The regulation of serum sodium after replacing carbamazepine with oxcarbazepine

Hyponatremia induced by antiepileptic drugs in patients with epilepsy

INTRODUCTION

Hyponatremia induced by antiepileptic drugs (AEDs) has not received sufficient attention in patients with epilepsy. Areas covered: We reviewed articles between 1966 and 2015 about hyponatremia as an adverse effect of AEDs in patients with epilepsy. The incidence, clinical symptoms, onset times of AEDs-induced hyponatremia are discussed in detail, as are the risk factors associated with AEDs-induced hyponatremia and mechanisms underlying its development. We also briefly describe strategies for treating AED-induced hyponatremia. Expert opinion: Carbamazepine and oxcarbazepine are the most common AEDs which induce hyponatremia in patients with epilepsy. Recently, other AEDs, such as eslicarbazepine, sodium valproate, lamotrigine, levetiracetam and gabapentin have also been reported to cause hyponatremia. Understanding the risk associated with AED-induced hyponatremia and taking effective measures to combat serum sodium imbalance induced by AED therapy are necessary.

Angiotensin type 1 receptor mediates chronic ethanol consumption-induced hypertension and vascular oxidative stress

OBJECTIVES

We hypothesized that chronic ethanol intake enhances vascular oxidative stress and induces hypertension through renin-angiotensin system (RAS) activation.

METHODS AND RESULTS

Male Wistar rats were treated with ethanol (20% v/v). The increase in blood pressure induced by ethanol was prevented by losartan (10mg/kg/day; p.o. gavage), a selective AT1 receptor antagonist. Chronic ethanol intake increased plasma renin activity (PRA), angiotensin converting enzyme (ACE) activity, plasma angiotensin I (ANG I) and angiotensin II (ANG II) levels and serum aldosterone levels. No differences on plasma osmolality and sodium or potassium levels were detected after treatment with ethanol. Ethanol consumption did not alter ACE activity, as well as the levels of ANG I and ANG II in the rat aorta or mesenteric arterial bed (MAB). Ethanol induced systemic and vascular oxidative stress (aorta and MAB) and these effects were prevented by losartan. The decrease on plasma and vascular nitrate/nitrite (NOx) levels induced by ethanol was prevented by losartan. Ethanol intake did not alter protein expression of ACE, AT1 or AT2 receptors in both aorta and MAB. Aortas from ethanol-treated rats displayed decreased ERK1/2 phosphorylation and increased protein expression of SAPK/JNK. These responses were prevented by losartan. MAB from ethanol-treated rats displayed reduced phosphorylation of p38MAPK and ERK1/2 and losartan did not prevent these responses.

CONCLUSIONS

Our study provides novel evidence that chronic ethanol intake increases blood pressure, induces vascular oxidative stress and decreases nitric oxide (NO) bioavailability through AT1-dependent mechanisms.

Oxcarbazepine and carbamazepine: expected and unexpected differences and similarities

Effects of Carbamazepine and Oxcarbazepine on the Reproductive Endocrine Function in Women with Epilepsy. Lofgren E, Tapanainen JS, Koivunen R, Pakarinen A, Isojarvi JI. Epilepsia 2006;47(9):1441–1446. PURPOSE: The aim of the study was to compare the effects of carbamazepine (CBZ) and oxcarbazepine (OXC) on the reproductive endocrine function in women with epilepsy. OXC is a novel antiepileptic drug (AED), and the occurrence of reproductive dysfunction in women treated with OXC monotherapy for epilepsy has not been studied previously. METHODS: Thirty-five women with epilepsy were examined in the Department of Neurology at Oulu University Hospital. Sixteen patients were treated with CBZ monotherapy, and nineteen patients were treated with OXC monotherapy. The subjects were clinically examined, vaginal ultrasonography was performed, and serum sex hormone concentrations were measured. RESULTS: The women taking CBZ or OXC had lower serum testosterone (T) levels and lower free androgen indexes (FAIs) than the control subjects. CBZ medication was associated with increased concentrations of serum sex hormone–binding globulin (SHBG). The patients taking OXC had higher concentrations of dehydroepiandrosterone sulfate (DHEAS) and androstendione (A) than did the women taking CBZ. Moreover, the prevalence of polycystic ovaries (PCOs) was high in the OXC-treated women. CONCLUSIONS: CBZ and OXC have different effects on the reproductive endocrine function. Although both drugs were associated with low serum T concentrations and low FAIs, only OXC was associated with a high frequency of elevated levels of A and DHEAS and with an increased prevalence of PCOs. These findings suggest that OXC may be disadvantageous for women with epilepsy and hyperandrogenism, whereas CBZ may be beneficial for these women.

Symptomatic Hyponatremia in Patients on Oxcarbazepine Therapy for the Treatment of Neuropathic Pain

Oxcarbazepine is an FDA approved anticonvulsant medication that has also been used clinically as a treatment for chronic neuropathic pain. Hyponatremia is occasionally seen with the older anticonvulsant carbamazepine, and oxcarbazepine is a derivative of that older drug. Two cases of hyponatremia associated with oxcarbazepine are reported and suggestions for monitoring for and managing this effect are provided.

