Oncology Pharm Flashcards
Log Kill Hypothesis
Cytotoxic drugs= first order kinetics
- Given dose, constant fraction of cells killed (not fixed number)
- Toxicity to normal tissues= major dose-limiting factor
- Need multiple cycles of chemo to eradicate tumor (ex: only killing 20% of cancer with each dose)
Gompertzian Kinetics
Increased doubling time as tumor burden increases
- Takes longer time for tumor to enlarge as it gets larger
- Subclinical–> diagnosis–> symptoms–> death
- Increases in cellularity occur over longer periods of time
Adjuvant therapy
Used after surgery or radiation therapy
- Eradicate residual tumor
Neoadjuvant therapy
Used before surgery/radiation
- Shrink tumor to make surgical removal easier
Alkylating agents
MOA: Alkylate DNA (N7 of guanine)
- DNA cross-linked, strand breaks, inhibits replication, transcription
- No cell cycle specificity
Includes:
- Nitrogen mustards
- Nitrosoureas
- Platinum Analogues
- Others
Toxicity: Dose limiting: - myelosuppression (febrile neutropenia) - Mucositis - Nausea and vomiting - Alopecia - Infertility - Secondary leukemias
Nitrogen mustards
Includes: bendamustine, chlorambucil, cyclophosphamide, ifosfamide, mechlorethamine (first anticancer drug- mustard gas–> lymphopenia), melphalan
Cyclophosamide
Broad spectrum nitrogen mustard
Prodrug. Activated by liver to active and toxic metabolites
IV and PO
Adverse effects:
- Hemorrhagic cystitis: production of acrolein causes irritation to bladder wall.
Treatment for AEs:
- Adequate hydration, Mesna with high doses
Ifosfamide
Analog of cyclophosphamide.
Also requires hepatic activation to same active metabolites
- Less potent, requires 4 x dose for efficacy
Adverse effects:
- Increased production of acrolein accumulates in bladder and causes hemorrhagic cystitis
- Administer with Mesna (IV/PO), hydration important.
Melphalan
Nitrogen mustard
Oral and IV
High dose used for Bone marrow transplant
Bendamustine
Nitrogen mustard: combination alkylating agent and purine analog
Nitrosoureas
Nitrogen mustard
- Lipophilic, good CNS penetration
- Delayed myelosuppression, 4 week nadir
AEs:
Severe N/V, pulmonary toxicity, hepatotoxicity
Carmustine implant: Gliadel Wafer
Dacarbazine
Other alkylating agent with CNS penetration
Temozalmide
Alkylating agnet
Oral, converts to Dacarbazine
Platinum Analogs
Binds to and causes double-stranded DNA breaks
Cisplatin
Platinum analogs
AEs: Nephrotoxic, ototoxic, N/V
- Avoid with hydration, antiemetics
Carboplatin
Platinum analog
AE:
- Myelosuppression
- less N/V, neuropathy, nephrotoxicity than cisplatin
Dosed NOT by weight
Oxaliplatin
Platinum analog
AE: acute: cold induced neuropathy, cumulative peripheral neuropathy,
Topoisomerase inhibitors
MOA:
Topoisomerases (I and II) are nuclear enzymes that unravel DNA for repair and replication
Specifically they participate in DNA replication and repair by:
- cleaving and resealing the phosphodiester bonds that comprise the backbone of DNA (Topo II)
- unwinding DNA (Topo I)
Inhibiting topoisomerases can induce DNA damage such as unrepairable strand breaks leading to cell apoptosis
Anthracycline
Topoisomerase II inhibitor
MOA:
- High affinity binding to DNA
- Intercalates between base pairs, inhibits the activity of enzymes involved in DNA replication (topoisomerase II)
- Anthracyclines form free radical compounds that damage biological macromolecules
AEs:
- Specifically can cause CHF when cumulative dose reached
- As dose approached, must monitor ejection fractions
Camptothecins:
Topoisomerase I inhibitor
Topotecan
Topoisomerase I inhibitor:
AE: dose-limiting marrow suppression
Irinotecan
Topoisomerase I inhibitor
AE:
- Diarrhea is a dose limiting side effect
1. Early form - Cholinergic syndrome treated with IV atropine
2. Late form - Direct GI toxicity. Loperamide 4 mg x 1, 2 mg q2hr.
- May cause serious dehydration
Bleomycin
Glycopeptide antibiotic
MOA: Bleomycin produces single and double strand breaks in DNA through the production of highly reactive free radicals
Toxicity:
- Pulmonary fibrosis (avoid cumulative dose >400 units, current radiation/oxygen).
- Hyperpigmentation, rash, fever, allergic rxn.
Vinca Alkaloids
Vinblastine, vincristine, vinorelbine
MOA:
Inhibit microtubule function in M phase
- inhibit the formation of tubulin, which prevents polymerization into microtubules
- CAN’T FORM
Toxicity:
- All vesicants
Vincristine:
- neurotoxicity, constipation
- Max dose 2 mg/week
Vinblastine/vinorelbine:
- Myelosuppression
- Less neurotoxicity
Docetaxel, Paclitaxel
Taxanes
MOA:
Inhibit microtubule function in M phase
- bind to beta tubulin and stabilize the alpha and beta tubulin heterodimers, preventing the breakdown of microtubules
- CAN’T BREAK DOWN
AEs:
Require premedication with steroids due to solubilizing agents
Paclitaxel: Neuropathy, Albumin-bound paclitaxel (Abraxane), no solubilizer
Docetaxel: Fluid retention syndrome: dex 8 mg PO BID x 3 days
Cabazitaxel: Crosses BBB, not affected by P-glycoprotein
Ixabepilone
Epothilones
MOA:
Inhibit microtubule function in M phase
- bind to beta tubulin and stabilize the alpha and beta tubulin heterodimers, preventing the breakdown of microtubules
AEs:
Require premedication with steroids due to solubilizing agents
Ixabepilone: Distinct tubulin binding site, not effected by Pgp
Antimetabolites
MOA:
- Mimic nucleotide cousins
- S-phase specific
- One or combination:
- inhibiting enzymes involved in nucleotide synthesis
- inhibiting enzymes involved in DNA replication
- replacing naturally occurring nucleotides in DNA that is actively being replicated. This serves to disrupt the natural structure of DNA, causing apoptosis.
Methotrexate
MOA: inhibitors dihydrofolate reductase
- decreases reduced folates, inhibits thymidylate synthase
ROA: IM, IV, IT< PO
PK: cleared renally, can accumulate in 3rd spaces
- Avoid in CHF, liver failure, renal failure causing ascites
AEs:
Mucositis, pneumonitis, renal failure, increased LFT’s
Purine analogs
Thioguanine (6-TG) and mercaptopurine (6-MP)
- Oral agents
- Metabolized by xanthine oxidase
AEs: Cause liver toxicity, mucositis
Fludarabine, cladrabine, pentostatin
AEs: Immunosuppression (lymphopenia)
Nelarabine
AEs: Neurotoxicity is dose-limiting