exam-2013-spring-2-answers

They would be increased 19 list four of 6 risk

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19. List FOUR (of 6) risk factors associated with adverse drug reactions (ADRs) (2 marks ). One half mark each for any four of the six listed Age (older patients as well as newborns) Gender Patients on multi-drug therapy Patients with a history of allergic disorders Patients who had previous adverse drug reactions Patients with some disease (typically renal or hepatic) 20. A tumour contains 10 16 cells. After one round of chemotherapy there are 10 12 cells left. How many cells will be left after the second round of therapy? How many cells will be left after a third round of therapy? ( 1 mark ) 10 8 after two rounds 10 4 after three rounds 21. Why are initial screening tests for possible carcinogens performed first in vitro rather than in vivo . Provide two reasons. ( 1 mark ) Cost and time . In vitro tests are far cheaper, allowing for more compounds to be screened, as well as a lot faster to conduct. 22. What is the mechanism of action of the anticancer alkaloids vincristine and vinblastine? (1 mark ) The vinca alkaloids vincristine and vinblastine bind to tubulin and thus inhibit spindle formation , resulting in metaphase arrest of cells undergoing mitosis.
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23. You are performing an Ames test on a new compound, testing it for its carcinogenic potential. You perform the following experiment. On your control plate (A) you culture just bacteria. On another plate B you culture bacteria in the presence of your compound. On a third plate C you culture bacteria plus rat liver homogenate. On a fourth plate D you culture bacteria plus your compound plus rat liver homogenate. Your results are as follows: plate A has 3 bacterial colonies, plate B has 3 colonies, plate C has 3 colonies and plate D has 40 colonies. Is this compound a possible carcinogen? Explain your experimental results one plate at a time (A-D). ( 2 marks ) Plate A: The 3 colonies describe the random mutagenesis of some bacteria , allowing them to make their own histidine and thus survive in the histidine-poor medium. Plate B: The same 3 colonies indicate that your compound does not have mutagenic properties , at least not in its present form. Plate C: Addition of rat enzymes to plate C is another control to ensure the enzymes on their own don’t produce a mutagen in the absence of your test compound - they don’t since you once again see only 3 colonies. Plate D: The 40 colonies seen in the presence of rat liver enzymes indicates that after the compound is metabolized by rat liver enzymes a metabolite is formed that does have mutagenic properties. Conclusion: Your compound is a possible carcinogen. 24. Briefly explain why activated charcoal can be useful in the treatment of morphine overdose. (1 mark ) Morphine, as a base, will become charged in acidic environments. If the non-ionized form leaves blood and enters the stomach it becomes ionized and has difficulty re-entering the bloodstream. Repeated dosing with activated charcoal can thus still be used in treating morphine overdose even if it is originally administered by injection. 25. After doing surgery for breast cancer on your patient you aren’t sure if you have removed the entire tumor. Because the cancer is estrogen-dependent you decide to treat her after surgery with tamoxifen to minimize the chance of cancer recurrence. This modality of cancer treatment is known as .... (0.5 marks ) Adjuvant chemotherapy
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