Preclinical toxicology of the anticonvulsant calcium valproate

Hepatotoxic Evaluation of N-(2-Hydroxyphenyl)-2-Propylpentanamide: A Novel Derivative of Valproic Acid for the Treatment of Cancer

Valproic acid (VPA) is a drug that has various therapeutic applications; however, it has been associated with liver damage. Furthermore, it is interesting to propose new compounds derived from VPA as N-(2-hydroxyphenyl)-2-propylpentanamide (HO-AAVPA). The HO-AAVPA has better antiproliferative activity than the VPA in different cancer cell lines. The purpose of this study was to evaluate the liver injury of HO-AAVPA by acute treatment (once administration) and repeated doses for 7 days under intraperitoneal administration. The median lethal dose value (LD50) was determined in rats and mice (females and males) using OECD Guideline 425. In the study, male rats were randomly divided into 4 groups (n = 7), G1: control (without treatment), G2: vehicle, G3: VPA (500 mg/kg), and G4: HO-AAVPA (708 mg/kg, in equimolar ratio to VPA). Some biomarkers related to hepatotoxicity were evaluated. In addition, macroscopic and histological studies were performed. The LD50 value of HO-AAVPA was greater than 2000 mg/kg. Regarding macroscopy and biochemistry, the HO-AAVPA does not induce liver injury according to the measures of alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, glutathione peroxidase, glutathione reductase, and catalase activities. Comparing the treatment with HO-AAVPA and VPA did not show a significant difference with the control group, while malondialdehyde and glutathione-reduced levels in the group treated with HO-AAVPA were close to those of the control (p ≤ 0.05). The histological study shows that liver lesions caused by HO-AAVPA were less severe compared with VPA. Therefore, it is suggested that HO-AAVPA does not induce hepatotoxicity at therapeutic doses, considering that in the future it could be proposed as an antineoplastic drug.

Clinical insights into drug-associated pancreatic injury

PURPOSE OF REVIEW

Drug-induced pancreatitis is one of the top three causes of acute pancreatitis. A drug exposure is traditionally determined to be the cause of pancreatitis only after other possible and common causes of pancreatitis have been excluded.

RECENT FINDINGS

In this review, we challenge this traditional notion of drug-induced pancreatitis as a diagnosis of exclusion. Instead, we propose to shift the paradigm of conceptualizing what we term drug-associated pancreatic injury (DAPI); as a continuum of pancreatic injury that can be concomitant with other risk factors. The aims of this targeted review are to harness recent literature to build a foundation for conceptualizing DAPI, to highlight specific drugs associated with DAPI, and to describe a framework for future studies of DAPI.

SUMMARY

Our hope is that probing and characterizing the mechanisms underlying the various types of DAPI will lead to safer use of the DAPI-inducing drugs by minimizing the adverse event of pancreatitis.

[Pharmacogenetic markers of metabolic disorders in the treatment with valproic acid]

The review includes studies on the association between the use of VA drugs and weight gain in patients with epilepsy as well as other valproate-induced adverse drug reactions, including insulin resistance. Understanding the mechanisms of significant weight gain of patients taking VA drugs will help personalize antiepileptic therapy and minimize the risk of valproate-induced obesity.

Changes in testicular function proteins and sperm acrosome status in rats treated with valproic acid

Valproic acid (VPA), an anti-epileptic drug, reduces testosterone levels and sperm quality. However, the degree to which testosterone levels and sperm quality are decreased under VPA treatment needs to be clarified. The aim of the present study was to investigate the testicular proteins involved in testosterone synthesis and spermatogenesis, histopathology and sperm acrosome status in VPA-treated rats. Adult rats were divided into control and experimental groups (n = 8 in each). Rats in the experimental group were treated with 500 mg kg–1, i.p., VPA for 10 consecutive days. Expression of Ki-67, tyrosine phosphorylated proteins and testicular steroidogenic proteins was examined. As expected, VPA-treated rats exhibited adverse changes in almost all reproductive parameters, particularly an increase in precocious acrosome reactions, compared with the control group. In addition, fibrosis of the tunica albuginea and tubule basement membrane was observed in testes from VPA-treated rats. Moreover, the expression of testicular Ki-67, cholesterol side-chain cleavage enzyme (P450scc) and phosphorylated proteins (41, 51 and 83 kDa) was decreased significantly in VPA-treated rats compared with control. In contrast, the expression of steroidogenic acute regulatory proteins in the VPA-treated group was significantly higher than in the control group. In conclusion, VPA treatment changes the expression of testicular proteins responsible for spermatogenesis and testosterone production, resulting in male infertility.

