A liposomal formulation of simvastatin and doxorubicin for improved cardioprotective and anti-cancer effect.

Anthracyclines such as doxorubicin (Dox) are the preferred chemotherapeutics for several cancers. However, Dox-induced cardiotoxicity limits its therapeutic potential. Liposomal encapsulation of Dox has been used for patients with risk to develop Dox induced cardiotoxicity but does not surpass the efficacy of the unencapsulated drug. Statins are widely used as cholesterol lowering drugs and have also demonstrated cardioprotective activity in cancer patients undergoing Dox therapy. We developed a liposome loaded with Dox and simvastatin (Sim) and investigated their effect on cardiomyocytes and zebrafish larvae. Furthermore, we investigated if the doses required for cardioprotection compromised the cytotoxicity of Dox in mammary and prostate cancer cells. Combination of Sim and Dox reduced ROS generation in cardiomyocytes, both given as free drugs, or co-encapsulated in liposomes. In contrast, Sim potentiated ROS-generation and cytotoxic activity of Dox towards cancer cells also when co-encapsulated in liposomes. In zebrafish larvae, Sim treatment reduced Dox-induced cardiac affection, and the liposomes did not induce any sign of Dox-induced cardiotoxicity. Our results show that liposomal co-encapsulation of Sim and Dox can be an efficient way of further reducing the risk of cardiotoxic events of liposomal Dox, while retaining, or even potentiating the anti-cancer effect of Dox.

Acute Myocardial Injury in a Patient with Attention Deficit Hyperactivity Disorder and History of Substance Abuse: A Multimodality Imaging Point of View.

Both cannabis and amphetamine are the most commonly used illegal substances worldwide and are associated with a number of adverse cardiovascular effects including transient coronary vasospasm. Here, we present the case of a 39-year-old male admitted to our institution with a 6-h history of severe chest pain and ST-segment elevation on the ECG. Coronary angiography on admission showed normal coronary arteries. The patient had a 14-year history of substance abuse, primarily amphetamine and cannabis, and was prescribed lisdexamfetamin (Aduvanz®) for attention deficit hyperactivity disorder (ADHD) for the past 2 years. A cardiac magnetic resonance (CMR) the following day showed widely distributed focal lesions of late gadolinium enhancement in mid- and sub-epicardial myocardium in the anterior, lateral and inferior walls, suggestive of chronic fibrotic lesions. There was no sign of acute myocardial edema. No viral cause was identified during a thorough investigation, including negative SARS-COV-2 and endomyocardial biopsy. Substance-abuse-induced coronary vasospasm leading to ST-segment elevation, myocardial damage with a rise and fall of cardiac TnT, as well as a slightly reduced left ventricular ejection fraction (48%) and regional wall motion abnormalities on echocardiography, was the most likely diagnosis.

Quetiapine, Misuse and Dependency: A Case-Series of Questions to a Norwegian Network of Drug Information Centers.

PURPOSE: The second-generation antipsychotic quetiapine has been associated with misuse and dependency. We aimed to review questions to the Norwegian network of drug information centers concerning this potential drug safety problem. METHODS: We conducted a Boolean search in the database of the Regional Medicines Information and Pharmacovigilance Centres in Norway (RELIS) combining the indexed categories "quetiapine" and "adverse drug reaction" with the text words "misuse" or "dependency". Question-answer pairs (Q/As) in the full-text, searchable RELIS database were defined as cases. Cases were analyzed for drug safety issues linked to use of quetiapine, including off-label use, polypharmacy and other patient risk factors. RESULTS: The search resulted in 54 cases. Forty-six cases (85%) were patient-related, and a majority came from physicians working in hospitals. Twenty-nine cases (54%) concerned patients with a history of addiction, 14 cases (26%) had polypharmacy, and off-label use of quetiapine for insomnia was identified in 14 of the cases (26%). Only three of the cases included a specific question about patient dependency of quetiapine, and these cases were all associated with insomnia. CONCLUSION: We conclude that our case series from the Norwegian network of drug information centres reflects that quetiapine frequently involves clinical narratives of a history of addiction, polypharmacy or insomnia (off-label use). However, the case series did not reveal new information about the drug's addictive potential.

