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Dose-dependent inhibition of CYP1A2, CYP2C19 and CYP2D6 by citalopram, fluoxetine, fluvoxamine and paroxetine

Objectives: The purpose of this pharmacokinetic study was to investigate the dose-dependent inhibition of model substrates for CYP2D6, CYP2C19 and CYP1A2 by four marketed selective serotonin reuptake inhibitors (SSRIs): citalopram, fluoxetine, fluvoxamine and paroxetine.Methods:The study was carried out as an in vivo single-dose study including 24 young, healthy men. All volunteers had been identified as sparteine- and mephenytoin-extensive metabolisers. The volunteers received in randomised order, at weekly intervals, increasing single oral doses of one of the four SSRIs, followed 3 h later by sparteine (CYP2D6), mephenytoin (CYP2C19) and caffeine (CYP1A2) tests. Fluoxetine was given at 3-week intervals because of the long half-life of fluoxetine and its metabolite norfluoxetine. Citalopram, fluoxetine and paroxetine were given in doses of 10, 20, 40 and 80 mg and fluvoxamine was given in doses of 25, 50, 100 and 200 mg.Results:With increasing doses, there was a statistically significant increase in the sparteine metabolic ratio (MR) (P < 0.01, Page’s test for trend) for all four SSRIs. The increase was modest after intake of citalopram and fluvoxamine, while the increase was more pronounced after fluoxetine intake, although no volunteers changed phenotype from extensive metabolisers to poor metabolisers. Three of the six volunteers changed phenotype from extensive metabolisers to poor metabolisers after intake of 40 or 80 mg paroxetine. There was a statistically significant increase in the mephenytoin S/R ratio (P < 0.01, Page’s test for trend) with increasing doses of fluoxetine and fluvoxamine, but not after citalopram and paroxetine. However, no volunteers changed phenotype from extensive to poor metabolisers of S-mephenytoin. After intake of fluvoxamine, the urinary excretion of the metabolites related to N3 demethylation of caffeine were below the limit of quantification, whereas there were no significant changes in the urinary caffeine metabolic ratios after intake of the other three SSRIs.Conclusion:This investigation confirms that paroxetine and fluoxetine are potent inhibitors of CYP2D6, that fluvoxamine and fluoxetine are moderate inhibitors of CYP2C19 and that fluvoxamine is a potent inhibitor of CYP1A2 in humans in vivo. The clinical prediction of interaction from single-dose experiments may have to take the degree of accumulation during steady-state after multiple doses into account.

8‐hydroxydeoxyguanosine as a urinary biomarker of oxidative DNA damage

Living organisms are continuously exposed to reactive oxygen species as a consequence of biochemical reactions as well as external factors. Oxidative DNA damage has been implicated in aging, carcinogenesis and other degenerative diseases. The urinary excretion of the DNA repair product 8-hydroxydeoxyguanosine (8OHdG) has been proposed as a noninvasive biomarker of oxidative DNA damage in humans in vivo. We have developed a three-dimensional HPLC analysis with electrochemical detection for the analysis of 8OHdG in urine and studied factors affecting the excretion of this biomarker in 83 healthy humans and in various laboratory animals, including dog, pig, and rat. Previously, other groups have used comparable HPLC methods or gas chromatography-mass spectrometry with selective ion monitoring for measuring the excretion of 8OHdG in humans, rats, mice, and monkeys. In the 169 humans studied so far, the average 8OHdG excretion was 200-300 pmol/kg per 24 h with a sevenfold range, and the coefficient of variation was 30-40%. This excretion corresponds 140-200 oxidative modification of guanine bases per cell per day. Thirty-two smokers from our study population excreted 50% (31-69%; 95% confidence interval) more 8OHdG than 53 nonsmokers. This indicates a 50% increased rate of oxidative DNA damage from smoking, adding to the other well-known health hazards of smoking. The biochemical-physiological basis is unknown but may be related to smoke constituents including or generating reactive oxygen species and/or consuming antioxidants and/or the well-known enhancing effect of smoking on the metabolic rate. In our 83 healthy subjects the 8OHdG excretion correlated with body composition. Thus, lean and/or male subjects excreted more than obese and/or female subjects, possibly related to differences in metabolic rate. In accordance, the excretion of 8OHdG decreased after calorie restriction, which will cause a decline in the metabolic rate. Across the investigated species, humans, dogs, pigs, and rats, the excretion of 8OHdG correlated with the specific metabolic rate, confirming data from other groups on humans, monkeys, rats, and mice. The excretion of 8OHdG decreased with age in rats in parallel with the decline in metabolic rate with advancing age. The excretion of 8OHdG reflects the formation and repair of only one out of approximately 20 described oxidative DNA modifications. So far, methods are not available for the determination of the corresponding repair products, except 8OHdG and thymidine glycol, in urine. Moreover, the importance in terms of mutagenicity, particularly regarding tumour suppressor genes and oncogenes, is mainly documented for 8OHdG in DNA.(ABSTRACT TRUNCATED AT 400 WORDS)