Valproic Acid Limits Pancreatic Recovery after Pancreatitis by Inhibiting Histone Deacetylases and Preventing Acinar Redifferentiation Programs

The mechanisms by which drugs induce pancreatitis are unknown. A definite cause of pancreatitis is due to the antiepileptic drug valproic acid (VPA). On the basis of three crucial observations-that VPA inhibits histone deacetylases (HDACs), HDACs mediate pancreas development, and aspects of pancreas development are recapitulated during recovery of the pancreas after injury-we hypothesized that VPA does not cause injury on its own, but it predisposes patients to pancreatitis by inhibiting HDACs and provoking an imbalance in pancreatic recovery. In an experimental model of pancreatic injury, we found that VPA delayed recovery of the pancreas and reduced acinar cell proliferation. In addition, pancreatic expression of class I HDACs (which are the primary VPA targets) increased in the midphase of pancreatic recovery. VPA administration inhibited pancreatic HDAC activity and led to the persistence of acinar-to-ductal metaplastic complexes, with prolonged Sox9 expression and sustained β-catenin nuclear activation, findings that characterize a delay in regenerative reprogramming. These effects were not observed with valpromide, an analog of VPA that lacks HDAC inhibition. This is the first report, to our knowledge, that VPA shifts the balance toward pancreatic injury and pancreatitis through HDAC inhibition. The work also identifies a new paradigm for therapies that could exploit epigenetic reprogramming to enhance pancreatic recovery and disorders of pancreatic injury.

Seminal fluid analysis and testicular volume in adults with epilepsy receiving valproate

Epilepsy and its medications adversely affect reproductive and sexual functions and fertility. This study aimed to assess sperm parameters and testicular volume in men with epilepsy on valproate (VPA). Included were 55 patients with idiopathic epilepsy with a mean age of 31.86 ± standard deviation (SD) 6.55 years, mean illness duration of 12.50 ± SD 5.10 years, and a mean treatment time of 9.55 ± SD 0.85 years. Sex hormone profile, semen analysis, testicular volume and total seminal plasma carnitine were determined. Compared to controls, patients had lower levels of free testosterone (p<0.01), sperm concentration (p<0.0001) and count (p<0.0001), carnitine (p<0.01), and testicular volume (p<0.01), and higher rates of immotile sperm (p<0.001) and abnormal forms (p<0.0001). Significant correlations were identified between sperm count, motility, immotile sperm, abnormal forms, testicular volume, carnitine levels and duration of illness, duration of treatment with VPA and VPA dose. Multivariable analysis demonstrated that duration of treatment with VPA, sperm count, motility and abnormal forms were significantly associated with seminal plasma carnitine. Long-term VPA treatment is adversely associated with reduced sperm count and motility, increased abnormal sperm count and reduced testicular volume. This may contribute to reduced fertility.

Seminal fluid analysis and testicular volume in adults with epilepsy receiving valproate

Epilepsy and its medications adversely affect reproductive and sexual functions and fertility. This study aimed to assess sperm parameters and testicular volume in men with epilepsy on valproate (VPA). Included were 55 patients with idiopathic epilepsy with a mean age of 31.86 ± standard deviation (SD) 6.55 years, mean illness duration of 12.50 ± SD 5.10 years, and a mean treatment time of 9.55 ± SD 0.85 years. Sex hormone profile, semen analysis, testicular volume and total seminal plasma carnitine were determined. Compared to controls, patients had lower levels of free testosterone (p<0.01), sperm concentration (p<0.0001) and count (p<0.0001), carnitine (p<0.01), and testicular volume (p<0.01), and higher rates of immotile sperm (p<0.001) and abnormal forms (p<0.0001). Significant correlations were identified between sperm count, motility, immotile sperm, abnormal forms, testicular volume, carnitine levels and duration of illness, duration of treatment with VPA and VPA dose. Multivariable analysis demonstrated that duration of treatment with VPA, sperm count, motility and abnormal forms were significantly associated with seminal plasma carnitine. Long-term VPA treatment is adversely associated with reduced sperm count and motility, increased abnormal sperm count and reduced testicular volume. This may contribute to reduced fertility.

