Carbamazepine diminishes the sensitivity of the plasma arginine vasopressin response to osmotic stimulation

Lithium for Carbamazepine-Induced Syndrome of Inappropriate Antidiuretic Hormone

OBJECTIVES

To examine the effectiveness of low-dose lithium carbonate for managing carbamazepine-induced hyponatremia.

METHODS

Single case study in an 88 year old man with bipolar illness and vascular dementia who had failed to respond to other mood stabilizers.

RESULTS

The patient had developed hyponatremia on two separate occasions when treated with carbamazepine. Introduction of low-dose lithium resulted in prompt normalization of serum sodium levels, which was maintained for the subsequent 8 weeks.

CONCLUSIONS

Carbamazepine may sometimes be the best or only viable treatment option for patients with bipolar illness or other conditions. When its use is complicated by syndrome of inappropriate ADH, dose reduction and fluid restriction are the simplest options but, if ineffective, addition of lithium may be a feasible, albeit somewhat complicated, alternative.

The effect of normalization of sodium on bone turnover markers in patients with epilepsy. A randomized single-blinded placebo-controlled trial

Hyponatremia [p[Na]<136 mmol/L] is an independent risk factor for decreased bone mineral density (BMD). However, whether hyponatremia represents a surrogate marker, or a direct causal relationship to bone loss remains unknown. The aim of the study was to investigate the effect of salt replacement therapy on bone turnover markers (BTM) and BMD in patients with epilepsy and chronic hyponatremia. This prospective single-blinded randomized trial investigated serum BTM and BMD, evaluated by Dual Energy X-ray Absorptiometry (DXA), in 21 patients at baseline and following three months of salt replacement therapy. Patients with two consecutive measurements of hyponatremia prior to baseline and no known osteoporosis were included from the epilepsy out-patient clinic at Rigshospitalet, Denmark. Seven patients were randomized to placebo and 14 to salt intervention. The baseline p[Na] was 134 (130.5-140) mmol/L (median (IQR)). All patients had BTM within age-specific reference ranges at baseline. Following 3 months of intervention with 3-9 g of salt daily there was no difference in levels of procollagen type 1 N-terminal propeptide (P1NP) or C-terminal cross-linking telopeptide of type 1 collagen (CTX) between placebo and intervention. Nor was there any difference in BMD evaluated at the lumbar spine (L1-L4) or at the femoral neck or total hip. In our study, salt replacement did neither affect BTM nor BMD. However, due to the small size of the study, more studies are needed to further investigate this.

Hyponatremia and metabolic bone disease in patients with epilepsy: A cross-sectional study

AIM

Patients with epilepsy frequently develop hyponatremia due to the treatment with antiepileptic drugs and have an increased risk of developing metabolic bone disease. Hyponatremia is known to be associated with osteoporosis. The aim of the study was to investigate the association between hyponatremia and osteoporosis in patients with epilepsy.

METHOD AND MATERIAL

This cross-sectional study included patients with epilepsy from a tertiary epilepsy out-patient clinic in Denmark, who had a Dual Energy X-ray Absorptiometry scan performed and an accompanying plasma sodium (p-Na) measured prior to or a maximum of 14 days after the scan. Information regarding the patients' health and medical conditions were obtained from their medical reports.

RESULTS

A total of 695 patients (females 53.8%, age 49 (34:63) years (median (quartiles)) were included. 10.4% had hyponatremia (p-Na ≤ 135 mmol/L). The hyponatremic patients had significantly lower T-scores in the lumbar spine, femoral neck and total femur (all p < 0.023) and the odds ratio of osteoporosis (T-score < -2.5) was significantly increased (2.91 (1.61-5.27) (95% confidence interval) (p = 0.001)). When adjusting for potential confounders the patients with moderate and severe hyponatremia (p-Na < 129 mmol/L) had a significantly lower mean T-score in the lumbar spine (p = 0.030).

CONCLUSION

We conclude that hyponatremia is common in patients with epilepsy and that moderate and severe hyponatremia is independently associated with decreased bone mineral density in the lumbar spine. Therefore, hyponatremia in a patient with epilepsy should warrant further examination of the patient for bone loss and osteoporosis.

Diabetes insipidus: Differential diagnosis and management

Diabetes insipidus (DI) is a syndrome characterized by the excretion of abnormally large volumes of dilute urine. It can be caused by any of 4 fundamentally different defects that must be distinguished for safe and effective management. They are: (1) pituitary DI, due to inadequate production and secretion of antidiuretic hormone, arginine-vasopressin (AVP); (2) gestational DI due to degradation of AVP by an enzyme made in placenta; (3) primary polydipsia, due to suppression of AVP secretion by excessive fluid intake; and (4) nephrogenic DI due to renal insensitivity to the antidiuretic effect of AVP. This review describes several methods of differential diagnosis, indicates the advantages and disadvantages of each and presents a new approach that is simpler and less costly but just as reliable as the best of the older methods. The various treatments for the different types of DI and recent findings on the genetic basis of the familial forms of DI are also discussed with emphasis on their contributions to improved diagnosis and management.

