The relationship between drug treatment and the clinical characteristics of febrile seizures

The effects of antihistamine on the duration of the febrile seizure: A single center study with a systematic review and meta-analysis

BACKGROUND

Several studies have investigated the potential effects of antihistamines on febrile seizure. However, these findings are inconsistent across the studies.

METHOD

A retrospective observational study was conducted on a total of 434 consecutive patients aged between 6 months and 5 years with the diagnosis of febrile seizure. Patients with chronic medical conditions were excluded. Multivariable generalized linear models were conducted to ascertain the effects of antihistamine use on duration of febrile seizure. Also, we conducted a systematic review and meta-analyses of the medical literatures to calculate the pooled estimates using random effects models.

RESULTS

The adjusted mean duration of febrile seizure in the antihistamine group was 4.9 min shorter than that in the non-user group (95% confidence interval (CI), 0.4-9.5). The risk of duration in febrile seizure >5 min among antihistamine users was also 0.83 times that among the non-users (95%CI, 0.58-1.19), whereas the risk of duration in febrile seizure >10 min among first-generation antihistamine users was 1.21 times that among non-users (95%CI, 0.69-2.13). According to the systematic review of the literature, 8 observational studies were included in the meta-analyses. Comparing to non-users, the antihistamine users had prolonged duration of febrile seizure by 1.07 min (95%CI, -1.13 to 3.27), elevated risk of duration in febrile seizure >5 min (Risk ratio, 1.16; 95%CI, 0.90-1.49), and similar duration from fever to febrile seizure onset (pooled mean difference, -0.01 h; -1.43 to 1.41), but these estimates were imprecise. Similar results were obtained when we stratified the data by types of antihistamine (first vs. second generation).

CONCLUSIONS

Our study may indicate the effects of antihistamine on prolonging febrile seizure duration, but they are still controversial given the limited evidence, highly heterogeneous results, and concerns of the internal and external validities.

The effects of antihistamines on the semiology of febrile seizures

OBJECTIVE

The aim of this study was to clarify the effects of antihistamines on the semiology of febrile seizures.

METHODS

The manifestations of febrile seizures were recorded using a structured questionnaire immediately after patients arrived at the hospital. We focused on events at seizure commencement, including changes in behavior and facial expression, and ocular and oral symptoms. The presence or absence of focal and limbic features was determined for each patient. Drugs taken within 6 h prior to seizure were noted. Seizure manifestations were compared between children who did not take antihistamines and those who took antihistamines.

RESULTS

Seizures lasting ≥5 min were relatively more frequent in children who did not take antihistamines, although the difference was not statistically significant. One or more focal features were present in 60 of 78 children with no antihistamines and 17 of 23 children with antihistamines. One or more limbic features were present in 32 of 78 children with no antihistamines and 9 of 23 children with antihistamines. No significant difference in the numbers of focal or limbic features was apparent between children who did not take antihistamines and those who took antihistamines.

CONCLUSION

Antihistamines did not significantly affect the semiology of febrile seizures.

Optimal Doses of H1 Antihistamines Do Not Increase Susceptibility to Febrile Convulsions in Children

BACKGROUND

The purpose of this study was to elucidate whether H1 antihistamine administration increases susceptibility to febrile convulsions in children.

METHODS

A single-center, retrospective observational study was conducted in Japan. The study included 380 children with febrile convulsions between the ages of six months and five years transported via ambulance from 2011 through 2016. They were divided into the preseizure H1 antagonist "use group" and the "nonuse group." The former consisted of children who took H1 antagonists within 24 hours before the seizure onset. The primary outcome (seizure duration) and the secondary outcome (interval from fever to seizure onset) were compared between the two groups.

RESULTS

Of the 380 study patients, 70 (18%) were identified as the use group. None of the patients was taking excessive doses of H1 antagonists. The prevalence of seizures lasting 15 minutes or longer was not different between the use group and the nonuse group (11% versus 8%, prevalence ratio 1.47 [95% confidence interval, 0.63 to 3.42], P = 0.37). The prevalence of fever to seizure onset less than six hours was significantly lower in the use group (26% versus 52%, prevalence ratio 0.33 [95% confidence interval 0.19 to 0.60], P < 0.001). Similar results were obtained when analyses were conducted separately by different generations (first and second) of H1 antagonists.

