Valproic Acid Plasma Levels Research Articles

Cas d’une intoxication sévère à l’acide valproïque : intérêt d’un traitement par épuration extrarénale combiné à la L-carnitine

We present the case of a 24-year-old-female patient, who made an attempt to autolysis with valproic acid, benzodiazepines and neuroleptic. The valproic acid plasma level was very high (1437 μg/mL), confirming it was a severe intoxication. She presents an acute encephalopathy with prolonged status epilepticus, a lactic metabolic acidosis and hematologic disorders such as bicytopenia. Treatment including L-carnintine and continuous veno-venous haemodialysis (CVVHD) was rapidly introduced to prevent the occurrence of cerebral oedema. The evolution was favourable despite the occurrence of a nosocomial ventilation acute lung injury. The patient had motor sequelae of cranial nerves following status epilepticus extended, which disappeared spontaneously after several days.

Inhibition mechanism of carbapenem antibiotics on acylpeptide hydrolase, a key enzyme in the interaction with valproic acid

We have reported that inhibition of acylpeptide hydrolase (APEH), identified as valproic acid glucuronide hydrolase in human liver cytosol, by carbapenem antibiotics could lead to a decrease of plasma levels of valproic acid. In this study, we examined the inhibition mechanism using human liver cytosol and purified porcine APEH with a similar property to human counterpart.After preincubation of human liver cytosol with panipenem or meropenem for 30 min, the inhibition of APEH activity was 20-fold stronger than that without preincubation. Porcine APEH activity inhibited by meropenem did not recover after dialysis. Meropenem bound to porcine APEH and the binding was blocked by a serine hydrolase inhibitor, diisopropyl fluorophosphate.Open β-lactam ring form of meropenem did not affect APEH activity in human liver cytosol. Likewise, other antibiotics, which have a different heterocycle adjacent to the β-lactam ring with an opposite configuration of the side chain from carbapenems, did not inhibit APEH activity.In conclusion, carbapenems inhibit APEH in both reversible and true irreversible manner and the irreversible inhibition is partially explained by binding to the active serine of APEH. The closed β-lactam ring is essential for inhibition and the heterocycle and/or the configuration of side chain would be important.

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.

Clinical and Biological Effects of Valproic Acid as a Histone Deacetylase Inhibitor on Tumor and Surrogate Tissues: Phase I/II Trial of Valproic acid and Epirubicin/FEC

The aim was to study the biological and molecular effects of the histone deacetylase (HDAC) inhibitor, valproic acid, in patients with solid tumor malignancies. A phase I dose escalation of valproic acid given on days 1 to 3 followed by epirubicin (day 3) was followed by a dose expansion of valproic acid combined with 5-fluorouracil, epirubicin, and cyclophosphamide (FEC100). Pharmacodynamic and pharmacokinetic studies entailed valproic acid and epirubicin plasma levels and their interaction, the effects of valproic acid on histone acetylation in peripheral blood mononuclear cells (PBMC) and tumor cells at baseline and day 3, and baseline expression of HDAC2 and HDAC6 as therapeutic targets. Forty-four patients were enrolled in the phase I part, with a disease-specific cohort expansion of 15 breast cancer patients (median age, 55 years; range, 28-66 years) receiving 120 mg/kg/day valproic acid followed by FEC100. Partial responses were seen in 9 of 41 (22%) patients during the phase I part. Objective responses were seen in 9 of 14 (64%) evaluable patients at the dose expansion with a median number of 6 administered cycles. Predominant toxicities were valproic acid-associated somnolence and epirubicin-induced myelosuppression. Valproic acid plasma levels were associated with short-term, reversible depletion of WBC and neutrophils within 48 hours. Histone acetylation in tumor samples and in PBMCs correlated with valproic acid levels and was further linked to baseline HDAC2 but not to HDAC6 expression. Valproic acid is a clinically relevant HDAC inhibitor, and PBMCs may serve as a surrogate for tumor histone acetylation in solid tumor malignancies. HDAC2 should be further considered as a relevant therapeutic target.