Patient With Severe Hyponatremia Caused by Adrenal Insufficiency Due to Ectopic Posterior Pituitary Lobe and Miscommunication Between Hypothalamus and Pituitary: A Case Report

Hyponatremia may be one of the clinical manifestations of adrenal insufficiency (AI) and during the diagnostic workup of hyponatremic patients investigation of AI should be included.We report the case of an 82-year-old patient who was admitted to our hospital with clinical symptoms and laboratory findings of hyponatremia. Following the diagnostic algorithm of hyponatremia we reached the diagnosis of AI. Clinician's attention must focus on the underlying cause of AI which in this case was hidden in a miscommunication between hypothalamus and pituitary due to an ectopic posterior pituitary lobe and became apparent by a pituitary magnetic resonance imaging (MRI) scan. Treatment with oral hydrocortisone resulted in full clinical recovery and electrolyte balance, which was maintained after 7 months of follow-up.Secondary AI is related with hyponatremia through increased ADH secretion. Although a hyponatremic episode may be the first presentation of AI, clinical suspicion is of high importance in order to place the right diagnosis. Disruption of communication between hypothalamus and pituitary is a rare but considerable cause of AI.

Use of Antiepileptic Drugs in Patients with Chronic Kidney Disease and End Stage Renal Disease

Epilepsy is a disorder with an approximate worldwide prevalence of 1%. Due to complexities of metabolism, protein-binding, renal elimination, and other pharmacokinetic parameters, the dosing of antiepileptic drugs (AEDs) in patients with chronic kidney disease (CKD) or end stage renal disease (ESRD) deserves special attention. This is a review of the most commonly prescribed AEDs with special focus on their indication, pharmacokinetics, and unique considerations for use in patients with CKD and ESRD. A review of their renal toxicities is also included.

Association between bipolar episodes and fluid and electrolyte homeostasis: a retrospective longitudinal study

OBJECTIVES

Imbalance of fluid and electrolyte homeostasis has been suggested to be associated with the neuropathological processes underlying bipolar disorder. However, longitudinal data regarding the association of bipolar episodes with fluid balance are still lacking. We hypothesized that mania may be associated with a relative fluid retention and hemodilution, and depression with a relative hemoconcentration.

METHODS

Patients with bipolar disorder (n = 43) admitted to a mental health center, both with depressive and manic episodes, were retrospectively followed between 2005 and 2013. Fluid balance and electrolyte serum indices were compared between their manic and depressive episodes. We adjusted for physical and psychiatric comorbidities and for psychotropic treatment, using two-way analysis of variance with repeated measures.

RESULTS

There was a significant reduction in serum fluid balance indices during mania compared to depression: mean hemoglobin concentration 13.9 ± 1.4 g/dL versus 14.5 ± 1.4 g/dL, paired t = -4.2, p < 0.0005; mean hematocrit 41.1 ± 4.1% versus 42.3 ± 3.7%, paired t = -3.0, p < 0.005; mean albumin concentration 4.2 ± 0.3 g/dL versus 4.5 ± 0.3 g/dL, paired t = -4.5, p < 0.0001; and mean sodium concentration 140.3 ± 2.0 mEq/L versus 141.0 ± 2.0 mEq/L, paired t = -2.1, p = 0.04, respectively. Controlling for physical and psychiatric comorbidities and psychotropic treatment did not alter these associations.

CONCLUSIONS

Our results support the notion of an imbalance of fluid and electrolyte homeostasis among bipolar episodes, which is suggestive for relative hemoconcentration during depressive episodes and relative hemodilution during manic episodes. These findings may eventually lead to novel therapeutic targets.

Disorders of sodium and water balance

Dysnatremias occur simultaneously with disorders in water balance. The first priority is to correct dehydration; once the patient is euvolemic, the sodium level can be reassessed. In unstable patients with hyponatremia, the clinician should rapidly administer hypertonic saline. In unstable patients with hypernatremia, the clinician should administer isotonic intravenous fluid. In stable patients with either hyponatremia or hypernatremia, the clinician should aim for correction over 24 to 48 hours, with the maximal change in serum sodium between 8 to 12 mEq/L over the first 24 hours. This rate of correction decreases the chances of cerebral edema or osmotic demyelination syndrome.