Cardiotoxicity in cancer patients treated with 5-fluorouracil or capecitabine: A systematic review of incidence, manifestations and predisposing factors

PURPOSE To systematically review the incidence, manifestations and predisposing factors for cardiovascular toxicity in cancer patients treated with systemic 5-fluorouracil or capecitabine. DESIGN We searched PubMed, EMBASE and Web of science for studies with ≥ 20 cancer patients evaluating cardiovascular toxicity of 5-fluorouracil and capecitabine. We hand searched the reference lists of all included studies. Study selection and assessment of risk of bias were performed by two authors independently. RESULTS We identified 30 eligible studies (1 meta-analyses of 4 RCTs, 18 prospective and 11 retrospective). Symptomatic cardiotoxicity occurred in 0-20% of the patients treated with 5-fluorouracil and in 3-35% with capecitabine. The most common symptom was chest pain (0-18.6%) followed by palpitations (0-23.1%), dyspnoea (0-7.6%) and hypotension (0-6%). Severe clinical events such as myocardial infarction, cardiogenic shock and cardiac arrest occurred in 0-2%. Mortality rates ranged from 0 to 8%. Asymptomatic cardiac influence was demonstrated on ECG, in NT-proBNP measurements and with ultrasonic cyclic variation of integrated backscatter. Predisposing factors were mostly tested in univariate analyses. Preexisting cardiac disease was a risk factor in some studies, but there were divergent results. There was some evidence for increased cardiotoxicity during continuous infusion schedules and with concomitant cisplatin treatment. The effects of previous or current chest-radiotherapy were ambiguous. CONCLUSION Larger studies suggest an incidence of symptomatic cardiotoxicity of 1.2-4.3% during fluorouracil treatment, however subclinical cardiac influence are common. Possible risk factors are cardiac co-morbidity, continuous infusion schedules and concomitant cisplatin treatment, but existing evidence are of insufficient quality.

Cytochrome P450 IA2 Activity in Man Measured by Caffeine Metabolism: Effect of Smoking, Broccoli and Exercise

The activity of 3 enzymes related to the bioactivation of toxic compounds and the development of cancer--cytochrome P450 IA2, N-acetyl transferase (NAT), and xanthine oxidase (XO)--can be measured from the ratios of formed metabolites excreted into urine. In the 3 experiments that comprised this study, subjects received at least 1 cup of coffee 2- 6 hours before spot urine samples were taken. The subjects included 335 healthy male and female volunteers who provided information on tobacco, caffeine, and broccoli intake in the preceding 2 weeks, 23 healthy men who exercised 8 hours/day for 30 days, and 9 subjects whose diet included green beans and broccoli. As expected, the ratio reflecting P450 IA2 activity was 66% and 70% higher, respectively, in men and women who smoked at least 10 cigarettes/day compared to male and female nonsmokers. The XO ratio also was significantly increased in smokers. 30 days of vigorous physical exercise increased the P450 IA2 ratio by 50% and the XO ratio by over 100%. Broccoli induced a 19% increase in P450 IA2 activity, while pregnancy and oral contraceptive use reduced this ratio by 29% and 20%, respectively. Since these ratios appear to yield reliable indicators of enzyme activity, prospective studies of their association with cancer development are recommended.

A systematic review of the pathophysiology of 5-fluorouracil-induced cardiotoxicity.

