Clinical Features of Carnitine Deficiency Secondary to Pivalate-Conjugated Antibiotic Therapy

Research on the Clinical Practical Use of Pivoxil-Conjugated Antibodies and the Risk of Carnitine Deficiency Using Real-World Data

In Japan, pivoxil-conjugated antibodies (PVs) are commonly used to treat infections. However, carnitine deficiency is a known adverse drug reaction associated with PV treatment. This study aimed to research the practical use of PV and assess the risk of carnitine deficiency in patients receiving PV compared to their amoxicillin (AM)-treated counterparts. The Pediatric Medical Information Collection System (P-MICS) served as the data source for this study. The study cohort comprised patients aged 0-15 years prescribed PV between April 2016 and March 2021. Data on the actual PV prescriptions were extracted for each patient. To evaluate the risk of carnitine deficiency, adverse events (AEs) were defined as carnitine deficiency and its associated symptoms. Propensity score matching was employed to compare the AE incidence between the PV and AM groups. The number of cases of PV prescriptions decreased year-on-year between 2016 and 2021, and >80% of prescriptions were dispensed in the clinic. The propensity score matching analysis demonstrated no statistically significant difference in the incidence of carnitine deficiency and its associated symptoms between the PV and AM groups. Our findings suggest that the risk of carnitine deficiency in children treated with PV is not significantly higher than that associated with other antibiotics.

Nocturnal Leg Cramping Caused by Carnitine Deficiency Due to Long-Term Pivalate Antibiotics Administration in a Patient With Chronic Kidney Disease

Carnitine deficiency is a known cause of leg cramps and is sometimes observed in patients taking certain medications such as pivalate-containing antibiotics. A 69-year-old Japanese woman presented with a progression of painful involuntary nocturnal leg cramping. She had been taking cefcapene-pivoxil for six months. Serum-free carnitine (FC) and acylcarnitine levels were decreased. Then, carnitine deficiency due to long-term pivalate-containing antibiotics administration was diagnosed. After initiating oral L-carnitine treatment, her symptoms improved. It should be aware of carnitine deficiency if a patient taking pivalate-containing antibiotics presents with leg cramping.

Cefcapene pivoxil-induced hypocarnitinemic hypoglycemia in elderly man with subclinical ACTH deficiency: a case report

BACKGROUND

Drug-induced hypocarnitinemia has been noted as a cause of hypoglycemia in children. However, adult cases are extremely rare and pre-existing conditions (including endocrine disorders and frailty) have been suggested to be involved. Hypoglycemia due to drug-induced hypocarnitinemia is quite rare, and there were few reports of pivoxil-containing cephalosporin (PCC)-induced hypocarnitinemia in adults.

CASE PRESENTATION

We present a case of an 87-year-old man with malnutrition, and frailty. He developed severe hypoglycemia with unconsciousness after taking cefcapene pivoxil hydrochloride, one of PCC, and hypocarnitinemia was diagnosed. Despite levocarnitine administration, asymptomatic mild hypoglycemia had persisted. Subsequent investigation revealed subclinical ACTH deficiency due to empty sella, which played a key role to maintain mild hypoglycemia as underlying disorder, and PCC-induced hypocarnitinemia triggered severe hypoglycemia. The patient responded to hydrocortisone therapy.

CONCLUSIONS

We need to be aware of the facts that PCC can induce severe hypocarnitinemic hypoglycemia in elderly adults associated with frailty, malnutrition, and subclinical ACTH syndrome.

Genetic and environmental risk factors of acute infection-triggered encephalopathy

Acute encephalopathy is a constellation of syndromes in which immune response, metabolism and neuronal excitation are affected in a variable fashion. Most of the syndromes are complex disorders, caused or aggravated by multiple, genetic and environmental risk factors. Environmental factors include pathogenic microorganisms of the antecedent infection such as influenza virus, human herpesvirus-6 and enterohemorrhagic Escherichia coli, and drugs such as non-steroidal anti-inflammatory drugs, valproate and theophylline. Genetic factors include mutations such as rare variants of the SCN1A and RANBP2 genes, and polymorphisms such as thermolabile CPT2 variants and HLA genotypes. By altering immune response, metabolism or neuronal excitation, these factors complicate the pathologic process. On the other hand, some of them could provide promising targets to prevent or treat acute encephalopathy.