Review of Clinical Questions Submitted to Norwegian Drug Information Centres Concerning Administration and Dosage to Older Patients of Relevance to Patient-Centric Care.

Patient-centric care entails optimising healthcare provision to patients based on their perspective and opinion. It involves appropriate treatment at a reasonable cost and a focus on patient characteristics in the decision-making process to make it more personally useful. The optimisation of medicines in the older population is a challenge due to physiological changes, comorbidity, and polypharmacy. Furthermore, patient-centric care is difficult to achieve due to the high proportion of patients with dementia and frailty. Decision support concerning the appropriateness of indication, formulation, dose, administration, co-prescribing, and length of treatment to older patients is frequently in demand. In the current study, we aimed to review clinical questions concerning administration and dosage to older patients of relevance to patient-centric care. We analysed questions concerning medicines to patients 65 years or older in the database of the network of Norwegian drug information centres from 2010 to 2020. The analysis included the distribution of drugs, diseases, and recurring topics among the questions. Through a Boolean search that combined the indexed categories of "older" and "administration and dosage", we retrieved 84 question-answer pairs. Questions about psychotropic and cardiovascular drugs in relation to therapy, adverse drug reactions, and pharmacokinetics dominated, and more than 60% of the questions came from physicians. Topics relevant to patient-centric pharmacotherapy were drug withdrawal (10 questions), drug formulation (8 questions), drug initiation (8 questions), and switching drugs (5 questions). One question concerned drug withdrawal and switching, and one question drug formulation and switching. Answers provided decision support regarding appropriate formulations of drugs to patients with dementia who chew capsules or tablets, the use of parenteral administration in patients who refuse to take oral formulations, and the pharmacokinetics of transdermal or rectal drug administration. The results highlight the importance of including pharmacological factors in the assessment of the acceptability and appropriateness of oral and parenteral medicine to older patients.

Ultrasound- and Microbubble-Assisted Gemcitabine Delivery to Pancreatic Cancer Cells.

Pancreatic ductal adenocarcinoma (PDAC) is a major cause of cancer death worldwide. Poor drug delivery to tumours is thought to limit chemotherapeutic treatment efficacy. Sonoporation combines ultrasound (US) and microbubbles to increase the permeability of cell membranes. We assessed gemcitabine uptake combined with sonoporation in vitro in three PDAC cell lines (BxPC-3, MIA PaCa-2 and PANC-1). Cells were cultured in hypoxic bioreactors, while gemcitabine incubation ± sonoporation was conducted in cells with operational or inhibited nucleoside membrane transporters. Intracellular active metabolite (dFdCTP), extracellular gemcitabine, and inactive metabolite (dFdU) concentrations were measured with liquid chromatography tandem mass spectrometry. Sonoporation with increasing US intensities resulted in decreasing extracellular gemcitabine concentrations in all three cell lines with inhibited membrane transporters. In cells with inhibited membrane transporters, without sonoporation, dFdCTP concentrations were reduced down to 10% of baseline. Sonoporation partially restored gemcitabine uptake in these cells, as indicated by a moderate increase in dFdCTP concentrations (up to 37% of baseline) in MIA PaCa-2 and PANC-1. In BxPC-3, gemcitabine was effectively inactivated to dFdU, which might represent a protective mechanism against dFdCTP accumulation in these cells. Intracellular dFdCTP concentrations did not change significantly following sonoporation in any of the cell lines with operational membrane transporters, indicating that the gemcitabine activation pathway may have been saturated with the drug. Sonoporation allowed a moderate increase in gemcitabine transmembrane uptake in all three cell lines, but pre-existing nucleoside transporters were the major determinants of gemcitabine uptake and retention.

Intracellular Cytidine Deaminase Regulates Gemcitabine Metabolism in Pancreatic Cancer Cell Lines.