Symptomatic hypocalcemia in an epileptic child treated with valproic acid plus lamotrigine: a case report

IntroductionAn epileptic child had been long treated with valproic acid and lamotrigine. After a few years of treatment, he manifested severe clinical signs of hypocalcemia. We retain that valproic acid could have caused such metabolic dysfunction.Case presentationWe report here the involvement of valproic acid in symptomatic hypocalcemia in an 11-year-old epileptic white patient in treatment with valproic acid and lamotrigine. During the treatment the patient developed hypocalcemia associated with high plasma levels of valproic acid, parathyroid hormone and alkaline phosphatase, indicating increased bone turnover. Plasma levels of Vitamin D were normal. Plasma calcium values significantly correlated with valproic acid haematic levels; reduction of valproic acid dose was accompanied by prompt normalization of calcemia.The specific mechanism through which valproic acid causes hypocalcemia is unknown, although the relationship between valproic acid dose and haematic levels of calcium appears very likely.ConclusionsIt seems necessary, during long term therapy with valproic acid, to monitor plasma calcium and alkaline phosphatase plasma levels. Also, these patients should undergo treatment and perhaps prescribe vitamin D and calcium treatment.

Decreased Valproate Level Caused by VPA-glucuronidase Inhibition by Carbapenem Antibiotics

The serum concentration of valproic acid (VPA) in epilepsy patients decreased in the administration of carbapenem antibiotics (CP), such as meropenem, panipenem, biapenem or imipenem, to a sub-therapeutic level. The liver is the key organ for the decrease of VPA concentration by CP, because it has been reported that no decrease of the VPA level by CP was found in hepatectomized rats. This effect was also shown with monkey and rat liver slices. In this report, we show the results of in vitro inhibition of VPA-glucuronidase in human liver microsomes and cytosol by CP. We found the highest metabolic activity of VPA-glucuronide in human liver cytosol. The level in liver cytosol was 149 pmol/min/mg protein. The level in human liver microsomes (HLM) was one-fifth of that in cytosol and the level in serum was negligible. We found that this hydrolysis depends on VPA-glucuronidase in cytosol, because digestion was inhibited by D-saccharic acid 1,4-lactonemonohydrate of a specific inhibitor of beta-glucuronidase, but not by phenylmethylsulfonylfluoride of an esterase inhibitor. We also found the inhibition of VPA-glucuronidase in cytosol by CP, and the maximum inhibition was found with panipenem (IC(50) = 3 microM). We also found inhibition of VPA-glucuronidase in HLM by meropenem. These results showed that the inhibition in liver slices depended on the inhibition of VPA-glucuronidase by CP. We considered that the inhibition of VPA-glucuronidase by CP in cytosol is a key factor to decrease the plasma VPA level.

Treatment with Sequential Valproic Acid (VPA) +/− Low Doses All Trans Retinoic Acid (LoATRA) and Low Doses Ara-C (LoDAC) for “De Novo” or Relapsed Acute Myeloid Leukaemia (AML).