Epidemiology, symptoms, and treatment characteristics of hyponatremic psychiatric inpatients

Hyponatremia is a common phenomenon in psychiatry occurring as an adverse effect to drugs or following polydipsia. We performed a retrospective in-depth analysis of hyponatremia cases in a large unselected population of psychiatric inpatients. During a 3-year period, all cases of hyponatremia were identified among patients admitted to a large psychiatric state and university hospital by the institution's electronic laboratory database. Demographic, treatment-related, and laboratory data were obtained by consecutive chart review, respectively. Hyponatremia occurred in 347 (4.9%) of 7113 cases, of which the majority (78%) displayed only a mild manifestation. Symptoms were recorded in 28.8% of cases, already occurred in mild forms, and comprised gait impairment (45%, including falls), confusion (30%), sedation (26%), and dyspepsia (41%). Age, female sex, nonpsychiatric drug polypharmacy-particularly with thiazides and/or angiotensin-converting enzyme inhibitors-and diagnosis of a mood disorder were associated with more severe hyponatremia, respectively. The proportion of hyponatremic patients treated with venlafaxine, trazodone, carbamazepine, oxcarbazepine, and first-generation antipsychotics, respectively, was significantly higher in the hyponatremia sample than in the normonatremic population. This was, surprisingly, not the case with selective serotonin reuptake inhibitors or any other antidepressant drug class. We found prescription with second-generation antipsychotics to be significantly associated with less severe hyponatremia.Hyponatremia may be mainly attributed to the syndrome of inappropriate antidiuretic hormone secretion, as indicated by decreased serum osmolarity in our sample. Besides old age and female sex, treatment with certain drugs-rather than whole drug classes-carries a substantially increased risk.

Clinical management of SIADH

Hyponatremia is the most frequent electrolyte disorder and the syndrome of inappropriate antidiuretic hormone secretion (SIADH) accounts for approximately one-third of all cases. In the diagnosis of SIADH it is important to ascertain the euvolemic state of extracellular fluid volume, both clinically and by laboratory measurements. SIADH should be treated to cure symptoms. While this is undisputed in the presence of grave or advanced symptoms, the clinical role and the indications for treatment in the presence of mild to moderate symptoms are currently unclear. Therapeutic modalities include nonspecific measures and means (fluid restriction, hypertonic saline, urea, demeclocycline), with fluid restriction and hypertonic saline commonly used. Recently vasopressin receptor antagonists, called vaptans, have been introduced as specific and direct therapy of SIADH. Although clinical experience with vaptans is limited at this time, they appear advantageous to patients because there is no need for fluid restriction and the correction of hyponatremia can be achieved comfortably and within a short time. Vaptans also appear to be beneficial for physicians and staff because of their efficiency and reliability. The side effects are thirst, polydipsia and frequency of urination. In any therapy of chronic SIADH it is important to limit the daily increase of serum sodium to less than 8-10 mmol/liter because higher correction rates have been associated with osmotic demyelination. In the case of vaptan treatment, the first 24 h are critical for prevention of an overly rapid correction of hyponatremia and the serum sodium should be measured after 0, 6, 24 and 48 h of treatment. Discontinuation of any vaptan therapy for longer than 5 or 6 days should be monitored to prevent hyponatremic relapse. It may be necessary to taper the vaptan dose or restrict fluid intake or both.

Syndrome of inappropriate antidiuretic hormone secretion: Revisiting a classical endocrine disorder

Hyponatremia occurs in about 30% of hospitalized patients and syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a common cause of hyponatremia. SIADH should be differentiated from other causes of hyponatremia like diuretic therapy, hypothyroidism and hypocortisolism. Where possible, all attempts should be made to identify and rectify the cause of SIADH. The main problem in SIADH is fluid excess, and hyponatremia is dilutional in nature. Fluid restriction is the main stay in the treatment of SIADH; however, cerebral salt wasting should be excluded in the clinical setting of brain surgeries, subarachnoid hemorrhage, etc. Fluid restriction in cerebral salt wasting can be hazardous. Sodium correction in chronic hyponatremia (onset >48 hours) should be done slowly to avoid deleterious effects in brain.

Hydrocortisone dose and postoperative diabetes insipidus in patients undergoing transsphenoidal pituitary surgery: a prospective randomized controlled study

