Pharmacokinetic evaluation of oral dantrolene in the dog

Heliox Preconditioning Exerts Neuroprotective Effects on Neonatal Ischemia/Hypoxia Injury by Inhibiting Necroptosis Induced by Ca2+ Elevation

Our previous studies have indicated that heliox preconditioning (HePC) may exert neuroprotective effects on neonatal hypoxic-ischemic encephalopathy (HIE). The present study was to investigate whether HePC alleviates neonatal HIE by inhibiting necroptosis and explore the potential mechanism. Seven-day-old rat pups were randomly divided into Sham group, HIE group, HIE + HePC group, HIE + Dantrolene (DAN) group, and HIE + Necrostatin-1 (Nec-1) group. HIE was induced by common carotid artery ligation and subsequent hypoxia exposure. The neurological function, brain injury, and molecular mechanism were evaluated by histological staining, neurobehavioral test, Western blotting, Ca²⁺, immunofluorescence staining, co-immunoprecipitation (Co-IP), and transmission electron microscopy (TEM). Results supported that the expression of necroptosis markers and p-RyR2 in the brain increased significantly after HIE. HePC, DAN, or Nec-1 was found to improve the neurological deficits after H/I and inhibit neuronal necroptosis. Interestingly, both HePC and DAN inhibited the increases in cytoplasmic Ca²⁺ and CaMK-II phosphorylation in the brain secondary to HIE, but Nec-1 failed to affect Ca²⁺. In conclusion, our results suggest HePC may alleviate cytoplasmic Ca²⁺ overload by regulating p-RyR2, which inhibits the necroptosis in the brain, exerting neuroprotective effects on HIE.

Retrospective analysis of hops toxicosis in dogs (2002-2014): 71 cases

OBJECTIVE

To describe a population of dogs with hops toxicosis, including clinical signs observed, treatments performed, patient outcome, and overall prognosis. Clinical findings and treatment interventions were evaluated for their potential effects on outcome. This study also aims to review hops toxicosis and treatment options.

DESIGN

Retrospective observational study.

SETTING

Poison Control Center.

ANIMALS

Seventy-one dogs presenting for hops ingestion.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Records of 71 dogs with known hops ingestion from the ASPCA - Animal Poison Control Center (ASPCA-APCC) database and the Tufts University medical record system were reviewed. Fifty-nine (77%) of the dogs survived. The most common clinical signs on presentation were hyperthermia and tachycardia, with presenting temperatures and heart rates significantly higher in nonsurvivors. There was no significant difference between survivors and nonsurvivors in regard to signalment. Time to presentation was shorter in survivors (5.0 vs 5.5 h; P < 0.0001). The median amount of hops ingested was higher in nonsurvivors (2 vs 2.5 oz; P < 0.0001). Hops ingestion caused hyperthermia in 96% (68/71) of dogs. The median time to death in the nonsurvivor group was 10.7 hours (2-30 h). None of the decontamination, cooling, or treatment measures (dantrolene, cyproheptadine, sedatives) evaluated in this population were associated with improved survival. After adjusting for cooling, time to presentation, and dantrolene administration, every degree of elevation in temperature was associated with a 78% increased chance of death. All dogs that survived to discharge had complete resolution of clinical signs.

CONCLUSIONS

Hops toxicosis can result in significant hyperthermia, tachypnea, and tachycardia. Seventy-seven percent of dogs survived with intensive treatment. Continued education of the potential for hops toxicosis is advised.

Ryanodine Receptors: A Potential Treatment Target in Various Neurodegenerative Disease

Progressive neuronal demise is a key contributor to the key pathogenic event implicated in many different neurodegenerative disorders (NDDs). There are several therapeutic strategies available; however, none of them are particularly effective. Targeted neuroprotective therapy is one such therapy, which seems a compelling option, yet remains challenging due to the internal heterogeneity of the mechanisms underlying various NDDs. An alternative method to treat NDDs is to exploit common modalities involving molecularly distinct subtypes and thus develop specialized drugs with broad-spectrum characteristics. There is mounting evidence which supports for the theory that dysfunctional ryanodine receptors (RyRs) disrupt intracellular Ca²⁺ homeostasis, contributing to NDDs significantly. This review aims to provide direct and indirect evidence on the intersection of NDDs and RyRs malfunction, and to shed light on novel strategies to treat RyRs-mediated disease, modifying pharmacological therapies such as the potential therapeutic role of dantrolene, a RyRs antagonist.