Neonatal screening for isovaleric aciduria: Reducing the increasingly high false-positive rate in Germany

Newborn screening (NBS) for isovaleric acidemia (IVA) is performed by flow injection tandem mass spectrometry quantifying C5 carnitines (C5). Isovalerylcarnitine, however, is isomeric with pivaloylcarnitine which can be present in blood due to maternal use of pivaloylester-containing antibiotics, available in Germany since late 2016. During a 36-month period (January 19-December 21), all newborns screened in Hamburg with a C5 above cutoff (NeoGram®: 0.50 μmol/L or Neobase®2: 0.45 μmol/L) were included in the study. As a second-tier test, a simple ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed to differentiate the C5 isomers pivaloyl-, 2-methylbutyryl-, isovaleryl-, and valerylcarnitine. Out of 156 772 newborns tested, one turned out to have genetically proven IVA while 99 were false positive (C5: 0.5-8.2 μmol/L) due to the presence of pivaloylcarnitine. These cases have increased year by year and show local clusters. Retrospective analysis of another 39 cases from 287 206 neonates tested at the NBS center in Heidelberg with C5 elevation (0.9-10.6 μmol/L) but clinical and biochemical exclusion of IVA yielded evidence of pivaloylcarnitine in all cases. Inclusion of a second-tier test into NBS significantly reduces the high and increasing false-positive rate of IVA screening. This avoids further diagnostic steps, prevents unnecessary stress and anxiety of parents in a remarkably high number of cases. If Hamburg data of 2021 are extrapolated to all of Germany, one can assume around 800 (1‰) false-positive cases in comparison to an average of two classic IVA cases per year. Unless licensing of pivaloylester-containing drugs for use during pregnancy is reconsidered, a second-tier test for C5 determination is indispensable.

The frequencies of very long-chain acyl-CoA dehydrogenase deficiency genetic variants in Japan have changed since the implementation of expanded newborn screening

Very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency has been a target of expanded newborn screening (ENBS) using tandem mass spectrometry in Japan. Since the implementation of ENBS, a number of novel ACADVL variants responsible for VLCAD deficiency have been identified. In this study, genotypic differences in Japanese patients with VLCAD deficiency were investigated before and after ENBS. The ACADVL variants in 61 subjects identified through ENBS (ENBS group) and in 40 patients who subsequently developed clinical symptoms without undergoing ENBS (pre-ENBS group) were compared. Subjects in the ENBS group underwent genetic testing and/or VLCAD enzyme activity measurements. Patients in the pre-ENBS group were stratified into three clinical phenotypes and underwent genetic testing. This study revealed that the variants p.K264E, p.K382Q and c.996dupT were found in both groups, but their frequencies were lower in the ENBS group (5.2%, 3.1% and 4.2%, respectively) than in the pre-ENBS group (16.5%, 12.7% and 10.1%, respectively). In addition, p.C607S, p.T409M, p.M478I, p.G289R, p.C237R, p.T260M, and p.R229* were exclusively identified in the ENBS group. Among these variants, p.C607S exhibited the highest frequency (18.8%). The patients who were heterozygous for p.C607S demonstrated 7-42% of control enzyme activity. p.C607S is suspected to be unique to Japanese individuals. According to a comparison of enzyme activity, patients with the p.C607S variant may exhibit higher enzyme activity than those with the p.A416T, p.A180T, p.R450H, and p.K264E variants, which are responsible for the myopathic form of the disease. The VLCAD deficiency genotypes have changed since the initiation of ENBS in Japan.

Prodrugs of pyrophosphates and bisphosphonates: disguising phosphorus oxyanions

Pyrophosphates have important functions in living systems and thus pyrophosphate-containing molecules and their more stable bisphosphonate analogues have the potential to be used as drugs for treating many diseases including cancer and viral infections. Both pyrophosphates and bisphosphonates are polyanionic at physiological pH and, whilst this is essential for their biological activity, it also limits their use as therapeutic agents. In particular, the high negative charge density of these compounds prohibits cell entry other than by endocytosis, prevents transcellular oral absorption and causes sequestration to bone. Therefore, prodrug strategies have been developed to temporarily disguise the charges of these compounds. This review examines the various systems that have been used to mask the phosphorus-containing moieties of pyrophosphates and bisphosphonates and also illustrates the utility of such prodrugs.

Effects of l-carnitine supplementation in patients with childhood-onset epilepsy prescribed valproate

BACKGROUND

The benefits of carnitine supplementation in patients treated with valproate (VPA) are not clear. Therefore, we retrospectively explored the benefits of carnitine supplementation by analyzing laboratory data.

