Antibiotics II Flashcards by Alston Calderon

Antifolate drugs are bacteriostatic but become bacteriocidal when?

Sulfonamethoxazole (SMX) + Trimethoprim (TMP)

combined = (Bactrim) = Synergism

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What does Sulfonamethoxazole inhibit?

Inhibits dihydropteroate synthase (DS)
Mimics PABA (Para-aminobenzoic acid)
Folate Competitive inhibitor
Prevents Dihydrofolic Acid formation

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What does Trimethoprim inhibit?

Inhibits Dihydrofolate reductase (DHFR)

- Preventing Tetahydrfolic Acid formation

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Bactrim uses synergistic effects which means?

In combination

Additive effects = Greater effect

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True or False

Trimethoprim (TMP) is a folate analog that binds to the bacterial DHFR 1000x more effectively than human DHFR ?

True

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What does Sulfamethoxazole mimic ?

PABA (Para AminoBenzoic Acid)
Absolute selective toxic
(Only in bacteria)
Humans depend on dietary folate

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What does Trimethoprim mimic?

Dihydrofolate reductase (DHFR)

- Relative selective toxic
Both in Humans and Bacteria

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What does SMX + TMP treat?

Topical MRSA

- AntiMycoplasma activity

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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

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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)

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Stevens Johnson Syndrome Delayed IV reaction is caused by what medications?

Sulfa drugs
Penicillins
Mouth and Mucus membranes always affected

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What does Ciprofloxain do ? MOA

DNA gyrase inhibitor
Blocks transcription
Blocks DNA replication

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DNA gyrase / Fluoroquinoloes are synthetic analogs of what?

Nalidixic Acid

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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)

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T of F

Divalent/trivalent cations and acids impair Ciprofloxacin absorption?

True

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What does Ciprofloxacin treat?

DOC for Anthrax
Chlamydia
Some antifungal activity

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T of F

Ciprofloxacin has a post antibiotic effect?

True

- Kills bacteria after treatment stops

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Nitrofurantoin (Macrobid) treats what type of infection?

Lower urinary tract infections
Bladder and Urethra ONLY
Urinary tract antiseptic

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Nitrofurantoin (Macrobid) is safe in pregnancy?

T or F

True

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Nitrofurantoin (Macrobid) is contraindicated in pt’s with?

Renal failure

- Drug can’t be cleared and builds up in body

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What are the 5 questions to ask before prescribing an antibiotic?

1) Patient (Host)
2) Syndrome
3) Pathogen
4) Drugs
5) Cost

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Two major mycobacterial infections in humans? that are difficult to treat?

Tuberculosis

- Leprosy

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What are the two strategies in fight mycobacterial infections?

Multi drug therapy

- Long treatment course (6 to 12 months)

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Two factors that my Mycobacteria hard to treat?

Intrinsic Factors

- Environmental factors

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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

Active TB disease treatment?

- Get RIPE - Rifampin - Isoniazid - Pyrazinamide - Ethambutol For 2 months Then - Rifampin - Isoniazid For 6 months

Latent TB Disease treatment?

- Isoniazid (9 months)

T or F Latent TB disease is always treated?

- False Only Tx when - High risk of active TB - HIV - Immuno Comp - CXR with TB changes - IV drug users - High risk settings (Correction facilities & Nursing homes)

What does multi drug therapy provide in mycobacteria diseases?

- Suppresses development of drug resistance | - Attacks fast and Attacks hard

MOA of Rifampin?

- Inhibitor of bacterial RNA polymerase from binding DNA - Jams up active site - Prevents elongation of RNA

T or F Rifampin can penetrate the CNS but only when the Meninges are inflamed?

- True

T or F Pt with liver disease can take Rifampin?

- False | - Extensive enterohepatic recirculation = hepatotoxicity

T or F Bright orange bodily fluids is a good sign that Rifampin is working in a pt?

- True | - Orange Tears, Sweat, Urine

What does Extensive enterohepatic recirculation mean?

- Drug secreted inot duodenum via the bile after liver metabolism - Reabsorbed downstream in the ilium - Take back to the liver - Taken back to the liver many times - Prolonged lifetime of the drug in the body

Isoniazid (INH) MOA ?

