Dactinomycin

Definition

Dactinomycin is a chemotherapeutic agent belonging to a family of medicines known as antineoplastic drugs. Alternative trade names or brand names for dactinomycin include Actinomycin-D and Cosmegen.

Description

Dactinomycin is one of the older chemotherapy drugs, having gained approval from the Food and Drug Administration (FDA) in 1982. This highly potent and effective cytotoxic agent is a mixture of substances produced by the bacteria Streptomyces parvullus. Its toxic properties prevent its use as an antibiotic.

Dactinomycin interferes with the growth of cancer cells by complexing with a cell's genetic material (deoxyribonucleic acid, or DNA). This prevents the cell from producing the proteins necessary to function and grow, thereby killing it. Dactinomycin may be used as a single chemotherapeutic agent or in conjunction with other antineoplastics (such as vincristine and cyclophosphamide) for greater efficacy.

Purpose

Dactinomycin is used in the treatment of Ewing's sarcoma, Wilms' tumor, rhabdomyosarcoma, gestational trophoblastic tumors, Kaposi's sarcoma, and soft tissue sarcomas. It is less commonly used for cancers of the uterus and testis.

Recommended dosage

The exact schedule and method of dactinomycin administration will be prescribed by an oncologist based on the type and stage of the cancer. An appropriate starting treatment regimen for adult patients is 500 mg/day for five consecutive days at two to four week intervals if the drug is tolerated. For children the dose is 15 mg/day over the same time course as prescribed for adults. Dactinomycin is not recommended for children less than one year of age; little clinical data is available on the use of dactinomycin in the elderly. Administration may be by intravenous (IV) injection, through a running IV infusion, or through a central line inserted under the skin into a vein near the collarbone.

Precautions

To maximize treatment effects, patients receiving dactinomycin should observe the following guidelines, as well as any modifications given by the oncologist:

• The area surrounding the injection site should be monitored.

• Patients should have regular laboratory testing for white blood cell count and kidney, liver, and bone marrow function.

• In order to reduce the possibility of immunosuppression, immunizations not approved or prescribed by the oncologist should be avoided.

• Patients should avoid contact with individuals taking or that have recently taken the oral polio vaccine, or individuals that have an active infection. When necessary a protective facemask should be worn.

• Oral hygiene procedures should be followed to reduce the risk of gum abrasion.

• Patients should not touch eye and nasal areas unless hands have been properly washed immediately prior to contact.

• To reduce bleeding and bruising complications, patients should exercise extreme caution when handling sharp instruments and decline participation in contact sports.

• Prior to treatment, the patient's medical history should be thoroughly reviewed to avoid complications that might arise from previous conditions such as gout, kidney stones, liver disease, chickenpox, shingles, or a history of allergic reactions to various drugs.

• The oncologist should be made aware if the patient is pregnant or if there is the possibility the patient might be pregnant, or if the patient is a breast-feeding mother.

• Only prescribed medications or over the counter (OTC) drugs approved by the oncologist should be taken by a patient receiving dactinomycin.

Side effects

Possible side effects of treatment with dactinomycin should be discussed with the patient prior to initiation of treatment. The patient should be instructed to notify the oncologist of any side effects. Side effects that may not be life threatening but give the patient cause for concern include hair loss (alopecia), intermittent diarrhea, nausea and vomiting, loss of appetite, difficulty swallowing, mouth sores or ulcers, and a general rash or change in skin tone. Side effects that should be reported immediately to the oncologist include unusual bleeding or bruising, black tarry stools, blood in the urine or stool, development of a cough, wheezing or hoarseness, fever or chills, lower back or side pain, painful or difficult urination, pinpoint red spots on the skin, and pain at the site of the injection. The oncologist will decide what type of intervention is best suited to control or extinguish the presented side effects, including changing the dosage, changing the treatment schedule, or discontinuing dactinomycin treatment.

Interactions

Certain medications should never be used together, but there are cases in which multiple drug treatment may be advisable even when drug interaction is well documented. Dactinomycin may be used in conjunction with other antineoplastic drugs or radiation therapy for increased efficacy of treatment. Under such conditions the oncologist will balance dosage and treatment schedules to maximize the positive effects of all drugs given and minimize any negative interactions.

It is essential that the oncologist be aware of any drugs that the patient is presently taking or has recently taken, or if the patient has recently received radiation therapy. A careful review of drugs that may interact with dactinomycin to lower its efficiency should be covered with the patient prior to treatment. These may include, but are not limited to, amphotericin B, antithyroid agents, azathioprine, chloramphenicol, flucytosine, ganciclovir, interferon, plicamycin, zidovudine, probenecid, and sulfinpyrazone.

KEY TERMS

Antineoplastics

Agents that inhibit or prevent the maturation and proliferation of malignant cells.

Cytotoxic

Toxic to cells.

Ewing's sarcoma

A highly malignant primary bone tumor most often found in young adults under the age of 30.

Gestational trophoblastic cancer

A pregnancy associated cancer in which a grape-like mole develops in the uterus instead of a fetus.

Kaposi's sarcoma

A type of cancer associated with the skin and mucous membranes.

Myeloma

A malignant tumor composed of plasma cells normally found in the bone marrow.

Oncologist

A doctor who specializes in the diagnosis and treatment of patients with cancer.

Rhabdomyosarcoma

A malignant tumor derived from striated muscle.

Wilms' tumor

A cancerous tumor found in the kidneys of children.