METHODS

We measured the serum-free carnitine (FC), VPA, aspartate aminotransferase, alanine aminotransferase, amylase, and ammonia levels, and the platelet count, in 69 patients with childhood-onset epilepsy treated with VPA. Eight patients had received carnitine supplementation. The serum FC and acylcarnitine levels were measured using an enzyme cycling method. We compared laboratory values between patients with and without carnitine supplementation and analyzed the correlations between serum FC levels and laboratory values.

RESULTS

The serum FC levels were normal (median, 48.8 μmol/L; range: 41.9-68.3 μmol/L) in all eight patients with carnitine supplementation, but below normal in 32 of 61 patients without supplementation. The median serum amylase levels were lower in the patients with carnitine supplementation (median, 48 U/L; range: 27-149 U/L) than in those without (median, 7 U/L; range: 14-234 U/L). The platelet count and serum ammonia levels did not differ significantly between patients with and without supplementation. There was no significant correlation between the serum FC level and the platelet count, serum amylase level, or ammonia level.

CONCLUSIONS

Carnitine supplementation helps maintain serum FC levels in patients treated with VPA. The lower serum amylase levels in patients with carnitine supplementation may reflect protective effects of carnitine against latent pancreatic injury.

Carnitine supplementation prevents carnitine deficiency caused by pivalate-conjugated antibiotics in patients with epilepsy prescribed valproate

We measured carnitine levels before and after pivalate-conjugated antibiotic (PCA) use in six patients with epilepsy who were prescribed valproate (VPA). Three of the patients were on carnitine supplementation when PCA use started. Serum FC levels were within the normal range (37.2-49.0 μmol/L) in all six patients before PCA use. After PCA use, the serum free carnitine (FC) levels remained within the normal range (48.0-68.2 μmol/L) in all three patients on carnitine supplementation, but were below the normal range (18.7-30.8 μmol/L) in the three patients not on carnitine supplementation. No remarkable changes in serum VPA levels, platelet count, amylase or ammonia level was evident in any patients in relation to PCA use. Carnitine deficiency due to PCA use was prevented by carnitine supplementation in patients with epilepsy who were taking VPA. Carnitine supplementation can support patients at risk of carnitine deficiency.

Duration of Pivalate-conjugated Antibiotics and Blood Glucose Levels Among Pediatric Inpatients: Causal Mediation Analyses and Systematic Review

BACKGROUND

Several cases of hypoglycemia potentially induced by pivalate-conjugated antibiotics have been reported. However, no observational studies have investigated the associations among children.

METHOD

A retrospective cohort study was conducted on 814 consecutive inpatients < 15 years of age with lower respiratory infections. We investigated whether the duration of lower respiratory symptoms and antibiotic use on blood glucose levels and their mediating/moderating effects using multivariable linear regression models and causal mediation analyses. Additionally, we performed a systematic review of the literature that reported the potential associations between pivalate-conjugated antibiotics and hypoglycemia.

RESULTS

Multivariable linear regression models showed that the duration of respiratory symptoms and fever had independent relationships with the reduction in blood glucose levels, whereas duration of pivalate-conjugated antibiotic use did not. Causal mediation analyses found that the controlled direct effects of respiratory symptom duration contributed to the reduction in blood glucose levels, but the mediating/moderating effects through antibiotic use did not. A systematic review of the literature included 7 reports written in English and 14 reports written in Japanese. No reports were observational studies; therefore, we were unable to conduct a meta-analysis.

CONCLUSIONS

Our study failed to demonstrate an association between duration of pivalate-conjugated antibiotic use and blood glucose levels. Further studies are required to illuminate the relationship.

