Hyperammonemia in patients receiving valproic acid in the hospital setting: A retrospective review

Sodium Valproate-Induced Hyperammonemia: A Case Series in a Tertiary Care Hospital

BACKGROUND

Sodium valproate (VPA) is an extensively used anti-convulsant, which is an effective drug for treatment of epilepsy in adults and children, as well as for conditions like migraine, bipolar disorder, mania, and trigeminal neuralgia. Sedation, vertigo, ataxia, dose-dependent tremors, headaches, and gastrointestinal side effects are the most often reported adverse effects associated with VPA. A potential life-threatening event reported with VPA is hyperammonemia (HA), which is defined as an increase in serum level of ammonia. Only 587 reported cases of HA were found in the VigiAccess database, representing a mere 0.6% of the 95,000 reported adverse events linked to VPA. Hence, this case series was conducted with emphasis on monitoring of increased serum ammonia levels with or without hepatic enzymes increase for patients who are on VPA.

AIMS AND OBJECTIVES

To assess elevated serum ammonia levels following VPA administration, and to ascertain the percentage of individuals with hepatic enzymes increased who took VPA and subsequently had elevated serum ammonia levels.

METHODS

This study was conducted at the adverse drug reaction (ADR) monitoring centre (AMC) of the Pharmacovigilance Programme of India (PvPI) and Department of Psychiatry, Christian Medical College and Hospital (CMC&H), Ludhiana. The study comprised of 12 patients who were exclusively on VPA and exhibited symptoms related to elevated serum ammonia. An informed consent form (ICF) was provided to the patient prior to taking their personal details. Laboratory investigations were done to establish the diagnosis and liver function tests (LFTs), chiefly ALT (alanine transferase) and AST (aspartate aminotransferase) were also performed. It is a descriptive study which was for a time period of six months.  Results: This study includes 12 patients who had HA confirmed by laboratory investigation. Out of these 12 patients, two patients (17%) had a corresponding increase in LFT. The average as of the patients was 53.08 years and average serum ammonia levels were 219.15. None of the patients who presented with HA progressed to hyperammonemic encephalopathy (HAE).

CONCLUSION

 This case series on valproate-induced HA should be of interest to psychiatrists, physicians, internists, family medicine physicians, hospitalists, and surgeons who will have patients on VPA. Delay in recognition of HA can result in the development of potentially life-threatening complications. Rapid diagnosis and management will help in reducing the number of cases which progress to encephalopathy which is highly fatal.

Drug-induced hyperammonaemia

Hyperammonaemia (HA) as a consequence of numerous primary or secondary causes, gives rise to clinical manifestations due to its toxic effects on the brain. The neurological consequences broadly reflect the ammonia level, duration and age, with paediatric patients being more susceptible. Drug-induced HA may arise due to either decreased ammonia elimination or increased production. This is associated most frequently with use of valproate and presents a dilemma between ongoing therapeutic need, toxicity and the possibility of an alternative cause. As there is no specific test for drug-induced HA, prompt discussion with a metabolic physician is recommended, as the neurotoxic effects are time-dependent. Specific guidelines for managing drug-induced HA have yet to be published and hence the treatment approach outlined in this review reflects that outlined in relevant urea cycle disorder guidelines.

Valproic Acid-Associated Hyperammonemia: A Systematic Review

BACKGROUND

Hyperammonemia is an adverse effect that poses clinical uncertainty around valproic acid (VPA) use. The prevalence of symptomatic and asymptomatic hyperammonemia and its relationship to VPA concentration is not well established. There is also no clear guidance regarding its management. This results in variability in the monitoring and treatment of VPA-induced hyperammonemia. To inform clinical practice, this systematic review aims to summarize evidence available around VPA-associated hyperammonemia and its prevalence, clinical outcomes, and management.

METHODS

An electronic search was performed through Ovid MEDLINE, Ovid Embase, Web of Science, and PsycINFO using search terms that identified hyperammonemia in patients receiving VPA. Two reviewers independently performed primary title and abstract screening with a third reviewer resolving conflicting screening results. This process was repeated during the full-text review process.