Recent reports indicated the clinical feasibility and biological therapeutic potentiality of epigenetic treatments with VPA + ATRA or ATRA alone and suggested the capability of these agents in rendering neoplastic cells more sensitive to chemotherapy. Therefore, we designed treatments consisting of LoDAC preceded by the sequential administration of VPA+/LoATRA or LoATRA alone, according to the clinical condition of patients, to treat AML patients not eligible for intensive therapy. Aims of this study were to evaluate:i.the efficacy of these approaches in term of response rate and toxicity;ii.the biological changes occurring in the leukemic clone in relation to the clinical response, by a multiparametric in vivo translational experimental approach.From September 2006 to June 2007, 5 patients (pts) with de novo and 5 with relapsed AMLs were enrolled.The median age was 66 years (range: 46–81 yrs), the mean percentage of BM leukemic infiltration was 60% (range 30–81%);as cytogenetics 5 pts showed complex karyotype. Four patients (1= de novo; 3=relapsed) received an induction treatment with VPA+LoATRA+LoDAC (VPA):VPA at the initial dose of 10 mg/kg/die orally escalated, to reach the therapeutic VPA plasma levels (>50μg/ml),days 1–55, LoATRA 25 mg/m2/die orally, days 7–55 and LoDAC 40 mg/sc at day (d)10 and 45 for 7 d. In responders, therapy was repeated up to a maximum of 3 cycles with a 20 days rest period. Six patients (4 = de novo; 2 = relapsed), received LoATRA alone (days 1–55) because of coexisting co-morbidities , followed by LoDAC as described. Peripheral blood (Pb) and BM samples for biological studies were collected at d 0,7,14,21,35,55. Responses were evaluated after the first cycle of therapy according to the IWC criteria. A complete remission (CR) was observed in 4 cases (2 relapsed = VPA; 2 de novo= LoATRA), while 2 de novo pts (LoATRA) showed a major response (MR).In the 6 responders PB recovery (Hb>9g/dl; PMN>1000/m 3and PLTS>50.000/m3), was observed within a median time of 42 d (range: 35–50 d), while the median time of BM blast clearance was 35 d (range 25–50 d). Of the remaining 4 pts, 1 died during induction, at 45 d for cardiac failure, 3 maintained a stable disease and died 7, 5 and 3 months(mo) later. As to July 2007, 2 pts (Lo ATRA) persisted in CR at 2 and 4 mo, while 2 pts (VPA) relapsed at 3 and 4 mo from CR. Five pts are still alive at 4+, 5+, 5+, 5+, and 9+ mo.Biological assays showed that in mononuclear samples from the 4 CR patients, phenotypic changes including:i.the increased percentage of cells in S phase;ii.cytochemical changes (myelo-monocytic differentiation);iii.decreased expression of early myeloid/progenitor immunophenotypic markers (HLA-DR, CD34, CD117), which paralleled the increase of late myeloid differentiation markers (CD11b, CD15 or CD14), started to be measurable before LoDAC administration.In conclusion, the sequential therapy with VPA and/or LoATRA + LoDAC are well tolerated out-patient therapies that enabled a CR in a sizeable portion of our cases. In addition, these treatments induce AML blast phenotypical changes that may increase their sensitivity to LoDAC, whose molecular basis is currently under investigation.

Hyperammonemia Due to Valproic Acid in the Psychiatric Setting

Hyperammonemia Due to Valproic Acid in the Psychiatric Setting

Hyperammonemia Due to Valproic Acid in the Psychiatric Setting

In 1980 Coulter and Allen (1) reported the first case of hyperammonemia, to our knowledge, with otherwise normal hepatic function tests in a child with epilepsy treated with valproic acid. Since that time, there have been several additional case reports and studies within the neurology literature that have established hyperammonemia with otherwise normal hepatic function as a potential side effect of valproic acid, especially in children and adolescents (2). Settle (3) published the first case of hyperammonemia, to our knowledge, in a psychiatric setting in 1995. Several additional cases have followed it. Unfortunately, to date, to our knowledge, there has only been one prospective study published within the psychiatric literature (4). We present here a patient’s history that illustrates how the symptoms of a psychiatric disorder might make the diagnosis of hyperammonemic encephalopathy difficult.

