A pharmacokinetic framework describing antibiotic adsorption to cardiopulmonary bypass devices.

Cardiopulmonary bypass (CPB) can alter pharmacokinetic (PK) parameters and the drug may adsorb to the CPB device, altering exposure. Cefazolin is a beta-lactam antibiotic used for antimicrobial prophylaxis during cardiac surgery supported by CPB. Adsorption of cefazolin could result in therapeutic failure. An ex vivo study was undertaken using CPB devices primed and then dosed with cefazolin and samples were obtained over 1 hour of recirculation. Twelve experimental runs were conducted using different CPB device sizes (neonate, infant, child, and adult), device coatings (Xcoating™, Rheoparin®, PH.I.S.I.O), and priming solutions. The time course of saturable binding, using Bmax (binding capacity), Kd (dissociation constant), and T2off (half-time of dissociation), described cefazolin adsorption. Bmax estimates for the device sizes were neonate 40.0 mg (95% CI 24.3, 67.4), infant 48.6 mg (95% CI 5.97, 80.2), child 77.8 mg (95% CI 54.9, 103), and adult 196 mg (95% CI 191, 199). The Xcoating™ Kd estimate was 139 mg/L (95% CI 27.0, 283) and the T2off estimate was 98.4 min (95% CI 66.8, 129). The Rheoparin® and PH.I.S.I.O coatings had similar binding parameters with Kd and T2off estimates of 0.169 mg/L (95% CI 0.01, 1.99) and 4.94 min (95% CI 0.17, 59.4). The Bmax was small (< 10%) relative to a typical total patient dose during cardiac surgery supported by CPB. A dose adjustment for cefazolin based solely on drug adsorption is not required. This framework could be extended to other PK studies involving CPB.

Ethnic disparity in clozapine dosing and cardiotoxicity in New Zealand.

AIMS: To investigate ethnic disparities in the treatment and incidence of cardiotoxicity for patients prescribed clozapine in New Zealand. METHODS: A post hoc analysis was undertaken using data from four studies investigating clozapine cardiotoxicities in New Zealand: two population studies (one prospective, one retrospective) conducted in the Auckland District Health Board (2011-2017), and two studies of coronial autopsy records (2001-2016). The relationship between ethnicity and cases (N=26) of myocarditis and/or cardiomyopathy was examined in comparison to non-cases in the rest of the study population (N=161). Patient demographics, comorbidities, and risk factors were investigated for any associations with ethnicity, where data was available. RESULTS: Maori and Pacific patients were over-represented in the population studies. Moreover, across the cohorts investigated 46% of myocarditis and cardiomyopathy cases were Maori. In contrast, only one case (4%) of cardiomyopathy was identified in a patient of Pacific descent. Where clozapine titration data was available, the rate of dose escalation was higher in Maori and Pacific peoples, as was the cumulative dose received before the first case of cardiotoxicity (day 13 of dose titration). Maori patients were more likely to be co-medicated with sodium valproate than others during clozapine titration, and sodium valproate was also significantly associated with myocarditis in these patients. CONCLUSIONS: The factors underpinning the more rapid titration of Maori and Pacific patients onto clozapine and the increased use of concomitant sodium valproate in Maori are unclear. While the latter may explain the heightened risk of clozapine-induced myocarditis in Maori, further work is required to mitigate the effects of this inequity on the safe use of clozapine in New Zealand.

Incidence and investigation of potential risk-factors for clozapine-associated myocarditis and cardiomyopathy in a New Zealand cohort.

Clozapine is a uniquely effective antipsychotic indicated for treatment-resistant schizophrenia. However, its use is underutilised and often delayed for years due to potential adverse reactions including myocarditis and cardiomyopathy. The purpose of this study was to conduct a retrospective review of the clinical records of patients initiating clozapine in the Auckland District Health Board (ADHB) region to determine the incidence of clozapine-associated myocarditis and cardiomyopathy and to identify potential risk factors associated with these cardiotoxicities. The incidence of clozapine-associated myocarditis and cardiomyopathy over a two-year period in the ADHB region was 3.8% and 1.3% respectively.