We report the results of a prospective randomized controlled trial, which looked at the incidence of postoperative diabetes insipidus (DI) following the use of three different hydrocortisone protocols, and the results of a study, on the incidence of DI and cortisol response in patients not given hydrocortisone. In study 1, 114 patients with pituitary macroadenoma were randomized into three groups: conventional dose (inj. hydrocortisone 100 mg IV 6-hourly for 3 days); intermediate dose (inj. hydrocortisone 100 mg IV 6-hourly on day 1, 100 mg IV 8-hourly on day 2, and 100 mg IV 12-hourly on day 3); low dose protocol (inj. hydrocortisone 25 mg IV 6-hourly on day 1, 25 mg IV 8-hourly on day 2 and 25 mg IV 12-hourly on day 3). Radical excision was achieved in 92 patients. The incidence of DI with the conventional dose was 52%, intermediate dose, 36% and low dose, 24% (p = 0.025). Study 2 included 16 consecutive patients with Hardy's grade A & B pituitary adenoma. These patients were randomized to receive (Group I) or not receive (Group II) hydrocortisone. Patients in Group II demonstrated normal cortisol response intraoperatively and no patient developed features of hypocortisolism; the incidence of DI in this group was 14%. The low dose hydrocortisone protocol reduced the incidence of DI by 46% when compared with the conventional dose hydrocortisone protocol. In patients with grade A and B tumour with normal preoperative cortisol levels, the use of perioperative hydrocortisone can be avoided.

A review of drug-induced hyponatremia

Hyponatremia (defined as a serum sodium level < 134 mmol/L) is the most common electrolyte abnormality in hospitalized patients. Certain drugs (eg, diuretics, antidepressants, and antiepileptics) have been implicated as established causes of either asymptomatic or symptomatic hyponatremia. However, hyponatremia occasionally may develop in the course of treatment with drugs used in everyday clinical practice (eg, newer antihypertensive agents, antibiotics, and proton pump inhibitors). Physicians may not always give proper attention in time to undesirable drug-induced hyponatremia. Effective clinical management can be handled through awareness of the adverse effect of certain pharmaceutical compounds on serum sodium levels. Here, we review clinical information about the incidence of hyponatremia associated with specific drug treatment and discuss the underlying pathophysiologic mechanisms.

Thirty years of clinical experience with carbamazepine in the treatment of bipolar illness: principles and practice

Carbamazepine began to be studied in a systematic fashion in the 1970s and became more widely used in the treatment of bipolar disorder in the 1980s. Interest in carbamazepine has been renewed by (i) the recent US FDA approval of a long-acting preparation for the treatment of acute mania; (ii) studies suggesting some efficacy in bipolar depression; and (iii) evidence of prophylactic efficacy in some difficult-to-treat subtypes of bipolar illness. A series of double-blind controlled studies of the drug were conducted at the US National Institute of Mental Health from the mid-1970s to the mid-1990s. This review summarises our experience in the context of the current literature on the clinical efficacy, adverse effects and pharmacokinetic interactions of carbamazepine. Carbamazepine has an important and still evolving place in the treatment of acute mania and long-term prophylaxis. It may be useful in individuals with symptoms that are not responsive to other treatments and in some subtypes of bipolar disorder that are not typically responsive to a more traditional agent such as lithium. These subtypes might include those patients with bipolar II disorder, dysphoric mania, substance abuse co-morbidity, mood incongruent delusions, and a negative family history of bipolar illness in first-degree relatives. In addition, carbamazepine may be useful in patients who do not adequately tolerate other interventions as a result of adverse effects, such as weight gain, tremor, diabetes insipidus or polycystic ovarian syndrome. We review our clinical and research experience with carbamazepine alone and in combination with lithium, valproic acid and other agents in complex combination treatment of bipolar illness. More precise clinical and biological predictors and correlates of individual clinical responsiveness to carbamazepine and other mood stabilisers are eagerly awaited.

Use of Antiepileptic Drugs in Patients with Kidney Disease

The number of medications used to treat different types of seizures has increased over the last 10-15 years. Most of the newer antiepileptic drugs (AEDs) are likely to be unfamiliar to many nephrologists. For both the older and newer AEDs, basic pharmacokinetic information, recommendations for drug dosing in patients with reduced kidney function or who are on dialysis, and adverse renal and fluid-electrolyte effects are reviewed. Newer AEDs are less likely to have significant drug-drug interactions than older agents, but are more likely to need dosage adjustment in patients with reduced kidney function. The most common renal toxicities of these drugs include metabolic acidosis, hyponatremia, and nephrolithiasis; interstitial nephritis and other adverse effects are less common. Little is known about the clearance of most of the newer AEDs with high-efficiency hemodialyzers or with peritoneal dialysis. Monitoring of drug levels when available, careful clinical assessment of patients taking AEDs, and close collaboration with neurologists is essential to the management of patients taking AEDs.

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.

