Skeletal muscle necrosis following membrane-active drugs plus serotonin

Chemical and Pharmacological Screening of Rhinella icterica (Spix 1824) Toad Parotoid Secretion in Avian Preparations

The biological activity of Rhinella icterica parotoid secretion (RIPS) and some of its chromatographic fractions (RI18, RI19, RI23, and RI24) was evaluated in the current study. Mass spectrometry of these fractions indicated the presence of sarmentogenin, argentinogenin, (5β,12β)-12,14-dihydroxy-11-oxobufa-3,20,22-trienolide, marinobufagin, bufogenin B, 11α,19-dihydroxy-telocinobufagin, bufotalin, monohydroxylbufotalin, 19-oxo-cinobufagin, 3α,12β,25,26-tetrahydroxy-7-oxo-5β-cholestane-26-O-sulfate, and cinobufagin-3-hemisuberate that were identified as alkaloid and steroid compounds, in addition to marinoic acid and N-methyl-5-hydroxy-tryptamine. In chick brain slices, all fractions caused a slight decrease in cell viability, as also seen with the highest concentration of RIPS tested. In chick biventer cervicis neuromuscular preparations, RIPS and all four fractions significantly inhibited junctional acetylcholinesterase (AChE) activity. In this preparation, only fraction RI23 completely mimicked the pharmacological profile of RIPS, which included a transient facilitation in the amplitude of muscle twitches followed by progressive and complete neuromuscular blockade. Mass spectrometric analysis showed that RI23 consisted predominantly of bufogenins, a class of steroidal compounds known for their cardiotonic activity mediated by a digoxin- or ouabain-like action and the blockade of voltage-dependent L-type calcium channels. These findings indicate that the pharmacological activities of RI23 (and RIPS) are probably mediated by: (1) inhibition of AChE activity that increases the junctional content of Ach; (2) inhibition of neuronal Na+/K+-ATPase, leading to facilitation followed by neuromuscular blockade; and (3) blockade of voltage-dependent Ca2+ channels, leading to stabilization of the motor endplate membrane.

Pre-clinical study of 21 approved drugs in the mdx mouse

Duchenne muscular dystrophy, a genetic disease caused by the absence of functional dystrophin, remains without adequate treatment. Although great hopes are attached to gene and cell therapies, identification of active small molecules remains a valid option for new treatments. We have studied the effect of 20 approved pharmaceutical compounds on the muscles of dystrophin-deficient mdx5Cv mice. These compounds were selected as the result of a prior screen of 800 approved molecules on a dystrophin mutant of the invertebrate animal model Cænorhabditis elegans. Drugs were administered to the mice through maternal feeding since 2weeks of life and mixed in their food after the 3rd week of life. The effects of the drugs on mice were evaluated both at 6weeks and 16weeks. Each drug was tested at two concentrations. Prednisone was added to the molecule list as a positive control. To investigate treatment efficiency, more than 30 histological, biochemical and functional parameters were recorded. This extensive study reveals that tricyclics (Imipramine and Amitriptyline) are beneficial to the fast muscles of mdx mice. It also highlights a great variability of responses according to time, muscles and assays.

Rhabdomyolysis associated with olanzapine treatment in a child with Autism

Children with autism often display difficult behaviors including tantrums, extreme irritability, and physical aggression. There is emerging evidence that olanzapine is useful in decreasing these disruptive behaviors. The most common adverse effects are weight gain and short-term sedation. On the other hand, olanzapine rarely causes rhabdomyolysis. We report a case with rhabdomyolysis in an autistic child just after 2 doses of olanzapine treatment. Initial creatine kinase value was 30,690 IU/L (range, 5-130 U/L), and rhabdomyolysis resolved with hydration and alkalinization over 7 days. Monitoring serum creatine kinase levels may be useful in pediatric cases after initiation of olanzapine treatment.

Elevated serum creatine kinase levels in psychiatric practice: differential diagnosis and clinical significance: A brief, practical guideline for clinicians

Introduction. Elevated serum CK levels often occur in psychiatric in-patient practice. Although the majority of cases are benign and temporary, it is important to recognize and treat these conditions. Aims. To discuss the etiology, the clinical significance and the management of elevated creatine kinase levels in psychiatric in-patient practice, focusing on antipsychotic-induced rhabdomyolysis. To compare the pathogenesis and the clinical features of rhabdomyolysis and neuroleptic malignant syndrome. Methods. Review of the literature. Results. A brief, practical guideline is introduced, which may help clinicians in the differential diagnosis and in the management of patients with elevated creatine kinase activity in emergent psychiatric practice. Conclusions. The most common etiologic factors (prescription drugs, alcohol, physical reasons, cardiac etiology) and clinical syndromes (rhabdomyolysis, neuroleptic malignant syndrome, acute coronary syndrome) should be considered, when elevated creatine kinase levels are encountered in psychiatric in-patients. Routine creatine kinase measurements in asymptomatic patients on antipsychotic medications are not recommended, but patients should be carefully followed for the development of rhabdomyolysis, when muscular symptoms arise. Careful monitoring of symptoms and potential complications is critical in order to avoid devastating clinical consequences. Cautiously challenging patients with another antipsychotic after an antipsychotic-induced rhabdomyolysis is recommended to decrease the possibility of recurrence.