Currently available antiepileptic drugs

Many new antiepileptic drugs (AEDs) have become available over the past 15 years. At the same time, the emphasis on treating patients with epilepsy has grown from stopping seizures to avoiding side effects and maximizing quality of life. This review summarizes currently available AEDs, and presents general treatment principles and guidelines for AED selection. Unfortunately, despite the increased treatment options of today, seizure freedom without side effects remains unattainable for too many patients with epilepsy. Consequently, there remains a significant need for further development of new therapies.

Early and persistent increase in serum lipoprotein (a) concentrations in epileptic children treated with carbamazepine and sodium valproate monotherapy

PURPOSE

The aim of this study was to investigate by a prospective, self-controlled method, whether treatment with carbamazepine (CBZ) and sodium valproate (VPA) monotherapy may alter serum lipoprotein (a) [Lp(a)] concentrations in epileptic children.

METHODS

Serum Lp(a) concentrations have been determined in 18 epileptic children before and at 6, 12 and 24 months of treatment with CBZ monotherapy and in 30 epileptic children before and at 6, 12 and 24 months of treatment with VPA monotherapy. Serum total cholesterol, triglycerides, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, apolipoproteins A-I and B concentrations and serum concentrations of biochemical markers of liver and renal function were also measured in the study participants.

RESULTS

Serum Lp(a) concentrations were significantly increased at 6, 12 and 24 months of CBZ and VPA monotherapy. There were no significant correlations between serum Lp(a) and serum lipids, lipoproteins, apolipoproteins, concentrations of biochemical markers of liver and renal function or antiepileptic-drugs concentrations.

CONCLUSIONS

Children who receive CBZ or VPA monotherapy may have significant and persistent increase in serum lipoprotein (a) concentrations, occuring early in the course of therapy. It may be useful to measure serum Lp(a) concentrations routinely in epileptic children taking these antiepileptic drugs, especially in those that are already at higher atherosclerotic risk.

Levetiracetam for Mood Stabilization and Maintenance of Seizure Control Following Multiple Treatment Failures

OBJECTIVE

To report the case of a patient who experienced adverse events in succession to antiepileptic medications being used for both antiepileptic and mood-stabilization benefit.

CASE SUMMARY

A 46-year-old white woman developed hyponatremia with carbamazepine, hyperammonemia with divalproex, cognitive impairment with topiramate, and hyponatremia with oxcarbazepine. The patient was stabilized physically and psychiatrically on levetiracetam without any noted adverse events.

DISCUSSION

The adverse events in this report have been associated with the medications in question. The patient's presentation is unique, as she developed adverse events in succession to antiepileptic drugs being used to treat both a seizure disorder and symptoms of mood instability. The Naranjo rankings for the reported adverse events indicated the associations were probable (carbamazepine, divalproex, oxcarbazepine) and possible (topiramate). After repeated incidences of intolerability to these drugs, levetiracetam was initiated and provided both seizure control and mood-stabilizing benefits, which eventually led to hospital discharge.

CONCLUSIONS

Levetiracetam may provide mood-stabilizing qualities through a mechanism that is unique from that of other antiepileptic agents used for their mood-stabilizing properties. There are potential advantages with levetiracetam, as no specific therapeutic drug monitoring parameters need to be followed after its introduction. Additionally, this case emphasizes the importance of therapeutic drug monitoring and frequent assessments to prevent physical and psychiatric adverse reactions.

Influence of Sodium Valproate on Sodium and Chloride Urinary Excretion in Rats, Gender Differences

Evidence exists indicating that sodium valproate (VPA) increases diuresis in rats. The chloriuretic and natriuretic effect of VPA has not previously been investigated, so the aim of the present study was to define the peculiarities of 24-hour urinary sodium (Na) and chloride (Cl) excretion in young adult Wistar rats of both genders, and to evaluate the effects of VPA. 24-hour urinary Na, Cl, creatinine and pH levels were measured in 28 control intact Wistar rats and 26 Wistar rats after a single intragastric administration of 300 mg/kg VPA. After VPA administration, 24-hour diuresis and 24-hour diuresis per 100 g of body weight were significantly higher in VPA rats of both genders. 24-hour urine Na and Cl excretion were significantly higher in VPA male and VPA female rats than in gender-matched controls. The 24-hour urinary Cl excretion was found to be significantly higher in VPA male than in VPA female rats. The study data show that VPA, alongside the diuretic effect, enhances Na and Cl excretion with urine. The 24-hour chloriuretic response to VPA in male rats was significantly higher than in female rats. The mechanism of such a gender-related effect is not yet clear.

What is the evidence that oxcarbazepine and carbamazepine are distinctly different antiepileptic drugs?

