Oncology (Chemo Agents) Flashcards
Pediatric Treatment Principles (3)
- Curative if at all possible
- Get more Chemo than adults
- Prevent long term complications
Dosing for anti-neoplastic agents
BSA is the standard for individualized based dosing
Mosteller Equation*****
Mosteller Equation
BSA = (ht*wt)/3600
ALL UNDER Sq root
ht = cm wt = kg
Other options for dose adjustments (4)
mg/m2 Units/m2 g/m2 Weight (kg) is sometimes used o Often used in children < 1 year of age
Corticosteroids (3)
Prednisone
Dexamethasone
Methylprednisone
Corticosteroids MOA
promotes decrease in lymphocytic cell lines
One of the mainstays, especially in Leukemia
Corticosteroids Side Effects (6)
Symptoms resolve by…
- Hyperglycemia: May even require insulin while they are on the steroids
- Fluid retention, facial swelling
- Increased appetite (helps with nausea during induction)
- Hypertension – Watch BP
- Mood changes: Especially in children; children can get very cranky on steroids
- Risk of GI ulcers
Symptoms typically resolve once treatment stops (typical duration of therapy is about 50 days)
Corticosteroids Special Considerations
Patients should be on acid suppression with a proton pump inhibitor or H2 receptor antagonist to protect against ulcers
Corticosteroids - tx of side effects (2)
Monitor blood pressure
Monitor blood sugar
Corticosteroids
What steroid is better at penetrating the spinal fluid?
Dexamethasone penetrates spinal fluid tissue better than prednisone
Choice of steroid however depends on the protocol
Alkylating Agents (4) MOA
Cell cycle
Highly reactive compounds
MOA - forms covalent (tight) bonds within DNA which leads to interference in cell replication
Cell cycle non-specific: Good thing
Common alkylating agents used in Pediatrics (3)
Cyclophosfamide
Ifosfamide
Busulfan
Used in pediatrics but more for bone marrow transplant conditioning
Less Commonly Used Alkylating agents in pediatrics (2)
o Decarbizine
o Temozolamide
Cyclophosfamide (Alkylating Agent)
Activated where?
Prodrug, must be activated in the liver to the active compound (CYP2B6 to 4-HC)
Cyclophosfamide (Alkylating Agent) Dosage forms (2)
IV doses used for cancers
PO used for other indications (FDA improved for minimal change disease in children)
Cyclophosfamide (Alkylating Agent) Side Effects (7)
- Hemorrhagic cystitis (high doses require treatment with mesna): Leads to severe bleeding
- Myelosupression: Since these agents cause bone marrow suppression, other non-cancer rapidly diving cells (ex: bone marrow, epithelial cells) will be affected
- N/V (acute and delayed)
- SIADH (Syndrome of Inappropriate Anti Diuretic Hormones)
- Nasal stuffiness (decreases with infusing at least over 1 hr)
- Pulmonary and cardiotoxicity
- Alopecia
Cyclophosfamide (Alkylating Agent) Special Considerations(3)
Doses > 1800 mg/m2 should be infused over 1 – 6 hrs
Typical hydration with higher doses is 125 ml/m2/hr (D5 1/2NS)
Monitor UOP
Urine specific gravity (SG) must be < 1.01 prior to initiating the infusion and maintain urine SG < 1.01 (test urine with each void)
o Should be in IVF during infusion
Ifosamide
Metabolized by?
Prodrug, must be metabolized to the active form (by CYP 3A4)
Ifosamide
Dosage form
IV
Ifosamide Side effects (7)
Neurotoxicty - requires neuro checks with infusions: See enceophalopathy, hallucinations, coma
Hemorrhagic cystitis - urine checks while on therapy is important
Nephrotoxicity: Fanconi syndrome due to renal tubular damage
Peripheral neuropathy
Cardiotoxicity – dose dependent
Interstitial pneumonitis, pulmonary fibrosis
Marrow supression, alopecia
Ifosamide Drug Interactions (4)
Metabolized to the active form by CYP3A4
Inhibitors = less effective, inducers = > risk of toxicity
Anything that inhibits CYP3A4 will inactive this drug
If you give something that upregulates CYP3A4 you will see increased effects of this drug
Hemorrhagic cystitis
What is it
Inflammation and damage to bladder epithelium leading to hematuria. Also can cause pain and irritation as well as long-term damage
o Caused by the metabolite, acrolein
Hemorrhagic cystitis
How can it be avoided?