Actual bioavailability of divalproex sodium extended-release tablets and its clinical implications

Divalproex sodium extended-release dosage form (divalproex-ER) has been promoted as innovative formulation for the treatment of epilepsy and manic disorders, and for migraine headache prevention, with the advantage of being dosing once a day. Due to a significant decreasing in the peak-trough fluctuation of plasma valproic acid levels, in comparison with the twice-daily dosing of conventional delayed-release formulations (divalproex-DR), concentration-dependent side effects would be prevented. However the main constraint for divalproex-ER usage is the need to be administered in a higher daily dose, because of its lower bioavailability, in order to prevent eventual breakthrough seizures when patients are switched from the twice-daily divalproex DR regimen. Taking into account free plasma drug levels, divalproex ER/DR relative bioavailability could be assessed as low as 75% in fasting condition. In order to overcome the need of increase divalproex-ER daily dose, maintenance of the twice-daily regimen is suggested. Divalproex-ER administered every 12 hours not only increases steady state trough concentration to a higher value in comparison with divalproex-DR, avoiding inefficacy of the treatment, but also achieves the safest manner to treat patients with valproic acid because of reaching practically a plateau profile of drug levels.

In Vitro Activation of Valproate Glucuronidation by 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. Studies to explain the decrease were carried out using almost rats by the following steps: absorption of VPA in the intestine, glucuronidation in the liver, disposition in blood and renal excretion. It is difficult to consider the inhibition of intestinal absorption, because carbapenem antibiotics are intravenously administered and do not reach the intestine at an effective concentration. The liver is the key organ for the decrease of VPA concentration by carbapenem antibiotics, because it has been reported that no decrease of the VPA level by carbapenem was found in hepatectomized rats. The most likely mechanism in liver is the activation of UDP-glucuronosyltransferase by carbapenem antibiotics. We found a 35% increase of VPA-glucuronidation activity by the pre-incubation of human liver microsomes with meropenem. We estimated that this increase fully compensates for the decrease of serum VPA level by carbapenem antibiotics in patients. Meanwhile, we could not find the in vitro activation of CYP2A6, CYP3A4, P-glycoprotein (P-gp, MDR1) and Multidrug resistance-associated protein 2 by pre-incubation with carbapenem antibiotics. Thus, we considered that the activation of VPA glucuronidation by carbapenem antibiotics is a key point in the decrease of plasma VPA level.

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 β-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 β-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.

Effect of valproate on plasma levels of interleukin-6 in healthy male humans

Valproate exerts many biochemical and physiological effects and may have a modulating effect on the immune system. The present study aimed to determine whether there is a treatment effect of valproate on plasma levels of the pro-inflammatory cytokine, interleukin (IL)-6, in healthy male humans. Plasma levels of IL-6 were measured in 10 healthy male humans before and after 7 days of treatment with 1000 mg per day of valproate (i.e. 500 mg in the morning and 500 mg in the evening). All the healthy subjects had no past or current psychiatric disorder. They reported to the outpatient clinic at 09.00 h for baseline sampling. Subsequently, they were commenced on valproate 1000 mg per day for 7 days. They took the last dose of valproate at 22.00 h on the day 7, and post-treatment blood sampling for plasma levels of IL-6 was carried out on day 8. An additional blood sample was also taken from each subject at the same time to measure plasma levels of valproic acid for drug compliance. We found a significant increase in plasma levels of IL-6 after the 7 days of valproate treatment in healthy male subjects. Furthermore, there was a significant positive correlation between the changes in plasma IL-6 and blood levels of valproic acid. The findings of this study are consistent with previous studies on subjects with epilepsy, suggesting a modulating effect of valproate on the pro-inflammatory cytokine IL-6 in humans. However, studies with a larger number of participants and employing a double-blind, placebo-control group are required to confirm the findings, and also the levels of other cytokines should be measured to generalize the effect to the immune system.