BackgroundCardiotoxicity is a serious side effect to treatment with 5-fluorouracil (5-FU), but the underlying mechanisms are not fully understood. The objective of this systematic review was to evaluate the pathophysiology of 5-FU- induced cardiotoxicity.MethodsWe systematically searched PubMed for articles in English using the search terms: 5-FU OR 5-fluorouracil OR capecitabine AND cardiotoxicity. Papers evaluating the pathophysiology of this cardiotoxicity were included.ResultsWe identified 27 articles of 26 studies concerning the pathophysiology of 5-FU-induced cardiotoxicity. The studies demonstrated 5-FU-induced: hemorrhagic infarction, interstitial fibrosis and inflammatory reaction in the myocardium; damage of the arterial endothelium followed by platelet aggregation; increased myocardial energy metabolism and depletion of high energy phosphate compounds; increased superoxide anion levels and a reduced antioxidant capacity; vasoconstriction of arteries; changes in red blood cell (RBC) structure, function and metabolism; alterations in plasma levels of substances involved in coagulation and fibrinolysis and increased endothelin-1 levels and N-terminal-pro brain natriuretic peptide levels. Based on these findings the proposed mechanisms are: endothelial injury followed by thrombosis, increased metabolism leading to energy depletion and ischemia, oxidative stress causing cellular damage, coronary artery spasm leading to myocardial ischemia and diminished ability of RBCs to transfer oxygen resulting in myocardial ischemia.ConclusionsThere is no evidence for a single mechanism responsible for 5-FU-induced cardiotoxicity, and the underlying mechanisms might be multifactorial. Further research is needed to elucidate the pathogenesis of this side effect.

Exercise may reduce depression but not anxiety in self-referred cancer patients undergoing chemotherapy. Post-hoc analysis of data from the ‘Body & Cancer’ trial

Abstract Background. The diagnosis and treatment of cancer may cause clinically significant and persistent psychological morbidity. The objective of this study was to determine the short-term effect of a six week exercise intervention on anxiety and depression in cancer patients undergoing chemotherapy (The ‘Body & Cancer’ trial). Methods. Two hundred and nine self-referred patients (52 males, 157 females, mean age 47 years) were randomised into an intervention group and a waiting-list control group. Anxiety and depression was measured by the Hospital Anxiety and Depression Scale. Results. At baseline, 23.5% and 11.5% of the population scored >8 on the HADS and were classified as suspicious or definite cases of anxiety and depression, respectively. Adjusted for baseline score, disease and demographic covariates the estimated intervention effect showed improvement at six weeks for depression of −0.7 points (95% confidence interval [CI] −1.27 to −0.14, p = 0.0153). No significant effect was seen on anxiety. Further subanalysis, including only suspicious or definite cases of depression, resulted in an estimated intervention effect of −2.53 points (95% CI, −0.64 to −0.42, p = 0.021). Conclusion. Anti-depressant effects could be caused by exercise in self-referred cancer patients undergoing chemotherapy. Dedicated trials and follow-up studies are needed to clarify the optimal duration and content of exercise interventions to meet the needs of clinically depressive or anxious patients.

Bevacizumab in combination with cetuximab and irinotecan after failure of cetuximab and irinotecan in patients with metastatic colorectal cancer

Abstract Background. The efficacy and safety of concurrent administration of irinotecan with the two monoclonal antibodies cetuximab and bevacizumab as fourth line therapy in heavily pretreated patients with metastatic colorectal cancer were evaluated. Patients and methods. Patients with metastatic colorectal cancer who had progressed on therapy with 5-FU, oxaliplatin and irinotecan in the first and second line setting and on the combination of irinotecan and cetuximab in third line setting independent of their KRAS mutation status, were treated with irinotecan and cetuximab combined with bevacizumab in a dosage of 5 mg/kg. All drugs were administered every second week. Results. From January 2007 to November 2008 27 patients were treated with cetuximab, irinotecan and bevacizumab. The triple-combination was well tolerated. Progression free survival (PFS) was 8.3 months and median overall survival (mOS) was 12.0 months. Two patients without KRAS mutation (7%) obtained a partial response and 17 (63%) had stable disease for at least two months. A retrospective KRAS mutation analysis revealed that there was a trend toward longer PFS and mOS in patients without KRAS mutations compared to patients with KRAS mutations with a PFS of 8.9 vs. 5.1 months and a mOS of 12.7 vs. 9.0 months. Conclusion. Bevacizumab is safe to add to irinotecan and cetuximab with a toxicity profile that seems to be similar to what would be expected from the agents alone. The results indicate that adding bevacizumab to irinotecan and cetuximab in a fourth line setting may induce a high rate of disease control in heavily pretreated patients with metastatic colorectal cancer.