The effect of sodium valproate on the biochemical parameters of reproductive function in male albino Wistar rats

Objective:

To assess the effects of sodium valproate on intratesticular testosterone and lactic dehydrogenase level in rats.

Methods:

Male Wistar rats (12 weeks old) were treated with sodium valproate and sacrificed at the end of the 2^nd, 4^th, 5^th, 7^th, 10^th and 15^th week, after the last exposure to sodium valproate. The testes were removed, weighed and processed for biochemical analysis.

Results:

The intratesticular testosterone level was significantly (P<0.001) reduced in 200 mg/kg and 400 mg/kg treated rats. The intratesticular lactate dehydrogenase (LDH) level was significantly (P<0.001) increased by valproate in a time dependent manner.

Conclusion:

Valproate causes reversible change in intratesticular testosterone and LDH level.

Reproductive toxicity of sodium valproate in male rats

Objectives:

To assess the effects of sodium valproate on rat sperm morphology, sperm count, motility, and histopathological changes in testis.

Materials and Methods:

Male Wistar rats (12 week old) were treated with sodium valpraote and sacrificed at the end of 2^nd, 4^th, 5^th, 7^th, 10^th and 15^th week after the last exposure to sodium valproate. Epididymal sperm count, sperm motility, sperm morphology, and histopathology of testes were analyzed.

Results:

Sperm count and sperm motility were decreased significantly by sodium valproate. The percentage of abnormal sperms increased in a dose-dependent manner. A histopathological study revealed that sodium valproate had caused sloughing of epithelial cells in testes.

Conclusion:

Sodium valproate causes reversible change in sperm motility, sperm count, morphology, and cytoarchitecture of testes.

Weight gain following treatment with valproic acid: pathogenetic mechanisms and clinical implications

In the last years, a growing body of literature indicates an association between valproic acid therapy and weight gain. Weight gain during valproate treatment can be observed within the first 3 months of therapy and women seem to be more susceptible than men. The mechanism through which valproic acid may induce a weight gain is still controversial. The scope of this paper is to investigate the possible causal link between treatment and weight gain in epileptic patients. Systematic review of published epidemiological studies has been done in order to evaluate the real extent of this side effect of valproic acid and its clinical implications, such as an increased risk of insulin resistance and other secondary metabolic abnormalities. The knowledge of the potential of valproic acid to cause significant changes in body weight will help in appropriate selection and modification of antiepileptic therapy to minimize the risk for weight abnormalities. Measurements of body weight before initiation of valproic acid therapy should be done as part of the monitoring of patients with epilepsy to detect changes before there are serious adverse consequences; an increase of 2 kg of body weight after 1 month of treatment should imply considerations to change antiepileptic drug therapy.

Effects of chronic treatment with valproate and oxcarbazepine on testicular development in rats

PURPOSE

The aim of this study was to examine the potential effects of valproate (VPA) and oxcarbazepine (OXC) on testicular development in rats.

METHODS

Forty-two Wistar rats were randomly divided into three groups of 14 rats each. Each group received the following via gavage over 90 days: group 1, tap water (control group); group 2, VPA (300mg/kg/day); group 3, OXC (100mg/kg/day). After sacrifice, body, testicular and epididymidis weights were measured. Testes were sampled, fixed and processed, and quantitative morphometric analysis of Sertoli cells, spermatocytes and spermatids was performed in stages II, V and XII by histopathological examination. Immunohistochemical staining was performed to transform growth factor beta 1 (TGF-β1) and p53, and the apoptotic index was assessed using the TUNEL method.

RESULTS

Testis and relative testis weights were significantly lower in the VPA group compared to the control group (p<0.05). Spermatogonia, pachytene spermatocyte and round spermatocyte numbers decreased in all stages in both the VPA and OXC groups compared to the control group, though this was not statistically significant (p>0.05). Apoptotic cell counts and p53 immunoreaction were significantly high and TGF-β1 expression was significantly lower in the VPA group compared to that of the control group (p<0.05). In the OXC group, p53 immunoreaction and TGF-β1 expression decreased compared to the control group, but this difference did not attain statistical significance (p>0.05).

