Immunosuppression and Chemotherapy Flashcards
What is the first-line therapy for general immunosuppression?
High dose glucocorticoids (prednisone, dexamethasone)
- Once the immune disease is under control, then the dose is gradually tapered over weeks/months with close monitoring
- Ex. IMHA start with high dose of steroids first couple of weeks until RBC stabilize then taper dose by 25% every 2 weeks while monitoring CBC
- Side effects are common at high doses and with chronic use (PU/PD/PP/panting)
[FYI] What is another immunosuppressive therapy drug that is classified under antimetabolites, but is avoided in cats due to liver and bone marrow toxicity?
Azathioprine (Imuran), oral
- Inhibit purine and pyrimidine synthesis thus impairing nucleic acid synthesis (DNA) particularly in rapidly dividing cells like immune cells (lymphocytes), as well as blocking signaling on T-cells
- (Mycophenolate mofetil and Leflunomide)
Which immunosuppressive therapy drug is used topically on the eye to treat keratoconjunctivitis sicca, used systemically (oral) to treat perianal fistulas or as an adjunct with glucocorticoids for other immune diseases?
Cyclosporine
- Cytokine inhibitor
- A polypeptide that binds to cyclophilin/calcineurin which reduces T-cell activation and response (decrease production of various cytokines, and decrease proliferation)
- Bioavailability varies widely between products
- Major side effects/toxicity: GI upset and gingival proliferation (usually Boxers)
Which immunosuppressive drug is used topically to manage peri-anal fistulas?
Tacrolimus topical
- Slightly different target than cyclosporine
T or F. Chemotherapy drugs are toxic to the target cell and have a narrow therapeutic index so special handling may be required.
True
Handling chemotherapy drugs is an occupational risk; what precautions can we take to reduce these risks?
- PPE: gloves, mask, gown
- Drug reconstitution and handling: use fume hood, away from high-traffic areas, biohazard disposal
What should you do in the case of extravasation after catheter placement of vesicant drugs (cause tissue necrosis)?
- Don’t just pull out!
- Remove as much of the chemo drug as possible
- Local infusion (saline +/- other substances)
- Hot or cold packing depending on the drug
What units are used in body surface area dosing?
Meter squared
- Used for many chemotherapy drugs
- Better reflects metabolic ‘size’ of patient
What do you need to know when handling oral chemotherapeutic drugs?
- Wear gloves
- No crushing or splitting of pills
- Make sure the pet consumed the drug
What do you need to know about elmination (feces, urine) of the drug in a patient?
- Wear gloves
- Collect excreta and seal in a plastic bag for disposal in the trash for several days after drug administration
Because chemotherapeutic drugs target rapidly dividing cells, what are possible adverse effects?
- GI signs (most common): antiemetics often used before and during treatment when nausea is expected
-
Bone marrow suppression/immunosuppression
- Neutropenia > thrombocytopenia > anema
- ‘Nadir’: lowest neutrophil count
- Generally predictable based on the drug used
- If neutropenia drops below a certain point, the next chemo treatment may be delayed
- If neutropenia is severe, prophylactic antibiotics may be started
- Hair loss (poodles, terrier, Old English sheepdogs, etc.): cats’ whiskers may fall out, shaved areas may be slow to regrow
- Specific toxicity: hemorrhagic cystitis, cardiotoxicity, nephrotoxicity
- Drug resistance/loss of efficacy
- Acute tumor lysis syndrome (when the cancer is killed off too fast > contents released into surrounding > inflammatory response > systemic)
What is the more frequently used oral at-home therapy that differs from traditional protocols in that lower doses of drugs are given over long periods of time?
Metronomic chemotherapy
- Sometimes issues with dosing and with risk of owner exposure