Cytidine deaminase (CDA) is a determinant of in vivo gemcitabine elimination kinetics and cellular toxicity. The impact of CDA activity in pancreatic ductal adenocarcinoma (PDAC) cell lines has not been elucidated. We hypothesized that CDA regulates gemcitabine flux through its inactivation and activation pathways in PDAC cell lines. Three PDAC cell lines (BxPC-3, MIA PaCa-2, and PANC-1) were incubated with 10 or 100 µM gemcitabine for 60 minutes or 24 hours, with or without tetrahydrouridine, a CDA inhibitor. Extracellular inactive gemcitabine metabolite (dFdU) and intracellular active metabolite (dFdCTP) were quantified with liquid chromatography tandem mass spectrometry. Cellular expression of CDA was assessed with real-time PCR and Western blot. Gemcitabine conversion to dFdU was extensive in BxPC-3 and low in MIA PaCa-2 and PANC-1, in accordance with their respective CDA expression levels. CDA inhibition was associated with low or undetectable dFdU in all three cell lines. After 24 hours gemcitabine incubation, dFdCTP was highest in MIA PaCa-2 and lowest in BxPC-3. CDA inhibition resulted in a profound dFdCTP increase in BxPC-3 but not in MIA PaCa-2 or PANC-1. dFdCTP concentrations were not higher after exposure to 100 versus 10 µM gemcitabine when CDA activities were low (MIA PaCa-2 and PANC-1) or inhibited (BxPC-3). The results suggest a regulatory role of CDA for gemcitabine activation in PDAC cells but within limits related to the capacity in the activation pathway in the cell lines. SIGNIFICANCE STATEMENT: The importance of cytidine deaminase (CDA) for cellular gemcitabine toxicity, linking a lower activity to higher toxicity, is well described. An underlying assumption is that CDA, by inactivating gemcitabine, limits the amount available for the intracellular activation pathway. Our study is the first to illustrate this regulatory role of CDA in pancreatic ductal adenocarcinoma cell lines by quantifying intracellular and extracellular gemcitabine metabolite concentrations.

A retrospective comparison of inappropriate prescribing of psychotropics in three Norwegian nursing homes in 2000 and 2016 with prescribing quality indicators.

BACKGROUND: Inappropriate prescribing of psychotropics is a persistent and prevalent problem in nursing homes. The present study compared inappropriate prescribing of psychotropics in nursing homes 16 years apart with prescribing quality indicators. The purpose was to identify any change in inappropriate prescribing of relevance for medical informatics. METHODS: Three Norwegian nursing homes were audited in 2000 and 2016 with regard to prescribing quality. Psychotropics among 386 patients in 2000, and 416 patients in 2016, included combinations of antidepressants, antipsychotics, anxiolytics-hypnotics, and antiepileptics. Prescribing quality indicators included psychotropic polypharmacy (defined as concurrent use of three or more psychotropics) and potential inappropriate psychotropic substances or combinations. Furthermore, potential clinically relevant psychotropic interactions were classified as pharmacodynamic or pharmacokinetic using an interaction database. The first ranked (most important) interaction in each patient was selected with the following importance of categories in the database; recommended action > documentation > severity. Three levels (from low to high) within each category were used for ranking. RESULTS: From 2000 to 2016, psychotropic polypharmacy increased from 6.2 to 29.6%, potential inappropriate psychotropic substances was reduced from 17.9 to 11.3% and potential inappropriate psychotropic combinations increased from 7.8 to 27.9%. Changes in polypharmacy and combinations were predominantly associated with prescribing of anxiolytics-hypnotics. Sixty-three patients (16.3%) had psychotropic interactions in 2000 increasing to 146 patients (35.1%) in 2016. The increase in interactions was associated with prescribing of antidepressants. First ranked interactions, more than 60% of all interactions in both years, were increasingly pharmacodynamic, from 69.9 to 91.0%. Interactions in 2016 were associated with a lower level of recommended action and documentation, but not severity compared to 2000. The inappropriate prescribing of antipsychotics and antiepileptics was reduced in 2016 compared to 2000. CONCLUSIONS: Using prescribing quality indicators we observed the importance of antidepressants and anxiolytics-hypnotics for inappropriate prescribing in 2016 while the role of antipsychotics and antiepileptics were reduced compared to 2000. A change to mainly pharmacodynamic interactions that lack good documentation was also observed. The present findings can be used for medical informatics-based approaches to address specific problems with prescribing, and prescribing quality indicators, in Norwegian nursing homes.