CONCLUSIONS

Our results show that VPA treatment from prepuberty to adulthood significantly negatively affects spermatogenesis, not only by reducing testicular weight, but also by increasing apoptotic death and p53 and decreasing TGF-β1 activation. OXC has a minimal side effect on testicular development.

Valproate attenuates accelerated atherosclerosis in hyperglycemic apoE-deficient mice: evidence in support of a role for endoplasmic reticulum stress and glycogen synthase kinase-3 in lesion development and hepatic steatosis

We have previously shown that glucosamine promotes endoplasmic reticulum (ER) stress in vascular cells leading to both inflammation and lipid accumulation--the hallmark features of atherosclerosis. Pretreatment with glycogen synthase kinase (GSK)-3 inhibitors protects cultured cells from ER stress-induced dysfunction. Here we evaluate the potential role of GSK-3 on the pro-atherogenic effects of hyperglycemia and ER stress. We show that GSK-3-deficient mouse embryonic fibroblasts do not accumulate unesterified cholesterol under conditions of ER stress. Furthermore, GSK-3 inhibitors, including valproate, attenuate ER stress-induced unesterified cholesterol accumulation in wild-type mouse embryonic fibroblasts. In vivo we show that hyperglycemic apoE-deficient mice have accelerated atherogenesis at the aortic root compared with normoglycemic control mice. Mice fed a diet supplemented with 625 mg/kg valproate have significantly reduced lesion volume relative to nonsupplemented controls. Valproate supplementation has no apparent effect on the plasma levels of either glucose or lipids or on the expression of diagnostic markers of ER stress in the lesion. Significant reductions were observed in total hepatic lipids (>50.4%) and hepatic GSK-3beta activity (>55.8%) in mice fed the valproate diet. In conclusion, dietary supplementation with low levels of valproate significantly attenuates atherogenesis in hyperglycemic apoE-deficient mice. The in vivo anti-atherogenic effects of valproate are consistent with its ability to inhibit GSK-3 and interfere with pro-atherogenic ER stress signaling pathways in vitro.

Serum and liver tissue biotinidase enzyme activity in rats which were administrated to valproic acid

Valproic acid (VPA) is an antiepileptic drug widely used and well-tolerated by most of patients. Its non-dose-dependent side effects seen mostly are the temporary gastrointestinal disturbances including anorexia and nausea, and hepatoxicity. As to its dose-dependent side effects are the weight loss, tremor, skin eruption and the alopecia. In this study we aimed to put forward the biotinidase deficiency considered as a possible cause of alopecia in the rats administered with valproic acid, and the correlation between liver and serum biotinidase enzyme activities (BEA) and transaminases, albumin and serum valproic acid levels. In our study, 4 groups of which one of them was a control group, each consisting of 15 male Wistar rats was organized. 200, 400, and 600 mg/kg/day of VPA, and distilled water, two divided doses per day, were administered per orally to VPA-1, VPA-2, VPA-3, and control group, respectively, in 60 days. Their serum and liver biotinidase enzyme activities, serum AST, ALT, albumin, and valproic acid levels were measured. Alopecia was seen in the subjects of 6.6% of VPA-1, 13.3% of VPA-2, and 26.6% of VPA-3. Significant difference in the liver tissues BEA was noted only between VPA-3 and the control group. Reductions were observed both in the liver tissues BEA and the serum BEA levels, which are inversely proportional to the VPA doses. A positive correlation between the liver biotinidase enzyme activities and the serum valproic acid levels, and the negative correlation between the liver tissues biotinidase activities and the serum valproic acid levels were noted, respectively. As a conclusion, the partial alopecia which is an initial symptom of reduced biotinidase activity may also be created depending on the reduction of biotinidase activity during valproic acid therapy. The alopecia which may further be observed in the patients receiving valproic acid therapy may be prevented by means of administration of biotin in a dose of 10 mg/day.

