 0-24 hours were 561.2 ± 77.0 and 531.3 ± 56.9 μg · hr/ml (geometric mean ratio 1.008, 90% confidence interval 0.999-1.017), respectively. Protein binding was concentration dependent (range 87.9-98.9%). A two-compartment model best described ertapenem pharmacokinetics with the following parameter estimates: clearance 1.89 ± 0.19 L/hr, volume of central compartment 5.04 ± 0.56 L, and transfer constants k12 0.43 ± 0.08/hr and k21 0.44 ± 0.07/hr. The probabilities of target attainment for 5- and 30-minute infusions were 97.0% and 97.9% at an MIC of 0.25 mg/L and 1.7% and 2.8% at an MIC of 0.5 mg/L, respectively.

CONCLUSION

Ertapenem administered as a rapid 5-minute infusion provides a well tolerated, bioequivalent, and pharmacodynamically equivalent regimen to the 30-minute infusion at clinically relevant MICs.

Epileptogenic potential of carbapenem agents: mechanism of action, seizure rates, and clinical considerations

Antimicrobials are the most frequently implicated class of drugs in drug-induced seizure, with β-lactams being the class of antimicrobials most often implicated. The seizure-inducing potential of the carbapenem subclass may be directly related to their β-lactam ring structure. Data on individual carbapenems and seizure activity are scarce. To evaluate the available evidence on the association between carbapenem agents and seizure activity, we conducted a literature search of the MEDLINE (1966-May 2010), EMBASE (1974-May 2010), and International Pharmaceutical Abstracts (1970-May 2010) databases. Reference citations from the retrieved articles were also reviewed. Mechanistically, seizure propensity of the β-lactams is related to their binding to γ-aminobutyric acid (GABA) receptors. There are numerous reports of seizure activity associated with imipenem-cilastatin, with seizure rates ranging from 3-33%. For meropenem, doripenem, and ertapenem, the seizure rate for each agent is reported as less than 1%. However, as their use increases and expands into new patient populations, the rate of seizures with these agents may increase. High-dose therapy, especially in patients with renal dysfunction, preexisting central nervous system abnormalities, or a seizure history increases the likelihood of seizure activity. Although specific studies have not been conducted, data indicate that carbapenem-associated seizure is best managed with benzodiazepines, followed by other agents that enhance GABA transmission. Due to the drug interaction between carbapenems and valproic acid, resulting in clinically significant declines in valproic acid serum concentrations, the combination should be avoided whenever possible. Clinicians should be vigilant regarding the possibility of carbapenem-induced seizures when selecting and dosing antimicrobial therapy.

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.

[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.

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.

Doripenem: an expected arrival in the treatment of infections caused by multidrug-resistant Gram-negative pathogens

BACKGROUND

Potent new drugs against multidrug-resistant Gram-negative bacteria, namely Pseudomonas aeruginosa and Acinetobacter spp. and pan-drug-resistant Klebsiella pneumoniae, which constitute an increasing medical threat, are almost absent from the future pharmaceutical pipeline.

OBJECTIVE

This drug evaluation focuses on the position of doripenem, a novel forthcoming carbapenem. Mechanisms of resistance and new drugs with anti-Gram-negative activity are also briefly reviewed.

METHODS

Literature search was performed for new carbapenems, new antibiotics, doripenem, metallo-beta-lactamase inhibitors, multidrug-resistant pathogens, antipseudomonal antibiotics and multidrug-resistant epidemiology.

RESULTS

Doripenem possesses a broad spectrum of activity against Gram-negative bacteria, similar to that of meropenem, while retaining the spectrum of imipenem against Gram-positive pathogens. Against P. aeruginosa, doripenem exhibits rapid bactericidal activity with 2 - 4-fold lower MIC values, compared to meropenem. Exploitation of pharmacokinetic/pharmacodynamic applications could offer a treatment opportunity against strains exhibiting borderline resistance to doripenem. Stability against numerous beta-lactamases, low adverse event potential and more potent in vitro antibacterial activity against P. aeruginosa and A. baumanni compared to the existing carbapenems, are its principal features.