Carnitine Inborn Errors of Metabolism

Carnitine plays essential roles in intermediary metabolism. In non-vegetarians, most of carnitine sources (~75%) are obtained from diet whereas endogenous synthesis accounts for around 25%. Renal carnitine reabsorption along with dietary intake and endogenous production maintain carnitine homeostasis. The precursors for carnitine biosynthesis are lysine and methionine. The biosynthetic pathway involves four enzymes: 6-N-trimethyllysine dioxygenase (TMLD), 3-hydroxy-6-N-trimethyllysine aldolase (HTMLA), 4-N-trimethylaminobutyraldehyde dehydrogenase (TMABADH), and γ-butyrobetaine dioxygenase (BBD). OCTN2 (organic cation/carnitine transporter novel type 2) transports carnitine into the cells. One of the major functions of carnitine is shuttling long-chain fatty acids across the mitochondrial membrane from the cytosol into the mitochondrial matrix for β-oxidation. This transport is achieved by mitochondrial carnitine–acylcarnitine cycle, which consists of three enzymes: carnitine palmitoyltransferase I (CPT I), carnitine-acylcarnitine translocase (CACT), and carnitine palmitoyltransferase II (CPT II). Carnitine inborn errors of metabolism could result from defects in carnitine biosynthesis, carnitine transport, or mitochondrial carnitine–acylcarnitine cycle. The presentation of these disorders is variable but common findings include hypoketotic hypoglycemia, cardio(myopathy), and liver disease. In this review, the metabolism and homeostasis of carnitine are discussed. Then we present details of different inborn errors of carnitine metabolism, including clinical presentation, diagnosis, and treatment options. At the end, we discuss some of the causes of secondary carnitine deficiency.

Hypoglycemia associated with pivalate-conjugated antibiotics in young children: A retrospective study using a medical and pharmacy claims database in Japan

INTRODUCTION

Acute bacterial infectious diseases are major causes for outpatient visits for young children. Pivalate-conjugated antibiotics (PCAs) are frequently prescribed for these situations in Japan, while several literatures have shown a potential risk of hypoglycemia associated with PCAs. This study aimed to evaluate the incidence of PCA-induced hypoglycemia in children, compared with other oral beta-lactam antibiotics.

METHODS

This retrospective cohort study using a Japanese medical and pharmacy claims database was performed on children aged 1 month to 5 years old with at least once prescription of PCAs or other oral beta-lactam antibiotics from January 2011 to December 2013. Hypoglycemia was defined based on diagnostic codes or the prescription of 10% or 20% glucose injection. We examined the prevalence of hypoglycemic events and performed multivariate analysis to investigate the risk of hypoglycemia with PCAs compared with the control oral beta-lactam antibiotics.

RESULTS

We identified 179,594 eligible patients in this population. In the PCA and control groups, there were 454,153 and 417,287 prescriptions and 3356 (0.74%, 95% confidence intervals [CI] 0.71-0.76) and 2605 (0.62%, 95% CI 0.60-0.65) hypoglycemic events, respectively. Multivariate analysis revealed that PCAs were associated with hypoglycemia (adjusted odds ratios [OR] 1.18, 95% CI 1.12-1.24), and even a shorter duration of PCAs prescribing (≤7 days) was significantly associated with hypoglycemia (adjusted OR 1.17, 95% CI 1.11-1.24).

CONCLUSION

These results suggest that in young children PCA use, even for a short period, is a risk factor of hypoglycemia.

Primary carnitine deficiency with severe acute hepatitis following rotavirus gastroenteritis

Rotavirus infection is a major cause of gastroenteritis, which occurs mainly in children. Liver dysfunction due to rotavirus gastroenteritis has been reported; however, acute hepatitis due to this disease is very rare. We present a rare case in which rotavirus gastroenteritis led to sequential diagnosis of acute hepatitis and systemic primary carnitine deficiency (CDSP) in a 1-year-old girl. The patient's symptoms (hypoglycemia, hepatomegaly, and elevated levels of serum transaminases and creatinine kinase) suggested a steatosis causing liver dysfunction. She was initially considered to have a beta oxygenation defect or secondary carnitine deficiency caused by pivalic acid-containing antibiotics; however, repetitive carnitine analysis and free carnitine clearance measurement confirmed primary carnitine deficiency (carnitine transporter deficiency). Children with severe liver dysfunction due to rotavirus infection and presenting with liver steatosis should undergo blood acyl carnitine analysis to detect potential carnitine or other beta oxidation deficiencies, especially if newborn screening for these diseases is not available.

Serum carnitine levels of children with epilepsy: Related factors including valproate

OBJECTIVE

This study measured the serum carnitine levels in patients with epilepsy and determined the factors contributing to low carnitine levels.

METHODS

We measured the serum carnitine levels in 94 consecutive patients with epilepsy, including the free carnitine (FC) and acylcarnitine fractions, using an enzyme cycling method. We defined a low FC as a serum FC level < 36 μmol/L. Age, body mass index (BMI), standard deviation score of BMI (BMI-SDS), use of valproate, cognitive disorder, and feeding problems differed between patients with low and normal FC. In patients taking valproate, the associations of the serum FC level with the platelet count and serum ammonia and amylase levels were analyzed.

