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PubMed2004

Meropenem decreases serum level of valproic acid.

Concomitant administration of meropenem has been reported to decrease serum level of valproic acid both in humans and in animals. This report describes three children who required simultaneous administration of valproic acid and meropenem. Meropenem rapidly decreased serum valproic acid concentration to subtherapeutic levels in all three children, and serum valproic acid levels were returned to therapeutic levels in a short time after discontinuing simultaneous meropenem therapy. Valproic acid was not changed to another antiepileptic agent, because no seizure activity was observed. To our knowledge, this is the first case report on the simultaneous administration of meropenem and valproic acid in childhood. In conclusion, it is clear that concomitant meropenem administration decreases serum valproic acid concentration, and we believe that there may be no need to change the antiepileptic drug during this period, provided that the patient has no seizure. More detailed studies are required.

Adolescent↗

PubMed2005

Lack of pharmacokinetic interactions between steady-state zonisamide and valproic acid in patients with epilepsy.

OBJECTIVES: This study evaluated the effect of the addition of zonisamide on valproic acid (valproate sodium) pharmacokinetics under steady-state conditions in patients with epilepsy. A second aim was to characterise zonisamide pharmacokinetics in the presence of valproic acid. METHODS: Twenty-two patients (males and females, 18-55 years of age) with their seizure disorder stabilised on valproic acid monotherapy were included in a two-centre, open-label, one-way drug-interaction trial. The zonisamide dose was gradually increased from 100 mg/day to 400 mg/day. Three pharmacokinetic profiles were obtained: on days -7 and -1, to assess pharmacokinetic parameters of oral valproic acid administered alone, and on day 35, after 14 days of zonisamide treatment at the maximal tolerated dose, to evaluate the effect of zonisamide on valproic acid pharmacokinetics and to characterise zonisamide pharmacokinetics in the presence of valproic acid. RESULTS: Seventeen patients completed the study, with 16 patients contributing to the pharmacokinetic analyses. Coadministration of zonisamide and valproic acid appeared reasonably well tolerated. Steady-state dosing of zonisamide (200mg twice daily) had no statistically significant effect on the mean (+/- SD) maximum observed plasma concentration (C(max)) [70.8 +/- 20.5 vs 69.2 +/- 27.0 microg/mL], area under the plasma concentration-time curve from the time of dosing to 12 hours post-dose (AUC(12)) [689.3 +/- 250.4 vs 661.8 +/- 251.3 microg . h/mL] or other evaluated pharmacokinetic parameters for valproic acid measured before and after zonisamide administration. Furthermore, 90% confidence intervals for the ratio of the geometric means (day 35/day -1) of valproic acid pharmacokinetic exposure measures fell only slightly outside the 'no effect' range of 0.80-1.25. In the presence of valproic acid, mean zonisamide oral clearance (1.23 L/h) and elimination half-life (52.5 hours) are generally consistent with values reported for healthy volunteers receiving zonisamide monotherapy. CONCLUSION: There is no apparent clinically significant effect of steady-state dosing of zonisamide on valproic acid pharmacokinetics, and valproic acid did not appear to affect the pharmacokinetics of zonisamide, indicating that no dosage adjustment of either drug should be required when they are used in combination in patients with epilepsy.

Adult↗

PubMed2006

Behavioral effects of short-term administration of lithium and valproic acid in rats.