Effect of antiepileptic drugs on reproductive endocrine function in individuals with epilepsy

It is well known that epilepsy, antiepileptic drugs (AEDs), and the reproductive system have complex interactions. Fertility is lower in both men and women with epilepsy than in the general population. Moreover, reproductive endocrine disorders are more common among patients with epilepsy than among the population in general. These disorders have been attributed both to epilepsy itself and to use of AEDs. The use of the liver enzyme-inducing AEDs phenobarbital, phenytoin and carbamazepine increases serum sex hormone-binding globulin (SHBG) concentrations in both men and women with epilepsy. Over time, the increase in serum SHBG levels leads to diminished bioactivity of testosterone and estradiol, which may result in diminished potency in men and menstrual disorders in some women, and thus to reduced fertility. Liver enzyme-inducing AEDs also reduce the efficacy of oral contraceptives. Valproic acid medication may have effects on serum androgen concentrations and it reduces serum follicle stimulating hormone levels in men with epilepsy. However, the clinical significance of valproic acid-related reproductive endocrine changes in men is unknown. On the other hand, in women, use of valproic acid appears to be associated with a frequent occurrence of reproductive endocrine disorders characterised by polycystic changes in the ovaries, high serum testosterone concentrations (hyperandrogenism) and menstrual disorders. These disorders are especially common among women who have gained weight during valproic acid treatment. There are some discrepancies regarding the reported occurrence of reproductive endocrine disorders in women taking valproic acid for epilepsy. However, most studies also including patients receiving valproic acid for other reasons than epilepsy, and studies in different non-epileptic animal models, have shown an association between valproic acid medication and hyperandrogenism and related reproductive endocrine disorders. From a practical point of view, the length of the menstrual cycles and bodyweight should be monitored in women with epilepsy after commencement of treatment with valproic acid. A serum testosterone assay is helpful in following the possible biochemical endocrine changes. Ultrasonography of the ovaries (preferably transvaginal) is indicated if clinical assessment and serum testosterone measurement imply that there is a clinically significant valproic acid-related reproductive endocrine problem. That would be the case if the menstrual cycles were irregular or prolonged (usually >35 days) and serum testosterone levels elevated, especially with associated weight gain. The endocrine effects of the new AEDs have not been widely studied. However, it seems they may offer an alternative if reproductive endocrine problems emerge during treatment with the older AEDs.

Antiepileptic drugs inhibit cell growth in the human breast cancer cell line MCF7

Several antiepileptic drugs (AEDs) are associated with anti-cancer activity. At the same time, many AEDs alter endocrine function with phenytoin (PHT) and phenobarbital (PB) causing-reduced free fractions of sex-steroid hormones, while VPA induces hyperandrogenism. Changes in sex-steroid hormone levels are known to affect apoptosis in endocrine tissue. The aim of the study was to investigate the influence of the antiepileptic drugs PHT, PB, VPA and lamotrigine (LTG) on estrogen-stimulated cell growth of human breast cancer cells (MCF-7), and to evaluate whether this effect could be related to a direct estrogen receptor (ER) binding. VPA reduced cell growth at therapeutically relevant concentrations; half-maximum effect of VPA on cell growth was 230 microM. PHT (100 microM) and PB (10 microM) reduced cell growth by 47 and 21%, respectively. None of the drugs had affinity to isolated estrogen receptors, and excess of estrogen was not able to abolish the growth inhibition provoked by VPA. However, sub-therapeutic concentrations of VPA (100 microM) mimicked estrogen by inducing cell growth (11%) in an estrogen-depleted medium, an effect that was abolished by adding an estrogen receptor antagonist. In conclusion; the estrogen receptor appear to be indirectly activated by sub-therapeutic concentrations of VPA, but therapeutic concentrations of VPA inhibits cell growth by mechanisms that do not seem to involve the estrogen receptor or estrogen stimulation.

Effects of chronic valproate treatment on reproductive endocrine hormones in female and male Wistar rats