RESULTS

Univariate analysis showed that a low BMI and BMI-SDS, the use of valproate, and cognitive disorder were more frequent in patients with a low FC. Logistic regression analysis revealed that a low BMI-SDS and cognitive disorders were independently associated with a low FC. Among the patients taking valproate, a low BMI-SDS and age were associated with a low FC. The serum FC and ammonia levels were inversely correlated, whereas no correlation was observed between the serum FC level and platelet count or serum amylase level.

CONCLUSION

A low BMI and cognitive disorders were related to a low FC in patients with epilepsy and the serum carnitine levels should be monitored in these patients.

Beta-ketothiolase deficiency: A case with unusual presentation of nonketotic hypoglycemic episodes due to coexistent probable secondary carnitine deficiency

Beta-ketothiolase (T2, mitochondrial acetoacetyl-CoA thiolase) deficiency is an autosomal recessive disorder of isoleucine catabolism and ketone body metabolism that is characterized by increased urinary excretion of 2-methylacetoacetate, 2-methyl-3-hydroxybutyrate, and tiglylglycine. Most patients with T2 deficiency develop their first severe ketoacidotic events between 5 and 24 months of age. We encountered a case of T2 deficiency who developed the first hypoglycemic crisis without ketosis during her neonatal period and repeated such nonketotic hypoglycemic crisis during her infancy and early childhood. This is a very atypical clinical phenotype in T2 deficiency. We finally realized that she also has severe carnitine deficiency which might suppress beta-oxidation resulting in nonketotic hypoglycemia. After carnitine supplementation, she actually developed episodes with ketonuria. Her carnitine deficiency was probably a secondary deficiency which is rare in T2 deficiency but if present, may modify the clinical manifestation of T2 deficiency from ketoacidotic events to hypoketotic hypoglycemic events.

Aspects of Newborn Screening in Isovaleric Acidemia

Isovaleric acidemia (IVA), an inborn error of leucine catabolism, is caused by mutations in the isovaleryl-CoA dehydrogenase (IVD) gene, resulting in the accumulation of derivatives of isovaleryl-CoA including isovaleryl (C5)-carnitine, the marker metabolite used for newborn screening (NBS). The inclusion of IVA in NBS programs in many countries has broadened knowledge of the variability of the condition, whereas prior to NBS, two distinct clinical phenotypes were known, an "acute neonatal" and a "chronic intermittent" form. An additional biochemically mild and potentially asymptomatic form of IVA and its association with a common missense mutation, c.932C>T (p.A282V), was discovered in subjects identified through NBS. Deficiency of short/branched chain specific acyl-CoA dehydrogenase (2-methylbutyryl-CoA dehydrogenase), a defect of isoleucine degradation whose clinical significance remains unclear, also results in elevated C5-carnitine, and may therefore be detected by NBS for IVA. Treatment strategies for the long-term management of symptomatic IVA comprise the prevention of catabolism, dietary restriction of natural protein or leucine intake, and supplementation with l-carnitine and/or l-glycine. Recommendations on how to counsel and manage individuals with the mild phenotype detected by NBS are required.

Brain carnitine deficiency causes nonsyndromic autism with an extreme male bias: A hypothesis

Could 10-20% of autism be prevented? We hypothesize that nonsyndromic or "essential" autism involves extreme male bias in infants who are genetically normal, but they develop deficiency of carnitine and perhaps other nutrients in the brain causing autism that may be amenable to early reversal and prevention. That brain carnitine deficiency might cause autism is suggested by reports of severe carnitine deficiency in autism and by evidence that TMLHE deficiency - a defect in carnitine biosynthesis - is a risk factor for autism. A gene on the X chromosome (SLC6A14) likely escapes random X-inactivation (a mixed epigenetic and genetic regulation) and could limit carnitine transport across the blood-brain barrier in boys compared to girls. A mixed, common gene variant-environment hypothesis is proposed with diet, minor illnesses, microbiome, and drugs as possible risk modifiers. The hypothesis can be tested using animal models and by a trial of carnitine supplementation in siblings of probands. Perhaps the lack of any Recommended Dietary Allowance for carnitine in infants should be reviewed. Also see the video abstract here: https://youtu.be/BuRH_jSjX5Y.