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Pharmacology: Pharmacodynamics: Mode of Action: 'Cosmegen' inhibits the proliferation of cells by forming a stable complex with DNA and interfering with DNA-dependent RNA synthesis.
Generally, the actinomycins exert an inhibitory effect on Gram-positive and Gram-negative bacteria and on some fungi. However, the toxic properties of the actinomycins (including dactinomycin) in relation to antibacterial activity are such as to preclude their use as antibiotics in the treatment of infectious diseases.
Because the actinomycins are cytotoxic, they have an antineoplastic effect which has been demonstrated in experimental animals with various types of tumour implant. This cytotoxic action is the basis for their use in the palliative treatment of certain types of cancer.
Pharmacokinetics: Dactinomycin is poorly absorbed from GIT; thus, it should be IV administered. It is rapidly distributed into tissues, with high concentrations in bone marrow and nucleated cells, including granulocytes and lymphocytes. Dactinomycin also crosses the placenta but crosses the blood-brain barrier poorly. Metabolism of the drug is minimal. Excretion of the drug is mainly in bile and urine.