Rituximab Serum Concentrations and Anti-Rituximab Antibodies During B-Cell Depletion Therapy for Myalgic Encephalopathy/Chronic Fatigue Syndrome.

PURPOSE: Previous Phase II trials indicated clinical benefit from B-cell depletion using the monoclonal anti-CD20 antibody rituximab in patients with myalgic encephalopathy/chronic fatigue syndrome (ME/CFS). The association between rituximab serum concentrations and the effect and clinical relevance of antidrug antibodies (ADAs) against rituximab in ME/CFS is unknown. We retrospectively measured rituximab concentrations and ADAs in serum samples from patients included in an open-label Phase II trial with maintenance rituximab treatment (KTS-2-2010) to investigate possible associations with clinical improvement and clinical and biochemical data. METHODS: Patients with ME/CFS fulfilling the Canadian criteria received rituximab (500 mg/m2) infusions: 2 infusions 2 weeks apart (induction), followed by maintenance treatment at 3, 6, 10, and 15 months. The measured rituximab concentrations and ADAs in serum samples included 23 of 28 patients from the trial. FINDINGS: There were no significant differences in mean serum rituximab concentrations between 14 patients experiencing clinical improvement versus 9 patients with no improvement. Female patients had higher mean serum rituximab concentrations than male patients at 3 months (P = 0.05). There was a significant negative correlation between B-cell numbers in peripheral blood at baseline and rituximab serum concentration at 3 months (r = -0.47; P = 0.03). None of the patients had ADAs at any time point. IMPLICATIONS: Clinical improvement of patients with ME/CFS in the KTS-2-2010 trial was not related to rituximab serum concentrations or ADAs. This finding is also in line with a recent randomized trial questioning the efficacy of rituximab in ME/CFS. Rituximab concentrations and ADAs still offer supplemental information when interpreting the results of these trials.

The Possibility of Therapeutic Drug Monitoring of the Most Important Interactions in Nursing Homes.

BACKGROUND: Therapeutic drug monitoring is a relevant tool in drug treatment of elderly patients. The aim of this study was to assess the possibility of therapeutic drug monitoring of the most important potential interactions in nursing homes. METHODS: A material of prescribed drugs to 446 patients in three nursing homes in Bergen, Norway from a single day in March 2016 was analysed. Clinically relevant drug interactions (pharmacodynamic or pharmacokinetic) were identified and classified with Stockley`s Interaction Alerts. The most important interaction among several in each patient were ranked by recommended action > severity > evidence according to Stockley`s. The possibility of therapeutic drug monitoring of drug combinations involved in the most important interactions was retrieved from a database of all laboratories performing clinical pharmacology in Norway (the Pharmacology Portal). RESULTS: Two or more drugs were used by 443 (99.3%) of 446 patients. Three-hundred and eightyfour patients (86.1%) had > 1 interaction. About 95% of the most important interactions were pharmacodynamic. In 280 (72.9%) of these interactions, Stockley`s recommended adjust dose or monitoring. Among the 384 most important interactions, 93% involved one drug and 41% involved two drugs available for therapeutic drug monitoring. CONCLUSION: In this pilot study, therapeutic drug monitoring was possible in the majority of the most important interactions in Norwegian nursing homes. This option is of importance since adjust dose or monitoring were frequently recommended actions associated with these interactions.

Challenges adhering to a medication regimen following first-time percutaneous coronary intervention: A patient perspective.