Incidence and risk factors for capecitabine-induced symptomatic cardiotoxicity: a retrospective study of 452 consecutive patients with metastatic breast cancer

Objectives Case reports of capecitabine cardiotoxicity resemble those seen with intravenous 5-fluorouracil (5-FU) with chest pain as the predominant manifestation, but few studies of capecitabine cardiotoxicity are available. We aimed to determine the incidence of symptomatic cardiotoxicity from capecitabine in patients with breast cancer and to identify risk factors. Methods We reviewed medical records of consecutive women with breast cancer treated with capecitabine (1000 mg/m2 two times per day) from 2002 to 2012 at one institution. Results 22 of 452 patients (4.9%) (95% CI 2.9% to 6.9%) had symptoms of cardiotoxicity (chest pain: n=13, dyspnoea: n=9, palpitations: n=2). 11 patients had changes on ECG (atrial fibrillation: n=5, ST deviations: n=3, T-wave abnormalities: n=2 and QTc prolongation: n=1). 2 patients (0.4%) sustained acute myocardial infarction. 1 patient (0.2%) developed cardiac arrest with lethal outcome. 4 of 6 patients (66%) retreated with capecitabine had recurrent symptoms at retreatment. Cardiac comorbidity (p=0.001), hypercholesterolaemia (p=0.005) and current smoking (p=0.023) were risk factors for cardiotoxicity in univariate analyses and remained significant when adjusted for age. Patients with cardiac comorbidity were 5.5 times (95% CI 2.0 to 14.8) more likely to develop cardiotoxicity. In the subgroup of patients with apparently no cardiac comorbidity, the incidence of cardiotoxicity was lower (3.7%) and hypercholesterolaemia (p=0.035) and current smoking (p=0.020) were risk factors of cardiotoxicity. Conclusions The incidence of cardiotoxicity from capecitabine resembles that of intravenous 5-FU (≈5%). Cardiac comorbidity, hypercholesterolaemia and current smoking were associated with development of cardiotoxicity.

Efficacy and safety of regorafenib in the treatment of metastatic colorectal cancer: A systematic review

PURPOSE Despite advances in the treatment of colorectal cancer, third-line treatment options are still limited. Regorafenib was approved in 2012 for the treatment of patients with metastatic colorectal cancer previously treated with approved standard therapy. The purpose of this review is to present existing clinical data on regorafenib. METHOD We systematically searched the PubMed and Embase databases, as well as ASCO and ESMO conference abstracts, for studies in English including ≥30 patients, evaluating the efficacy and safety of regorafenib in patients with metastatic colorectal cancer. A meta-analysis was conducted on the published, randomized phase III trials. RESULTS 24 eligible studies were included. In two phase III trials, regorafenib significantly increased overall survival (OS), progression free survival (PFS), and disease control rate when compared to placebo. Survival benefits of 1.4 and 2.5 months were presented. The meta-analysis indicated a significant greater treatment effect on OS (hazard ratio 0.67) and PFS (hazard ratio 0.40), compared to placebo. The non-randomized studies mostly supported these results. The most frequently reported adverse events were hand-foot-skin reaction (25%-86%), hypertension (11%-47%) and fatigue (2%-73%). CONCLUSION Large phase III randomized trials indicate that regorafenib provides a benefit in OS and PFS when compared to placebo. Adverse events were common, but manageable and typical of multi-target tyrosine kinase inhibitors. Further research is needed to investigate alternative approaches to the dosing of regorafenib and to explore clinical and molecular biomarkers that can guide patient selection.

The “Interval Walking in Colorectal Cancer” (I-WALK-CRC) study: Design, methods and recruitment results of a randomized controlled feasibility trial

Background Low physical activity level is associated with poor prognosis in patients with colorectal cancer (CRC). To increase physical activity, technology-based platforms are emerging and provide intriguing opportunities to prescribe and monitor active lifestyle interventions. The “Interval Walking in Colorectal Cancer“(I-WALK-CRC) study explores the feasibility and efficacy a home-based interval-walking intervention delivered by a smart-phone application in order to improve cardio-metabolic health profile among CRC survivors. The aim of the present report is to describe the design, methods and recruitment results of the I-WALK-CRC study. Methods/Results: The I-WALK-CRC study is a randomized controlled trial designed to evaluate the feasibility and efficacy of a home-based interval walking intervention compared to a waiting-list control group for physiological and patient-reported outcomes. Patients who had completed surgery for local stage disease and patients who had completed surgery and any adjuvant chemotherapy for locally advanced stage disease were eligible for inclusion. Between October 1st, 2015, and February 1st, 2017, 136 inquiries were recorded; 83 patients were eligible for enrollment, and 42 patients accepted participation. Age and employment status were associated with participation, as participants were significantly younger (60.5 vs 70.8 years, P < 0.001) and more likely to be working (OR 5.04; 95%CI 1.96–12.98, P < 0.001) than non-participants. Conclusion In the present study, recruitment of CRC survivors was feasible but we aim to better the recruitment rate in future studies. Further, the study clearly favored younger participants. The I-WALK-CRC study will provide important information regarding feasibility and efficacy of a home-based walking exercise program in CRC survivors.