Valproate (VPA) has been claimed to induce endocrine disorders in both sexes in humans. There is sparse information regarding the mechanisms behind these disturbances. By using an animal model, we wanted to study the effect of valproate on hormonal function in non-epileptic rats. Female rats were given 0 (vehicle control, n=15), 200mg/kg (n=15), or 300 mg/kg (n=20) valproate twice daily by gavage for 90 days, resulting in mean valproate concentrations within the therapeutic range 4-6h after the last dose given. Serum testosterone concentrations remained unchanged, while estradiol levels were significantly reduced in both treatment groups, leading to significantly increased testosterone/estradiol ratios. Follicle stimulating hormone (FSH) levels remained unaltered in valproate treated rats, whereas the luteinizing hormone (LH) concentrations were reduced at the lowest valproate dose. Male rats received 0 (vehicle control, n=15), 200mg/kg (n=15), or 400mg/kg (n=20) valproate twice daily by gavage for 90 days, resulting in mean valproate concentrations within the therapeutic range 4-6h after the last dose. Serum testosterone levels were not significantly changed, but there was a highly significant increase in FSH and LH concentrations at the high dose. In conclusion, the study demonstrates a drug-induced effect of valproate on endocrine function in both male and female rats. The results indicate that the drug exerts its effect primarily at the gonadal level, although a centrally mediated effect cannot be ruled out.

Morphological changes in the testis after long-term valproate treatment in male Wistar rats

Uncertainty exists about the effect of antiepileptic drugs on gonadal function. In females, long-term valproate treatment has been shown to induce endocrine disturbances and an increased number of ovarian cysts. The aim of the present study was to investigate whether valproate can also induce morphological changes in the testis of male animals. In addition, possible morphological changes in the liver, heart, lungs, lymphatic nodes, pancreas, kidney or brain were studied. The carcinogenic implications were evaluated by the measurement of p53. Male Wistar rats were fed perorally with valproate mixture 200 mg kg(-1)(n= 15) or 400 mg kg(-1)(n= 20), or control solution (n= 15) twice daily for 90 days. Serum concentrations measured 4-6 hours after the last dose were 105 and 404 micromol l(-1)in low- and high-dose valproate treated animals respectively. There was a highly significant, 51% decrease (P< 0.001) in testicular weight in the high-dose treated valproate rats with no changes in the other groups. There was widespread testicular atrophy with histologically verified spermatogenic arrest in 15/20 of the high-dose valproate treated animals. No changes in the testis were seen in the low-dose valproate treated rats, nor in the control rats. There were no morphological changes in the other investigated organs. None of the groups showed over-expression of p53. In conclusion, a dose-dependent effect of chronic valproate treatment was found on testicular morphology in rats. Caution must be taken before these results can be applied to humans.

Valproate, but not lamotrigine, induces ovarian morphological changes in Wistar rats

Valproate (VPA) medication is associated with development of polycystic ovaries, menstrual disorders and hormonal changes in women with epilepsy. We sought to determine if changes in the ovaries also occurred in an animal model without epilepsy, and whether this effect could be related to a carcinogenic effect expressed by overexpression of p53. A potentially alternative antiepileptic drug, lamotrigine (LTG), was evaluated simultaneously. To this end, female Wistar rats were fed perorally with VPA 400 mg/kg/day (n = 15), VPA 600 mg/kg/day (n = 20), LTG 10 mg/kg/day (n = 15) or control solution (n = 15) for 90-95 days. There was a significant, dose-dependent increase in the number of follicular cysts, reduction in the number of corpora lutea and reduction of ovarian weight in the VPA group. No ovarian pathology was observed in the LTG group. In neither of the groups were morphological changes seen in other organs, nor was there any overexpression of the tumor suppressor gene p53 found. An alternative antiepileptic drug, LTG, showed no ovarian pathology, and there were no light microscopic changes in other organs, or evidence of pathologic p53 overexpression in the LTG-treated animals.

Long-term valproate treatment induces changes in ovarian morphology and serum sex steroid hormone levels in female Wistar rats

Long-term valproate treatment is associated with polycystic ovaries and endocrine disorders in women with epilepsy. The mechanisms responsible for these effects are unknown, but both the epilepsy itself and the drug per se may be of importance. The aim of this study was to investigate possible effects of the drug on gonadal structure and function in animals with no epileptic disorders. Three groups, each of 15 female Wistar rats, were fed perorally with a valproate mixture (50 mg / kg or 200 mg / kg) or control solution once daily for 90 days, giving mean valproate concentrations within the normal human range. A significant, 20% increase in ovary weight was found in both low- (P = 0.027) and high- (P < 0.001) dose animals together with a significantly increased number of ovarian follicular cysts. Mean serum testosterone concentration was significantly reduced in both low- and high-dose animals. There was a non-significant trend towards reduced estrogen levels, while progesterone levels were unchanged. Even if the hormonal changes are somewhat different from those in humans, the findings demonstrate that changes in gonadal structure and endocrine function also occur in intact animals indicating a drug-specific effect. Our findings encourages further studies using animal models to elucidate possible mechanisms involved in the endocrine side-effects of antiepileptic drugs.