At higher doses mesna can be given to bind to the metabolite and limit the exposure to the bladder
Maintain good hydration
Hemorrhagic cystitis
Tx (3)
Increase mesna dosing to 100% ifosfamide dose
Maintain good hydration
Sometimes patients may require bladder irrigations to washout the chemical
Mesna
MOA
Binds to the urotoxic metabolites (acrolein and 4-hydroxyifosfamide) of ifosfamide and cyclophosphamide (to a lesser extent)
With ifosfamide doses _____ mesna should be administered
> 1.2 g/m2
- 60 – 100% of ifosfamide dose
- Up to 6% will still develop urotoxicity with mesna
Why do we use mesna?
to prevent bladder toxicity from ifosfamide and cyclophosfamide
Dacarbazine (DTIC)
Used for
Dosage form
Side effects(2)
Used for solid and heme malignancies
Dosage form: IV only
Similar side effects to other alkylating agents
o Myelosuppression
o N/V
Temozolamide (Temodar®)
Benefit
Newer alkylating agent
Benefit = PO administration
o IV formulation is available but used less
o Metabolized the active decarbazine
Temozolamide (Temodar®)
FDA approved for (2)
FDA approved for glioblastoma and refractory astrocytoma therapies.
Temozolamide (Temodar®)
Studied in children with… (2)
Studied in children for meduloblastoma, PNS tumors
Platinum Alkylating Agent
MOA (3)
Cell phase…
Contains…
o Mechanism
Forms a covalent (strong) bond with DNA, platinum compound bound to DNA leads to inability for the cell to repair the DNA and ultimately cell death
- Contain heavy metal (platinum)
- Cell phase non-specific
Platinum Alkylating Agent
Toxicity
• Toxicity – lots! Remember there will be a lot of toxicity with these
Platinum Alkylating Agent
• Commonly used agents in pediatrics
o Cisplatin
o Carboplatin
Cisplatin (Platinum Alkylating Agent)
Dosage form
Side effects (6)
• Dosage form: IV
- Nephrotoxicity – Renal tubular nephropathy - associated with cation wasting (watch Mg, Na, and K)Requires aggressive hydration & high urine output
- Prolonged myleosupression, thrombocytopenia
- Hepatotoxicity
- Peripheral neuropathy: Give Gabapentin for this pain – In general Gabapentin is given for the pain associated with alkylating agent side effect pain
- Nausea and vomiting – see delayed nausea
- Ototoxicity
Cisplatin (Platinum Alkylating Agent)
Administration
Should be given with aggressive hydration – fluids should contain K+ and Mg+
Carboplatin
(Platinum Alkylating Agent)
Dosage form
Special Considerations (2)
Dosage Form: IV – Usually dosed based on BSA or AUC
Special Considerations
- Cleared vis renal excretion, so good kidney function is essential with hydration
- Delayed nausea so dexamethasone can be used with anti-emetic regimen (unless otherwise contraindicated)
Carboplatin
(Platinum Alkylating Agent)
Side effects are similar to cisplatin (2)
Notable exceptions…
- Less emetogenic, nephrotoxic, and neurotoxic
- More myelosupressive
S phase specific drugs (2)
cytosine arabinoside
hydroxyurea
S Phase specific - self-limiting (2)
6-mercaptopurine
methotrexate
M phase specific drugs (3)
vincristine
vinblastine
paclitaxel
Cycle non-specific drug (6)
alkaylating agents nitrosources antitumor antibiotics procarbazine cisplatin dacarbazine