Chronic impact of topiramate on acid-base balance and potassium in childhood

Acetazolamide and topiramate lower intracranial pressure through differential mechanisms: The effect of acute and chronic administration

BACKGROUND AND PURPOSE

Diseases of raised intracranial pressure (ICP) cause severe morbidity and mortality. Multiple drugs are utilised to lower ICP including acetazolamide and topiramate. However, the evidence for their use is unclear. We aimed to assess the ICP modulatory effects and molecular effects at the choroid plexus (CP) of acetazolamide and topiramate.

EXPERIMENTAL APPROACH

Female rats were implanted with telemetric ICP probes for physiological, freely moving 24/7 ICP recordings. Randomised cross-over studies were performed, where rats received acute (24 h) high doses of acetazolamide and topiramate, and chronic (10 days) clinically equivalent doses of acetazolamide and topiramate, all via oral gavage. Cerebrospinal fluid (CSF) secretion assays, and RT-qPCR and western blots on in vitro and in vivo CP, were used to investigate drug actions.

KEY RESULTS

We demonstrate that acetazolamide and topiramate achieved maximal ICP reduction within 120 min of administration, and in combination doubled the ICP reduction over a 24-h period. Chronic administration of acetazolamide or topiramate lowered ICP by 25%. Topiramate decreased CSF secretion by 40%. Chronic topiramate increased the gene expression of Slc12a2 and Slc4a10 and protein expression of the sodium-dependent chloride/bicarbonate exchanger (NCBE), whereas chronic acetazolamide did not affect the expression of assessed genes.

CONCLUSIONS AND IMPLICATIONS

Acetazolamide and topiramate are effective at lowering ICP at therapeutic levels. We provide the first evidence that topiramate lowers CSF secretion and that acetazolamide and topiramate may lower ICP via distinct molecular mechanisms. Thus, the combination of acetazolamide and topiramate may have utility for treating raised ICP.

Mitochondrial disorders and drugs: what every physician should know

Mitochondrial disorders are a group of metabolic conditions caused by impairment of the oxidative phosphorylation system. There is currently no clear evidence supporting any pharmacological interventions for most mitochondrial disorders, except for coenzyme Q10 deficiencies, Leber hereditary optic neuropathy, and mitochondrial neurogastrointestinal encephalomyopathy. Furthermore, some drugs may potentially have detrimental effects on mitochondrial dysfunction. Drugs known to be toxic for mitochondrial functions should be avoided whenever possible. Mitochondrial patients needing one of these treatments should be carefully monitored, clinically and by laboratory exams, including creatine kinase and lactate. In the era of molecular and ‘personalized’ medicine, many different physicians (not only neurologists) should be aware of the basic principles of mitochondrial medicine and its therapeutic implications. Multicenter collaboration is essential for the advancement of therapy for mitochondrial disorders. Whenever possible, randomized clinical trials are necessary to establish efficacy and safety of drugs. In this review we discuss in an accessible way the therapeutic approaches and perspectives in mitochondrial disorders. We will also provide an overview of the drugs that should be used with caution in these patients.

Metabolic disturbances and renal stone promotion on treatment with topiramate: a systematic review

AIMS

The use of topiramate, which is prescribed for the management of epilepsy, for migraine headache prophylaxis and as a weight-loss agent, has been associated with the development of metabolic acidosis, hypokalaemia and renal stone disease. We systematically reviewed all the literature.

METHODS

The systematic review of the literature was realized using the principles underlying the UK Economic and Social Research Council guidance on the conduct of narrative synthesis and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement.

RESULTS

Fourty-seven reports published between 1996 and 2013 were retained for the final analysis. Five case-control studies and six longitudinal studies addressed the effect of topiramate on acid-base and potassium balance. A significant tendency towards mild-to-moderate hyperchloraemic metabolic acidosis (with bicarbonate ≤21.0 mmol l(-1) in approximately every third case) and mild hypokalaemia (with potassium ≤3.5 mmol l(-1) in 10% of the cases) was noted on treatment with topiramate, which was similar in children and adults. A single study observed that topiramate causes mild hyperuricaemia in male adults. A tendency towards hypocitraturia, a recognized promoter of renal stone formation, was noted in all patients on topiramate.

CONCLUSIONS

Increasing evidence supports the use of topiramate. Topiramate is generally well tolerated, and serious adverse events are rare. Nonetheless, the present systematic review of the literature indicates that its use is linked with the development of acidosis, hypokalaemia, hyperuricaemia and hypocitraturia.

Topiramate-induced refractory hypokalemia

Topiramate belongs to the new class of neuromodulators, which has carbonic anhydrase inhibitor activity and been associated with renal calculi. It has also been shown to cause renal potassium wasting; however, it is generally clinically insignificant. Here, we describe a case of refractory hypokalemia in a patient with severe comorbidities who was on topiramate for seizures.

Safety of topiramate for treating migraines

INTRODUCTION

Migraine is a very common medical disorder characterized by attacks of moderate-severe headache, nausea and disability. Topiramate is an effective, popular prophylactic migraine treatment, which is approved for use in adults and adolescents. Due to its multiple mechanisms of action, topiramate has multiple potential safety issues, including systemic and CNS adverse events, which may complicate therapy.

