3.2 - Inhibition of Metabolic Pathways (Midterm 2)

Question 1

Why is folate important to bacteria?

Answer 1

Folate is necessary for the synthesis of nucleotides and some amino acids. Most bacteria are unable to absorb folate from their environment and must synthesize is from the precursor molecule para-aminobenzoic acid (PABA)

Question 2

What is PABA?

Answer 2

Para-aminobenzoic acid
–> Combined with pteridine to form folate

Question 3

What do sulfonamides, such as sulfamethoxazole, do? What class of drugs are they

Answer 3

Folate Antagonist
–> The structure of sulfonamides resembles the precursor or PABA
–> Competition between the drug and PABA prevents the bacteria from producing folate

Question 4

What does trimethoprim do? What class of drug is it?

Answer 4

Folate Antagonists
–> Trimethoprim inhibits conversion of folate to activated folate

Question 5

Why is trimethoprim not dangerous for humans?

Answer 5

Because it acts selectively on bacteria
–> but it is not 100% selective, and so we will not prescribe to individuals planning to be pregnant.

Question 6

Sulfamethoxazole and trimethoprim are often used in combination, what is this combination called?

Answer 6

co-trimoxazole

Question 7

What are folate antagonists used to treat?

Answer 7

–> UTIs
–> Skin abscess

Question 8

What are some adverse effects of folate antagonists?

Answer 8

–> N&V, diarrhea
Other than…
–> Allergies
–> Crystalluria (so drink plenty of fluid)
–> Watch folate levels (especially when pregnant or planning to be)

Question 9

Most sulfonamides are well absorbed PO, except for…

Answer 9

sulfasalazine, that has a bioavailability of 15%.
–> Used to treat inflammatory bowel disease and other inflammatory conditions (bc it breaks down into an anti-inflammatory compound)

Question 10

What is an adverse effect specific to trimethoprim?

Answer 10

Risk for hyperkalemia
–> Deadly arrythmias

Question 11

What is Stevens-Johnson Syndrome/ Toxic Epidermal Necrolysis?

Answer 11

A rash that develops of various levels of cutaneous and extra cutaneous (GI, Resp, renal) and mucous membrane (mouth, eyes, genitals) that leads to blistering and peeling with associated bleeding.
–> Might include secondary infections (cellulitis) and sepsis

Question 12

How long does it take for SJS or TEN to develop? What drugs is it associated with?

Answer 12

Associated with sulfonamides, anti-seizure meds, allopurinol (gout), and some NSAIDS (oxicams)
–> Within 8 weeks following exposure, usually 4-30 days.

Question 13

Where are lesions associated with SJS or TEN most common?

Answer 13

Around the head, neck, and trunk.

Question 14

What symptoms present initially when a patient has SJS?

Answer 14

Flu-like symptoms
–> Aching joints and muscles, and worsening fever