BACKGROUND: Percutaneous coronary intervention is the most common therapeutic intervention for patients with narrowed coronary arteries due to coronary artery disease. Although it is known that patients with coronary artery disease often do not adhere to their medication regimen, little is known about what patients undergoing percutaneous coronary interventions find challenging in adhering to their medication regimen after hospital discharge. OBJECTIVES: To explore patients' experiences in adhering to medications following early post-discharge after first-time percutaneous coronary intervention. DESIGN: An abductive qualitative approach was used to conduct in-depth interviews of patients undergoing first-time percutaneous coronary intervention. SETTINGS: Participants were recruited from a single tertiary university hospital, which services a large geographical area in western Norway. Patients fulfilling the inclusion criteria were identified through the Norwegian Registry for Invasive Cardiology. PARTICIPANTS: Participants were patients aged 18 years or older who had their first percutaneous coronary intervention six to nine months earlier, were living at home at the time of study inclusion, and were prescribed dual antiplatelet therapy. Patients who were cognitively impaired, had previously undergone cardiac surgery, and/or were prescribed anticoagulation therapy with warfarin or novel oral anticoagulants were excluded. Purposeful sampling was used to include patients of different gender, age, and geographic settings. Twenty-two patients (12 men) were interviewed between December 2016 and April 2017. METHODS: Face-to-face semi-structured interviews were conducted, guided by a set of predetermined open-ended questions to gather patient experiences on factors relating to medication adherence or non-adherence. Transcribed interviews were analysed by qualitative content analysis. FINDINGS: Patients failed to adhere to their medication regimen for several reasons; intentional and unintentional reasons, multifaceted side effects from heart medications, scepticism towards generic drugs, lack of information regarding seriousness of disease after percutaneous coronary intervention, psychological impact of living with coronary artery disease, and these interacted. There were patients who felt that the medication information they received from physicians and nurses was uninformative and inadequate. Side effects from heart medications were common, ranging from minor ones to more disabling side effects, such as severe muscle and joint pain and fatigue. Patients found well established medication taking routines and aids to be necessary, and these improved adherence. CONCLUSION: Patients undergoing first-time percutaneous coronary intervention face multiple, interacting challenges in trying to adhere to prescribed medications following discharge. This study highlights the need for a more structured follow-up care in order to improve medication adherence and to maximise their self-care abilities.

Use of References in Responses from Scandinavian Drug Information Centres.

Background: The aim of this study was to compare use of references in responses from Scandinavian drug information centres (DICs). Methods: Six different fictitious drug-related queries were sent to each of seven Scandinavian DICs. The six queries concerned adverse effects, pharmacokinetics, pregnancy, complementary medicine, polypharmacy, and breast feeding. References in the responses were categorised into five types of drug information sources: primary (original studies), secondary (reviews), tertiary (drug monographs, handbooks, etc.), DIC database, or personal communication. Results: Two hundred and forty-four references were used in the 42 responses. The mean number of references varied from 3.0 to 10.6 for the six queries. The largest difference between centres with regard to number of references used (range 1⁻17) was found for the query on complementary medicine. In total, 124 references (50.8%) were tertiary, and only 10 of the 42 responses (23.8%) did not have any tertiary references included. Complementary medicine, breast feeding, and pregnancy were query types associated with relatively frequent use of primary references. Use of DIC database was not uncommon, but personal communications were seldom used. Conclusions: Scandinavian DICs differ substantially in number and type of references to identical drug-related queries. Tertiary sources are mainly preferred irrespective of type of query.

A human clinical trial using ultrasound and microbubbles to enhance gemcitabine treatment of inoperable pancreatic cancer.