Increased erythrocyte distribution of valproic acid in pharmacokinetic interaction with carbapenem antibiotics in rat and human

Carbapenem antibiotics cause pharmacokinetic interaction with valproic acid (VPA) in clinical pharmacotherapy. Here, we investigated the mechanism of interaction from the viewpoint of erythrocyte distribution of VPA in rats and humans. Imipenem or panipenem was administered intravenously and then VPA intravenously or into the intestinal lumen in rats. Both imipenem and panipenem significantly decreased plasma VPA levels. In contrast, these antibiotics did not affect, or rather increased, VPA levels in whole blood, and increased the erythrocyte distribution of VPA in vivo. In clinical, two patients receiving VPA were given imipenem intravenously, because of intractable infectious diseases. Imipenem lowered plasma VPA levels by approximately 40%–60% of original levels, and increased the erythrocyte distribution of VPA, as observed in rats. In conclusion, the pharmacokinetic interaction between VPA and carbapenem antibiotics, in which plasma VPA levels were markedly reduced, may partly be derived from the increased erythrocyte distribution of VPA.

Phase I trial of the histone deacetylase inhibitor, valproic acid and the topoisomerase II inhibitor, epirubicin: A clinical and translational Study

3084 Background: Pre-clinical data show that histone deacetylase inhibitors(HDACi) potentiate the DNA damage induced by topoisomerase II inhibitors (topo II). Exposure to HDACi results in histone hyperacetylation and chromatin decondensation thereby facilitating the access of topo II inhibitors to DNA. Valproic acid (VPA) is a well-tolerated, orally bio-available, anti-seizure drug that has recently been shown to inhibit HDAC. Epirubicin is a widely utilized topo II inhibitor with a favorable toxicity profile. Methods: A Phase I dose escalation study explored the toxicity, efficacy and the pharmacokinetics (PK) of VPA and epirubicin. Histone acetylation and topo II expression was evaluated in tumor samples and peripheral blood mononuclear cells (PBMC). VPA was administered as an IV loading dose followed by 5 doses of oral VPA given every 12 hours. Epirubicin was infused on day 3. Treatment cycles were repeated at 3 week intervals and tumor restaging was done every 2 cycles. Enrollment was opened to all metastatic solid tumors. Results: To date, 16 patients (pts) [8 females, median age 62 (44–78)] have been treated at 4 dose levels: VPA 15, 30, 45, and 60 mg/kg; with epirubicin at 75 mg/m2. The maximum tolerated dose has not been reached and dose escalation is continuing. Tumor types enrolled included: 8 melanoma (8), breast (5), cervical, lung, and adrenal carcinoma. The most common treatment related adverse events encountered included neutropenia (69%, G3/4), anemia (6% G1/3), nausea (31%, G1/2) and fatigue (25%, G1/2). Radiation recall was seen in all patients with prior radiation (6 pts). Major responses were observed in all tumor types including in anthracycline failures and in anthracycline-resistant cancers such as melanoma and cervical carcinoma (CR/PR 4/13; SD 3/13; PD 6/13). VPA PK data showed a linear increase with dose. Conclusions: A sequence-specific combination using the HDACi, VPA and epirubicin is feasible and with acceptable toxicity. VPA plasma levels exceeded concentrations needed for in-vitro synergy. The significant anti-tumor activity seen in this heavily pretreated patient population warrants further exploration. Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Pfizer

Carnitine Levels in Valproic Acid-Treated Psychiatric Patients

Carnitine facilitates the transport of long-chain fatty acids across the mitochondria for beta oxidation, and the removal of potentially toxic acylcoenzyme-A metabolites from the inner aspect of mitochondrion as acylcarnitines. Previous studies suggest a significant decrease in carnitine concentrations and changes in the ratio of acylcarnitine to free carnitine in seizure-disoriented patients treated with valproic acid (VPA), which may lead to clinical manifestations of carnitine deficiency. This study sought to explore whether the same decrease in plasma free carnitine and increase in acylcarnitines are seen when VPA is used in the treatment of patients with psychiatric disease. Thirty psychiatric patients treated with VPA for at least six months were selected for the study and granted informed consent for participation. Exclusion criteria included liver disorder or pancreatitis, metabolic defects known to affect plasma carnitine levels, or noncompliance with VPA regimen. Plasma free carnitine, total carnitine, VPA, and amylase levels were determined, and liver function tests (LFTs) were performed. Pearson correlations were conducted between VPA levels, levels and ratios of carnitines, as well as LFTs and amylase levels. Plasma free and total carnitine levels were lower than the reported normal range for the laboratory performing the assay, and the ratio of acylcarnitine to free carnitine was increased. There was a significant positive correlation of VPA levels and acylcarnitine-free carnitine ratio, a trend toward significance between VPA levels and acylcarnitine levels, and a marginal negative correlation between VPA levels and free carnitine levels. VPA levels correlated also with several LFTs and acylcarnitine levels. Octanoyl carnitine and acylcarnitine levels, as well as acylcarnitine-free carnitine and octanoyl-free carnitine ratios, correlated significantly with amylase levels. Although the study was limited by a cross-sectional design without direct control comparison, the findings suggest that patients with various psychiatric conditions treated with polypharmacy that includes VPA may have lower plasma carnitine levels than would be expected in healthy controls.