Marked elevation of serum creatine kinase associated with olanzapine therapy

OBJECTIVE

To report a case of marked elevation of serum creatine kinase (CK) associated with olanzapine therapy.

CASE SUMMARY

A 39-year-old white Jewish schizophrenic man treated with olanzapine developed an elevated serum CK concentration with a peak concentration of 4000 IU/L (normal < 230). No other diagnostic criteria for neuroleptic malignant syndrome (NMS) were present. On discontinuation of the drug, serum CK concentrations returned to normal within eight days.

DISCUSSION

Olanzapine, like other atypical antipsychotic drugs, may cause muscle injury with concomitant elevations of serum CK of muscle origin. We suggest that in patients treated with olanzapine, CK concentrations should be checked on initiation of therapy, within the first 48 hours, and weekly thereafter for at least one month. In addition, patients with clinical signs suggestive of NMS should be monitored more carefully. For those patients with a history of NMS, or even of isolated serum CK elevation during antipsychotic therapy, follow-up should be stricter.

CONCLUSIONS

Marked elevation of serum CK may be a possible complication of olanzapine therapy.

Serotonin uptake in blood platelets of Duchenne muscular dystrophy patients

Serotonin (5-HT) uptake was studied in the blood platelets of 10 patients with Duchenne-type muscular dystrophy (DMD) and 7 age-matched controls. Vmax (maximum number of uptake sites) of platelet 5-HT uptake in the DMD patients was significantly less than that of the normal controls. There was no difference in the affinity for 5-HT (Km) between the two groups. There was a significant negative correlation between serum creatine kinase activity and Km of 5-HT uptake in blood platelets of these patients. However, no correlation was found between Km or Vmax and ambulatory status of DMD.

Blood flow and uptake of glucose and amino acids in ischemic muscle

In order to examine muscle ischemia, muscle blood flow in the rat hindlimb was decreased by vessel ligation. Amino acid uptake, studied with [14C]alpha-aminoisobutyric acid, was decreased in ischemic Type I (soleus) muscle. Glucose uptake, studied with [14C]deoxyglucose, was increased in Type I muscle. These changes were temporally associated with histologic changes of ischemia in soleus muscle. Denervation, atrophy, and hypertrophy also produced uptake changes with these techniques, and although more prominent in soleus, the changes were also seen in Type II muscle.

The effect of 5-hydroxytryptamine on the chick biventer cervicis muscle

The actions of 5-hydroxytryptamine have been studied in the chick biventer cervicis nerve--muscle preparation. At concentrations between 2.5 X 10(-3) and 3.7 X 10(-3) M, 5HT produced a transient increase in responses to indirect stimulation, but not to direct stimulation. At higher concentrations, 5HT produced a reversible depression of twitches, which was much more marked in indirectly than in directly stimulated preparations. In a concentration range of 2.5-3.7 X 10(-3) M, 5HT increased the response to exogenous acetylcholine but reduced the response to carbachol. After pretreatment with neostigmine, 5HT inhibited responses to both acetylcholine and carbachol. It is suggested that the facilitatory effects of 5HT are due to its anticholinesterase activity. The blocking actions of 5HT are thought to be curare-like. In addition, irreversible toxic effects on the muscle preparations were found after repeated exposures to high concentrations of 5HT.

The roles of prostaglandins and calcium accumulation in muscular dystrophy

There is good evidence that abnormal calcium accumulation may be a final common pathway of muscle degeneration in the muscular dystrophies. Prostaglandins are able to promote calcium entry into cells and excess prostaglandin activity coupled with a defect in intracellular calcium release could cause toxic accumulations of calcium in intracellular organelles such as mitochondria. Serotonin stimulates prostaglandin synthesis while tricyclic antidepressants inhibit calcium release from intracellular organelles thus possibly accounting for the models of muscular dystrophy reported using this combination. The prostaglandin/calcium hypothesis can account for the effects of vitamin E, steroids and local anaesthetic-like drugs in muscular dystrophy. Since many drugs already in clinical use for other purposes can be used to control prostaglandin synthesis or action this hypothesis has immediate potential clinical applications.

Nerve, muscle, and serotonin

Effects of serotonin one neuromuscular transmission and muscle contraction were studied in the tibialis anterior of rabbits. Serotonin antagonised the Mg++-induced block of transmission, and also provided dual effects on the curare-induced block, anti-curare phase followed by curare-potentiating phase. Independent of transmission processes, serotonin caused a reduction in twitch tension, mainly associated with decreased acceleration of twitch development. These serotonin actions were independent of vascular changes; pharmacological mechanisms are discussed in comparison with those of adrenaline and isoprenaline. A possible role of serotonin in causing a myopathy is proposed.