BACKGROUND: The primary aim of our study was to evaluate the safety and potential toxicity of gemcitabine combined with microbubbles under sonication in inoperable pancreatic cancer patients. The secondary aim was to evaluate a novel image-guided microbubble-based therapy, based on commercially available technology, towards improving chemotherapeutic efficacy, preserving patient performance status, and prolonging survival. METHODS: Ten patients were enrolled and treated in this Phase I clinical trial. Gemcitabine was infused intravenously over 30min. Subsequently, patients were treated using a commercial clinical ultrasound scanner for 31.5min. SonoVue® was injected intravenously (0.5ml followed by 5ml saline every 3.5min) during the ultrasound treatment with the aim of inducing sonoporation, thus enhancing therapeutic efficacy. RESULTS: The combined therapeutic regimen did not induce any additional toxicity or increased frequency of side effects when compared to gemcitabine chemotherapy alone (historical controls). Combination treated patients (n=10) tolerated an increased number of gemcitabine cycles compared with historical controls (n=63 patients; average of 8.3±6.0cycles, versus 13.8±5.6cycles, p=0.008, unpaired t-test). In five patients, the maximum tumour diameter was decreased from the first to last treatment. The median survival in our patients (n=10) was also increased from 8.9months to 17.6months (p=0.011). CONCLUSIONS: It is possible to combine ultrasound, microbubbles, and chemotherapy in a clinical setting using commercially available equipment with no additional toxicities. This combined treatment may improve the clinical efficacy of gemcitabine, prolong the quality of life, and extend survival in patients with pancreatic ductal adenocarcinoma.

Drug Information Services Today: Current Role and Future Perspectives in Rational Drug Therapy.

Polypharmacy and complex drug treatment regimens are becoming increasingly common, which may lead to adverse drug reactions, drug interactions, medication nonadherence, and increasing costs and thus challenge the rational use of drugs. At the same time, the accessibility of drug information increases, and health care professionals may have limited opportunities and capabilities to search and critically evaluate drug information. Clinicians have reported difficulties in searching the best evidence and translating study findings into clinically meaningful information applicable to specific patients. Consequently, it remains a challenge to ensure the rational use of drugs in the years to come. Drug information centers (DICs) have been established to promote the rational use of drugs. One of the most important tasks of DICs is the question and answer services for health care professionals posing drug-related questions. DICs staffed by pharmacists and clinical pharmacologists hold expertise in searching for drug information and critical evaluation of the literature. The uniqueness in this service lies not only in the identification and interpretation of the scientific literature but also in the adaptation of the findings into specific clinical situations and the discussion of possible solutions with the enquirer. Thus, DICs could provide valuable decision support to the clinic. Taking into account the increasing number of possible drug-related questions that will arise today and in the future, the DICs will remain highly relevant in the years to come. However, the DICs must follow the developments in health information technology to disseminate relevant, unbiased drug information to old and new users of the service. Moreover, the DICs are important tools to counterbalance the drug information published by the pharmaceutical industry.

Preanalytical Stability of Gemcitabine and its Metabolite 2', 2'-Difluoro-2'-Deoxyuridine in Whole Blood-Assessed by Liquid Chromatography Tandem Mass Spectrometry.

Gemcitabine (2',2'-difluoro-2'-deoxycytidine, dFdC) and metabolite (2',2'-difluoro-2'-deoxyuridine, dFdU) quantification is warranted for individualized treatment strategies. Analyte stability is crucial for the validity of such quantification. We therefore studied the impact of the time interval from blood sampling to separation of plasma on gemcitabine stability. Blood from gemcitabine-treated patients was drawn into tetrahydrouridine (THU)-spiked heparin and ethylenediaminetetraacetic acid tubes and kept on ice until separation. Plasma was separated sequentially up to 24 h after sampling and dFdC and dFdU were quantified by liquid chromatography tandem mass spectrometry (LC-MS/MS). The change in plasma concentrations over time was compared with the highest imprecision for concentrations above the lower limit of quantification of the LC-MS/MS method. Analyte concentrations decreased slightly over time, but for samples stored for 4 h on ice, the decline was smaller than the expected analytical imprecision. After 24 h, the maximum decline was 14.0%, which exceeded the expected analytical imprecision. dFdC and dFdU stabilities were acceptable for at least 4 h when THU-spiked whole blood samples were kept on ice. This is within the scope of routine sampling procedures. Further, variations in separation time intervals within this time frame are negligible when interpreting drug concentrations.

Liquid chromatography/tandem mass spectrometry method for simultaneous quantification of eight endogenous nucleotides and the intracellular gemcitabine metabolite dFdCTP in human peripheral blood mononuclear cells.