- Vitamin B6 (pyridoxine) analog - Prevents the synthesis of Mycolic acid - By Inhibiting InhA reductase enzyme

Isoniazid inhibits what in the mycobacteria?

- Inhibits the growing fatty acid chain necessary for the completion of Mycolic acid Syn

What dose Isoniazid (INH) + NAD (Suicide Complex) prevent in Mycobactria?

- Prevents key reduction step necessary for Mycolic acid syn - Inhibits INhA that prevents the saturation (Reduction) of Acyl chains - No Acyl chains = No Mycolic acid syn

What are the two adverse side effects of INH (Isoniazid) ?

- INH Induced hepatitis | - INH Induced Neuropathy

What happens when a pt develops INH Induced hepatitis ?

- Stop taking Isoniazid ASAP

What happens when a pt develops INH Induced Neuropathy?

- Treat them with B6 Pyridoxine to reverse the symptoms

B6 Deficiency classically presents with?

- Seborrhoeic Dermatitis - Craddle cap in Newborns - Sore tongue - Neurological effects - Sideroblastic Anemia (Heme syn impaired)

What is Pyridoxine ?

- Dietary form of B6 - Serves as a cofactor for enzyme reactions - AA metabolism - Glucose metabolism - Lipid metabolism

What medication is an analog of Vitamin B3 ?

- Pyrazinamide (PZA)

MOA of Pyrazinamide (PZA)?

- Enters mycobacteria via passive diffusion - activated by pncA enzyme - Accumulates in non-dividing cells and ultimately damages cell membranes to cause death

How does PZA enter the Mycobacteria?

- Via passive diffusion

What converts Pyrazinamide (PZA) | prodrug into its active metabolite Pyrazinoic Acid (POA) ?

- Mycobacteria Pyrazinamdase (pncA)

T or F The Mycobacteria pumps POA out of the intracellular into the extracellular but then POA gets protonated and becomes uncharged and diffuses back into the cell.

- True - Pumping only occurs in active TB - Drug accumulates when the TB metabolism shuts down - Driving Toxic acidification of the cytosol

What is the major resistance of Pyrazinamide (PZA) ?

- Mutations in the pncA Enzyme

T or F PZA is highly effective against intracellular pathogens?

- True - Sterilizing agent - Diffuses through cell membranes @ Physiological ph - Taken up by Macrophages

T or F PZA only becomes POA - Protonated in the Low pH of the Lysosome but NOT neutral pH?

- True | - Prodrug into active Drug metabolite

Major side effect of Pyrazinamide (PZA) ?

- Hyperuricemia | - Gouty arthritis due to decreased renal excretion or urate

What medication blocks mycobacteria cell wall syn by Inhibiting Arabinosyltransferases?

- Ethambutol (Myambutol)

What does arabinosyltransferases do in the mycobactria?

- Catalyzes the attachment of Arabinose to Galactose to create Arabinogalactan

Why is Arabinogalactan important in mycobacteria?

- Needed for the hub attachment of Mycolic Acids

What layer does Ethambutol act on?

- Acts on the Arabinogalactan layer | - Acts on the layer upstream from the Isoniazid target, above the peptidoglycan layer

How is Ethambutol excreted?

- Renal 50% - Liver 30% - Feces 20%

Adverse effects of Ethambutol?

- Retrobulbar (optic) neuritis - Damages optic nerve (Myelin Sheath) - Causes red and green color blindness

Contraindication of Ethambutol ?

- Kids too young for an eye test

Only Aminoglycoside approved for treatment of TB?

- Streptomycin

MOA of Streptomycin?

- Multi modal activity all through ribosome 30S 1) Blocks ribosome initiation complex 2) Promotes translation errors 3) Blocks ribosomal translocation

When is Ethambutol used to treat TB?

- When Antimycobacterial agents are resistant - Resistance mutations of Ribisomal subunits rpsl or rrs - Or when injectable drug is needed

True of False Ethambutol is very pain when given IM?

- True

What are the two major toxicity's associated with Ethambutol?

- Ototoxicity Hearing lose - Nephrotoxicity Kidney damage

T or F Ethambutol is contraindicated in pregnancy?

- True | - Risk of deafness in infant

What does Isoniazid (INH) treat?

- Mycobacterial infections | - Nosocomial CAP (Pneumonia)

Antibiotics II Flashcards

(66 cards)