As plasma levels of epirubicinol are lower than those of the unchanged drug and the metabolite has an in vitro cytotoxic activity 10% of that of epirubicin, it is unlikely to reach in vivo concentration sufficient for cytotoxicity. No significant toxicity has been reported for the other metabolites. Epirubicinol is the 13(S)-dihydro derivative formed via the reduction of the C-13 keto-group. Both the unchanged drug and epirubicinol can be conjugated with glucuronic acid, creating the 2 glucuronides. This glucuronidation pathway is unique to epirubicin metabolism in humans  as epirubicin is the only anthracycline that serves as a substrate for beta-glucuronidation. This unique pathway might explain the better tolerability of this drug compared with doxorubicin.The 4 aglycones are formed by losing the amino sugar moiety through a hydrolytic process or redox process, creating the doxorubicin and doxorubicinol aglycones and 7-deoxy-doxorubicin and 7-deoxy-doxorubicinol aglycones, respectively. Excretion
Epirubicin and its metabolites are primarily eliminated through biliary excretion. About 11 to 15% of the administered dose is eliminated as an unchanged drug, which makes up 6 to 7% of the excreted compounds, and metabolites. Side effects
The most common side effects of the Epirubicin are alopecia, nausea/vomiting, cardiotoxicity, leukopenia, and stomatitis. Cardiotoxicity is a severe side effect and the exact pathway is still unknown. However, there is good evidence to suggest that cardiotoxicity is caused at least in part by the avid interaction of anthracyclines with iron, resulting in the formation of metal ion complexes.
Sarecycline is a narrow-spectrum tetracycline-derived antibiotic. It is specifically designed for the treatment of acne, and was approved by the FDA in October 2018 for the treatment of inflammatory lesions of non-nodular moderate to severe acne vulgaris in patients 9 years of age and older. Two randomized and well-controlled clinical trials reported efficacy data on both facial and truncal acne (back and chest). Efficacy was assessed in a total of 2002 subjects 9 years of age and older. Unlike other tetracycline-class antibiotics, sarecycline has a long C7 moiety that extends into and directly interact with the bacterial messenger RNA (mRNA). The spectrum of activity is limited to clinically relevant Gram-positive bacteria, mainly Cutibacterium acnes, with little or no activity against Gram-negative bacterial microflora commonly found in the human gastrointestinal tract. Sarecycline has not been tested in spirochetes. References
External links
"Sarecycline". Drug Information Portal. U.S. National Library of Medicine.