Lithium and valproic acid are mood-stabilizing agents that are often used to manage the episodes of mania and depression that characterize bipolar disorder. These agents develop clinical efficacy with chronic treatment, but the neurobiological actions that contribute to their therapeutic effects remain unclear. The present work was designed to study and compare various behavioral effects of short-term administration of lithium chloride (LiCl) and valproic acid (VPA) in rats. Specifically, we examined the effects of acute and sub-acute injections of these agents on locomotor activity, behavior in the forced swim test (FST), and intracranial self-stimulation (ICSS) thresholds. Locomotor activity studies were used to identify the range of doses with gross behavioral effects in rats. At doses below those that suppressed activity (total distance traveled, in cm) in 1-h test sessions, LiCl had prodepressant-like effects: it increased immobility in the FST, an effect opposite to that typically seen with standard antidepressants, and it increased ICSS thresholds, an effect similar to that typically seen during withdrawal from drugs of abuse. In contrast, VPA had no effects in the FST or on ICSS thresholds. This work identifies potentially important characteristics that distinguish the drugs at doses below those that produce non-specific behavioral effects, and thus serves as a basis for designing and interpreting studies of long-term treatment.

Animals↗

PubMed1994

Reduced in vitro displacement of valproic acid from protein binding by salicylate in uremic sera compared with normal sera. Role of uremic compounds.

Limited studies indicate increased free fraction of valproic acid in uremia. One study also described displacement of valproic acid from protein binding by salicylate in children with epilepsy. The authors studied in vitro interaction of valproic acid and salicylate in uremic sera and compared their results with same interactions in normal sera. As expected, the concentrations of free valproic acid were always significantly higher in uremic sera compared with normal sera. When uremic sera were supplemented with both valproic acid and salicylate, a much lower displacement of valproic acid by salicylate was observed, compared with the effects observed in normal sera. Treatment of uremic sera with charcoal removed those uremic compounds, and the concentration of free valproic acid in charcoal-treated uremic sera were comparable to the concentrations observed in normal sera. When uremic compounds were extracted from charcoal with methanol, lyophilized, and added to normal serum, an increase in free valproic acid concentration in normal serum was observed, indicating that uremic compounds, rather than altering albumin structure, are responsible for elevated free valproic acid concentration in uremia. However, uremic extract failed to produce any further displacement of valproic acid in normal serum in the presence of salicylate. The authors concluded that uremic compounds are responsible for elevated free valproic acid concentrations, but the displacement of valproic acid by salicylate in uremic sera are less remarkable compared with such effect in normal sera.

Charcoal↗

PubMed2005

Valproic acid selectively inhibits conversion of arachidonic acid to arachidonoyl-CoA by brain microsomal long-chain fatty acyl-CoA synthetases: relevance to bipolar disorder.

RATIONALE: Several drugs used to treat bipolar disorder (lithium and carbamazepine), when administered chronically to rats, reduce the turnover of arachidonic acid, but not docosahexaenoic acid, in brain phospholipids by decreasing the activity of an arachidonic acid-selective phospholipase A(2). Although chronic valproic acid produces similar effects on brain arachidonic acid and docosahexaenoic acid turnover, it does not alter phospholipase A(2) activity, suggesting that it targets a different enzyme in the turnover pathway. MATERIALS AND METHODS/RESULTS: By isolating rat brain microsomal long-chain fatty acyl-CoA synthetases (Acsl), we show in vitro that valproic acid is a non-competitive inhibitor of Acsl, as it reduces the maximal velocity of the reaction without changing the affinity of the substrate for the enzyme. While valproic acid inhibited the synthesis of arachidonoyl-CoA, palmitoyl-CoA, and docosahexaenoyl-CoA, the K (i )for inhibition of arachidonoyl-CoA synthesis (14.1 mM) was approximately one fifth the K (i) for inhibiting palmitoyl-CoA (85.4 mM) and docosahexaenoyl-CoA (78.2 mM) synthesis. As chronic administration of valproic acid in bipolar disorder achieves whole-brain levels of 1.0 to 1.5 mM, inhibition of arachidonoyl-CoA formation can occur at brain concentrations that are therapeutically relevant to this disease. Furthermore, brain microsomal Acsl did not produce valproyl-CoA. CONCLUSIONS: This study shows that valproic acid acts as a non-competitive inhibitor of brain microsomal Acsl, and that inhibition is substrate-selective. The study supports the hypothesis that valproic acid acts in bipolar disorder by reducing the brain arachidonic acid cascade, by inhibiting arachidonoyl-CoA formation.