Altered expression of renal acid-base transporters in rats with lithium-induced NDI

Prolonged lithium treatment of humans and rodents often results in hyperchloremic metabolic acidosis. This is thought to be caused by diminished net H+ secretion and/or excessive back-diffusion of acid equivalents. To explore whether lithium treatment is associated with changes in the expression of key renal acid-base transporters, semiquantitative immunoblotting and immunocytochemistry were performed using kidneys from lithium-treated (n = 6) and control (n = 6) rats. Rats treated with lithium for 28 days showed decreased urine pH, whereas no significant differences in blood pH and plasma HCO3- levels were observed. Immunoblot analysis revealed that lithium treatment induced a significant increase in the expression of the H+-ATPase (B1-subunit) in cortex (190 +/- 18%) and inner stripe of the outer medulla (190 +/- 9%), and a dramatic increase in inner medulla (900 +/- 104%) in parallel to an increase in the expression of type 1 anion exchanger (400 +/- 40%). This was confirmed by immunocytochemistry and immunoelectron microscopy, which also revealed increased density of intercalated cells. Moreover, immunoblotting and immunocytochemistry revealed a significant increase in the expression of the type 1 electrogenic Na+-HCO3- cotransporter (NBC) in cortex (200 +/- 23%) and of the electroneutral NBCn1 in inner stripe of the outer medulla (250 +/- 54%). In contrast, there were no changes in the expression of Na+/H+ exchanger-3 or of the Cl-/HCO3- exchanger pendrin. These results demonstrate that the expression of specific renal acid-base transporters is markedly altered in response to long-term lithium treatment. This is likely to represent direct or compensatory effects to increase the capacity for HCO3- reabsorption, NH4+ reabsorption, and proton secretion to prevent the development of systemic metabolic acidosis.

Management of the negative symptoms of schizophrenia: new treatment options

This article presents a systematic review of pharmacological treatment for negative symptoms of schizophrenia, based on MEDLINE searches from 1995 to September 2002 to identify pertinent clinical trials. The pharmacotherapy of negative symptoms in schizophrenia includes novel/atypical antipsychotics and classical antipsychotics, as well as antidepressants, glutamatergic compounds, antiepileptic drugs and estrogens. In the assessment of therapy for negative symptoms of schizophrenia, it is imperative that better studies of sound methodology are performed. In such studies, some important aspects to be considered include an accurate definition and assessment of negative symptoms (including well designed, valid and reliable rating scales), the differentiation between primary and secondary negative symptoms, an appropriate selection of standard comparators, adequate dosages of comparators (e.g. haloperidol dosages) and an overall optimal study design. Most of the available studies on treating negative symptoms in schizophrenia have focused on the atypical antipsychotics, while other potential candidates, mostly in the context of add-on therapy, have not been so intensively investigated. Atypical antipsychotics have been proven in placebo-controlled trials to be effective in treating negative symptoms of acute schizophrenic episodes. In many of the comparator studies, they showed efficacy in treating negative symptoms that was superior to that of typical antipsychotics. Data on stable, predominant negative symptoms in subchronic or chronic cases of schizophrenia, although limited, have demonstrated the efficacy of atypical antipsychotics. If the beneficial tolerability profile with respect to extrapyramidal symptoms is also taken into account during clinical decision making, the atypical antipsychotics should be preferred for the treatment of negative symptoms. It is also worth noting that the traditional antipsychotics have the risk of inducing negative symptoms in the context of akinesia. The benefits of add-on therapy with SSRIs or a glutamatergic compound are well documented. Estrogen add-on therapy seems promising. Other traditionally suggested approaches, such as comedication with an antiepileptic drug, lithium or beta-adrenoceptor antagonist, cannot generally be recommended on the basis of the available data.

Postoperative endocrine management of pituitary tumors

Pituitary tumors are common and are often associated with endocrine abnormalities. Furthermore, pituitary surgery itself may result in additional hormonal changes, including impairment of anterior pituitary hormone secretion and, more commonly, abnormalities of ADH regulation. Endocrine management of patients with pituitary or other sellar lesions involves acute hospital-based and longer term office-based evaluation and treatment. In the immediate postoperative period, careful attention must be directed toward sodium and water balance as well as toward recognition of changes in endocrine function. Postoperative measurement of serum hormone levels also helps to determine if resection of a hypersecreting tumor has been successful. To minimize postoperative morbidity, perioperative endocrine assessment and management of patients undergoing pituitary surgery should consist of a team approach, involving both the neurosurgeon and the endocrinologist.

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.

The regulation of serum sodium after replacing carbamazepine with oxcarbazepine

PURPOSE

To evaluate changes in serum electrolyte balance and underlying regulatory mechanisms in 10 male patients with epilepsy 2 and 6 months after replacing long-term carbamazepine (CBZ) monotherapy with oxcarbazepine (OCBZ) monotherapy. Arginine vasopressin (AVP) is thought to be most important underlying mechanism of CBZ-related hyponatremia via direct or kidney tubular mechanisms. Furthermore, AVP is as well hormonally regulated by the renin-angiotensin-aldosterone system and atrial natriuretic peptide (ANP).