CONCLUSIONS

Prolonged seizure duration and shortened interval from fever to seizure were not observed in children who received H1 antagonists. This study provides evidence that H1 antagonists at optimal doses could be safely used in febrile children with allergic symptoms.

The histaminergic system is involved in psychological stress-induced hyperthermia in rats

The histaminergic system modulates numerous physiological functions such as wakefulness, circadian rhythm, feeding, and thermoregulation. However, it is not yet known if this system is also involved in psychological stress-induced hyperthermia (PSH) and, if so, which histamine (H) receptor subtype mediates the effect. Therefore, we investigated the effects of pretreatments with intraperitoneal injections of mepyramine (an H1 receptor inverse agonist), cimetidine (an H2 receptor antagonist), and ciproxifan (an H3 receptor inverse agonist) on cage-exchange stress-induced hyperthermia (a model of PSH) by monitoring core body temperature (T_c) during both light (10:00 am-12:00 pm) and dark (10:00 pm-12:00 am) phases in conscious, freely moving rats. We also investigated the effects of these drugs on stress-induced changes in locomotor activity (L_a) to rule out the possibility that effects on T_c are achieved secondary to altered L_a Cage-exchange stress increased T_c within 20 min followed by a gradual decrease back to baseline T_c during both phases. In the light phase, mepyramine and cimetidine markedly attenuated PSH, whereas ciproxifan did not affect it. In contrast, in the dark phase, mepyramine dropped T_c by 1°C without affecting cage-exchange stress-induced hyperthermia, whereas cimetidine and ciproxifan did not affect both postinjection T_c and PSH Cage-exchange stress induced an increase in L_a, especially in the light phase, but none of these drugs altered cage-exchange stress-induced L_a in either circadian rhythm phase. These results suggest that the histaminergic system is involved in the physiological mechanisms underlying PSH, particularly through H1 and H2 receptors, without influencing locomotor activity.

New guidelines for management of febrile seizures in Japan

In 2015, the Japanese Society of Child Neurology released new guidelines for the management of febrile seizures, the first update of such guidelines since 1996. In 1988, the Conference on Febrile Convulsions in Japan published "Guidelines for the Treatment of Febrile Seizures." The Task Committee of the Conference proposed a revised version of the guidelines in 1996; that version released in 1996 was used for the next 19years in Japan for the clinical management of children with febrile seizures. Although the guidelines were very helpful for many clinicians, new guidelines were needed to reflect changes in public health and the dissemination of new medical evidence. The Japanese Society of Child Neurology formed a working group in 2012, and published the new guidelines in March 2015. The guidelines include emergency care, application of electroencephalography, neuroimaging, prophylactic diazepam, antipyretics, drugs needing special attention, and vaccines. While the new guidelines contain updated clinical recommendations, many unsolved questions remain. These questions should be clarified by future clinical research.

Anticonvulsant effects of isomeric nonimidazole histamine H3 receptor antagonists

