Today's Veterinary Nurse

SEP-OCT 2017

Practical, peer reviewed, state-of-the-art companion animal nursing and technical educational articles with CE. Promotes better health for animals and career growth and development for veterinary technicians and veterinary assistants.

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PEER REVIEWED 52 | TODAY'S VETERINARY TECHNICIAN | September/October 2017 Most chemotherapy protocols have 2 phases: induction and consolidation. The induction phase consists of weekly treatments designed to place the pet into remission rapidly. It is more dose intensive than the consolidation phase, which is designed to kill any remaining tumor cells and requires less frequent treatment. Lymphoma is ideally managed with a combination of drugs. Several different protocols are used, but most are based on a combination of drugs commonly abbreviated as CHOP, or L-CHOP. The drugs are as follows: Æ L ( l -asparaginase): This enzyme degrades the amino acid asparagine. Asparagine, which is synthesized by normal cells, is necessary for protein synthesis; however, lymphoma cells are unable to synthesize asparagine. Rapidly dividing cells need to produce large amounts of protein to progress through the cell cycle. If deprived of asparagine, they cannot progress and thus undergo apoptosis. The most significant adverse reaction seen with l -asparaginase is hypersensitivity. Patients with prior exposure to the drug are predisposed to hypersensitivity reactions. Premedication with diphenhydramine and dexamethasone sodium phosphate, as well as SC administration of the drug, minimizes these reactions. Pancreatitis and coagulopathies (secondary to decreased protein synthesis) are also seen with l -asparaginase to a lesser extent. Significant myelosuppression is rare unless l -asparaginase is given simultaneously with vinca alkaloids. The mechanism of this interaction is unknown, but it is thought that l -asparaginase may inhibit liver function, thus interfering with hepatic excretion of vinca alkaloids. It is reported that up to 25% of canine patients treated with vincristine and l -asparaginase concurrently will develop significant myelosuppression. It is common to "split" induction in clinically ill lymphoma patients (ie, separate administration of the drugs by several days) to minimize this toxicosis. 1,2,4 Æ C (Cyclophosphamide): This alkylating agent interferes with DNA replication and RNA transcription. It is nonspecific for cell cycle phase. It can be given intravenously or in capsule form. Side effects can include sterile hemorrhagic cystitis. Cyclophosphamide is not substantially myelosuppressive at the doses used in veterinary medicine. 1,2,4 Æ H (Doxorubicin): This anthracycline antineoplastic antibiotic intercalates with DNA, thereby inhibiting protein synthesis and promoting the formation of free radicals. It is nonspecific for cell cycle phase. Although doxorubicin does have antimicrobial activity, it is considered too toxic to be used as an antimicrobial; instead it is used for its antitumor activity against a wide range of neoplasms. 1,2,4 Familiarity with the side effects of doxorubicin is extremely important for the administrator. The drug can have both acute and cumulative effects. Doxorubicin can cause immediate histamine-mediated hypersensitivity reactions (pruritus, dyspnea, or vomiting in dogs). It is also associated with cumulative cardiotoxicity; therefore, thorough cardiac evaluation is needed before each dose. Any new murmurs or arrhythmias warrant echocardiography. 1,2,4 Doxorubicin should be administered only by a trained individual because it is a severe vesicant, and administration outside of the vein results in severe, progressive tissue necrosis. Canine Multicentric Lymphoma: An Overview FIGURE 2. A patient waiting for treatment.

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