Epirubicin is extensively and rapidly metabolized by the liver and is also metabolized by other organs and cells, including red blood cells. Four main metabolic routes have been identified: (1) reduction of the C-13 keto-group with the formation of the 13(S)-dihydro derivative, epirubicinol; (2) conjugation of both the unchanged drug and epirubicinol with glucuronic acid; (3) loss of the amino sugar moiety through a hydrolytic process with the formation of the doxorubicin and doxorubicinol aglycones; and (4) loss of the amino sugar moiety through a redox process with the formation of the 7-deoxy-doxorubicin aglycone and 7-deoxy-doxorubicinol aglycone. Epirubicinol has in vitro cytotoxic activity one-tenth that of epirubicin. As plasma levels of epirubicinol are lower than those of the unchanged drug, they are unlikely to reach in vivo concentrations sufficient for cytotoxicity. No significant activity or toxicity has been reported for the other metabolites.
Secondary alcohol metabolites have been proposed to mediate chronic cardiotoxicity induced by doxorubicin (DOX) and other anticancer anthracyclines. In this study, NADPH-supplemented human cardiac cytosol was found to reduce the carbonyl group in the side chain of the tetracyclic ring of doxorubicin, producing the secondary alcohol metabolite doxorubicinol (DOXol). A decrease in the level of alcohol metabolite formation was observed by replacing doxorubicin with epirubicin (EPI), a less cardiotoxic analogue characterized by an axial-to-equatorial epimerization of the hydroxyl group at C-4 in the amino sugar bound to the tetracyclic ring (daunosamine). A similar decrease was observed by replacing doxorubicin with MEN, a novel anthracycline with preclinical evidence of reduced cardiotoxicity. MEN is characterized by the lack of a methoxy group at C-4 in the tetracyclic ring and by intercalation of 2, 6-dideoxy-L-fucose between daunosamine and the aglycone. Multiple comparisons with methoxy- or 4-demethoxyaglycones, and a number of mono- or disaccharide 4-demethoxyanthracyclines, showed that both the lack of the methoxy group and the presence of a disaccharide moiety limited alcohol metabolite formation by MEN. Studies with enzymatically generated or purified anthracycline secondary alcohols also showed that the presence of a disaccharide moiety, but not the lack of a methoxy group, made the metabolite of MEN less reactive with the [4Fe-4S] cluster of cytoplasmic aconitase, as evidenced by its limited reoxidation to the parent carbonyl anthracycline and by a reduced level of delocalization of Fe(II) from the cluster. Collectively, these studies (i) characterize the different influence of methoxy and sugar substituents on the formation and [4Fe-4S] reactivity of anthracycline secondary alcohols, (ii) lend support to the role of alcohol metabolites in anthracycline-induced cardiotoxicity, as they demonstrate that the less cardiotoxic EPI and MEN 10755 share a reduction in the level of formation of such metabolites, and (iii) suggest that the cardiotoxicity of MEN might be further decreased by the reduced [4Fe-4S] reactivity of its alcohol metabolite.
Many antineoplastic drugs were found to have carcinogenic, mutagenic and teratogenic potential. The aim of this study was to carry out cytogenetic and internal dose monitoring of hospital pharmacy personnel regularly involved in the preparation of cytostatic agents, in order to test possible cytostatics-induced genotoxic effects due to occupational exposure under routine working conditions, and in cases of accidental contamination. ... Platinum in whole blood and anthracyclines in plasma were measured to assess internal exposure to cytostatics. The level of cytogenetic damage was determined in peripheral blood lymphocytes with the micronucleus test and the sister chromatid exchange assay. Five series of monitoring were performed over a period of 2 years. ... No significant differences in the mean frequencies of sister chromatid exchanges (SCE) and micronuclei (MN) were found between occupationally exposed probands and controls (9.9 +/- 1.4 vs 10.1 +/- 1.2 SCEs/cell and 21.2 +/- 7.2 vs 23.3 +/- 7.5 MN/2000 binucleated (BN) cells, n = 16). Significant elevations of SCE or MN were detected in seven out of 12 cases of accidental contamination at the workplace, whereas no increase in platinum in blood and anthracyclines in plasma was observed in these probands. Two cases of non-reported contamination were identified by measurement of epirubicin in plasma. Smoking was found to increase the SCE significantly. No correlation between individual SCE scores and MN scores was observed. ... /The authors/ findings support a transient increase in SCE or MN after relevant exposure to cytostatic drugs in cases of accidental contamination. The lack of significant differences in SCE and MN between hospital pharmacy personnel and unexposed controls, points to high standards of safety at the corresponding workplaces.
