Exam (elaborations)
PHCY220 Antimicrobials Exam Questions And Accurate Answers
- Course
- Institution
PHCY220 Antimicrobials Exam Questions And Accurate Answers ...
[Show more]
Content preview
PHCY220 Antimicrobials ExamQuestions And Accurate
Answers
What is a type A unwanted effect of antibiotics? - Answer Dose-dependent, predictable
unwanted effect based on pharmacology
Most common are:
Gastrointestinal toxicity; effect bacteria of the microbiota/flora causing changes of the
microbiota resulting in nausea, pain, vomiting and diarrhoea.
Nephrotoxicity: with antibiotic metabolised/excreted by liver
What is a type B unwanted effect of antibiotics? - Answer Idiosyncratic reaction; cannot
be predicted by pharmacology
Rare; do not occur in most patients at any dose
Can effect any organ system, but usually:
Skin e.g. rashes, eruption, itching
Liver (hepatotoxicity)
Blood cells (haematological toxicity e.g. anaemia)
Folate synthesis - Answer Folate is required for DNA/RNA synthesis (bacterial and
mammalian cells)
In humans folate is from the diet
Bacteria make folate from scratch from PABA the precursor and involved the enzyme
dihydrofolate reductase
What are antibiotics that interfere with the synthesis or action of folate? - Answer
Sulphonamides e.g. sulfasalazine, sulfadiazine and sulphamethoxazole
Trimethoprim
What are examples of sulphonamides - Answer Sulfasalazine, sulfadiazine and
sulphamethoxazole
Pharmacokinetics of sulphonamides - Answer Well absorbed orally
,Metabolised in liver (acetylation), genetic polymorphisms
Products have no antibacterial action (but risk of toxicity)
Excreted by kidney (half life = 12 hours)
(Taken orally, metabolised by liver and excreted by the kidney)
Mechanism of action of sulphonamides - Answer Structurally similar to PABA (the
precursor of folate synthesis) and completes for key enzyme in folate synthesis
inhibiting folate synthesis
Bacteriostatic
Both gram negative and gram positive
Unwanted effects of sulphonamides - Answer Nausea, vomiting and headache
Serious adverse effects (stop therapy):
hepatitis, bone marrow suppression, hypersensitivity reaction (e.g. rash, fever,
anaphylaxis)
Stevens-Johnson Syndrome (toxic epidermal necrolysis) - particular type of allergic
reaction
Clinical use of sulphonamides - Answer Limited by resistance
Inflammatory bowel disease (sulfasalazine)
For infected burns (topical: silver sulfadiazine)
Mechanism of action of trimethoprim - Answer inhibits bacterial dihydrofolate reductase
an enzyme involved in folate synthesis
Synergistically prevent folate synthesis
Bacteriostatic; gram negative and gram positive
Synergism with sulfamethoxazole (co-trimoxazole)
Pharmacokinetics of trimethoprim - Answer Given orally
Fully absorbed in GI tract
High concentration in lung, kidney, cerebral spinal fluid
Weak base, eliminated by kidney (half-life 24 hours)
Unwanted effects of trimethoprim - Answer Folate deficiency --> megaloblastic anaemia
(long term use)
,(Humans have the same dihydrofolate reductase enzyme trimethoprim has a higher
affintiy to bacteria but can have an effect if long term use)
Nausea, vomiting
Blood disorders
Rashes
Clinical use of trimethoprim - Answer Alone: urinary tract infections
As co-trimoxazole:
- toxoplasmosis (protozoal)
- noncardiosis (bacterial)
What cell functions are Class III reaction targets of antibiotics - Answer Assembly of
macromolecules
- DNA, RNA (quinolones)
- Proteins (tetracyclines, aminoglycosides, macrolides)
- peptioglycans
What cell functions are Class II reaction targets of antibiotics - Answer Unique pathways
or differing sensitivities
- synthesis of essential growth factors
- e.g. folate synthesis (sulphonamides, trimethoprim)
What cell functions are Class I reaction targets of antibiotics - Answer Host and
organism similar
Bacteria can use alternative energy sources
What is topoisomerase - Answer Best enzyme target in bacterial DNA replication.
DNA unwound ahead of replication fork "break, rotate, reseal"
Removes excess DNA supercoils
Separates intertwined progeny DNA
Two main types:
- DNA gyrase (topoisomerase II) (gram negative)
- Topoisomerase IV (gram positive)
What are examples of quinolones (fluoroquinolones) - Answer Ciprofloxacin,
, moxifloxacin, ofloxacin
Mechanism of action of quinolones (fluoroquinolones) - Answer Inhibits DNA gyrase
(gram negative) and topoisomerase IV (gram positive)
Bactericidal (broad spectrum)
Pharmacokinetics of quinolones (fluoroquinolones) - Answer Well absorbed orally
Accumulate in kidney, prostate, lung
Don't cross BBB (except ofloxacin)
Metabolised by CYP1A2 therefore inhibit other drugs and lead to interactions
Excreted predominately by the kidney (dosage adjusted in renal failure)
Unwanted effects of quinolones (fluoroquinolones) - Answer Infrequent, usually mild,
reversible
Most frequent:
- GI (ciprofloxcin, c. difficle colitis)
- Skin rashes
Tendon rupture (elderly + corticosteriods)
Arthropathy (young pateints)
CNS symptoms: headache, dizziness
Clinical use of quinolones (fluoroquinolones) - Answer Rarely first line, reserved for
serious infection
Travellers diarrhoea (moderate/severe)
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller Zayla. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $11.99. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
75323 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now