METHODS

The medication of the patients was changed from CBZ to OCBZ. Serum electrolytes, creatinine, albumin, aldosterone, and the N-terminal fragment of ANP (NT-proANP) concentrations were measured before and 2 and 6 months after the change in the medication.

RESULTS

The mean serum sodium level diminished after the medication was changed. Serum sodium levels decreased below the reference range in two (20%) patients during OCBZ medication. Serum sodium levels decreased altogether in four patients, and remained unaltered in six patients. Serum aldosterone levels increased in the six patients whose serum sodium concentrations did not decrease, but no increase was found in the patients with decreased sodium levels during OCBZ medication. Serum NT-proANP levels decreased in all patients.

CONCLUSIONS

Serum sodium levels decrease after replacing CBZ with OCBZ. The low serum NT-proANP concentrations appear to reflect the decreased serum sodium levels, but a compensatory aldosterone response may prevent the development of hyponatremia in some patients during OCBZ medication.

Effect of the 5-HT3 receptor antagonist ondansetron on plasma AVP secretion: a study in cancer patients

The aim of the present study was to investigate the effects of a serotonin subtype 3 receptor antagonist, ondansetron, on arginine vasopressin secretion in humans. Plasma vasopressin concentrations were determined in 24 breast cancer patients undergoing adjuvant chemotherapy, before and after ondansetron intravenous (i.v.) administration. Ondansetron (8 mg i.v. at time 0 and 8 mg po at time 240 min) was administered alone in 12 patients and afterwards in combination with chemotherapy in all patients. No changes in hormone levels were found after ondansetron alone and in 17 patients who did not claim nausea and/or emesis after chemotherapy. In seven patients who experienced nausea and /or emesis, vasopressin levels significantly (P < 0.01) increased (from 6.3 +/- 0.9 ng/L in basal conditions to 15.1 +/- 3.3 ng/L at 10 h; P < 0.05 vs baseline). The results suggest the possibility that in humans, serotoninergic mechanisms, which modulate vasopressin secretion, may involve the activation of the serotonin receptors recognised by ondansetron.

Arginine vasopressin and osmolality in the elderly

OBJECTIVES

To evaluate the influence of age on plasma arginine vasopressin (AVP) concentrations and the relationship between plasma AVP and serum osmolality in younger and older subjects, and in the elderly, to assess the effect of gender on plasma AVP concentration and to determine the impact of prostaglandin blockade on renal responsiveness to AVP.

DESIGN

Cross-sectional study; randomized, double-blind, crossover, placebo-controlled study.

SETTING

The Renal Laboratory, Royal North Shore Hospital (younger adults) and Clinical Room, St Vincents Hospital (elderly subjects).

PARTICIPANTS

45 younger adults (35 +/- 9 years), and 41 elderly subjects (29 males, 12 females; 78 +/- 3 years). All subjects were healthy and non-institutionalized. The elderly subjects were screened to exclude significant pathology (clinical assessment, multiple investigations).

INTERVENTION

Blood samples were drawn from all younger and elderly subjects. The elderly subjects were randomly allocated indomethacin or placebo for 1 month. Following a 1 to 2-week washout, the alternative was administered for a further 1 month.

MAIN OUTCOME MEASURES

Plasma AVP and serum osmolality and plasma AVP, serum, and urine osmolality at baseline were measured on indomethacin and placebo.

RESULTS

In the elderly subjects, baseline plasma AVP concentration was significantly higher than in the younger subjects studied (4.7 +/- 0.7 vs 2.1 +/- 0.2 pg/mL respectively; P = 0.0003). Plasma AVP was strongly correlated with serum osmolality in the younger subjects (r = 0.76, P = 0.0001) but not in the elderly cohort (r = -0.18, P = 0.26). No difference was found between the sexes in plasma AVP (P = 0.89), and indomethacin treatment did not alter the plasma AVP/urine osmolality ratio (P = 0.85) in the elderly subjects. In addition, changes in plasma AVP with indomethacin therapy did not correlate with changes in serum osmolality (r = 0.16, P = 0.09).

CONCLUSIONS

Aging is accompanied by an increase in plasma AVP concentrations. In healthy, elderly subjects, plasma AVP is not dependent on serum osmolality and is not influenced by gender. Indomethacin has no effect on the renal responsiveness to plasma AVP.

Review of carbamazepine-induced hyponatremia

1. Carbamazepine (CBZ), a commonly prescribed medication in psychiatry and neurology, produces deleterious side effects with an incidence rate ranging from 33-50%; although most of these side effects are mild, transient, and reversible. CBZ-induced hyponatremia is a moderately well described side effect and may be responsible for some of the more highly reported signs and symptoms associated with CBZ adverse effects. 2. Data from case reports and clinical studies are examined to ascertain the characteristics of CBZ-induced hyponatremia. Predisposing risk factors such as: age, dosage/level of CBZ, and polypharmacy have been explored in numerous clinical studies; however, minimal consensus has been found regarding both dosage/level of CBZ and polypharmacy as a predisposing risk factor, whereas age is most probably not a predisposing risk factor in CBZ-induced hyponatremia. 3. Mechanistic studies, both clinical and basic science, also fail to acknowledge the mechanism for the antidiuretic effect of CBZ. The most probable mechanism involves an alteration in either the sensitivity or set point of the osmoreceptor.