Acyl Coenzyme A↗

PubMed1994

Valproic acid. A reappraisal of its pharmacological properties and clinical efficacy in epilepsy.

Valproic acid is a branched-chained fatty acid, structurally unrelated to any other antiepileptic drug. Since publication of the original review in the Journal in 1977, several clinical trials have documented its efficacy and safety in adults and children for the treatment of generalised seizures (absence, tonic-clonic, myoclonic), partial seizures (simple, complex, secondarily generalised) and compound/combination seizures (including those refractory to treatment with other antiepileptic drugs). Valproic acid monotherapy has demonstrated efficacy equivalent to that of carbamazepine, phenytoin, and phenobarbital in the treatment of both generalised and partial seizures and ethosuximide in the treatment of absence seizures. Adverse effects associated with the drug are primarily gastrointestinal (nausea, vomiting, dyspepsia) in nature, although the use of enteric-coated formulations has reduced the incidence of abdominal discomfort. Weight gain, tremor and transient hair loss are commonly reported. Importantly, valproic acid has minimal neurological adverse effects (sedation, ataxia, impairment of cognitive function) compared with other antiepileptic drugs, a finding that may be of particular relevance in many patients with epilepsy. The incidence of rare, fatal liver failure has been greatly reduced by identifying and avoiding administration of valproic acid to high risk patient populations. An estimated risk of 1 to 2% for neural tube defects, predominantly spina bifida aperta, with maternal use of valproic acid therapy has been reported. Valproic acid inhibits hepatic drug metabolism and displaces other highly bound drugs from their plasma protein binding sites. Therefore, coadministered drugs which are highly protein bound or hepatically metabolised may require dosage adjustment. Enzyme-inducing antiepileptic drugs may increase valproic acid metabolism and necessitate increasing its dosage. Thus, comparative trials and extensive clinical experience have demonstrated the efficacy and tolerability of valproic acid and support its role as a valuable and well established first-line treatment for patients with a broad range of seizure types.

Adult↗

PubMed2004

Valproic acid intoxication: sense and non-sense of haemodialysis.

INTRODUCTION: Valproic acid is increasingly used in the treatment of epilepsy, and also prescribed for bipolar affective disorders, schizoaffective disorders, schizophrenia and migraine prophylaxis. We describe two case reports involving valproic acid intoxication with ingestion of ethanol. METHODS: One patient was treated by supportive care, one patient received haemodialysis. RESULTS: From analysis of plasma concentrations before and during haemodialysis (pre- and post-filter) it is shown that valproic acid can be effectively eliminated by haemodialysis when plasma levels are way above 100 microg/ml. In the literature, plasma protein binding is reported to be around 90% for levels within the therapeutic range. In our patient plasma protein binding was around 50% after treatment with haemodialysis. CONCLUSION: These findings make haemodialysis in valproic acid intoxication a sensible therapeutic option with increasing efficiency when plasma concentration is high. Furthermore our findings suggest that lowering valproic acid concentrations to a therapeutic level by haemodialysis does not necessarily result in an immediate, simultaneous increase in plasma protein binding of valproic acid.

Adult↗

PubMed1984

The effects of neuroleptics (haloperidol and chlorpromazine) on the pharmacokinetics of valproic acid in schizophrenic patients.