AREAS COVERED

This review evaluates common adverse events as seen in the pivotal trials of topiramate for migraine as well as those observed in postmarketing studies. These include weight loss, metabolic acidosis, renal calculi, acute angle closure glaucoma, visual distortions and cognitive slowing. Topiramate use during pregnancy is associated with an increased risk of cleft lip. This review highlights both common and unusual safety issues associated with topiramate use, including important drug interactions and a comparison with other migraine prophylactic agents.

EXPERT OPINION

Topiramate is highly effective in migraine prophylaxis but clinicians using the drug need to be aware of the potential for bothersome or serious adverse events. When treating with topiramate, use a slow titration to the goal dose of 100 mg or the lowest dose, which helps prevent migraine.

Effect of Long-term Topiramate Therapy on Serum Bicarbonate and Potassium Levels in Adult Epileptic Patients

BACKGROUND

Topiramate (TPM) is a sulfamate-substituted monosaccharide that is structurally different from other antiepileptic drugs. TPM inhibits carbonic anhydrase activity, which is associated with loss of bicarbonate from the kidney and consequently metabolic acidosis or electrolyte imbalance.

OBJECTIVE

The objectives of the study were to investigate the influence of TPM therapy on bicarbonate and potassium levels in adult epileptic patients.

METHODS

Data were collected from 59 adult patients on monotherapy or co-therapy of TPM and other antiepileptic drugs. Serum bicarbonate and potassium levels were available from all patients. Steady-state TPM trough concentrations were determined in blood samples by high-performance liquid chromatography. Data analysis was performed by SPSS software (version 17, Chicago, IL).

RESULTS

Patients were divided into group A (duration of therapy shorter than or equal to 5 years) and group B (duration of therapy longer than 5 years). Significant difference (P < 0.05) in serum bicarbonate levels was observed between these 2 groups. Bicarbonate levels were linearly related to the TPM therapy duration. No correlation was found between the TPM dose or patient age and bicarbonate or potassium levels, as well as between therapy duration and potassium level. Linear regression analysis showed no significant association among 54 available TPM trough concentrations and bicarbonate or potassium levels.

CONCLUSIONS

Results highlight the frequent occurrence of lower bicarbonate level associated with prolonged TPM therapy. Monitoring bicarbonate levels in patients on long-term TPM therapy might be useful.

Prevalence and spot urine risk factors for renal stones in children taking topiramate

INTRODUCTION

Topiramate (TPM), an anti-epileptic drug with >4 million users, increases renal stones in adults. We screened outpatient TPM-treated children without history of stones to estimate the prevalence of renal stones and to characterize urine stone-risk profiles.

METHODS

Children taking TPM ≥1 month underwent an interview, renal ultrasound, and spot urine testing in this prospective study. Normal spot urine values were defined as: calcium/creatinine ratio ≤0.20 mg/mg (>12 months) or ≤0.60 mg/mg (≤12 months), citrate/creatinine ratio >0.50 mg/mg, and pH ≤ 6.7.

RESULTS

Of 41 patients with average age of 9.2 years (range 0.5-18.7), mean TPM dose of 8.0 mg/kg/day (range 1.4-23.6), and mean treatment duration of 27 months (range 1-112), two (4.9%) had renal stones. The majority of children taking TPM had lithogenic abnormalities on spot urine testing, including 21 (51%) with hypercalciuria, 38 (93%) with hypocitraturia, and 28 (68%) with pH ≥ 6.7. Hypercalciuria and hypocitraturia were independent of TPM dose and duration; urine pH increased with dose. 24-h urine parameters improved in 1 stone-former once TPM was weaned.

CONCLUSIONS

Asymptomatic stones were found in 2/41 (4.8%) children taking TPM. Risk factors for stones were present in the spot urine of most children, including hypocitraturia (93%) and hypercalciuria (51%), independent of TPM dose and duration. High urine pH, found in 68%, correlated with TPM dose. Pediatric specialists should be aware of increased risks for stones, hypercalciuria, hypocitraturia, and alkaline urine in children taking TPM.

Effect of topiramate monotherapy on height in newly diagnosed children with epilepsy

We conducted a post hoc assessment of the effect of ≥6 months of topiramate monotherapy on height in pediatric patients with newly diagnosed partial-onset seizure. Data on height measured nonsystematically up to 4 years from two randomized, double-blind studies and their open-label extensions were combined and converted to z scores and percentiles by patient's sex and age. Height velocity values (centimeters per year) and the associated z scores were computed for each postbaseline year using normative data. Median height velocity (centimeters per year) values and the associated z scores for patients ages 6-9 years were, year 1: 4.7 (-0.91); year 2: 4.2 (-1.62); year 3: 4.5 (-1.87); and for patients ages 10-15 years were, year 1: 4.0 (-0.76); year 2: 2.8 (-1.34); year 3: 3.1 (-0.74). There was a significant correlation between height velocity z score and change from baseline in height z score (r = 0.94 [n = 117]; P < 0.0001). Patient's bicarbonate status (low was defined as two postbaseline serum bicarbonate values <20 mmol/L) and sex had no effect on height velocity. In both age groups, continued growth was observed; however, the growth rate was slower than expected compared with a matched normal population from years 1 to 2 and showed minimal recovery from years 2 to 3.

Arterial Blood Gases

Arterial blood gases (ABG) results reflect underlying pathology and interpretation of the results are often compounded by ongoing disease processes and clinical interventions. While ABG specimens should be analysed immediately for optimal results the Clinical and Laboratory Standards Institute (CLSI) has recommended a window of 30 minutes at room temperature from blood collection to ABG analysis. A fresh and simple approach to interpreting ABG is provided.