The use of aromatase inhibitors in boys with short stature: what to know before prescribing?

ABSTRACT Aromatase is a cytochrome P450 enzyme (CYP19A1 isoform) able to catalyze the conversion of androgens to estrogens. The aromatase gene mutations highlighted the action of estrogen as one of the main regulators of bone maturation and closure of bone plate. The use of aromatase inhibitors (AI) in boys with short stature has showed its capability to improve the predicted final height. Anastrozole (ANZ) and letrozole (LTZ) are nonsteroidal inhibitors able to bind reversibly to the heme group of cytochrome P450. In this review, we describe the pharmacokinetic profile of both drugs, discussing possible drug interactions between ANZ and LTZ with other drugs. AIs are triazolic compounds that can induce or suppress cytochrome P450 enzymes, interfering with metabolism of other compounds. Hydroxilation, N-dealkylation and glucoronidation are involved in the metabolism of AIs. Drug interactions can occur with azole antifungals, such as ketoconazole, by inhibiting CYP3A4 and by reducing the clearance of AIs. Antiepileptic drugs (lamotrigine, phenobarbital, and phenytoin) also inhibit aromatase. Concomitant use of phenobarbital or valproate has a synergistic effect on aromatase inhibition. Therefore, it is important to understand the pharmacokinetics of AIs, recognizing and avoiding possible drug interactions and offering a safer prescription profile of this class of aromatase inhibitors. Arch Endocrinol Metab. 2017;61(3):391-7.

Use of anastrozole in the chemoprevention and treatment of breast cancer: A literature review / Uso do anastrozol na quimioprevenção e no tratamento do câncer de mama: uma revisão da literatura

Summary Aromatase inhibitors have emerged as an alternative endocrine therapy for the treatment of hormone sensitive breast cancer in postmenopausal women. The use of third-generation inhibitors represented by exemestane, letrozol and anastrozole is currently indicated. Anastrozole is a nonsteroidal compound and a potent selective inhibitor of the aromatase enzyme. Although a few studies have shown that its pharmacodynamic and pharmacokinetic properties may be affected by interindividual variability, this drug has been recently used in all configurations of breast cancer treatment. In metastatic disease, it is currently considered the first-line treatment for postmenopausal women with estrogen receptor-positive breast tumors. Anastrozole has shown promising results in the adjuvant treatment of early-stage breast cancer in postmenopausal women. It has also achieved interesting results in the chemoprevention of the disease. Therefore, due to the importance of anastrozole both for endocrine treatment and chemoprevention of hormone-sensitive breast cancer in postmenopausal women, we proposed the current literature review in the SciELO and PubMed database of articles published in the last 10 years.

Resumo Os inibidores de aromatase têm emergido como uma endocrinoterapia alternativa para o tratamento de câncer de mama sensível a hormônios em mulheres pós-menopáusicas. A utilização de inibidores de terceira geração, representados por exemestano, letrozol e anastrozol, é atualmente indicada. Anastrozol é um composto não esteroide e um inibidor potente e seletivo da enzima aromatase. Embora alguns estudos tenham demonstrado que as suas propriedades farmacodinâmicas e farmacocinéticas podem ser afetadas pela variabilidade interindividual, esse fármaco tem sido recentemente utilizado em todas as configurações de tratamento do câncer de mama. Na doença metastática, é atualmente considerado o tratamento de primeira linha em mulheres pós-menopáusicas com tumores de mama e receptor de estrogênio positivo. O anastrozol tem mostrado resultados promissores no tratamento adjuvante do câncer de mama em estágio inicial em mulheres na pós-menopausa. Ele também conseguiu resultados interessantes na quimioprevenção da doença. Portanto, em virtude da importância do anastrozol tanto no tratamento endócrino quanto na quimioprevenção do câncer de mama hormoniossensível em mulheres na pós-menopausa, propusemos a atual revisão da literatura na base de dados SciELO e PubMed de artigos publicados nos últimos 10 anos.

Pattern of enzyme changes in rabbits administered linamarin or potassium cyanide.

Diseases like tropical ataxic neuropathy and endemic goitre have been reported to have definite correlation with a chronic ingestion of cassava (Manihot esculenta Crantz). The toxicity of cassava has been attributed to its two cyanogenic glycosides, linamarin and lotaustralin. In this study, an attempt has been made to understand the pattern of changes in certain clinically significant enzymes brought about by the chronic administration of sublethal doses of linamarin to rabbits. The profound elevation in rhodanese activity observed in the linamarin and cyanide treated rabbits indicated the attempt of the tissues to detoxify cyanide. That intact linamarin could be hydrolysed in vivo was a significant finding from the study. The mode of toxicity of linamarin was similar to that of cyanide by producing a gradual shift from aerobic to anaerobic metabolism.