Phenytoin (PHT), valproic acid, and modern antiepileptic drugs (AEDs), eg, remacemide, loreclezole, and safinamide, are only effective within a maximum of 70%–80% of epileptic patients, and in many cases the clinical use of AEDs is restricted by their side effects. Therefore, a continuous need remains to discover innovative chemical entities for the development of active and safer AEDs. Ligands targeting central histamine H₃ receptors (H₃Rs) for epilepsy might be a promising therapeutic approach. To determine the potential of H₃Rs ligands as new AEDs, we recently reported that no anticonvulsant effects were observed for the (S)-2-(4-(3-(piperidin-1-yl)propoxy)benzylamino)propanamide (1). In continuation of our research, we asked whether anticonvulsant differences in activities will be observed for its R-enantiomer, namely, (R)-2-(4-(3-(piperidin-1-yl)propoxy)benzylamino)propaneamide (2) and analogs thereof, in maximum electroshock (MES)-, pentylenetetrazole (PTZ)-, and strychnine (STR)-induced convulsion models in rats having PHT and valproic acid (VPA) as reference AEDs. Unlike the S-enantiomer (1), the results show that animals pretreated intraperitoneally (ip) with the R-enantiomer 2 (10 mg/kg) were moderately protected in MES and STR induced models, whereas proconvulsant effect was observed for the same ligand in PTZ-induced convulsion models. However, animals pretreated with intraperitoneal doses of 5, 10, or 15 mg/kg of structurally bulkier (R)-enantiomer (3), in which 3-piperidinopropan-1-ol in ligand 2 was replaced by (4-(3-(piperidin-1-yl)propoxy)phenyl)methanol, and its (S)-enantiomer (4) significantly and in a dose-dependent manner reduced convulsions or exhibited full protection in MES and PTZ convulsions model, respectively. Interestingly, the protective effects observed for the (R)-enantiomer (3) in MES model were significantly greater than those of the standard H₃R inverse agonist/antagonist pitolisant, comparable with those observed for PHT, and reversed when rats were pretreated with the selective H₃R agonist R-(α)-methyl-histamine. Comparisons of the observed antagonistic in vitro affinities among the ligands 1–6 revealed profound stereoselectivity at human H₃Rs with varying preferences for this receptor subtype. Moreover, the in vivo anticonvulsant effects observed in this study for ligands 1–6 showed stereoselectivity in different convulsion models in male adult rats.

Anticonvulsant and procognitive properties of the non-imidazole histamine H3 receptor antagonist DL77 in male adult rats

It has become clear that histamine H3 receptors (H3Rs) are implicated in modulating epilepsy and memory in laboratory animals. The new non-imidazole H3R antagonist DL77 has excellent selectivity profile and shows high in-vivo potency as well as in-vitro antagonist affinity with ED50 values of 2.1 ± 0.2 mg/kg and 8.4 ± 1.3 [nM], respectively. In the present study, the anticonvulsant effects of DL77 on maximal electroshock (MES)-, pentylenetetrazole (PTZ)-, and strychnine (STR)-induced seizure models were investigated. Moreover, the procognitive properties of DL77 were tested on acquisition, consolidation and retrieval processes in a one-trial inhibitory avoidance task in male Wistar rats. The results indicate that DL77 (5, 10, and 15 mg/kg, i.p.) significantly and dose-dependently reduced MES-induced seizure duration, whereas no protection was observed in PTZ- or STR-induced seizures. Importantly, the protective action observed for DL77 in MES-induced seizure was comparable to that of the reference antiepileptic drug (AED) phenytoin (PHT), and was also reversed when rats were pretreated with the CNS penetrant pyrilamine (PYR) (10 mg/kg, i.p.), or with the selective H3R agonist R-(α)-methyl-histamine (RAMH) (10 mg/kg, i.p.). Furthermore, the procognitive studies indicate that acute pre-training systemic administration of DL77 (2.5 mg/kg, i.p.) facilitated acquisition, whereas pre-testing acute administration of DL77 (5 and 10 mg/kg, i.p.) improved retrieval. Interestingly, the procognitive effect of DL77 on retrieval was completely abrogated when rats were pretreated with the centrally-acting H2R antagonist zolantidine (ZOL) but not the centrally acting H1R antagonist PYR, indicating that histaminergic pathways through activation of H2Rs appear to be participating in neuronal circuits involved in retrieval processes. Taken together, our results show that DL77 demonstrates anticonvulsant properties in the MES-induced seizure model and improves cognitive performance through actions on different memory stages. Therefore, H3Rs may have implications for the treatment of degenerative disorders associated with impaired memory function and may represent a novel therapeutic pharmacological target to tackle cognitive problems associated with the chronic use of antiepileptic drugs. This article is part of the Special Issue entitled 'Histamine Receptors'.

Histamine H1 antagonists and clinical characteristics of febrile seizures

Background

The purpose of this study was to determine whether seizure susceptibility due to antihistamines is provoked in patients with febrile seizures.