RESULTS

A total of 240 articles were included. Prevalence of asymptomatic hyperammonemia (5%-73%) was higher than symptomatic hyperammonemia (0.7%-22.2%) and occurred within the therapeutic range of VPA serum concentration. Various risk factors were identified, including concomitant medications, liver injury, and defects in carnitine metabolism. With VPA discontinued, most symptomatic patients returned to baseline mental status with normalized ammonia level. There was insufficient data to support routine monitoring of ammonia level for VPA-associated hyperammonemia.

CONCLUSIONS

Valproic acid-associated hyperammonemia is a common adverse effect that may occur within therapeutic range of VPA. Further studies are required to determine the benefit of routine ammonia level monitoring and to guide the management of VPA-associated hyperammonemia.

Valproic acid-induced hyperammonemia in neuropsychiatric disorders: a 2-year clinical survey

INTRODUCTION

Valproic acid (VPA)-induced hyperammonemia (HA) is a rare adverse effect reported even at therapeutic VPA levels. The present study aimed to investigate the characteristics of VPA-induced HA and its association with the total dose, duration, and level of VPA. This study also investigated whether the use of VPA in combination with other medications has any effect on elevating serum ammonia levels.

METHODS

A total of 316 patients with a history of VPA prescribed for underlying neuropsychiatric disorders were found eligible for the study. Data including demographic information, medical history and diagnosis, VPA dosage, VPA treatment duration, VPA level, and ammonia serum level were extracted and reviewed from our hospital records. The history of other neuropsychiatric medications was also included.

RESULTS

Among 316 patients receiving VPA, HA was observed in 54 (17%) patients, and 15 patients were symptomatic among them. There was no significant difference in demographics between symptomatic and asymptomatic HA groups except for the number of co-administrated medications (p = 0.044). Besides, VPA duration and dose did not show a significant difference between the two groups. Additionally, the VPA level was significantly higher in patients who used risperidone in addition to VPA (p = 0.019). Eventually, VPA level showed a significant association with ammonia level (p = 0.025) and symptomatic HA (p = 0.033) after adjusting for possible confounders.

CONCLUSION

VPA level showed a significant association with ammonia level and symptomatic HA. Moreover, co-administrated medications such as risperidone might have an impact on the serum level of VPA. Further studies are recommended to confirm these findings.

Clinical findings of patients with hyperammonemia affected by urea cycle disorders with hepatic encephalopathy

Urea Cycle Disorders (UCD) are a group of genetic diseases caused by deficiencies in the enzymes and transporters involved in the urea cycle. The impairment of the cycle results in ammonia accumulation, leading to neurological dysfunctions and poor outcomes to affected patients. The aim of this study is to investigate and describe UCD patients principal clinical and biochemical presentations to support professionals on urgent diagnosis and quick management, aiming better outcomes for patients. We explored medical records of thirty patients diagnosed in a referral center from Brazil to delineate UCD clinical and biochemical profile. Patients demonstrated a range of signs and symptoms, such as altered levels of consciousness, acute encephalopathy, seizures, progressive loss of appetite, vomiting, coma, and respiratory distress, in most cases combined with high levels of ammonia, which is an immediate biomarker, leading to an UCD suspicion. The most prevalent UCD detected were ornithine transcarbamylase deficiency (11), followed by citrullinemia type I (10), hyperargininemia (5), carbamoyl phosphate synthase 1 deficiency (2) and argininosuccinic aciduria (2). Clinical symptoms were highly severe, being the majority developmental and neurological disabilities, with 20% of death rate. Laboratory analysis revealed high levels of ammonia (mean ± SD: 860 ± 470 μmol/L; reference value: ≤ 80 μmol/L), hypoglycemia, metabolic acidosis, and high excretion of orotic acid in the urine (except in CPS1 deficiency). We emphasize the need of urgent identification of UCD clinical and biochemical conditions, and immediate measurement of ammonia, to enable the correct diagnosis and increase the chances of patients survival, minimizing neurological and psychomotor damage caused by hepatic encephalopathy.