The steady state trough concentrations (Cmin) and pharmacokinetics of valproic acid were investigated in schizophrenic patients during the treatment of valproic acid, 200 mg, twice daily and after the one dose of 400 mg, respectively, with and without haloperidol (6 to 10 mg/day, N = 6) or chlorpromazine (100 to 300 mg/day, N = 6). Four to 5 Cmin were monitored just before the morning valproic acid dose for 3 to 4 days preceding the kinetic study. The overall Cmin of valproic acid with chlorpromazine (33.2 +/- 1.7 micrograms/ml, N = 25) was significantly (p less than 0.01) greater than without (27.1 +/- 1.4 micrograms/ml, N = 25). The majority of the mean valproic acid concentrations observed after the 400-mg dose were significantly (p less than 0.05 to 0.01) greater during the chlorpromazine treatment as compared to those without the phenothiazine. The mean t1/2 was shortened from 15.4 +/- 1.4 to 13.5 +/- 1.2 hours (p less than 0.05) with a comparable increase in the clearance from 7.18 +/- 0.38 to 8.32 +/- 0.34 ml/hour/kg (p less than 0.01) after the discontinuation of chlorpromazine. All the patients revealed an increase in the valproic acid clearance after the chlorpromazine therapy was discontinued. When viewed overall, such a trend as found in the chlorpromazine group was not observed in the haloperidol group. The results suggest that chlorpromazine, but not haloperidol, inhibits the metabolism of valproic acid. However, the clinical significance of the interaction awaits future study.

Adult↗

PubMed2000

Evidence for a trigger function of valproic acid in xenobiotic-induced hepatotoxicity.

The influence of the antiepileptic drug, valproic acid (2-n-propylpentanoic acid), on the hepatocellular capacity, to cope with an extrinsic oxidative stress was investigated. Freshly isolated rat hepatocytes exposed to therapeutic concentrations of valproic acid (0.25-1.0 mmol/l) were less resistant than controls, as evidenced by a significant cytotoxic response after challenge of the cells with a non-toxic dose of allyl alcohol (2-propen-1-ol). Valproic acid alone was not toxic to hepatocytes even at ten times higher concentrations (10 mmol/l), suggesting that cell damage was not a mere additive effect. Incubation with valproic acid plus allyl alcohol induced an irreversible depletion of hepatocellular glutathione, in contrast to allyl alcohol alone which induced a transient loss. Hepatocytes treated with valproic acid plus allyl alcohol were protected by N-acetylcysteine, a precursor of glutathione. These findings indicate that valproic acid affects hepatocellular defence mechanisms and suggest that a predisposition of hepatocytes to oxidative stress may play a role in the fatal hepatotoxicity of valproic acid in epileptic patients.

Acetylcysteine↗

PubMedDate not supplied

Effects of three antacids on the bioavailability of valproic acid.

The effects of three antacid products on the bioavailability of valproic acid were evaluated. Each of seven normal, healthy volunteers received a 500-mg dose of valproic acid alone on one occasion and then with each of three commonly used antacids. Specifically, equal neutralizing capacity doses of 160 meq of Maalox (62 ml), Trisogel (97 ml), or Titralac (42 ml) were administered one and three hours after meals and at bedtime on the same day. Blood samples were obtained at 0, 1, 2, 4, 6, 8, 10, 24, and 32 hours and analyzed for valproic acid by gas liquid chromatography. There was a significant increase in total area under the curve (AUC) (range 3% to 28%, mean 12%) when valproic acid was administered with Maalox (p = 0.026 for total AUC and p = 0.009 for AUC to 32 hours). There was an insignificant trend toward an increase in AUC when valproic acid was administered with the other two antacids. No differences were observed in time to peak serum concentration, height of peak serum concentration, volume of distribution, half-life, or first order elimination rate constant. Caution should be exercised if valproic acid and antacids are administered concomitantly.

Adult↗

PubMed1982

Asymptomatic hyperammonemia in patients receiving valproic acid.

To determine the frequency of hyperammonemia in asymptomatic patients receiving valproic acid, plasma ammonia concentrations were measured in 55 patients receiving this drug and in 12 patients receiving other anticonvulsants. Twenty-nine of the 55 patients receiving valproic acid and none of the control patients had plasma NH3 levels above the normal range. Ten of the 11 patients receiving both valproic acid and phenytoin sodium in combination had elevated NH3 levels, as did five of six patients receiving both valproic acid and phenobarbital sodium. Elevations in plasma NH3 levels, as high as 140 mumole/L, were well tolerated, and valproic acid dose reductions were not necessary. Based on our findings, hyperammonemia is not an indication for reducing or eliminating valproic acid therapy.

