Toxicology of antimicrobial drugs P1

What are the learning outcomes for antimicrobial toxicology? (4 points)

1. Understand how common antimicrobials cause phototoxicity

2. Understand the difference between phototoxicity and photoallergy

3. Appreciate biochemical mechanisms driving phototoxicity

4. Outline patient risk factors pharmacists should be aware of

ow does UV light exposure cause damage? (4 points)

1. Damages DNA, proteins, lipids, and cells

2. Acute exposure leads to sunburn via inflammatory response

3. Chronic exposure can lead to skin cancer via DNA damage

4. DNA damage causes apoptosis; sufficient cell death causes skin peeling

Q: What is melanin-s role in sun exposure? (2 points)

1. UV light stimulates melanin production as a defence mechanism

2. Melanin darkens skin and provides limited protection from UV

What causes skin peeling and cancer from sun exposure? (2 points)

1. Apoptosis from DNA damage leads to peeling

2. Repeated damage and cell death increase cancer risk

How do reactive oxygen species (ROS) contribute to toxicity? (2 points)

1. ROS are key drivers of oxidative damage in cells

2. Excess ROS leads to oxidative stress and cell death

Q: How do tetracyclines cause phototoxicity? (1 point

. They amplify oxidative stress when exposed to UV light

What is redox cycling and its role in toxicity? (4 points)

1. Redox cyclers undergo repeated oxidation/reduction

2. This process generates superoxide (O2-)

3. Excess superoxide causes oxidative stress and apoptosis

4. Drugs with redox potential are more likely to cause phototoxicity

What is the role of quinone redox cycling in phototoxicity? (3 points)

1. Quinone drugs can be reduced to semi-quinone

2. Semi-quinone reoxidised back to quinone releases superoxide

3. Leads to ROS formation and cellular damage

Which tetracyclines have increasing phototoxicity? (3 points)

1. Minocycline

2. Doxycycline

3. Demeclocycline

: What are the risk factors for phototoxicity? (4 points)

1. Phototoxicity is more concerning than photoallergy due to wider prevalence

2. Fair skin, freckles, and sunbed use increase risk

3. Advice should be given to all patients, especially high-risk groups

4. Mechanism involves ROS that enhance sunburn severity

What is the summary of phototoxicity from antimicrobials? (4 points)

1. Phototoxicity linked to oxidative stress via ROS

2. Triggered by bioactivation under UV light

3. Tetracycline phototoxicity mechanism examined

4. Patient risk factors and counselling are essential