Circulating microRNA as biomarkers of clozapine-induced cardiotoxicity.

Purpose: This work investigated the utility of circulating microRNA (miRNA) as biomarkers of clozapine (CLZ)-induced cardiotoxicities: serious adverse events with an unusually high incidence in Australia and New Zealand.Methods: Global plasma miRNA expression was analysed by microarray in patients taking CLZ, to investigate differential expression between CLZ-induced cardiotoxicity cases (n = 6) and matched control patients (n = 12). The results were validated by RT-qPCR using a panel of 17 miRNA, and their expression was examined in both CLZ-naïve healthy volunteers (n = 12) and an expanded cohort of CLZ-taking patients (n = 21). Temporal changes were also examined in two healthy volunteers and two CLZ-induced cardiotoxicity patients.Results: No miRNA were differentially expressed between cases of CLZ-induced cardiotoxicity and control patients. Circulating levels of several miRNA were significantly altered in CLZ-taking patients compared to healthy volunteers, with miR-16-5p, miR-25-3p, miR-92a-3p, miR-320a-3p, and miR-486-3p upregulated and miR-22-3p, miR-126-3p, and miR-142-3p downregulated in the patients. Five of these (miR-16-5p, miR-22-3p, miR-92a-3p, miR-126-3p, miR-142-3p) were stably expressed over time in both CLZ-induced cardiotoxicity patients and CLZ-naïve healthy volunteers.Conclusions: Plasma miRNA are not useful biomarkers of CLZ-induced cardiotoxicity, however patients taking CLZ have significantly altered circulating miRNA compared to healthy volunteers.

Subcutaneous nicotine delivery via needle-free jet injection: A porcine model.

Subcutaneous delivery of nicotine was performed using a novel electrically-operated needle-free jet injector, and compared to hypodermic needle delivery in a porcine model. Nicotine was delivered as a single, one-milligram dose into the abdominal skin, formulated as a 50 microliter aqueous solution. Plasma levels of nicotine and cotinine, its main metabolite, were then monitored over 2 h, following which the injection site was excised for histological examination. No irritation or tissue damage were found at the injection sites, and the jet-injected nicotine exhibited comparable absorption into the systemic circulation to that injected using a conventional needle and syringe. The needle-free jet injection of nicotine is a promising and well tolerated method. The data presented from this porcine model will support a first in human trial towards a new promising nicotine replacement therapy.

A systematic review of clozapine-induced myocarditis.

BACKGROUND: Clozapine is an atypical antipsychotic that is beneficial to some patients who failed to have an adequate clinical response to other antipsychotic drugs. Its clinical use is limited due to several potentially fatal adverse reactions including myocarditis. Careful monitoring of patients on clozapine is required. METHODS: We conducted a systematic review of the literature on myocarditis associated with clozapine therapy. The search engines used to identify cases were MEDLINE, EMBASE, PsycINFO and Cochrane reviews. The references included in the manuscripts reviewed were searched to identify additional reports. RESULTS: We identified a total of 3347 articles that addressed the cardiac complications of clozapine. Of these, 82 articles detailed cases of clozapine-induced myocarditis. The median age of patients and dose of clozapine at presentation was 30years and 250mg/day respectively. Symptoms and signs of myocarditis developed in 87% of patients within the first month of treatment. Clinical presentation included: shortness of breath (67%), fever (67%) and tachycardia (58%). Cardiac markers were elevated in 87% of the 54 cases that reported these markers. Global ventricular dysfunction was the predominant echocardiogram finding (57%). CONCLUSIONS: Patients on clozapine require routine monitoring for symptoms and signs of myocarditis during the first three months of therapy. This adverse drug reaction is difficult to diagnose due the non-specific nature of the symptoms and signs. Alternate causes of myocarditis should be ruled out before attributing the myocarditis to clozapine.

