8. anti cancer therapy

Question 1

two type of anti-metabolites

Answer 1

methatrexate:

• Folate antagonist AND inhibits purine & pyrimidine synthesis
• give high dose of folic acid after

Pemetrexed

• folate analogue
• Lead to folate deficiency

dihydrofolate reductase- this enzyme is blocked so thymidine is starved so body cannot produce base pairs

Question 2

false substrates mode of action

Answer 2

erg 5-Fluoruracil

• Pyrimidine analogues
• Inhibits thymidylate synthase (dUMP to dTMP)
• Incorporated into DNA as false metabolites and lead to damage of the DNA

Question 3

alkylating agents mode of action

Answer 3

• Cause chemical cross-linking of DNA leading to defective DNA replication.

Question 4

Platinum compounds mode of action

Answer 4

• Inhibition of DNA synthesis by intrastrand cross linking guanine residues.
• Testicular cancer

Question 5

Anthracycline antibiotics mode of action

Answer 5

• Interfere with nucleotide synthesis by intercalating between DNA strands, inhibiting topoisomerase (unwinding DNA) and generating free radicals
• Cardiotoxic

Question 6

Topoisomerase inhibitors

Answer 6

• Inhibition of topoisomerase II (re-linking)
• Prevents religation of DNA, leading to breaks in the DNA strand

Question 7

Microtubule inhibitors

Answer 7

• Interfere with mitosis
• Vinca alkaloids block the formation of the mitotic spindle
• Taxanes (eg paclitaxel) stabilise spindle fibres- too static cant pull chromosomes apart
• Neurotoxic

Question 8

Answer 8

Question 9

Side Effects (from IV injection) – of systemic drugs

Answer 9

• Inhibit all fast growing cells (gut epithelia, hair loss). Myelosuppression (bone marrow) for all -except vincristine and bleomycin –
  
  • Monitor blood cell counts and Hb.
• Myelosuppression:
  
  • anaemia,
  • decreased resistance to infection
    
    • NEUTROPENIC SEPSIS
  • increasing bleeding
• Overcome reduced white counts with Colony-Stimulating Factors.
• Prevent infections with antibiotics and antifungals
• Nausea: common esp with Platinum compounds- emetogenic
• Use of anti-emetics- supress urge to vomit
• Hair loss- cooling cap prevents entry of drugs to hair follicles
• Infertility
• Cardiotoxicity with anthracycline antibiotics

Question 10

Palliative care

Answer 10

• Pain relief
• Use strong opioids
  
  • Morphine and diamorphine (heroin)- more water soluble used in late stages so smaller volume infused subcutaneously for continuous pain relief
  • Oromorph for breakthrough pain
  • Constipation and nausea- anti emetics
  • Fentanyl patches- opioids given on skin to help those who cant swallow
• Syringe drivers
• Hospice care