A double-blind trial of carbamazepine in negative symptom schizophrenia

Twenty-eight residual schizophrenics hospitalized in a chronic institution with a 9 to 30 year history of disease, with predominantly negative symptoms were given carbamazepine. Carbamazepine was administered in a double-blind trial and therapeutic effects were measured by the Scale for the Assessment of Negative Symptoms (SANS). Patients were also assessed for positive symptoms using the Brief Psychiatric Rating Scale (BPRS), for depression using the Hamilton Depression Scale, for extrapyramidal symptoms by the Simpson and Angus scale, to rule out these symptoms as sources of secondary negative symptoms. The study continued for 7 weeks with therapeutic carbamazepine levels achieved during the last 5 weeks. There was no significant positive effect of carbamazepine on negative symptoms.

The consulting psychiatrist and the polydipsia-hyponatremia syndrome in schizophrenia

OBJECTIVE

The authors seek to extend understanding and treatment of hospitalized schizophrenics presenting with complications of polydipsia and dilutional hyponatremia. Attending physicians may ask the consultation/liaison psychiatrist to see schizophrenics with hyponatremically-induced delirium or other psychiatric syndromes. The referring physician may or may not have identified polydipsia and dilutional hyponatremia and their complications. This article will help the consultation/liaison psychiatrist recognize early evidence of water imbalance, describe evaluation, and provide somatic and behavioral treatment approaches to this life-threatening syndrome.

METHOD

Over the past ten years, the authors have treated more than 100 patients with the polydipsia-hyponatremia syndrome. The authors discuss their and others' experience with drugs that help and hinder patients suffering from dilutional hyponatremia. They review current key articles from the polydipsia-hyponatremia syndrome literature including articles identified via Medline search 1985-94.

RESULTS

Schizophrenics with the polydipsia-hyponatremia syndrome most commonly present with polydipsia, polyuria, urinary incontinence, cognitive, affective, and behavioral changes, seizures, or coma. Quantitating polydipsia, hyponatremia, and diurnal changes in body weight facilitate therapeutic interventions. Treatment include patient and caregiver education, drug therapies to better treat psychosis and better treat osmotic dysregulation, behavioral interventions to interdict polydipsia, and diurnal weight monitoring.

CONCLUSIONS

Once recognized, acute, subacute, and chronic complications of the polydipsia-hyponatremia syndrome are readily treatable. Besides treating the patient, consultation/liaison psychiatrists can teach their medical colleagues about this syndrome. In so doing, they will enhance the quality of their patients' lives and help the internist and surgeon feel more comfortable when working with schizophrenics.

Hyponatremia associated with carbamazepine and oxcarbazepine therapy: a review

Hyponatremia, an electrolyte disturbance usually without clinical significance, may sometimes lead to serious complications when overlooked or not treated appropriately. One cause of hyponatremia, the syndrome of inappropriate antidiuretic hormone (SIADH) secretion, has been associated with some drugs, including carbamazepine (CBZ). Because of its antidiuretic effects, CBZ has been used successfully to treat diabetes insipidus centralis. Possible mechanisms for the antidiuretic effects of CBZ have been proposed. Altered sensitivity to serum osmolality by the hypothalamic osmoreceptors appears likely, but an increased sensitivity of the renal tubules to circulating ADH cannot be excluded. CBZ has led to hyponatremia in patients with epilepsy, neuralgia, mental retardation, and psychiatric disorders with a frequency varying from 4.8 to 40%. Oxcarbazepine (OCBZ), which is structurally related to CBZ, has shown similar hyponatremic effects, but whether hyponatremia occurs more often than with CBZ is not yet clear. Experience with OCBZ is still limited, and there is no definite explanation for a possible difference in antidiuretic potency. Most patients with CBZ/OCBZ-induced hyponatremia are asymptomatic. In rare cases, water intoxication has been reported, necessitating treatment discontinuation.