Biochemical basis of sodium valproate hepatotoxicity and renal tubular disorder: time dependence of peroxidative injury

Mice fed with sodium valproate for 7, 14 and 21 days were evaluated for hepatotoxicity and renal tubular disorder. The drug was administered as an aqueous solution with an increasing concentration up to five days gradually reaching up to 0.71% w/v, which persisted throughout the study period. Mice fed with sodium valproate for 7, 14 and 21 days showed, marked hepatic injury and renal tubular disorder, evidenced by increased levels of malondialdehyde as a measure of lipid peroxidation. Administration of sodium valproate affected the glutathione contents both in liver and kidney tissue at all the three time points. However, this reduction in glutathione concentration was more pronounced in kidney when compared to control group. These results support the hypothesis that lipid peroxidation mediates the effect of sodium valproate on liver and kidney. Furthermore, the valproate induced toxicity is time related and the increase in lipid peroxide levels and depletion of glutathione occur time dependent even if the dose is clinically appropriate.

Drug-induced pancreatitis

Few data exist about the incidence of drug-induced pancreatitis in the general population. 20 cases of drug-related pancreatitis were reported in Switzerland over a period of 12 years. The proportion of cases of pancreatitis caused by drugs is estimated to be around 2% in the general population, with much higher proportions in specific subpopulations, such as children and patients who are HIV positive. The literature about drug-induced pancreatitis consists mainly of anecdotal case reports. Clear evidence of a definite association with pancreatitis, by means of rechallenge tests, or consistent case reports, supported by animal experiments or data on the incidence of acute pancreatitis in drug trials exists for didanosine, valproic acid (sodium valproate), aminosalicylates, estrogen, calcium, anticholinesterases and sodium stibogluconate. An association with drug-induced pancreatitis is likely but not definitely proven for thiazide diuretics, pentamidine, ACE inhibitors, asparaginase, vinca alkaloids, some nonsteroidal anti-inflammatory drugs and clozapine. Pancreatitis is possibly caused by azathioprine, furosemide (frusemide), tetracycline, metronidazole, isoniazid, rifampicin (rifampin), sulphonamides, cyclosporin and some antineoplastic drugs. Many drugs have been reported to be associated with acute pancreatitis. However, lack of rechallenge evidence, consistent statistical data, or evidence from experimental studies on a possible mechanism prohibit definitive conclusions about most of them. The high incidence of concurrent illnesses known to induce acute pancreatitis, makes a trigger role or co-factor role for the drug seem most likely.

Calcium valproate-induced uterine adenocarcinomas in Wistar rats

Calcium valproate is an anticonvulsant agent with pharmacokinetic properties similar to sodium valproate and valproic acid. Potential carcinogenesis of calcium valproate was evaluated in B6C3F1 mice and Wistar rats given 125, 250 and 500 mg/kg in the diet for 104 weeks. Survival in treated rats increased in a dose-related pattern despite a tumorigenic response in females. Adenocarcinomas of the uterus and cervix were increased in treated rats when compared to controls. The incidence of uterine neoplasia was 8, 20, 14 and 32% in the control, 125, 250 and 500 mg/kg groups, respectively. Neoplasia in treated rats were detected against a higher than expected background of adenocarcinomas in concurrent controls, since 8% incidence in controls was substantially above the laboratory historical database value of 0.6%. Tumors varied from epithelial masses confined to the endometrium, to transmural, highly desmoplastic neoplasms that invaded the serosa lining and the peritoneal cavity. These tumors metastasized in treated rats but not in controls. The statistically significant (P less than 0.01) increase in uterine adenocarcinomas found in females given 500 mg/kg of calcium valproate contrasts the absence of this tumor type in a previous rat carcinogenicity bioassay with valproic acid. Subcutaneous fibrosarcomas were significantly increased in valproic acid-treated males, but no uterine tumors were reported in females. It is puzzling that a true carcinogenic potential would be expressed by markedly different target organs as obtained with the acid and calcium salt of this moiety.