Effects of oral administration of 5 immunosuppressive agents on activated T-cell cytokine expression in healthy dogs

BACKGROUND

Dogs are often adminstered >1 immunosuppressive medication when treating immune-mediated diseases, and determining whether these different medications affect IL-2 expression would be useful when performing pharmacodynamic monitoring during cyclosporine therapy.

HYPOTHESIS/OBJECTIVES

To determine the effects of 5 medications (prednisone, cyclosporine, azathioprine, mycophenolate mofetil, and leflunomide) on activated T-cell expression of the cytokines IL-2 and interferon-gamma (IFN-γ).

ANIMALS

Eight healthy dogs.

METHODS

Randomized, cross-over study comparing values before and after treatment, and comparing values after treatment among drugs. Dogs were administered each drug at standard oral doses for 1 week, with a washout of at least 21 days. Activated T-cell expression of IL-2 and IFN-γ mRNA was measured by quantitative reverse transcription polymerase chain reaction. Blood drug concentrations were measured for cyclosporine, mycophenolate, and leflunomide metabolites.

RESULTS

Least squares means (with 95% confidence interval) before treatment for IL-2 (2.91 [2.32-3.50] ΔCt) and IFN-γ (2.33 [1.66-3.00 ΔCt]) values were significantly lower (both P < .001) than values after treatment (10.75 [10.16-11.34] and 10.79 [10.11-11.46] ΔCt, respectively) with cyclosporine. Similarly, least squares means before treatment for IL-2 (1.55 [1.07-2.02] ΔCt) and IFN-γ (2.62 [2.32-2.92] ΔCt) values were significantly lower (both P < .001) than values after treatment (3.55 [3.06-4.00] and 5.22 [4.92-5.52] ΔCt, respectively) with prednisone. Comparing delta cycle threshold values after treatment among drugs, cyclosporine was significantly different than prednisone (IL-2 and IFN-γ both P < .001), with cyclosporine more suppressive than prednisone.

CONCLUSIONS AND CLINICAL IMPORTANCE

Prednisone and cyclosporine both affected expression of IL-2 and IFN-γ, suggesting that both have the ability to influence results when utilizing pharmacodynamic monitoring of cyclosporine treatment.

Recovery of T-cell function in healthy dogs following cessation of oral cyclosporine administration

Cyclosporine is a potent immunosuppressive agent used to treat immune‐mediated disorders in dogs. Secondary infections sometimes necessitate withdrawal of cyclosporine, but it is not known how long it takes for the immune system to recover after cessation of cyclosporine. Our goal was to utilize a validated RT‐qPCR assay in dogs to assess recovery time of the T‐cell cytokines IL‐2 and IFN‐γ after discontinuation of cyclosporine. Six healthy dogs were given oral cyclosporine (10 mg/kg every 12 hr) for 1 week, with samples collected for measurement of cytokine gene expression prior to treatment, and on the last day of therapy. Cyclosporine was then discontinued, and samples were collected daily for an additional 7 days. Results revealed that there was a significant difference in cytokine expression when comparing pre‐treatment and immediate post‐treatment values, corresponding to marked suppression of T‐cell function. There was no significant difference between pre‐treatment values for either cytokine when compared with any day during the recovery period. Cytokine expression, evaluated as a percentage of pre‐treatment baseline samples, demonstrated progressing return of T‐cell function after drug cessation, with full recovery seen in all dogs by Day 4 of the recovery period.