Adolescent↗

PubMed1993

[A case of acute pancreatitis during administration of valproic acid].

We reported a case of acute pancreatitis occurring during administration of valproic acid for epilepsy. About four years prior to the first onset of acute pancreatitis, treatment with valproic acid for his seizures was started. The first pancreatitis improved by conservative therapy within a week. He continued valproic acid after the first episode. Two months later, the second acute pancreatitis occurred. The second episode was complicated with disseminated intravascular coagulation, but responded to conservative therapy. After the second episode, the valproic acid was discontinued and pancreatitis has not recurred. Pancreatitis associated with valproic acid may be severe, and therefore valproic acid should be used with caution.

Acute Disease↗

PubMed2001

Pancreatitis associated with valproic acid: a review of the literature.

Black box warnings for valproic acid caution clinicians of the potential for fatal hepatotoxicity and teratogenicity. Since 1979, case reports of pancreatitis induced by valproic acid have been published in the medical literature. As a result, pancreatitis was added to the black box warnings for valproic acid. We performed searches of MEDLINE and International Pharmaceutical Abstracts and found valproic acid-induced pancreatitis in 45 patients from 31 published articles. Demographics, clinical characteristics, and outcomes of these patients are summarized. Recommendations for monitoring the potential for pancreatitis to develop in patients receiving valproic acid therapy are described, as are potential mechanisms for inducement of pancreatitis by valproic acid.

Amylases↗

PubMed2007

Meropenem -valproic acid interaction in patients with cefepime-associated status epilepticus.

PURPOSE: Two case reports of rapid decreases in valproic acid levels after initiation of meropenem in patients who developed new-onset seizure activity during treatment with cefepime are presented. SUMMARY: A 60-year-old Caucasian woman with myelodysplasia was transferred to the medical intensive care unit (MICU) on day 11 of her hospitalization. Cefepime was given as empiric therapy for febrile neutropenia. Pulmonary invasive aspergillosis was diagnosed. On day 16 of hospitalization, epileptic activity was confirmed. Valproic acid was initiated. Cefepime was discontinued and meropenem was initiated for treatment of cefepime-resistant pneumonia. Serum valproic acid levels decreased to subtherapeutic levels within 24 hours. Meropenem was discontinued and ceftazidime was started on day 22; serum valproic acid levels gradually increased but never reached therapeutic levels again. The patient died of intractable invasive aspergillosis on day 33. A 54-year-old Caucasian man with myelodysplasia was admitted to the MICU for nonconvulsive status epilepticus. Ten days before admission, cefepime had been started empirically for the treatment of neutropenic fever. One day before MICU admission, valproic acid was initiated as treatment for status epilepticus. The next day, serum valproic acid levels were therapeutic; cefepime was switched to meropenem. Serum valproic acid levels decreased within 24 hours and phenytoin was added. On day 4, the patient's serum valproic acid levels decreased further and meropenem was discontinued. Although the valproic acid dosage was increased, valproic acid levels did not return to the therapeutic range. The patient died on day 11. CONCLUSION: Following cefepime therapy, a clinically important interaction between meropenem and valproic acid occurred in two critically ill patients with new-onset status epilepticus.

Anti-Bacterial Agents↗

PubMed2001

Methsuximide reduces valproic acid serum levels.