There is compelling in-vitro evidence that the evaluation of doxorubicin or epirubicin pharmacokinetics based solely on plasma concentration may not fully elucidate the differences between the two drugs. Both compounds bind to erythrocytes and their different binding to hemoglobin may influence their disposition in the body. The purpose of the present study was to compare the pharmacokinetics and metabolism of doxorubicin and epirubicin based on the plasma concentration, amount associated with blood cells and simultaneous monitoring of biliary and urinary elimination of unchanged drug and metabolites after single- and multiple-dose injections. The level of sarcoplasmic reticulum Ca2+ATPase in the heart was also measured as a biomarker of cardiotoxicity. Male Sprague-Dawley rats were treated in a parallel design with doxorubicin or epirubicin on a multiple-dosing basis (4 mg kg(-1) per week) or as a single dose injection (20 mg kg(-1)). Blood, urine and bile samples were collected periodically after each dose in the multiple-dosing regimen and the single dose injection, and at the end of each experiment the hearts were removed. The concentrations of each drug in plasma, blood cells, bile and urine samples were determined, and by simultaneous curve-fitting of plasma and bile data according to compartmental analysis, the pharmacokinetic parameters and constants were estimated. The concentration of drug associated with blood cells was analyzed according to non-compartmental analysis. The bile and urine samples provided the in-vivo metabolic data. The level of Ca2+ATPase in the heart, determined by Western blotting, was used as the toxicodynamic parameterto correlate with the kinetic data. Multiple-dosing regimens reduced the total plasma clearance and increased the area under the plasma concentration-time curve of both drugs. Also, the area under the curve of doxorubicin associated with blood cells increased with the weekly doses, and the related mean residence time (MRT) and apparent volume of distribution (Vdss) were steadily reduced. In contrast to doxorubicin, the mean residence time and Vdss of epirubicin increased significantly. Metabolic data indicated significant differences in the level of alcohol and aglycones metabolites. Doxorubicinol and doxorubicin aglycones were significantly greater than epirubicinol and epirubicin aglycone, whereas epirubicinol aglycone was greater than doxorubicinol aglycone. The area under the blood cells concentration-time curve correlated linearly with the changes in Ca2+ATPase net intensity. The results of this study demonstrate the importance of the kinetics of epirubicin and doxorubicin associated with blood cells. Linear correlation between the reduction of net intensity of the biomarker with the area under the curve of doxorubicin associated with blood cells confirms that the differences between the two compounds are related to their interaction with blood cells. This observation together with the observed differences in metabolism may underline a significant role for blood cells in distribution and metabolism of doxorubicin and epirubicin.
The pharmacokinetics of epirubicin (4' epidoxorubicin; I), and doxorubicin (11) following intravenous bolus injection of 50 mg/sq m, were investigated in 4 advanced cancer patients. Drug decay is triphasic, with long terminal half life. Plasma and blood levels of I metabolite, epirubicinol (13 dihydro 4' epidoxorubicin; III), are lower than those of 1. Glucuronides of I and 11 are also present in plasma, bile and urine. Plasma clearance of I is consistently higher and mean residence time lower than the corresponding III parameters. In addition, elimination of II was also faster than that of doxorubicinol. After an initial induction period, I concentration is higher in whole blood than in plasma. Blood clearance is lower than plasma clearance; volume of distribution at steady state is lower if blood concentration data are used in the pharmacokinetic analysis. Mean residence time is similar in blood and plasma. A statistically significant reduction of clearance parameters is observed in patients with liver metastases, even in the absence of altered bilirubin levels.
Serum aminotransferase elevations occur in up to 40% of patients on doxorubicin therapy, but elevations are generally asymptomatic and transient, resolving even with continuation of therapy. However, instances of acute liver injury with symptoms and jaundice have been reported with doxorubicin and rarely also with epirubicin and idarubicin. In most instances, multiple cancer chemotherapeutic agents were being administered and the anthracite antibiotic was believed to enhance the toxicity of the other agents (such as cyclosphosphamide, methotrexate or mercaptopurine). Combination antineoplastic regimens can cause sinusoidal obstruction syndrome, but the role of doxorubicin, epirubicin and idarubicin in this outcome is often not clear. Valrubicin is administered locally in the bladder (intravesical) and has little systemic absorption and has not been linked to serum enzyme elevations during therapy or to clinically apparent liver injury.
Likehood score (doxorubicin): B (likely cause of clinically apparent liver injury).
Likehood score (epirubicin and idarubicin): E* (unproven but suspected cause of clinically apparent liver injury).
Likehood score (valrubicin): E (unlikely cause of clinically apparent liver injury).
The methylparaben present in the epirubicin HCl formulation enhances the dissolution rate by disrupting bonding between epirubicin & other components. /Epirubicin HCl/
Lleukopenic and/thrombocytopenic effects of epirubicin may be increased with concurrent or recurrent therapy if these medications /blood dyscrasia-causing medications/ cause the same effects; dosage of epirubicin should be based on blood counts in these cases.