Severe Valproic Acid Intoxication is Associated with Atrial Tachycardia: Secondary Detoxication by Hemoperfusion

Valproic acid is an anticonvulsant drug which is associated with serious toxicity including fatal outcome in case of severe intoxication. Secondary detoxication by hemodialysis or hemoperfusion has been employed successfully in valproic acid intoxication. Cardiac arrhythmias have only been described rarely in valproic acid intoxication in humans. We report on a 15 year-old boy with severe valproic acid intoxication (valproic acid plasma level on admission: 1 150 mg/l) who presented with coma, hypernatremia and atrial tachycardia. The patient was successfully treated with hemoperfusion and intensive supportive care without implementation of a specific antiarrhythmic therapy. We conclude that patients with severe valproic acid intoxication may benefit from secondary detoxication. In addition to generally known symptoms valproic acid intoxication may also be associated with cardiac arrhythmias.

Valproic Acid Plus Retinoic Acid Induce Myeloid Differentiation in Chemotherapy-Resistant Acute Myeloid Leukemia Patients.

The anti-epileptic drug valproic acid (VPA) acts as an inhibitor of histone deacetylases. In combination with retinoic acid (RA), VPA triggers myeloid differentiation of primary acute myeloid leukemia (AML) blasts in vitro. In vivo, VPA posses an antineoplastic activity as indicated by pre-clinical studies in murine models of leukemia, renal and lung metastatic tumors. Therefore, we have designed a phase II clinical study in which VPA was combined with RA (VPA-RA) in the AML treatment. Eigth chemotherapy-resistant or high risk AML patients not eligible for additional intensive therapy (median age 61.5 yrs), were treated at the Hematology Units of the Universities “La Sapienza” and “Tor Vergata” Rome-Italy. VPA (Depakin[Sanofi-Wintrop]) was administrated from day 1 to day 28, at the initial dosage of 10 mg/kg/die p.o. with dose escalation until optimal VPA plasma levels (80–110ug/ml). RA (Vesanoid [Roche]) at the dosage of 45 mg/m2 p.o./d, divided in two administrations, was added once the optimal VPA plasma levels were reached or at day 14 and continued until day 28. Four patients had a history of MDS, three patients had a FAB M0, M1 and M2 de novo AMLs, while the remaining case was a myeloid blast crisis (FAB M0) of a Ph+ve CML. Cytogenetic characterization in the other patients revealed normal karyotype in one case, a pseudodiploid [der(12)] in one, hyperdiploid (+8) in one, complex K with a 7q- alteration in one, while in the three remaining cases the karyotype was not evaluable. Pre-treatment leukemic infiltration ranged from 22% to 95%. VPA plasma level >60mg/ml was reached between 8 to 28 days (median 14.5 days). In three patients, VPA-RA treatment induced hyperleukocytosis (>50x 109/l) at day 16, 21 and 24, respectively, that was treated with chemotherapy (HU in two cases and low dose Ara-C in 1 case). Hematological improvement (≥50% decrease in packed red blood cell or platelet transfusion requirement) was observed in one case, a stable disease in five cases and disease progression in two cases. Peripheral blood and/or bone marrow samples were collected at day 0,3,7,14,21,28 for morphologic, immunophenotypic, cytogenetic and molecular studies. All patients showed features of myeloid-monocytic and/or erythroid differentiation of the leukemic clone, as revealed by morphologic, cytochemical, immunophenotypic analyses and by Q-RT-PCR of myeloid gene expression (GATA 1, MPO, CSF2Rb, etc.). Of note that high degree of myeloid differentiation correlated with early achievement of therapeutic VPA plasma levels and histone hyper-acetylation, as measured by immunocytochemistry and immunoblotting using antiacetylated histone H3 and H4 antibodies. Finally, differentiation of the leukemic clone was proven by FISH analysis showing the presence of the +8 and 7q- in maturing elements in patients whose leukemia blasts carried these cytogenetic lesions. The VPA-RA combination is a well tolerated treatment that induces phenotypic changes of the leukemic clone through chromatine remodelling. Further studies are needed to optimise this regimen with the aim of improving clinical response in leukemia patients.

