Dactinomycin Health Dictionary

See DACTINOMYCIN.... actinomycin d

Cytotoxic means destructive to living cells. Cytotoxic drugs possess anti-cancer properties but also have the potential to damage normal tissue. Their use is twofold: to eliminate a cancer and so prolong life; or to alleviate distressing symptoms, especially in patients whose prospects of a cure are poor. In many cases CHEMOTHERAPY with cytotoxic drugs is combined with surgery, RADIOTHERAPY or both. Chemotherapy may be used initially to reduce the size of the primary TUMOUR (a process called neoadjuvant therapy) before using radiotherapy or surgery to eliminate it. Cytotoxic drugs may also be used as adjuvant treatment to prevent or destroy secondary spread of the primary tumour that has either been removed by surgery or treated with radiotherapy. All chemotherapy causes side-effects: the ONCOLOGIST – a specialist in cancer treatment – has to strike a balance between hoped-for bene?ts and acceptable (for the patient) toxic effects, which include nausea and vomiting, BONE MARROW suppression, ALOPECIA (hair loss) and teratogenic effects (see TERATOGENESIS).

Cytotoxic drugs are used either singly or in combination, when an enhanced response is the aim. Chemotherapy of cancer is a complex process and should be supervised by an oncologist in co-operation with physicians, surgeons, radiotherapists and radiologists as appropriate.

The cytotoxic drugs include:

(1) The alkylating agents which act by damaging DNA, thus interfering with cell reproduction. Cyclophosphamide, ifosfamide, chlorambucil, kelphalan, busulphan, thiotepa and mustine are examples of alkylating agents.

(2) There are a number of cytotoxic antibiotics used in the treatment of cancer – doxorubicin, bleomycin, dactinomycin, mithramycin and amsacrine are examples. They are used primarily in the treatment of acute leukaemia and lymphomas.

(3) Antimetabolites – these drugs combine irreversibly with vital enzyme systems of the cell and hence prevent normal cell division. Methotrexate, cytarabine, ?uorouracil, mercaptopurine and azathioprine are examples.

(4) Another group of cytotoxic drugs are the vinca alkaloids such as vincristine, vinblastine and vindesima.

(5) Platinum compounds such as carboplatin, cisplatin and oxaliplatin are e?ective. All of them are given intravenously, but the latter two tend to have more unpleasant side-effects. Carboplatin and cisplatin are useful in the treatment of solid tumours. Carboplatin, a derivative of cisplatin, is given intravenously in ovarian cancer and in small-cell lung cancer. Better tolerated than cisplatin, the drug causes less nausea and vomiting, nephrotoxicity, neurotoxicity and ototoxicity. Where platinum-containing therapy has failed, intravenous treatment with paclitaxel may be tried. With only a limited success rate, it is relatively toxic and should be carefully supervised; responses, however, are sometimes prolonged.

Also of increasing importance in treating cancer are interferons. These are naturally occurring proteins with complex effects on immunity and cell function. Although toxic, with numerous adverse effects, they have shown some anti-tumour e?ect against certain lymphomas and solid tumours.... cytotoxic

any drug that damages or destroys cells: usually refers to those drugs used to treat various types of cancer. There are various classes of cytotoxic drugs, including *alkylating agents (e.g. *chlorambucil, *cyclophosphamide, *melphalan), *antimetabolites (e.g. *fluorouracil, *methotrexate, *mercaptopurine), *anthracycline antibiotics (e.g. *doxorubicin, *daunorubicin, *dactinomycin), *vinca alkaloids, and platinum compounds (e.g. *carboplatin, *cisplatin). Other cytotoxic drugs include *taxanes and *topoisomerase inhibitors, and some *monoclonal antibodies (e.g. *bevacizumab, *trastuzumab) have cytotoxic activity. All these drugs offer successful treatment in some conditions and help reduce symptoms and prolong life in others. Cytotoxic drugs destroy cancer cells by interfering with cell division, but they also affect normal cells, particularly in bone marrow (causing *myelosuppression), hair follicles (causing hair loss), the stomach lining (resulting in severe nausea and vomiting), mouth (causing soreness), and fetal tissue (they should not be taken during the later stages of pregnancy). Dosage must therefore be carefully controlled. See also chemotherapy.... cytotoxic drug

n. a rare malignant tumour, usually of childhood, originating in, or showing the characteristics of, striated muscle. Pleomorphic rhabdomyosarcoma occurs in late middle age, in the muscles of the limbs. Embryonal rhabdomyosarcomas, affecting infants, children, and young adults, are classified as botryoid (in the vagina (see sarcoma botryoides), bladder, ear, etc.), embryonal (most common in the head and neck, particularly the orbit); and alveolar (at the base of the thumb). The pleomorphic and alveolar types respond poorly to treatment; botryoid tumours are treated with a combination of radiotherapy, surgery, and drugs. The embryonal type, if treated at an early stage, can often be cured with a combination of radiotherapy and drugs (including vincristine, dactinomycin, and cyclophosphamide).... rhabdomyosarcoma

n. a genus of aerobic mouldlike bacteria. Most species live in the soil, but some are parasites of animals, humans, and plants; in humans they cause *Madura foot. They are important medically as a source of such antibiotics as *streptomycin, *neomycin, *dactinomycin, and *chloramphenicol.... streptomyces