Quantification of endogenous nucleotides is of interest for investigation of numerous cellular biochemical processes, such as energy metabolism and signal transduction, and may also be applied in cancer and antiretroviral therapies in which nucleoside analogues are used. For these purposes we developed and validated a sensitive and high accuracy ion-pair liquid chromatography tandem mass spectrometry (IP LC-MS/MS) method for simultaneous quantification of eight endogenous nucleotides (ATP, CTP, GTP, UTP, dATP, dCTP, dGTP, dTTP) and 2',2'-difluoro-2'-deoxycytidine triphosphate (dFdCTP), an intracellular metabolite of the nucleoside analogue gemcitabine. The assay was validated using 200µL aliquots of peripheral blood mononuclear cell (20×10(6)cells/ml, 4×10(6)cells) extracts, pretreated with activated charcoal and spiked with unlabeled nucleotides, deoxynucleotides and dFdCTP. Analytes were extracted by simple precipitation with cold 60% methanol containing isotope labeled internal standards and separated on a porous graphitic carbon column. For method validation, the concentration ranges were: 0.125-20.8pmol injected for deoxynucleotides, 0.25-312.5pmol injected for dFdCTP and 5-3200pmol injected for nucleotides. The highest coefficients of variation (CV) were 12.1% for within run assay and 11.4% for between run assay, both representing the precision at the lowest analyte concentrations. The method was applied to monitor dFdCTP and changes in endogenous nucleotides in patients who were receiving gemcitabine infusions.

Diazoxide protects against doxorubicin-induced cardiotoxicity in the rat.

AIM: Chemotherapy with doxorubicin is limited by cardiotoxicity. Free radical generation and mitochondrial dysfunction are thought to contribute to doxorubicin-induced cardiac failure. In this study we wanted to investigate if opening of mitochondrial KATP-channels by diazoxide is protective against doxorubicin cardiotoxicity, and if 5-hydroxydecanoate (5-HD), a selective mitochondrial KATP-channel antagonist, abolished any protection by this intervention. METHODS: Wistar rats were divided into 7 groups (n = 6) and followed for 10 days with 5 intervention groups including the following treatments: (1) Diazoxide and doxorubicin, (2) diazoxide and 5-hydroxydecanoate (5-HD), (3) 5-HD and doxorubicin, (4) diazoxide and saline and (5) 5-HD and saline. On day 1, 3, 5 and 7 the animals received intraperitoneal (i.p.) injections with 10 mg/kg diazoxide and/or 40 mg/kg 5-HD, 30 minutes before i.p. injections with 3.0 mg/kg doxorubicin. One control group received only saline injections and the other control group received saline 30 minutes prior to 3.0 mg/kg doxorubicin. On day 10 the hearts were excised and Langendorff-perfused. Cardiac function was assessed by an intraventricular balloon and biochemical effects by release of hydrogen peroxide (H2O2) and troponin-T (TnT) in effluate from the isolated hearts, and by myocardial content of doxorubicin. RESULTS: Doxorubicin treatment produced a significant loss in left ventricular developed pressure (LVDP) (p < 0.05) and an increase in both H2O2 and TnT release in effluate (p < 0.05). Diazoxide significantly attenuated the decrease in LVDP (p < 0.05) and abolished the increased release of H2O2 and TnT (p < 0.05). 5-HD abolished the effects of pretreatment with diazoxide, and these effects were not associated with reduced myocardial accumulation of doxorubicin. CONCLUSIONS: Pretreatment with diazoxide attenuates doxorubicin-induced cardiac dysfunction in the rat, measured by physiological indices and TnT and H2O2 in effluate from isolated hearts. The effect could be mediated by opening of mitochondrial KATP-channels, reduced doxorubicin-associated free radical generation and decreased cardiomyocyte damage. Diazoxide represents a promising protective intervention against doxorubicin-induced acute cardiotoxicity.

Morphine enhances doxorubicin-induced cardiotoxicity in the rat.