Non-lithium pharmacological treatment of manic depression: a review

Objectives:To examine the reasons why manic-depressive patients often fail to respond to lithium and, the chief purpose of this paper, to review the present state of knowledge concerning alternative pharmacotherapies to lithium in this disorder.Method:Literature review.Findings:Lithium produces a clinically useful effect in 70-80% of cases. Factors such as non-compliance, side-effects, serum levels, and enduring psychosocial influences on the patient must be considered before treatment failure is diagnosed. Carbamazepine is the most studied alternative drug to date, and the most likely predictors of response to this agent are rapid-cycling, absence of a family history of affective disorder, mania, severe illness, and non-response to lithium.Conclusions:In view of the 20-25% of patients who do not respond to lithium, and the increased likelihood that lithium-responders may fail to respond again once the drug has been stopped for a period, further research is needed to find better and safer prophylactics against depression in bipolar disorders and to refine our knowledge of the indications for use of those already available.

Effects of antiepileptic drugs on hormones

A hormone is an intrinsic substance carried via the blood to a target organ which is then functionally stimulated. Similar to extrinsically administered medications, the metabolism and function of the hormones may be altered by antiepileptic drugs (AEDs). The proposed mechanisms are (a) enhanced metabolism (natural steroids, synthetic steroids, e.g., decadron and birth control pills, thyroxine, and vitamin D3), (b) altered protein bonding (thyroxine, sex hormones), (c) impaired release into the systemic circulation (calcitonin, insulin, vitamin K clotting factors) and (d) altered end-organ effect. The AEDs most likely to interact with hormones are barbiturates, carbamazepine, and phenytoin.

Hyponatraemia during oxcarbazepine therapy

A clinical and pharmacokinetic study was carried out progressively substituting a new anticonvulsant oxcarbazepine for its congener carbamazepine in a group of patients with refractory epilepsy. Although oxcarbazepine showed possible though not statistically significant advantages of better seizure control and was probably less sedating, its use was associated with a dose-dependent reduction in plasma sodium levels in 12 of 15 patients. The mean plasma sodium level fell from 137.5 +/- 5.2 (s.d.) to 128.5 +/- 6.1 mE/l. Imposed restriction of fluid intake may have minimized the degree of hyponatraemia. This adverse effect may limit the role of the drug as an anticonvulsant or necessitate special precautions when it is used. However, the possibility of employing the drug in diabetes insipidus may be worth exploring.

Water intoxication and syndrome of inappropriate secretion of antidiuretic hormone in schizophrenic patients evaluated by water deprivation and load tests

A study was conducted on 16 schizophrenic patients with compulsive water drinking (CWD) and 10 normal controls, and the relation between serum antidiuretic hormone (ADH) and serum osmolality measured under ordinary conditions of free water intake. A water deprivation test and a water load test were also carried out on 10 schizophrenics with CWD and 10 normal controls. A comparison between the patients and controls showed the following results: the patients showed a significantly high level of serum ADH for their serum osmolality level, and 3 of them were consistent with the syndrome of inappropriate secretion of ADH (SIADH); the urine osmolality after the water deprivation in the patients was relatively low for their serum ADH; inhibition of ADH secretion after the water load was insufficient in the patients; and the water load test proved favorable to water diuresis (106%) in the patients with CWD of less than a 5-year duration, and insufficient diuresis (62.6%) in the patients with CWD of more than a 5-year duration. Two cases of the latter group had SIADH. The dilution and concentration of the urine after the water load were delayed also in the schizophrenic patients without SIADH. These findings suggest a strong possibility that the regulatory mechanism of ADH secretion might be impaired in the schizophrenic patients with CWD.

Effects of carbamazepine on serum electrolytes in affectively ill patients

The effects on serum electrolytes of carbamazepine, an acute and prophylactic treatment for manic-depressive illness, were assessed in subjects with primary affective disorder. Carbamazepine caused statistically significant, but clinically insubstantial, reductions in serum sodium and calcium, but not in the other electrolytes measured. Decreases in serum sodium and calcium were not related to carbamazepine dose, blood levels, or the degree of clinical improvement. The theoretical implications of these findings are discussed.

Release of human neurophysin I during insulin-induced hypoglycemia in depressed patients is abolished after recovery with clomipramine treatment

Release of human neurophysin I (hNp I) and neurophysin II (hNp II) during insulin-induced hypoglycemia was studied in 10 unipolar depressed women before and after 4-5 weeks of standard antidepressant drug treatment with daily intravenous infusions of clomipramine. Before treatment, a significant increase of hNp I but not of hNp II serum levels in response to hypoglycemia was observed. At retest during clomipramine administration, a marked clinical amelioration occurred in all patients as determined with the Hamilton Rating Scale for Depression; the hNp I response to insulin was abolished, but no effect on hNp II concentration could be demonstrated. No correlation was found between the degree of the depression score decrease and the amplitude of the inhibition of hNp I release or serum levels of clomipramine or its metabolite, desmethylclomipramine. The meaning of this difference in reactivity of the neurohypophyseal system in the course of depressive illness, based on the pharmacological and biochemical profiles of clomipramine action, is discussed.