Approaches to Optimizing Dantrolene Neuroprotection for the Treatment of Alzheimer's Disease

Alzheimer's Disease (AD), a neurodegenerative disorder with high incidence and mortality, is leading its way to the top of the list of the deadliest diseases without an effective disease-modifying drug. Ca2+ dysregulation, specifically abnormal release of Ca2+ via over activated ryanodine receptor (RyR), has been increasingly considered as an alternative upstream mechanism in AD pathology. Consequently, dantrolene, a RyR antagonist and FDA approved drug to treat malignant hyperthermia and chronic muscle spasms, has been shown to ameliorate memory loss in AD transgenic mice. However, the inefficiency of dantrolene to pass the Blood Brain Barrier (BBB) and penetrate the Central Nervous System needs to be resolved, considering its dose-dependent neuroprotection in AD and other neurodegenerative diseases. In this mini-review, we will discuss the current status of dantrolene neuroprotection in AD treatment and a strategy to maximize its beneficial effects, such as intranasal administration of dantrolene.

Determination and tissue distribution studies of dantrolene sodium with hydroxypropyl-β-cyclodextrin in rat tissue by HPLC/MS/MS

The established analytical method for determining the concentration of dantrolene sodium (Da) in rat tissues by HPLC/MS/MS technique was successfully applied to tissue distribution studies of Da in rats. Tissue homogenate samples were pretreated by protein precipitation with pre-cooled methanol. Chromatographic separation was achieved on an Acquity HPLC column (Kromat Universil XB-C₁₈ , 2.1 × 150 mm, 3 μm). Mass spectrometry was conducted with an electrospray ionization interface in negative ionization mode and multiple reaction monitoring was used for quantitative analysis. The results showed that Da was rapidly and widely distributed in tissues and reached the maximum concentration within 0.5 h in all tissues after oral administration of Da-hydroxypropyl-β-cyclodextrin (DHC). It was then metabolized by liver and finally excreted from kidney,which indicated that DHC inclusion complex has better absorption and higher oral bioavailability than Da. The results also provided evidence for the safety and effectiveness of drug clinical application.

TREATMENT OF SUSPECTED EXERTIONAL MYOPATHY USING DANTROLENE IN A COYOTE ( CANIS LATRANS)

  A 3-yr-old spayed female coyote ( Canis latrans) developed clinical signs of exertional myopathy after fighting with a conspecific. A diagnosis of exertional myopathy was made based on physical examination findings, probable myoglobinuria, and elevations in serum creatinine kinase activity, alanine aminotransferase activity, and potassium concentration. Dantrolene, a hydantoin analog, as well as supportive and symptomatic therapies, was used to successfully treat exertional myopathy. This is the first reported use of dantrolene in wildlife or zoo animals.

Effect of dantrolene premedication on various cardiovascular and biochemical variables and the recovery in healthy isoflurane-anesthetized horses

OBJECTIVE

To determine the effect of dantrolene premedication on various cardiovascular and biochemical variables and recovery in isoflurane-anesthetized horses.

ANIMALS

6 healthy horses.

PROCEDURES

Each horse was anesthetized twice with a 21- to 28-day washout period between anesthetic sessions. Food was not withheld from horses before either session. During each session, dantrolene (6 mg/kg in 2 L of water) or water (2 L) was administered via a nasogastric tube 1 hour before anesthesia was induced. Anesthesia was maintained with isoflurane for 90 minutes, during which blood gas analyses and lithium-dilution cardiac output (CO) measurements were obtained every 10 minutes. Serum creatine kinase activity was measured before and at 4, 8, and 12 hours after anesthesia.

RESULTS

When horses were premedicated with dantrolene, CO at 25, 35, and 45 minutes after induction of anesthesia was significantly lower than that when horses were premedicated with water after which time difficulty in obtaining valid measurements suggested a continued decrease in CO; plasma potassium concentration progressively increased during anesthesia, whereas serum creatine kinase activity remained fairly stable and within reference limits through 12 hours after anesthesia; and 2 of 6 horses developed cardiac arrhythmias that required medical intervention. The quality of anesthetic recovery was slightly better when horses were premedicated with dantrolene versus water, although the time required for recovery did not differ significantly between treatments.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that dantrolene premedication prevented muscle damage without affecting anesthetic recovery but impaired CO and precipitated hyperkalemia and cardiac arrhythmias in healthy isoflurane-anesthetized horses.