20 Chemotherapy

Question 1

What is fractional dosing and why is it used for chemotherapy?

Answer 1

Fractional dosing= drug given in fractionated doses

Why?

Each dose- kills healthy bone marrow

Give bone marrow cells time to recover (hopefully faster than tumour cells)

Question 2

Give 4 types of drugs that can be used as chemotherapies.

Answer 2

1. Antimetabolites
2. Alkylating agents
3. Intercalating agents
4. Spindle poisons eg:
   
   1. Vinca alkaloids: Vincristine
   2. Taxanes: Paclitaxel

Question 3

How do antimetabolites work as chemotherapies and give 2 examples.

Answer 3

Antimetabolites: prevent DNA synthesis

Eg:

1. 5-Fluorouracil
2. Methotrexate

Question 4

What is 5-Fluorouracil (antimetabolite) used as a chemotherapy for and how does it work?

Answer 4

5-Fluorouracil- used for GI cancers

Inhibits enzyme thymidylate synthase

Stops incorporation of pyrimidines into DNA molecule

Question 5

How do alkylating agents work as chemotherapy drugs?

Answer 5

Prevent DNA replication

Create bonds so strands can’t split for replication

Question 6

How do intercalating agents work as chemotherapy drugs? Give an example.

Answer 6

Prevent DNA synthesis

Cause strand breaks

Eg. Platinum compound: Cisplatin

Question 7

Give an example of a method we can use to monitor chemotherapy treatment.

Answer 7

• Tumour markers
• Imaging CT
• Creatinine clearance

Question 8

Give some of the side effects which can be caused by chemotherapy and explain why these are caused.

(chemo targets rapidly replicating cells)

Answer 8

Renal failure

Cells undergo apoptosis

release urate crystals- affect kidneys

DIC (Disseminated intravascular coagulopathy)

Vomiting

Alopecia

Skin toxicity

if cannula badly placed

if taking too many chemotherapy pills–> ulcerated pressure sores + hyperpigmentation

Mucositis

Mouth mucosa:

• Oral thrush
• Sore mouth - ulcers

GI tract mucosa:

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Question 9

Give 3 mechanisms by which drug resistance to chemotherapy can occur.

Answer 9

1. DNA repair mechanisms
   
   1. Intercalating agents- cause DNA breaks
      
      1. Body has DNA break repair mechanisms
2. Decreased entry
   
   1. Proteins on cancer cell membrane- decrease entry of drug
3. Inactivation of agents
   
   1. Proteins in cancer cell- bind to drug and prevent it having effect

Question 10

Give some examples of substances which can increase plasma concentrations of chemotherapies:

Answer 10

1. Antifungals
2. Grapefruit juice
3. St Johns Wort

Question 11

Give some examples of how chemotherapy can alter the way drugs are taken in and metabolised?

Answer 11