Dactinomycin, also known as actinomycin D, is a chemotherapy medication used to treat different types of cancers that affect kidneys, uterus, testicles, bones, muscles, joints, soft tissues, and solid tumors.1 Dactinomycin is extracted from the bacterium Streptomyces parvulus and is a member of the cytotoxic antibiotic family of medications. Its antineoplastic action involves binding to DNA and inhibiting DNA-dependent RNA synthesis. It also causes single-strand DNA breaks.2 Damage to DNA and its activities inhibit cell division and help to stop cancer growth.
This antibiotic was approved for medical use in the United States in 1964. Interestingly, it is on the World Health Organization’s List of Essential Medicines, which are considered to be the most effective and safe medicines needed in a health system;3 however, it is not currently used as an antimicrobial. More recently, it has been employed as a chemotherapeutic for dogs and humans.
Dactinomycin is used to treat the following conditions:4
Dactinomycin is available as a powder which is then prepared as a solution by your veterinarian and injected intravenously (IV); it can also be injected directly into a specific organ or region in the body in order to treat the area where a tumor is located.4 The length of treatment depends on the types of drugs your pet is taking, the type of cancer being treated, and your pet’s response to the drug.4 The amount of dactinomycin your pet receives and how often it is administered depends on many factors, including height and weight, general health, other health problems, and the type of cancer or condition being treated. Depending on your pet’s response, your veterinarian may adjust the dose in order to reduce the potential for adverse effects.
Chemotherapy drugs that affect cells only when they are dividing are called cell-cycle specific; however, dactinomycin is cell-cycle non-specific and is not typically given in cycles.2 Your veterinarian will determine your animal’s dose and schedule, and may use the drug in combination with other chemotherapeutic drugs such as vincristine, cyclophosphamide or ifosfamide.5
It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are giving your pet, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit your vet or if your pet is admitted to a hospital. The list is also important in case of emergencies.
Tell your veterinarian if your pet is allergic to dactinomycin, ingredients mixed with the drug, or reacts to other medications, vitamins or supplements. You can always ask your pharmacist for a list of “other ingredients” included in any medication. This is important since the product may contain inactive ingredients which can cause allergic reactions or other problems. If your pet has taken dactinomycin before, but the cancer did not respond to the medication, your veterinarian will probably choose to prescribe a different chemotherapeutic.
Before and during your dog’s treatment, your veterinarian will order blood tests to check blood cell counts, metabolite and enzyme levels. This information is used to evaluate immune system function as well as the drug’s effect on kidney and liver. It is important to let your veterinarian know if your pet has a history of the following:4
Since Dactinomycin is a medication categorized as a vesicant, it can cause serious damage if it contacts tissue. Health care providers must use extreme caution when infusing the drug into your pet’s vein. If there is pain or swelling around the infusion site, contact your vet immediately.4
Chemotherapeutic drugs were designed to destroy cancer cells, including those that may have spread beyond the main tumor. Unlike surgery or radiation, most types of chemotherapy, or “chemo,” don’t target a particular tumor or a particular part of the body. Recently there has been an effort to develop newer “designer drugs” that target and destroy cancer cells specifically; however, most of these drugs are still under research and development. Unfortunately, most forms of chemotherapy attack all rapidly dividing cells, not just cancer cells. In fact, the cells lining the stomach and cells of the hair follicle are particularly susceptible due to their rapid division rates. In part, this explains why patients undergoing chemotherapy have problems with their gastrointestinal functions and often lose their hair. Because the drugs affect all types of cells in your pet’s body, they will feel worse, at least temporarily, after a round of chemotherapy. Since certain drugs have worse side effects than others, be sure to keep a list of side effects that your dog may experience and share this with your veterinarian.6
As with most chemotherapeutic drugs, dactinomycin may cause side effects. Common side effects include bone marrow suppression, vomiting, mouth ulcers, hair loss, liver problems, infections, and muscle pains. Other serious side effects include future cancers, allergic reactions, and tissue death at the site of injection.
The following symptoms require medical attention but are not emergency situations. Tell your vet if any of these symptoms are severe or do not go away within 24 hours:7
Allergic reactions may also occur. Contact your veterinarian immediately if your pet shows any of the following symptoms :
In case your dog is accidentally overdosed, call your vet IMMEDIATELY. Signs of overdose may include the following symptoms:7
Drug interactions may change how your pet’s medications work or increase risk for serious side effects. Keep a list of all the products your pet uses (including prescription/nonprescription drugs and herbal products) and share it with your vet. Do not give your pet aspirin or products containing aspirin unless your vet specifically permits this medication to be administered.
Dactinomycin is often prescribed in combination with other cytotoxic chemotherapeutics. This approach has been associated with an increased risk of additive toxicity to bone marrow and the GI system.8 For example, potentiation of 5-fluorouracil (5-FU) neurotoxicity by dactinomycin was observed when both drugs were used in a combination protocol. In this study, six of 15 dogs (40%) developed unacceptable neurotoxicity with the combination of 5-FU, cyclophosphamide, and dactinomycin.9 Increased cellular uptake of Amphotericin B occurs in response to dactinomycin, and combining the drug with vincristine, methotrexate, and 5-FU have been shown to decrease its effectiveness.8 Serious interactions may also occur if your dog has recently been immunized with a vaccine.
Do not start, stop, or change the dosage of any medicines without your doctor’s approval.
If your pet loses their appetite and stops eating, try the following:
Nausea, Vomiting and Diarrhea
Other suggestions for the use of the dactinomycin.