Oxcarbazepine (OXC, Trileptal) is a modern antiepileptic drug (AED) used as both monotherapy and adjunctive therapy for the treatment of partial seizures with or without secondary generalization in adults and children above 4 years (USA) or 6 years (Europe) of age. Although OXC has been developed through structural variation of carbamazepine (CBZ) with the intent to avoid metabolites causing side effects, significant differences have emerged between the two drugs. The mechanism of action of OXC involves mainly blockade of sodium currents but differs from CBZ by modulating different types of calcium channels. In contrast to CBZ, which is oxidized by the cytochrome P-450 system, OXC undergoes reductive metabolism at its keto moiety to form the monohydroxy derivative (MHD), which is glucuronidated and excreted in the urine. The involvement of the hepatic cytochrome P-450-dependent enzymes in the metabolism of OXC is minimal. Although it does not prevent interaction with oral contraceptives, it explains why OXC can be more effectively combined with other AEDs such as valproate compared with CBZ. Switching from CBZ to OXC normalized CBZ-associated thyroid and sexual hormone abnormalities and pathological lipid values in small patient samples. OXC is often better tolerated than CBZ and causes fewer rashes than CBZ. Add-on or substitution treatment with OXC was effective in controlled trials even when CBZ did not achieve sufficient seizure control. This constitutes compelling clinical evidence that OXC and CBZ are distinctly different medications. From postmarketing experience in over 1,000,000 patient years, OXC had an advantageous risk-benefit balance also in comparison to other new AEDs. OXC should be preferred over CBZ and other older AEDs because of its proven efficacy and excellent side effect profile in children, adolescents, and adults with partial seizures.

New medication treatment options for bipolar disorders

OBJECTIVE

To assess new treatment options for bipolar disorders.

METHOD

Controlled studies of new treatments for bipolar disorders were identified by computerized searches and reviews of scientific meeting proceedings, and were compiled by drug category.

RESULTS

Two main categories of medications, newer anticonvulsants and newer antipsychotics, are yielding emerging new treatment options for bipolar disorders. Newer anticonvulsants have diverse psychotropic profiles, and although not generally effective for acute mania, may have utility for other aspects of bipolar disorders (e.g. lamotrigine for maintenance or acute bipolar depression), or for comorbid conditions (e.g. gabapentin for anxiety or pain, topiramate for obesity, bulimia, alcohol dependence, or migraine, and zonisamide for obesity). In contrast, newer antipsychotics generally appear effective for acute mania, and some may ultimately prove effective in acute depression (e.g. olanzapine combined with fluoxetine, quetiapine) and maintenance (e.g. olanzapine).

CONCLUSION

Emerging research is yielding new treatment options for bipolar disorders and comorbid conditions.

Causes and management of hyponatremia

OBJECTIVE

To review clinical information on the incidence and causes of hyponatremia (defined as a serum sodium level <130 mEq/L), the most common electrolyte abnormality seen in general hospital patients, and to discuss the diagnosis and treatment of hyponatremia in relation to these factors.

DATA SOURCES

Primary sources and review articles were identified via MEDLINE (1981-July 2003) for entries on hyponatremia. We limited the search to specific topics including incidence, risk factors, diagnosis, treatment, and clinical disorders and medications associated with hypotonic hyponatremia.

STUDY SELECTION AND DATA EXTRACTION

All of the articles identified were evaluated, and relevant and representative information was included in this review.

DATA SYNTHESIS

Hyponatremia can result from several disease states, injury, surgery, physical exercise, or the administration of certain drugs (e.g., antidepressants, antiepileptics) and is associated with advanced age. Drug-induced hyponatremia is often asymptomatic and usually resolves following water restriction and monitoring of medication. Symptoms of hyponatremia are primarily neurologic; the principal danger of hyponatremia relates to effects on central nervous system function due to changes in brain size.

CONCLUSIONS

Although hyponatremia can be a serious condition, appropriate measures for the management of at-risk and affected patients will lead to full recovery in most cases.

Effects of oxcarbazepine on sodium concentration and water handling

Oxcarbazepine, a keto-analogue of carbamazepine, was recently approved in the United States for the treatment of seizures of partial onset. Some patients treated with oxcarbazepine showed the development of hyponatremia, which in most instances was asymptomatic. Understanding the mechanisms by which oxcarbazepine can lead to a reduction of serum sodium levels could have therapeutic implications for the few patients in whom symptomatic hyponatremia develops. In this study, we evaluated sodium and water handling in patients with epilepsy and in healthy subjects titrated over 3 weeks to a maximum daily oxcarbazepine dose of 2,400mg. All subjects were evaluated in a hospital setting after an overnight fast and after an acute water-load test performed before oxcarbazepine exposure and after maintenance on the medication for 3 weeks. Before oxcarbazepine exposure, the percentage of water load excreted was normal as both groups excreted more than 80% of the administered water load. After the intake of oxcarbazepine, the water load resulted in a reduction of the serum sodium and free water clearance without a concomitant increase in the arginine vasopressin serum levels. Most subjects in both groups failed to excrete 80% or more of the water load, suggesting that the effect of oxcarbazepine is physiological. We found that, after the water load, serum sodium and free water clearance were diminished in both groups without a concomitant increase in the arginine vasopressin serum levels. These findings indicate that oxcarbazepine-induced hyponatremia is not attributable to the syndrome of inappropriate secretion of antidiuretic hormone. Possible mechanisms include a direct effect of oxcarbazepine on the renal collecting tubules or an enhancement of their responsiveness to circulating antidiuretic hormone.