The authors investigated whether methsuximide affects serum levels of valproic acid. Pre-morning-dose serum valproic acid levels were measured in 17 patients (12 male, 5 female; age range, 8-19; mean, 14.5 years) who either started or stopped taking methsuximide but whose dose of valproate and other medication remained unchanged. Four of these patients both started and stopped taking methsuximide. For the whole group the mean valproic acid level (+/- standard error) while not taking methsuximide was 81.9 +/- 5.3 mg/L and while taking methsuximide was 55.7 +/- 4.3 mg/L. The difference between the means was highly significant (paired t test, p < 0.001). The mean valproic acid serum level before taking methsuximide was 85.4 +/- 4.5 mg/L (14 patients), which decreased to 58.2 +/- 4.8 mg/L while taking methsuximide (difference highly significant, p < 0.001). In the eight patients who stopped taking methsuximide the mean serum level increased from 49.8 +/- 7.5 mg/L to 71.7 +/- 8.5 mg/L (difference significant p = 0.025). Because methsuximide reduces valproic acid serum levels, it may be necessary to increase the valproate dose when methsuximide is added or reduce the valproate dose when methsuximide therapy stops, to avoid loss of seizure control or valproate toxicity respectively.

Adolescent↗

PubMed1991

Single dose and steady state pharmacokinetics of valproic acid in adult epileptic patients.

The pharmacokinetics of valproic acid was studied in ten adult epileptic patients (five f + five m, 19-48 years; 28 +/- 12, mean +/- SD, and body mass 45 to 70 kg; 61 +/- 7, mean +/- SD) both after single dose and at the steady state. Sodium valproate was given in a 900 mg single oral dose on the first day of therapy, followed by 3 x 300 mg/day during the three subsequent days (at the intervals of 7, 8 and 9 h). During the first day, plasma was obtained just before the drug was given, and at 0.5, 1, 2, 3, 4, 5, 6, 8, 10 and 12 h after drug administration. On the fourth day of therapy (at steady state), plasma was obtained just before the next dose and 3 h after the drug administration. The plasma concentrations of valproic acid were measured by gas chromatography with flame ionization detection, after extraction with chloroform. The pharmacokinetic parameters, necessary to define the pharmacokinetics of valproic acid, were calculated both after single dose: Cmax, tmax, kel, t1/2, Vd, AUC and Cl, and at steady state: Cminss Cmaxss and Fl%. These parameters, as well as plasma levels of the drug, were used to describe the pharmacokinetic behaviour of valproic acid under these clinical conditions, and mainly were in agreement with the values published in the literature.

Administration, Oral↗

PubMed1980

[Metabolic interaction of valproic acid (author's transl)].

Valproic acid produces a marked competitive inhibition of the aminophenazone N-demethylation and the codeine phosphate O-demethylation by 9000 g-supernatant of rat liver homogenates, but it exerts virtually no effect on the aniline hydroxylation and the p-nitrophenol glucuronidation which are slightly inhibited only if its tenfold amount is allowed to react on the substrate.

Aminopyrine↗

PubMedDate not supplied

[Hepatotoxicity of valproic acid treatment].

Hepatotoxicity of valproic acid (VPA) is reported in a psychomotor retarded boy. A four-month antiepileptic therapy was followed by a combined VPA/phenytoin treatment where-upon, two months later, the patient died in a hepatic coma. In the final state the metabolic pattern of VPA was still found within the normal range with the exception of the two abnormal metabolites 4-en-VPA) (2-propyl-4-pentenoic acid) and 4.4'-dien-VPA (2-(2-propenyl-4-pentenoic acid) detected only in low concentration. The amino acid pattern in plasma was characterized by a decrease or branched chain amino acids by 50% in contrast to the increase of the aromatic amino acids. Methionine, however, was in the normal range. Due to lack of a biochemical parameter indicating a possibly irreversible development of VPA induced hepatotoxicity stopping of VPA therapy should be obligatory if abnormal unsaturated VPA metabolites are detected or if dien-VPA/3, a normal metabolic compound, is increased above the normal range. L-carnitine treatment is recommended as a prophylactic therapy.

Child, Preschool↗