Antibiotics II Flashcards
Antifolate drugs are bacteriostatic but become bacteriocidal when?
Sulfonamethoxazole (SMX) + Trimethoprim (TMP)
combined = (Bactrim) = Synergism
What does Sulfonamethoxazole inhibit?
- Inhibits dihydropteroate synthase (DS)
- Mimics PABA (Para-aminobenzoic acid)
Folate Competitive inhibitor - Prevents Dihydrofolic Acid formation
What does Trimethoprim inhibit?
- Inhibits Dihydrofolate reductase (DHFR)
- Preventing Tetahydrfolic Acid formation
Bactrim uses synergistic effects which means?
- In combination
Additive effects = Greater effect
True or False
Trimethoprim (TMP) is a folate analog that binds to the bacterial DHFR 1000x more effectively than human DHFR ?
- True
What does Sulfamethoxazole mimic ?
- PABA (Para AminoBenzoic Acid)
- Absolute selective toxic
(Only in bacteria) - Humans depend on dietary folate
What does Trimethoprim mimic?
- Dihydrofolate reductase (DHFR)
- Relative selective toxic
Both in Humans and Bacteria
What does SMX + TMP treat?
- Topical MRSA
- AntiMycoplasma activity
Trimethoprim can block sodium channels in the kidney collecting tube leading to hyperkalemia and thus should be avoided in patients taking?
- Potassium-elevating agents
- ACE inhibitors
- Angiotensin receptor blockers
- Spironolactone
What are the three major side effects of bactrim?
- Hemolysis in G6PD deficiency
- Hypersensitivity to Sulfa (Do not prescribe to sulfa allergic pt’s)
- Stevens Johnson Syndrome Delayed IV reaction (Must Monitor)
Stevens Johnson Syndrome Delayed IV reaction is caused by what medications?
- Sulfa drugs
- Penicillins
- Mouth and Mucus membranes always affected
What does Ciprofloxain do ? MOA
- DNA gyrase inhibitor
- Blocks transcription
- Blocks DNA replication
DNA gyrase / Fluoroquinoloes are synthetic analogs of what?
- Nalidixic Acid
Ciprofloxain is NOT used first line, why?
- Because of all the adverse effects
- GI irritation
- Photosensitivity
- Risk of tendon rupture (x100)
- Aortic aneurysm
- Teratogen (Not in Prego)
T of F
Divalent/trivalent cations and acids impair Ciprofloxacin absorption?
- True
What does Ciprofloxacin treat?
- DOC for Anthrax
- Chlamydia
- Some antifungal activity
T of F
Ciprofloxacin has a post antibiotic effect?
- True
- Kills bacteria after treatment stops
Nitrofurantoin (Macrobid) treats what type of infection?
- Lower urinary tract infections
- Bladder and Urethra ONLY
- Urinary tract antiseptic
Nitrofurantoin (Macrobid) is safe in pregnancy?
T or F
- True
Nitrofurantoin (Macrobid) is contraindicated in pt’s with?
- Renal failure
- Drug can’t be cleared and builds up in body
What are the 5 questions to ask before prescribing an antibiotic?
1) Patient (Host)
2) Syndrome
3) Pathogen
4) Drugs
5) Cost
Two major mycobacterial infections in humans? that are difficult to treat?
- Tuberculosis
- Leprosy
What are the two strategies in fight mycobacterial infections?
- Multi drug therapy
- Long treatment course (6 to 12 months)
Two factors that my Mycobacteria hard to treat?
- Intrinsic Factors
- Environmental factors
What are the Mycobacteria environmental factors?
- Goes Dormant (Non-dividing)
- Cell Division (Long dividing time 1200mins)
- Physical barriers (Granuloma formation protects microb)
Intrinsic factors of Mycobacteria?
- Mycolic Acid (Sugar / Waxy fatty acid coating)
- Peptidoglycan (Unusual L - D linkage)
Insensitive to Vancomycin