Use of Coronial Post-mortem Tissue for Research in New Zealand.

Forensic pathology is remarkably under-represented in research: considering the obstacles a researcher must overcome to obtain post-mortem tissue for research, it is perhaps not surprising. We are investigating whether there is any role for altered drug metabolism in potentially fatal clozapine-associated myocarditis and/or cardiomyopathy. As part of this research, the use of post-mortem tissue taken during a coronial autopsy from individuals who have died from, or with, these clozapine-associated cardiotoxicities was considered fundamental. Currently, there is no clear pathway for using coronial post-mortem tissue for research in New Zealand. We have worked through the Coroners Act 2006 NZ, the Human Tissue Act 2008 NZ and the medico-legal death investigation process in New Zealand to use coronial post-mortem tissue for research. The process to obtaining tissue(s) in New Zealand is probably representative of pathways in other coronial systems.

Varenicline improves motor and cognitive deficits and decreases depressive-like behaviour in late-stage YAC128 mice.

OBJECTIVE: Studies in the post mortem human brain and in genetic mouse model suggest that dysfunctional cholinergic neurotransmission, through a loss of agonist rather than receptors may be a significant contributing factor to HD pathology. If correct, pharmacological replacement may therefore be a potential treatment strategy. We have investigated whether chronic administration of the selective nicotinic partial agonist varenicline improved motor, cognitive and affective symptoms in a transgenic mouse model of Huntington's disease. METHOD: The performance of 15 month old YAC128 mice and age-matched wild-type littermates was assessed in the rotarod, T-maze, novel object recognition, novelty suppressed feeding and forced swim tests prior to and after treatment with varenicline (5 mg/kg/day for 28 days via miniosmotic pump). Thymidine analogues, whilst DARPP32 and EM48 immunohistochemistry were used to assess the effect of varenicline on progenitor cell proliferation and survival, medium spiny neurons and aggregate formation respectively. RESULTS: Chronic treatment with varenicline significantly improved motor coordination, delay-dependent memory and reduced depressive-like behaviour in late stage YAC128 mice. Varenicline also produced genotype-independent improvements in recognition memory and reduced anxiety. In addition, varenicline displayed anxiolytic effects and improved spatial memory in the absence of compromised function. Functional improvements were accompanied by neuropathological changes including increased aggregate formation, neuroprotection and increased progenitor cell proliferation and survival. INTERPRETATION: Our findings provide evidence that administration of an exogenous nicotinic agonist may be of clinical benefit in the treatment of late-stage Huntington's disease.

Varenicline improves motor and cognitive symptoms in early Huntington's disease.

The aim of this study was to describe the effects of varenicline, a smoking cessation aid that acts as a nicotinic agonist, on cognitive function in patients with early clinical Huntington's disease (HD) who were current smokers. Three gene-positive patients transitioning to symptomatic HD were evaluated using the Unified Huntington's Disease Rating Scale part I and III (motor and behavioral subscales) at baseline and after 4 weeks of treatment. Cognitive function was assessed using a touch screen computer-based neurocognitive test battery (IntegNeuro®). Varenicline (1 mg twice daily) significantly improved performance in executive function and emotional recognition tasks. Our case reports describe no clinically significant adverse effects and suggest that varenicline improves aspects of cognitive function in patients with early HD. A randomized controlled study is now underway.

Synthesis and methemoglobinemia-inducing properties of benzocaine isosteres designed as humane rodenticides.

A number of isosteres (oxadiazoles, thiadiazoles, tetrazoles and diazines) of benzocaine were prepared and evaluated for their capacity to induce methemoglobinemia-with a view to their possible application as humane pest control agents. It was found that an optimal lipophilicity for the formation of methemoglobin (metHb) in vitro existed within each series, with 1,2,4-oxadiazole 3 (metHb%=61.0±3.6) and 1,3,4-oxadiazole 10 (metHb%=52.4±0.9) demonstrating the greatest activity. Of the 5 candidates (compounds 3, 10, 11, 13 and 23) evaluated in vivo, failure to induce a lethal end-point at doses of 120mg/kg was observed in all cases. Inadequate metabolic stability, particularly towards hepatic enzymes such as the CYPs, was postulated as one reason for their failure.

