Possible central effect of dantrolene sodium in neuroleptic malignant syndrome

Emergent Treatment of Neuroleptic Malignant Syndrome Induced by Antipsychotic Monotherapy Using Dantrolene

Neuroleptic malignant syndrome (NMS) is a rare but potentially fatal complication resulting from neuroleptic drug therapy. Presentation of NMS can vary, and diagnosis relies primarily upon medical history and symptomatology. Due to the potential delay in diagnosis, emergency physicians should remain vigilant in recognizing the symptoms of NMS and be prepared to initiate immediate treatment following diagnosis. Dantrolene, which has been used for spasticity and malignant hyperthermia, has been reported as a potential treatment for NMS and led to off-label use for NMS. We report two cases of NMS induced by antipsychotic monotherapy for which dantrolene was administered.

Neuroleptic malignant syndrome and serotonin syndrome

This chapter is focused on drug-induced hyperthermia with special regard to use of antipsychotics and antidepressants for the treatment of schizophrenia and major depression, respectively. Neuroleptic malignant syndrome (NMS) develops during the use of neuroleptics, whereas serotonin syndrome is caused mainly by serotoninergic antidepressants. Although both syndromes show various symptoms, hyperthermia is the main clinical manifestation. In this review we describe the historical background, clinical manifestations, diagnosis, and differential diagnosis of these two syndromes based on our observations on the experimental and clinical data.

Genetic predisposition to neuroleptic malignant syndrome : implications for antipsychotic therapy

The pathogenetic mechanism of neuroleptic malignant syndrome (NMS), a potentially lethal adverse effect of antipsychotics, is not well understood. In addition to acquired risk factors, clinical observations suggest a number of genetic factors predisposing patients to NMS. Recent findings in pharmacogenetics indicate that the genetic polymorphisms for drug-metabolizing enzymes, drug transporters, and possibly drug-targeting molecules, are associated with the interindividual differences in drug responses concerning both efficacy and adverse reactions. Genetic association studies have sought to identify polymorphisms influencing susceptibility to NMS, especially with respect to the dopamine D(2) receptor, serotonin receptor, and cytochrome p450 2D6. While a few candidate polymorphisms were associated with NMS, a large controlled study is needed to attain statistical power. On the other hand, NMS might include heterogeneous conditions with common characteristic symptoms but different causative mechanisms. Further analysis of individuals with identified genetic mutations or polymorphisms should advance our understanding of mechanisms underlying NMS.

Clinical features of malignant syndrome in Parkinson's disease and related neurological disorders

INTRODUCTION

We elucidated the cause and clinical characteristics of malignant syndrome (MS) in patients with Parkinson's disease (PD), early-onset parkinsonism (EOP), and other neurological disorders.

MATERIALS AND METHODS

Subjects were 260 patients with PD or EOP, and three patients with other neurological disorders associated with MS. We studied clinical symptoms before and after the onset of MS, and evaluated autonomic function particularly before the onset of MS.

RESULTS

The overall incidence of MS accompanying PD and EOP in our department was eight of 260 patients (3.1%). The incidence of MS in EOP was significantly higher than that in PD. All patients with MS showed comparatively longer duration of illness and advanced stage of PD and EOP. Factors triggering MS included reduced dosage or discontinuation of anti-parkinsonian drugs, reduction of oral intake, dehydration, infectious disease, postoperative state, and treatment with major tranquilizers. Although patients demonstrated marked autonomic symptoms at the onset of MS, in many cases autonomic dysfunction developed before the onset of MS. Even EOP patients, who usually demonstrated milder autonomic dysfunction, showed abnormalities in the correlation between circadian rhythm of blood pressure and pulse rate, and/or abnormal gastric emptying test, suggesting that autonomic dysfunction plays an important role in the cause of MS. Cooling the body, fluid replacement, resumption or increasing the dosage of anti-parkinsonian drugs and administration of dantrolene sodium overcame MS in all cases.

