I'mCustomerand would be glad to help with your question about your dog. I did find a journal reference for a metronomic dose of chlorambucil used at 4mg/m^2 once daily for TCC. This dose is also listed in the 8th edition of Plumb's Veterinary Drug Handbook.
An 18 lb dog is 0.4 m^2 so the chlorambucil dose works out to 1.6 mg once daily. Using 1.5 mg once daily is reasonable. In order to achieve this dose, the drug would need to be compounded: the manufactured (2 mg) tablets are not meant to be broken.
You may also dose in an alternative manner to avoid compounding. That is, if your dog needs 1.5 mg/day or 6 mg in 4 days, then you could give 2 mg once daily for three days, then take a day off. I would discuss this option with your vet to avoid the costs and possible efficacy issues of compounding.
Some additional information on monitoring and the journal article reference are pasted below:
Plumb's Veterinary Drug Handbook:
CBC, Platelets once weekly (or once stable, every other week) during therapy; once stable, dogs may require only monthly monitoring. If neutrophils are <3,000/microL hold drug until recovered and reduce dose by 25% or increase dosing interval. Other references recommend CBCs at 0, 1, 2, 4, 8, & 12 weeks and then every 3-6 months (Mueller 2000) or in cats, CBCs at 2 to 3 weeks after starting therapy and every 3-6 months thereafter (Ashley 2009). Also monitor liver enzymes; if warranted.
Give this drug with food.
Chlorambucil is a chemotherapy (cancer) drug. The drug and its byproducts can be hazardous to other animals and people that come in contact with it. On the day your animal gets the drug and then for a few days afterward, all bodily waste (urine, feces, litter), blood, or vomit should only be handled while wearing disposable gloves. Seal the waste in a plastic bag and then place both the bag and gloves in with the regular trash.
Chlorambucil can be very toxic
to the gastrointestinal tract and cause vomiting and gastrointestinal upset.
Contact your veterinarian immediately if you notice abnormal bleeding
, bruising, depression, infection, shortness of breath, bloody diarrhea, etc.
Metronomic administration of chlorambucil for treatment of dogs with urinary bladder transitional cell carcinoma.
J Am Vet Med Assoc. June 1, 2013;242(11):1534-8.
Diane R Schrempp1; Michael O Childress; Jane C Stewart; Tiffany N Leach; Kean Ming Tan; Andrew H Abbo; Amalia E DeGortari; Patty L Bonney; Deborah W Knapp
1Department of Veterinary Clinical Sciences, Purdue University, West Lafayette, IN 47907, USA.
Companion Notes are VIN generated expanded abstracts containing greater detail
Objective-To determine the antitumor effects and toxicoses of metronomic oral administration of a low dose of chlorambucil in dogs with transitional cell carcinoma (TCC).
Design-Prospective clinical trial.
Animals-31 client-owned dogs with TCC for which prior treatments had failed or owners had declined other treatments.
Procedures-Chlorambucil (4 mg/m(2), PO, q 24 h) was administered to dogs. Before and at scheduled times during treatment, evaluations of dogs included physical examination, CBC, serum biochemical analyses, urinalysis, thoracic and abdominal imaging including cystosonography for measurement of TCCs, and grading of toxicoses.
Results-29 of 31 dogs had failed prior TCC treatment. Of the 30 dogs with available data, 1 (3%) had partial remission (≥ 50% reduction in tumor volume), 20 (67%) had stable disease (< 50% change in tumor volume), and 9 (30%) had progressive disease (≥ 50% increase in tumor volume or development of additional tumors
); 1 dog was lost to follow-up. The median progression-free interval (time from the start of chlorambucil treatment to the day progressive disease was detected) for the dogs was 119 days (range, 7 to 728 days). The median survival time of dogs from the time of the start of chlorambucil treatment was 221 days (range, 7 to 747 days). Few toxicoses were detected; chlorambucil administration was discontinued because of toxicoses in only 1 dog.
Conclusions and Clinical Relevance-Metronomic administration of chlorambucil was well tolerated, and 70% of dogs had partial remission or stable disease. Metronomic administration of chlorambucil may be a treatment option for dogs with TCC
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