Synthesis and methemoglobinemia-inducing properties of analogues of para-aminopropiophenone designed as humane rodenticides.

A number of structural analogues of the known toxicant para-aminopropiophenone (PAPP) have been prepared and evaluated for their capacity to induce methemoglobinemia--with a view to their possible application as humane pest control agents. It was found that an optimal lipophilicity for the formation of methemoglobin (metHb) in vitro existed for alkyl analogues of PAPP (aminophenones 1-20; compound 6 metHb% = 74.1 ± 2). Besides lipophilicity, this structural sub-class suggested there were certain structural requirements for activity, with both branched (10-16) and cyclic (17-20) alkyl analogues exhibiting inferior in vitro metHb induction. Of the four candidates (compounds 4, 6, 13 and 23) evaluated in vivo, 4 exhibited the greatest toxicity. In parallel, aminophenone bioisosteres, including oximes 30-32, sulfoxide 33, sulfone 34 and sulfonamides 35-36, were found to be inferior metHb inducers to lead ketone 4. Closer examination of Hammett substituent constants suggests that a particular combination of the field and resonance parameters may be significant with respect to the redox mechanisms behind PAPPs metHb toxicity.

Glucuronidation of anticancer prodrug PR-104A: species differences, identification of human UDP-glucuronosyltransferases, and implications for therapy.

PR-104, the phosphate ester of a dinitrobenzamide mustard [PR-104A; 2-((2-bromoethyl)-2-{[(2-hydroxyethyl) amino] carbonyl}-4,6-dinitroanilino)ethyl methanesulfonate], is currently in clinical trial as a hypoxia- and aldo-keto reductase 1C3 (AKR1C3)-activated prodrug for cancer therapy. Here, we investigate species (human, dog, rat, mouse) differences in metabolism to the corresponding O-glucuronide, PR-104G, and identify the human UDP-glucuronosyltransferase (UGT) isoforms responsible. After intravenous PR-104, plasma area under the concentration-time curve ratios (PR-104G/PR-104A) decreased in the order of dog (2.3) > human (1.3) > mouse (0.03) > rat (0.005). The kinetics of uridine 5'-diphosphoglucuronic acid-dependent glucuronidation by liver microsomes in vitro fitted the single-enzyme Michaelis-Menten equation with similar K(m) (∼150 µM) but differing V(max) (472, 88, 37, and 14 nmol/h/mg for dog, human, rat, and mouse, respectively), suggesting that facile glucuronidation is responsible for the anomalously rapid clearance of PR-104A in dogs. In vitro-in vivo extrapolation of PR-104A glucuronidation kinetics is consistent with this also being a major clearance pathway in humans. Recombinant UGT screening identified UGT2B7 as the only commercially available human isoform able to conjugate PR-104A, and UGT2B7 protein concentrations were highly correlated (r = 0.93) with PR-104A glucuronidation by liver microsomes from 24 individuals. The active hydroxylamine metabolite of PR-104A, PR-104H, was also glucuronidated by UGT2B7, although with slightly lower specificity and much lower rates. UGT2B7 mRNA expression was highly variable in human tumor databases. Glucuronidation of PR-104A greatly suppressed nitroreduction by AKR1C3 and NADPH-supplemented anoxic human liver S9 (9000g postmitochondrial supernatant). In conclusion, PR-104A is glucuronidated by UGT2B7 with high specificity and seems to make a major contribution to clearance of PR-104A in humans, but it also has the potential to confer resistance in some human tumors.

The combined impact of CYP2C19 and CYP2B6 pharmacogenetics on cyclophosphamide bioactivation.