CONCLUSION

Autonomic dysfunction is related to the cause and clinical features of MS in PD, EOP and some other neurological disorders.

Effect of dantrolene on KCl- or NMDA-induced intracellular Ca2+ changes and spontaneous Ca2+ oscillation in cultured rat frontal cortical neurons

Dantrolene has been known to affect intracellular Ca2+ concentration ([Ca2+]i) by inhibiting Ca2+ release from intracellular stores in cultured neurons. We were interested in examining this property of dantrolene in influencing the [Ca2+]i affected by the NMDA receptor ligands, KCl, L-type Ca2+ channel blocker nifedipine, and two other intracellular Ca2(+)-mobilizing agents caffeine and bradykinin. Effect of dantrolene on the spontaneous oscillation of [Ca2+]i was also examined. Dantrolene in microM concentrations dose-dependently inhibited the increase in [Ca2+]i elicited by NMDA and KCl. AP-5, MK-801 (NMDA antagonists), and nifedipine respectively reduced the NMDA and KCl-induced increase in [Ca2+]i. Dantrolene, added to the buffer solution together with the antagonists or nifedipine, caused a further reduction in [Ca2+]i to a degree similar to that seen with dantrolene alone inhibiting the increase in [Ca2+]i caused by NMDA or KCl. At 30 microM, dantrolene partially inhibited caffeine-induced increase in [Ca2+]i whereas it has no effect on the bradykinin-induced change in [Ca2+]i. The spontaneous oscillation of [Ca2+]i in frontal cortical neurons was reduced both in amplitude and in base line concentration in the presence of 10 microM dantrolene. Our results indicate that dantrolene's mobilizing effects on intracellular Ca2+ stores operate independently from the influxed Ca2+ and that a component of the apparent increase in [Ca2+]i elicited by NMDA or KCl represents a dantrolene-sensitive Ca2+ release from intracellular stores. Results also suggest that dantrolene does not affect the IP3-gated release of intracellular Ca2+ and that the spontaneous Ca2+ oscillation is, at least partially, under the control of Ca2+ mobilization from internal stores.

Dantrolene sodium reverses the increase in cAMP response element and TPA responsive element DNA-binding activity in the rabbit brain following haloperidol administration and heat stress

Using electrophoretic mobility-shift assay (EMSA), we examined DNA-binding activity of cAMP response element (CRE), onto its responsive element CRE, as well as TPA responsive element (TRE) in the medial hypothalamus and striatum of the experimental rabbits administered with haloperidol under heat stress exposure and studied the effects of dantrolene sodium to the transcriptional factor. In EMSA with nuclear extracts from the rabbit brain, the DNA-binding activities of CRE and TRE in medial hypothalamus and striatum increased following haloperidol and heat stress. These increases were maintained by coadministration with atropine. The treatment with dantrolene sodium markedly reversed such increases. The alterations of activities of these transcriptional factors may reflect the therapeutic effect of dantrolene sodium.

Neuroleptic malignant syndrome-like state in a patient with Down syndrome and basal ganglia calcification

We report a case of rhabdomyolysis in a 13-year-old Down syndrome patient with progressive quadriplegia, choreoathetosis and dystonia. Cranial CT demonstrated bilateral basal ganglia calcification. He experienced the sudden onset of high fever, cloudiness of consciousness, muscle rigidity and severe opisthotonus. The diagnosis was made on the basis of the marked increases in serum creatine kinase and myoglobin. There was remarkable elevation of 5-hydroxyindoleacetic acid, homovanillic acid and methoxy-hydroxyphenyl glycol in the cerebrospinal fluid during hyperpyrexia. This case exhibited almost all the diagnostic criteria of the neuroleptic malignant syndrome. It was suggested that abnormalities of monoamines in the central nervous system may be related to the pathologic etiology of this state and rhabdomyolysis.