Serum Valproate Levels with Oral Contraceptive Use

Valproic Acid Induces Endocytosis-Mediated Doxorubicin Internalization and Shows Synergistic Cytotoxic Effects in Hepatocellular Carcinoma Cells

Valproic acid (VPA), a well-known histone deacetylase (HDAC) inhibitor, is used as an anti-cancer drug for various cancers, but the synergistic anti-cancer effect of VPA and doxorubicin (DOX) combination treatment and its potential underlying mechanism in hepatocellular carcinoma (HCC) remain to be elucidated. Here, we evaluate the mono- and combination-therapy effects of VPA and DOX in HCC and identify a specific and efficient, synergistic anti-proliferative effect of the VPA and DOX combination in HCC cells, especially HepG2 cells; this effect was not apparent in MIHA cells, a normal hepatocyte cell line. The calculation of the coefficient of drug interaction confirmed the significant synergistic effect of the combination treatment. Concurrently, the synergistic apoptotic cell death caused by the VPA and DOX combination treatment was confirmed by Hoechst nuclear staining and Western blot analysis of caspase-3 and poly (ADP-ribose) polymerase (PARP) activation. Co-treatment with VPA and DOX enhanced reactive oxygen species (ROS) generation and autophagy, which were clearly attenuated by ROS and autophagy inhibitors, respectively. Furthermore, as an indication of the mechanism underlying the synergistic effect, we observed that DOX internalization, which was induced in the VPA and DOX combination-treated group, occurred via by the caveolae-mediated endocytosis pathway. Taken together, our study uncovered the potential effect of the VPA and DOX combination treatment with regard to cell death, including induction of cellular ROS, autophagy, and the caveolae-mediated endocytosis pathway. Therefore, these results present novel implications in drug delivery research for the treatment of HCC.

Neuroendocrinological aspects of epilepsy: important issues and trends in future research

Neuroendocrine research in epilepsy focuses on the interface among neurology, endocrinology, gynecology/andrology and psychiatry as it pertains to epilepsy. There are clinically important reciprocal interactions between hormones and the brain such that neuroactive hormones can modulate neuronal excitability and seizure occurrence while epileptiform discharges can disrupt hormonal secretion and promote the development of reproductive disorders. An understanding of these interactions and their mechanisms is important to the comprehensive management of individuals with epilepsy. The interactions are relevant not only to the management of seizure disorder but also epilepsy comorbidities such as reproductive dysfunction, hyposexuality and emotional disorders. This review focuses on some of the established biological underpinnings of the relationship and their clinical relevance. It identifies gaps in our knowledge and areas of promising research. The research has led to ongoing clinical trials to develop hormonal therapies for the treatment of epilepsy. The review also focuses on complications of epilepsy treatment with antiepileptic drugs. Although antiepileptic drugs have been the mainstay of epilepsy treatment, they can also have some adverse effects on sexual and reproductive function as well as bone density. As longevity increases, the prevention, diagnosis and treatment of osteoporosis becomes an increasingly more important topic, especially for individuals with epilepsy. The differential effects of antiepileptic drugs on bone density and their various mechanisms of action are reviewed and some guidelines and future directions for prevention of osteoporosis and treatment are presented.

Antiepileptic drugs and other medications: what interactions may arise?

Many patients with epilepsy are on lifelong therapy with antiepileptic drugs (AEDs), and AEDs are used for other conditions such as mood stabilization and headache prophylaxis. These drugs have high potential for clinically significant interaction with nonepilepsy drugs. Interactions occur largely through altered pharmacokinetics. One drug may increase the hepatic clearance of another, leading to attenuated efficacy of the affected drug. Alternatively, inhibition of liver metabolism by one drug can cause acute toxicity by reducing clearance of another drug. To identify potential drug interactions before they lead to toxicity or therapy failure, the treating clinician should combine knowledge of the patient's overall history with a general knowledge of comorbid conditions in which significant interactions involving AEDs are most likely to occur. Treatments susceptible to interactions include anticoagulants, antiarrhythmics, antibiotics, antiretroviral drugs, immunosuppressives, antineoplastics, and contraceptives. Therefore, it is important to obtain periodically a thorough history of medical problems, use of medications or herbal remedies, and adverse effects of medications. Physicians managing epilepsy patients should also strive to avoid potential drug interactions by favoring low-interaction AEDs in patients taking many other types of drugs. There is quite a large degree of patient heterogeneity in the extent of any given interaction between an AED and another drug. Indeed, some groups of patients may have different susceptibilities to such interactions because of genetic and environmental influences on drug metabolism. Effective treatment with AEDs should include attention to drug interactions.

Pharmacokinetic interactions between contraceptives and antiepileptic drugs

The occurrence of bi-directional drug interactions between antiepileptic drugs (AEDs) and combined oral contraceptives (OCs) pose potential risks of un-intended pregnancy and as well as seizure deterioration. It is well established that several of the older AEDs (carbamazepine, phenytoin and phenobarbital), are strong inducers of the hepatic cytochrome P450 (CYP) 3A4 enzyme system, and are associated with increased the risk of contraceptive failure. In addition, it is demonstrated that also some of the newer AEDs, oxcarbazepine and topiramate influence on the pharmacokinetics of OCs, which is thought to be due to a more selective induction of subgroups of the hepatic enzyme system. Estrogens containing OCs induce the glucuronosyltransferase and may reduce the plasma levels and the effect of AEDs cleared by glucuronidation. This has been most intensively studied for lamotrigine but also other AEDs, which undergoes glucuronidation processes, such as valproate and oxcarbazepine, may be affected by OCs. The magnitude of the drug-drug interactions show in general wide inter-individual variability and the change in the elimination rate is often unpredictable and can be influenced by a number of co-variants such as co-medication of other drugs, as well as genetic and environmental factors. It is therefore recommended that change in OC use is assisted by AED monitoring whenever possible.