AIMS: The role of CYP pharmacogenetics in the bioactivation of cyclophosphamide is still controversial. Recent clinical studies have suggested a role for either CYP2C19 or CYP2B6. The aim of this study was to clarify the role of these pharmacogenes. METHODS: We used a combined in vitro-in vivo approach to determine the role of these pharmacogenes in the bioactivation of the prodrug to 4-hydroxy cyclophosphamide (4-OHCP). Cyclophosphamide metabolism was determined in a human liver biobank (n= 14) and in patients receiving the drug for treatment of lupus nephritis (n= 16) RESULTS: In livers of known CYP2C19 and CYP2B6 genotype and protein expression we observed that there was a combined role for both CYP2C19 and CYP2B6 in the bioactivation of cyclophosphamide in vitro. The presence of at least one loss of function (LoF) allele at either CYP2C19 or CYP2B6 resulted in a significant decrease in both V(max) (P= 0.028) and CL(int) (P= 0.0017) compared with livers with no LoF alleles. This dual genotype relationship was also observed in a preliminary clinical study, with patients who had ≥1 LoF allele at either CYP2C19 or CYP2B6 also displaying significantly (P= 0.0316) lower bioactivation of cyclophosphamide. The mean 4-OHCP : CP bioactivation ratio was 0.0014 (95% CI 0.0007, 0.002) compared with 0.0071 (95% CI 0.0001, 0.014) in patients with no LoF alleles at either of these genes. CONCLUSIONS: The presence of ≥1 LoF allele(s) at either CYP2B6 or CYP2C19 appeared to result in decreased bioactivation of cyclophosphamide both in vitro and in patients. Further clinical studies to confirm this relationship are warranted.

Validation of an LC-MS method for the detection and quantification of BZP and TFMPP and their hydroxylated metabolites in human plasma and its application to the pharmacokinetic study of TFMPP in humans.

An LC-MS method was developed for benzylpiperazine (BZP) and trifluoromethylphenylpiperazine (TFMPP), constituents of "party pills" or "legal herbal highs," and their metabolites in human blood plasma. Compounds were resolved using a mixture of ammonium formate (pH 4.5, 0.01 M) and acetonitrile (flow rate of 1.0 mL/min) with a C18 column. Calibration curves were linear from 1 to 50 ng/mL (R(2) > 0.99); the lower limit of quantification (LLOQ) was 5 ng/mL; the accuracy was >90%; the intra- and interday relative standard deviations (R.S.D) were <5% and <10%, respectively. Human plasma concentrations of TFMPP were measured in blood samples taken from healthy adults (n = 6) over 24 h following a 60-mg oral dose of TFMPP: these peaked at 24.10 ng/mL (±1.8 ng/mL) (C(max) ) after 90 min (T(max)). Plasma concentrations of 1-(3-trifluoromethyl-4-hydroxyphenyl) piperazine peaked at 20.2 ng/mL (±4.6 ng/mL) after 90 min. TFMPP had two disposition phases (t(½) = 2.04 h (±0.19 h) and 5.95 h (±1.63 h). Apparent clearance (Cl/F) was 384 L/h (±45 L/h).

In vivo interactions between BZP and TFMPP (party pill drugs).

AIM: This study explores potential drug-drug interactions between BZP and TFMPP. This was achieved by comparing the metabolism and pharmacokinetics of BZP and TFMPP when taken together with previously published data on their individual metabolism and pharmacokinetics. METHOD: Blood and urine samples were collected from seven participants given a combined dose of BZP (100 mg) and TFMPP (30 mg) and analysed by LC-MS in order to quantify the concentrations of BZP, TFMPP, and their major hydroxylated metabolites 3-OH BZP, 4-OH BZP, and 4-OH TFMPP. RESULTS: The metabolic profiles of both drugs were altered when co-administered. Both BZP and TFMPP lost one metabolite, 3-OH BZP and 4-OH TFMPP, respectively. Some differences in the pharmacokinetic properties of TFMPP were also noted. CONCLUSION: Metabolic interactions between BZP and TFMPP are clearly observed in this study along with some changes to the pharmacokinetics of TFMPP. As these drugs are often co-administered, the interactions between them are both relevant and concerning. Awareness of these interactions can assist clinicians in understanding toxicities relating to the co-administration of BZP and TFMPP or other party pill drugs.