Interventions to reduce the cardiotoxicity of doxorubicin are clinically relevant. Pharmacological preconditioning mimicking ischemic preconditioning has been demonstrated with morphine and represents an acceptable clinical intervention. The purpose of this study was to examine if pretreatment in vivo with morphine could reduce doxorubicin-induced cardiotoxicity ex vivo in a rat model. Wistar rats were divided into six groups and pretreated with an intraperitoneal (i.p.) injection of 3 or 10 mg/kg morphine, 1 mg/kg naloxone and saline, 1 mg/kg naloxone and 3 mg/kg morphine or saline, 60 min before excision of the heart. Biochemical indices such as troponin T (TnT) and hydrogen peroxide (H2O2) in effluate were measured together with physiological parameters in Langendorff hearts before and after doxorubicin infusion (2 mg/mL 0.05 mL/min for 45 min). Myocardial content of doxorubicin was measured at the end of infusion. Pretreatment with morphine, irrespective of dosage, produced a significant loss in left ventricular-developed pressure and an increase of TnT and H2O2 in effluate before doxorubicin infusion (p < 0.05). Morphine also produced a significant increase in left ventricular end-diastolic pressure and an increase of TnT and H2O2 in effluate (p < 0.05) at the end of doxorubicin infusion. Naloxone, a non-selective opioid receptor antagonist, abolished the effects of morphine both before and after doxorubicin infusion. Morphine, irrespective of dosage, increased myocardial content of doxorubicin compared to pretreatment with saline (p < 0.05). Pretreatment with morphine is associated with a cardiodepressive effect and enhances cardiotoxicity of doxorubicin measured by increased myocardial accumulation of doxorubicin and physiological and biochemical indices. The negative effects observed in our rat model are abolished by naloxone.

A short-time model to study relevant indices of cardiotoxicity of doxorubicin in the rat.

AIM: Short-time models (STM) to study the cardiotoxicity (acute or chronic) of doxorubicin in rats are of interest to assess protective interventions and pathways. STM promotes more ethical animal treatment with less stress, and at a lower cost compared to established long-time models (LTM). We wanted to investigate if an STM of 9 d yields the same information regarding cardiotoxicity as an LTM of 9 weeks. METHODS: Male Wistar rats received identical drug administration protocols in STM and LTM. The two intervention groups (n = 6) received intraperitoneal (i.p.) injections of 2 mg/kg doxorubicin every day for five consecutive days, with a total cumulative dose of 10 mg/kg. The two control groups (n = 6), received an equivalent volume of saline injected every day for five consecutive days. Hearts from STM and LTM were excised and Langendorff-perfused after 9 d or 9 weeks, respectively, after the first drug injection. Cardiotoxicity was assessed in paced Langendorff hearts by a release of hydrogenperoxide (H2O2) and troponin T (TnT) in effluent, by myocardial accumulation of doxorubicin and its metabolite doxorubicinol, and by physiological parameters recorded during pressure, or volume-regulated perfusion. RESULTS: In STM, hearts exposed to doxorubicin demonstrated a 15% reduction in left ventricular developed pressure (LVDP) irrespective of flow mode, and a 13% increase in aortic pressure (AoP), during volume-regulated perfusion, an index of coronary resistance, compared to controls. Left ventricular end-diastolic pressure (LVEDP) was increased by 72% during pressure-regulated perfusion and 100% during volume-regulated perfusion in STM. In LTM, hearts exposed to doxorubicin demonstrated a 40% reduction in LVDP during pressure-regulated perfusion and a 20% reduction during volume-regulated perfusion. LVEDP was 70% higher in doxorubicin-treated hearts during pressure-regulated perfusion and 80% higher during volume-regulated perfusion. In addition, aortic pressure was increased by 30% during volume-regulated perfusion. In both STM and LTM, hearts exposed to doxorubicin demonstrated a higher H2O2 and TnT release, compared to respective controls. The difference was most pronounced in STM. Myocardial content of doxorubicin was detectable in both STM and LTM. However, doxorubicinol was only detectable in STM. CONCLUSION: STM is comparable to LTM to study relevant indices of cardiotoxicity of doxorubicin in rat hearts. Biochemical differences are more pronounced in STM, while contractile differences are more pronounced in LTM. STM could be a preferred model for preliminary studies of protective interventions.