Increased Apparent Oral Clearance of Valproic Acid during Intake of Combined Contraceptive Steroids in Women with Epilepsy

PURPOSE

To determine potential changes in total and unbound serum valproic acid (VPA) concentrations at steady-state during a cycle of intake of combined hormonal contraceptive (HC) steroids.

METHODS

Blood samples were collected from nine women stabilized on VPA monotherapy on two separate randomized occasions: (i) at the end of the 4- to 7-day HC-free interval, and (ii) on the last day of the HC intake period. Trough concentrations of VPA in serum and serum ultrafiltrates were determined by fluorescence polarization immunoassay.

RESULTS

In all women, total and unbound VPA concentrations were higher during the HC-free interval than during HC intake (means +/- SD: 425 +/- 184 vs. 350 +/- 145 micromol/L, respectively, for total VPA, p = 0.002, and 55 +/- 37 vs. 39 +/- 25 micromol/L, respectively, for unbound VPA, p = 0.005). Compared with the HC-free interval, HC intake was associated with a mean 21.5% increase in VPA total apparent oral clearance (from 8.0 +/- 5.2 to 9.7 +/- 6.4 ml/h/kg, p = 0.01) and a 45.2 % increase in VPA unbound apparent oral clearance (from 79 +/- 81 to 115 +/- 121 ml/h/kg, p = 0.029).

CONCLUSIONS

The apparent oral clearance of total and unbound VPA increases during the HC intake period compared with the HC-free interval, probably due to induction of glucuronosyltransferase by ethinylestradiol. The magnitude of the change varies across individuals, being potentially clinically relevant in some cases. Serum VPA concentrations should be monitored when adding or discontinuing HC steroids, and possibly during the on-off intervals of a HC cycle.

Clinically relevant drug interactions with antiepileptic drugs

Some patients with difficult-to-treat epilepsy benefit from combination therapy with two or more antiepileptic drugs (AEDs). Additionally, virtually all epilepsy patients will receive, at some time in their lives, other medications for the management of associated conditions. In these situations, clinically important drug interactions may occur. Carbamazepine, phenytoin, phenobarbital and primidone induce many cytochrome P450 (CYP) and glucuronyl transferase (GT) enzymes, and can reduce drastically the serum concentration of associated drugs which are substrates of the same enzymes. Examples of agents whose serum levels are decreased markedly by enzyme-inducing AEDs, include lamotrigine, tiagabine, several steroidal drugs, cyclosporin A, oral anticoagulants and many cardiovascular, antineoplastic and psychotropic drugs. Valproic acid is not enzyme inducer, but it may cause clinically relevant drug interactions by inhibiting the metabolism of selected substrates, most notably phenobarbital and lamotrigine. Compared with older generation agents, most of the recently developed AEDs are less likely to induce or inhibit the activity of CYP or GT enzymes. However, they may be a target for metabolically mediated drug interactions, and oxcarbazepine, lamotrigine, felbamate and, at high dosages, topiramate may stimulate the metabolism of oral contraceptive steroids. Levetiracetam, gabapentin and pregabalin have not been reported to cause or be a target for clinically relevant pharmacokinetic drug interactions. Pharmacodynamic interactions involving AEDs have not been well characterized, but their understanding is important for a more rational approach to combination therapy. In particular, neurotoxic effects appear to be more likely with coprescription of AEDs sharing the same primary mechanism of action.

Epilepsy as a consequence of cerebral malaria in area in which malaria is endemic in Mali, West Africa

PURPOSE

Cerebral malaria (CM) is suspected to be a potential cause of epilepsy in tropical areas, but little information is available. The purpose of this study was to evaluate the role of CM in epilepsy among children in Mali.

METHODS

An exposed-nonexposed study was performed to identify children who had epilepsy after malaria in the 0- to 15-year age group. The exposure factor was CM defined according to World Health Organization (WHO) criteria, and the nonexposure factor was symptomatic malaria without the characteristics of CM (NCM). All the children underwent a screening questionnaire and were examined by a medical physician. After the screening phase, a specialist in neuropediatrics examined the children suspected to have epilepsy. EEG and computed tomography (CT) scans were performed in some of these patients.

RESULTS

In total, 101 subjects who had had CM and 222 who had had NCM were included. Fifty-four children (CM, 34; NCM, 20) were suspected to have epilepsy, and six were confirmed (CM, five; NCM, one). The incidence rate was 17.0 per 1000 person-years in the CM group and 1.8 per 1000 person-year in the NCM group; thus the relative risk (RR) was 9.4 [95% confidence interval (CI), 1.3-80.3; p = 0.02]. After adjustment on age and duration of follow-up, the RR was 14.3 (95% CI, 1.6-132.0; p = 0.01).

CONCLUSIONS

The risk of sequelar epilepsy is significantly higher in the CM group compared with the NCM group. A reevaluation of this cohort should be carried out later to search for temporal epilepsy that appeared after age 10 years.