Aminoglutethimide (with hydrocortisone) induced agranulocytosis in primary breast cancer

Idiosyncratic Drug-Induced Neutropenia and Agranulocytosis in Elderly Patients

Agranulocytosis is a rare, but serious and life-threatening hematologic disorder in elderly patients. Idiosyncratic drug-induced agranulocytosis (IDIA) has been classically defined by a neutrophil count below 0.5 × 10⁹/L. The annual incidence of IDIA in Europe is about 1.6–9.2 cases per million inhabitants. Increasing age and female sex have been considered as risk factors for the development of this condition. Besides, it is well known that older people take on average more drugs than younger people. This condition is most often associated with the intake of antibacterial agents, antiplatelets, antithyroids, antipsychotics, antiepileptics and nonsteroidal anti-inflammatory drugs (NSAIDs). Initially, agranulocytosis may present without symptoms, but may quickly progress to a severe infection and sepsis. The causative drug should be immediately stopped. In febrile patients, blood cultures and where indicated, site-specific cultures should be obtained and early treatment with empirical broad-spectrum antibiotics started. Even with adequate treatment, the mortality rate is higher in elderly patients reaching up to 20%. Hematopoietic growth factors have proven to be useful as they shorten the duration of neutropenia. However, data on neutropenia and agranulocytosis in the elderly meeting the criteria of evidence-based medicine are still poor in the literature. This review analyzes the results of our experience as well as other published studies of the universal literature.

In vitro and animal models of drug-induced blood dyscrasias

Drug-induced blood dyscrasias can be either acute and predictable or delayed and unpredictable (idiosyncratic). The predictable toxicity is relatively easy to reproduce with in vitro models, although they may not work for drugs that require bioactivation. It is very unlikely that idiosyncratic blood dyscrasias can be modeled in vitro, although some drugs (or their reactive metabolites) that cause idiosyncratic reaction are toxic to bone marrow cells in vitro. Although the mechanisms of idiosyncratic reactions are poorly understood, there is evidence that most are due to reactive metabolites and some are immune-mediated. Therefore screening drugs for their bioactivation by myeloperoxidase, the major oxidative enzyme in bone marrow, may provide some measure of the risk that a drug will cause blood dyscrasias. Several examples of drug-induced idiosyncratic agranulocytosis, aplastic anemia and thrombocytopenia are presented, but better in vivo models are clearly needed to gain a clearer understanding of these adverse reactions.

Aminoglutethimide-induced leucopenia in a mouse model: effects of metabolic and structural determinates

A model of human leucopenia has been developed further in the female mouse. Following daily administration to female mice of 50 mg/kg of the aromatase inhibitor aminoglutethimide, significant falls in platelet and white cell counts occurred after 2 and 3 weeks. At week 4, drug dosage was stopped and the cell counts recovered at the end of that week, although on rechallenge at the beginning of week 5, both platelet and white cell counts fell rapidly. Administration to the mice of structural analogues of aminoglutethimide, such as WSP-3, glutethimide and 4-nitroglutethimide, showed no reductions in platelet and white cell counts. The haemotoxicity of aminoglutethimide over 21 days was unaffected by the presence of either the P-450 inhibitor SKF-525A or the hepatic P-450 inducer phenobarbitone. However, the co-administration of cimetidine abolished the haemotoxicity of aminoglutethimide in terms of platelet and white cell levels. In in vitro studies, both aminoglutethimide and WSP-3 were oxidised to cytotoxic species, although aminoglutethimide was significantly more cytotoxic than WSP-3. The NADPH-dependent covalent binding of (14)C aminoglutethimide to mouse microsomes in vitro was significantly reduced by the presence of cimetidine. The activation of the compound to reactive species in vitro, the inhibitory effects of cimetidine in vivo and in vitro, as well as the rapid fall in the in vivo white cell count on rechallenge with aminoglutethimide suggest that this model illustrates a form of leucopenia which may be related to hapten formation and subsequent immune-mediated platelet and white cell lysis.

Aromatase inhibitors in malignant diseases of aging

Aromatase inhibition is an established endocrine treatment modality in postmenopausal breast cancer and is currently considered as an interesting experimental treatment approach in other malignant conditions such as endometrial carcinomas and prostatic cancer. While the 'classic' aromatase inhibitor aminoglutethimide causes many adverse effects that makes it unfit for use in elderly patients, several novel aromatase inhibitors with minimal adverse effects are currently being investigated. These drugs may provide important new tools in the endocrine treatment of malignant diseases in aging patients.