Mechanism of the drug interaction between valproic acid and carbapenem antibiotics in monkeys and rats.

The Ministry of Health and Welfare, Japan banned coadministration of carbapenems, such as panipenem/betamipron (PAPM), meropenem (MEPM), and valproic acid (VPA) because clinical reports have indicated that the coadministration caused seizures in epileptic patients due to lowered plasma levels of VPA. In this study, we have clarified the mechanism of the drug-drug interaction using PAPM, MEPM, and doripenem [S-4661; (+)-(4R,5S,6S)-6-[(1R)-1-hydroxyethyl]-4-methyl-7-oxo-3-[[(3S,5S)-5-[(sulfamoylamino)methyl]-3-pyrrolidinyl]thio]-1-azabicyclo[3.2.0]hept-2-ene-2-caboxylic acid monohydrate], a newly synthesized carbapenem. In vitro experiments using monkey liver slices suggested that the apparent synthetic rate of VPA glucuronide (VPA-G) increased in the presence of carbapenems. However, no such increase was observed in the experiment using monkey liver microsomes. Although no increase of uridine 5'-diphosphate D-glucuronic acid was found in monkey liver slices in the presence of carbapenems, potent inhibitory activity of carbapenems for the hydrolysis of VPA-G was found in monkey and rat liver homogenate. In vivo hydrolysis of VPA-G was clearly shown by the existence of VPA in plasma after dosing of VPA-G to rats, and its inhibition by carbapenems was also clearly shown by the negligible levels of VPA in rat plasma after coadministration of carbapenems and VPA-G. These results clearly indicate one of the important causes of drug interaction as follows: carbapenems would inhibit the hydrolytic enzyme, which is involved in the hydrolysis of VPA-G to VPA, resulting in a decrease of plasma concentration of VPA.

Comparison of clinical, magnetic resonance and evoked potentials data in a case of valproic-acid-related hyperammonemic coma

Magnetic resonance (MR) multimodality evoked potentials (MEPs) and clinical findings were correlated in a 47-year-old epileptic man in whom parenteral valproic acid (VPA) therapy induced severe comatose hyperammonemic encephalopathy without biological signs of hepatotoxicity (or hepatocytic dysfunction). Although the plasma VPA level remained within a normal therapeutic range, the ammoniemia increased to a toxic peak level at 411 micromol/l 24 h after symptom onset, requiring VPA therapy discontinuation. Brain MR monitoring demonstrated early cytotoxic edema evolving into delayed vasogenic edema and final brain atrophy. Concomitantly to abnormalities within the brainstem on MR images, an increase in brainstem conduction at MEPs and clinical disturbance of brainstem reflexes were observed at the initial phase of the disease course. Later, the resolution of the MR and MEPs abnormalities paralleled the clinical recovery of the reflexes.