Metabolic interactions with piperazine-based 'party pill' drugs.

OBJECTIVES: 'Party pills' have found use worldwide as a substitute for amphetamine-derived designer drugs. Whilst some information exists about the metabolism of these drugs, there is little information about their ability to inhibit the metabolism of co-administered drugs. This study aimed to determine whether predictions can be made about global interactions between 'party pills' constituents and other drugs metabolised by the same cytochrome P450 (CYP) isoenzymes. METHODS: The inhibitory effects of seven benzyl and phenyl piperazines were measured in microsomal incubation assays of probe substrates for five major CYP isoenzymes. In addition, the metabolism of benzylpiperazine and trifluoromethylphenylpiperazine, the two most commonly used constituents of 'party pills', was investigated using human liver microsomes assays and known inhibitors of CYP isoenzymes. KEY FINDINGS: All piperazine analogues tested showed significant inhibitory activity against most, if not all, isoenzymes tested. The metabolism of benzylpiperazine (BZP) and trifluoromethylphenylpiperazine (TFMPP) involved CYP2D6, CYP1A2 and CYP3A4. Furthermore, BZP and TFMPP inhibited each other's metabolism. CONCLUSIONS: Fluorophenylpiperazine, methoxyphenylpiperazine, chlorophenylpiperazine, methylbenzylpiperazine and methylenedioxybenzylpiperazine had significant inhibitory effects on CYP2D6, CYP1A2, CYP3A4, CYP2C19 and CYP2C9 isoenzymes but each piperazine had a different inhibitory profile. The metabolic interaction between BZP and TFMPP may have clinical implications, as these agents are often combined in 'party pills'.

'Party pill' drugs--BZP and TFMPP.

BZP and TFMPP are amphetamine-like recreational drugs and the major active components of 'party pills'. The pharmacodynamic effects of these neurally active drugs are thought to be dependent on their activity at DA and 5-HT receptors and several studies report drug-drug interactions at a pharmacodynamic level. Their metabolism involves the hepatic P450 enzymes CYP2D6, CYP1A2 and CYP3A4 resulting in inhibited metabolism of other drugs and medicines, as well as compromised metabolism in poor metabolisers for CYP2D6. Basic pharmacokinetic properties are described for both BZP and TFMPP when taken alone and in combination. Several studies have shown that these drugs cause several drug-drug interactions.

Comparative protein binding, stability and degradation of satraplatin, JM118 and cisplatin in human plasma in vitro.

1. Satraplatin is an investigational orally administered platinum-based antitumour drug. The present study compared the plasma protein binding, stability and degradation of satraplatin with that of its active metabolite JM118 and cisplatin. 2. The platinum complexes were incubated in human plasma for up to 2 h at 37 degrees C and quantified in plasma fractions by inductively coupled plasma-mass spectrometry on- or off-line to high-performance liquid chromatography. 3. All three platinum drugs became irreversibly bound to plasma proteins and showed negligible reversible protein binding. They were also unstable in plasma and generated one or more platinum-containing degradation products during their incubation. However, the three platinum complexes differed in the kinetics of their instability and protein binding, as well as in the number of degradation products formed during their incubation. 4. In conclusion, the plasma protein binding, instability and degradation of satraplatin and its active metabolite JM118 are qualitatively similar to that of cisplatin and other clinically approved platinum-based drugs. Quantitative differences in their irreversible protein binding and degradation were related to their respective physiochemical properties and bioactivation mechanisms.