4-hydroxyandrostenedione--further clinical and extended endocrine observations

4-Hydroxyandrostenedione (4-OHA) was administered (250 mg intramuscularly 2-weekly) in a phase 2 clinical trial to 20 postmenopausal patients with advanced breast cancer, who had failed other endocrine therapy. Seven out of 18 assessable patients (39%) responded with minimal toxicity. Endocrine studies demonstrated that the drug produced significant initial falls in oestradiol and oestrone levels, but that these levels rose toward pretreatment levels as the study progressed. Sex hormone binding globulin (SHBG) levels gradually fell during the study suggesting that the drug has a minor degree of androgenic activity albeit of no clinical significance. There was a transient reduction of adrenal steroid levels, which remained however within the normal range. There were no symptoms of adrenal insufficiency.

Mechanisms of action of aminoglutethimide as endocrine therapy of breast cancer

During the last decade aminoglutethimide has been recognised as a valuable alternative in endocrine therapy for advanced breast cancer. Although some side effects do occur, most often these are initial effects which subside within a few weeks, and cessation of therapy is not usually indicated. Aminoglutethimide was originally introduced as an inhibitor of steroidogenesis in the adrenal cortex. It was soon recognised, however, that inhibition of the non-glandular aromatase, blocking the conversion of androgenic prohormones to oestrogens, was more important, resulting in decreased blood levels of oestrogens. In this review the role of aromatase inhibition as the only important aspect of the mechanism of action of aminoglutethimide is challenged. Evidence has accumulated during the last few years that aminoglutethimide is a most potent inducer of microsomal enzymes. In addition to the pharmacological implications this has (suggesting important interactions), it also points to the possibility that levels of oestrogens are decreased due to accelerated metabolism of these hormones. Based on new experimental data, and also clinical work with alternative aromatase inhibitors, it appears that the antitumour activity of aminoglutethimide may be due to both aromatase inhibition and accelerated metabolism of oestrogens. This seriously challenges the importance of aromatase inhibition alone as a strategy in endocrine therapy of breast cancer, and furthermore suggests that accelerated metabolism of key hormones is an alternative strategy to be explored.

Aminoglutethimide as second-line hormonal therapy in advanced breast cancer: response and toxicity

Seventy-nine postmenopausal patients received aminoglutethimide (AG; 750 mg daily) and hydrocortisone therapy for metastatic or locally recurrent breast cancer following the failure of other hormonal therapy. Fourteen of 64 patients, tolerating the drug and assessable for response, achieved a complete or partial response. Disease stabilisation occurred in a further 2 patients giving a response rate of 25% in these patients. Median duration of response was 10 months. Response rates to AG were not significantly different whether or not there had been a response to previous hormonal therapy but a trend to higher response rates in ER rich tumours was observed. Those with a longer interval from first relapse to the start of AG appeared more likely to respond. Side-effects were noted in 35 patients overall (44%) and in 70% of those over the age of 65 years. Treatment was discontinued because of toxicity in 10 patients and there was one death due to agranulocytosis. AG is active in postmenopausal breast cancer following failure of first-line hormonal therapy, toxicity limiting its use earlier in the disease.

Inhibition of aromatase activity in the rat by aminoglutethimide and related compounds

Two compounds possessing aromatase inhibitory activity have been evaluated for their effects on oestradiol (E2) biosynthesis in the rat. These compounds, structurally related to aminoglutethimide (1), were administered intra-peritoneally at two dose levels to 10 week old female rats previously treated with pregnant mares' serum gonadotrophin (PMSG, 100 i.u. subcutaneously every other day for 9 days). Three hours after dosing, blood was collected and plasma oestradiol levels determined by RIA. Aminoglutethimide, 3-(4'-aminophenyl-3-ethylpyrrolidine-2,5-dione (2) and N-methyl-3-(4'-aminophenyl)-3-ethylpyrrolidine-2,5-dione (3) decreased E2 blood levels by 98, 97 and 82% of control levels respectively (n = 6) at a dose of 50 mg/kg. Similarly effective inhibition was also observed at a dose of 25 mg/kg (n = 4). Ovarian aromatase activity, assessed by incubating the homogenised ovaries of treated rats with tritium-labelled androstenedione (0.2 microM) or testosterone (1 microM), indicated that residual enzyme activity was reduced compared with controls. Aminoglutethimide, and the new pyrrolidinedione aromatase inhibitors 2 and 3, are therefore effective inhibitors of E2 biosynthesis in the rat with functioning ovarian activity.