Methods

The current descriptive study was carried out from April 2009 to February 2011 in 250 infants and children who visited the Madinah Maternity and Children’s Hospital as a result of febrile convulsions. They were divided into two groups according to administration of antihistamines at the onset of fever.

Results

Detailed clinical manifestations were compared between patients with and without administration of antihistamines. The time from fever detection to seizure onset was significantly shorter in the antihistamine group than that in the nonantihistamine group, and the duration of seizures was significantly longer in the antihistamine group than in the nonantihistamine group. No significant difference was found in time from fever detection to seizure onset or seizure duration between patients who received a first-generation antihistamine and those who received a second-generation antihistamine.

Conclusion

Due to their central nervous system effects, H1 antagonists should not be administered to patients with febrile seizures and epilepsy. Caution should be exercised regarding the use of histamine H1 antagonists in young infants, because these drugs could potentially disturb the anticonvulsive central histaminergic system.

Seizure susceptibility due to antihistamines in febrile seizures

The aim of this study was to determine whether seizure susceptibility due to antihistamines is provoked in patients with febrile seizures. The study population comprised 14 patients with simple febrile seizures and 35 patients with complex febrile seizures. Detailed clinical manifestations were compared between patients with and without administration of antihistamine. The time from fever detection to the seizure onset was significantly shorter in the antihistamine group than that in the nonantihistamine group, and the duration of seizures was significantly longer in the antihistamine group than that in nonantihistamine group. Interleukin-1beta is thought to be associated with causing febrile seizures via its dual role as a pyrogen and convulsant substance. Moreover, interleukin-1beta may activate the turnover of hypothalamic neural histamine. These considerations, along with the present results, suggest that the depletion of hypothalamic neuronal histamine induced by antihistamines may increase neuronal excitability, thereby increasing seizure susceptibility in patients with febrile seizures.

Histamine in neurotransmission and brain diseases

Apart from its central role in the mediation of allergic reactions, gastric acid secretion and inflammation in the periphery, histamine serves an important function as a neurotransitter in the central nervous system. The histaminergic neurons originate from the tuberomamillary nucleus of the posterior hypothalamus and send projections to most parts of the brain. The central histamine system is involved in many brain functions such as arousal, control of pituitary hormone secretion, suppression ofeating and cognitive functions. The effects of neuronal histamine are mediated via G-protein-coupled H1-H4 receptors. The prominent role of histamine as a wake-promoting substance has drawn interest to treat sleep-wake disorders, especially narcolepsy, via modulation of H3 receptor function. Post mortem studies have revealed alterations in histaminergic system in neurological and psychiatric diseases. Brain histamine levels are decreased in Alzheimer's disease patients whereas abnormally high histamine concentrations are found in the brains of Parkinson's disease and schizophrenic patients. Low histamine levels are associated with convulsions and seizures. The release of histamine is altered in response to different types of brain injury: e.g. increased release of histamine in an ischemic brain trauma might have a role in the recovery from neuronal damage. Neuronal histamine is also involved in the pain perception. Drugs that increase brain and spinal histamine concentrations have antinociceptive properties. Histaminergic drugs, most importantly histamine H3 receptors ligands, have shown efficacy in many animal models of the above-mentioned disorders. Ongoing clinical trials will reveal the efficacy and safety of these drugs in the treatment of human patients.

Theophylline-associated status epilepticus in an infant: pharmacokinetics and the risk of suppository use

BACKGROUND

Theophylline has been widely used to treat asthma, but recent studies have revealed that the possible risks for seizure may result in the revision of the therapeutic guidelines.

METHODS

An 8-month-old boy who had been treated with oral sustained-release theophylline and additional aminophylline suppository was hospitalized. A combination of diazepam, lidocaine and thiopental was required to stop his convulsion.

RESULTS

The pharmacokinetic study indicated that the usage of a sustained-release formula should not usually be over 15 mg/ml, but the additional use of an aminophylline suppository elevated the concentration to over 20 mg/ml and resulted in the severe adverse effects.

CONCLUSION

The parents of children and also physicians should be educated to ensure the proper use of the suppository formula.