Pharmacology Quiz: Quinolones and Antibiotics

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Questions and Answers

What is the basis for classifying fluoroquinolones into 'generations'?

Their ability to inhibit DNA gyrase

Their antimicrobial targets (correct)

Their ability to penetrate porin channels

Their potency against gram-positive bacteria

What is the primary difference between second-generation and third-generation fluoroquinolones?

Activity against anaerobic organisms

Activity against gram-positive bacteria (correct)

Activity against intracellular infections

Potency against MRSA

What is the primary mechanism of action of fluoroquinolones?

Inhibition of bacterial protein synthesis

Inhibition of bacterial cell wall synthesis

Disruption of bacterial membrane integrity

Inhibition of DNA gyrase and topoisomerase IV (correct)

What is the name of the first quinolone?

Nalidixic acid Signup and view all the answers

What is a potential consequence of widespread fluoroquinolone use?

Increased susceptibility to Clostridium difficile infection Signup and view all the answers

Which generation of fluoroquinolones is active against anaerobic organisms?

Fourth generation Signup and view all the answers

What is the mechanism by which fluoroquinolones enter bacterial cells?

Through porin channels Signup and view all the answers

What is the primary difference between first-generation and later-generation fluoroquinolones?

Presence or absence of fluorination Signup and view all the answers

Which type of infections are typically treated with fluoroquinolones due to their broad range of coverage?

Bone, joint, and soft tissue infections Signup and view all the answers

What is the name of the bacterium that causes hemolytic uremic syndrome?

E. coli Signup and view all the answers

Which of the following fluoroquinolones has poor activity against Streptococcus pneumoniae?

Ofloxacin Signup and view all the answers

What is the name of the combination of trimethoprim and sulfamethoxazole?

Cotrimoxazole Signup and view all the answers

Which of the following is NOT a type of folate antagonist?

Ciprofloxacin Signup and view all the answers

Which of the following is an indicator of the broad spectrum of coverage of sulfonamides?

Their ability to cover both Gram-positive and Gram-negative bacteria Signup and view all the answers

What is the name of the antibiotic that is useful for treating atypical mycobacterial infections?

Ciprofloxacin Signup and view all the answers

Which of the following is NOT a characteristic of fluoroquinolones?

They are effective against anaerobes Signup and view all the answers

What is the combination of sulfamethoxazole with trimethoprim effective against?

Urinary tract infections Signup and view all the answers

What is the primary cause of urinary obstructions in patients taking sulfamethoxazole and sulfadiazine?

Crystallization in acid urine Signup and view all the answers

Which of the following is a rare toxicity of sulfonamides in the hematopoietic system?

All of the above Signup and view all the answers

What is the combination of pyrimethamine with sulfadiazine used to treat?

Toxoplasmosis Signup and view all the answers

What is the common toxicity of sulfonamides?

Nausea and anorexia Signup and view all the answers

Which of the following can prevent urinary obstructions caused by sulfamethoxazole and sulfadiazine?

Both A and B Signup and view all the answers

What is the condition associated with deficiency of glucose-6-phosphate dehydrogenase activity in RBC?

Acute hemolytic anemia Signup and view all the answers

What is the serious skin reaction associated with sulfonamide toxicity?

Both A and B Signup and view all the answers

What is the pH level at which methenamine decomposes to produce formaldehyde?

pH 5.5 or less Signup and view all the answers

Why is methenamine not effective in upper UTIs?

Because the urine pH is not acidic enough to produce formaldehyde Signup and view all the answers

What is the primary mechanism by which methenamine achieves antibacterial effects?

By producing formaldehyde, which is toxic to most bacteria Signup and view all the answers

Why is methenamine contraindicated in patients with hepatic insufficiency?

Because elevated levels of circulating ammonium ions would be toxic to the CNS Signup and view all the answers

What is the primary adverse effect of methenamine at higher doses?

Albuminuria, hematuria, and rashes Signup and view all the answers

Why is methenamine mandelate contraindicated in patients with renal insufficiency?

Because mandelic acid may precipitate Signup and view all the answers

What is the primary difference between methenamine and nitrofurantoin?

Methenamine is less commonly employed for treating UTIs, while nitrofurantoin is more commonly used Signup and view all the answers

What is the primary reason for the contraindication of methenamine in patients with indwelling catheters?

Because methenamine should not be used in patients with indwelling catheters Signup and view all the answers

Which of the following age groups should avoid fluoroquinolones?

Pregnant women and children under 18 years of age Signup and view all the answers

What is a potential cardiac effect of moxifloxacin and other fluoroquinolones?

Prolongation of the QT interval Signup and view all the answers

Which of the following medications may have its serum levels increased by ciprofloxacin?

All of the above Signup and view all the answers

What is a limitation of norfloxacin?

It is not effective in systemic infections Signup and view all the answers

What is a characteristic of ciprofloxacin?

It is effective against Pseudomonas aeruginosa Signup and view all the answers

What is a potential benefit of ciprofloxacin compared to other antibiotics?

It is less toxic than the aminoglycosides Signup and view all the answers

What is a characteristic of levofloxacin?

It is an isomer of ofloxacin Signup and view all the answers

What is a potential use of ciprofloxacin in third-world countries?

Treating typhoid fever Signup and view all the answers

Study Notes

Fluoroquinolones

First quinolone: Nalidixic acid, a byproduct of chloroquine synthesis
Current fluoroquinolones are fluorinated 4-quinolones
Fluoroquinolones are classified into four generations based on their antimicrobial targets
First generation: Nalidixic acid, narrow spectrum of susceptible organisms
Second generation: Ciprofloxacin and norfloxacin, active against aerobic gram-negative, atypical bacteria, and intracellular infections
Third generation: Levofloxacin, increased activity against gram-positive bacteria
Fourth generation: Moxifloxacin, active against anaerobic and gram-positive organisms

Mechanism of Action

Fluoroquinolones enter bacteria through porin channels
Inhibit DNA gyrase (bacterial topoisomerase II) and bacterial topoisomerase IV
Prevention of DNA strand breakage
Articular cartilage erosion (arthropathy) observed in immature animals exposed to fluoroquinolones

Adverse Reactions and DDR

Moxifloxacin and other fluoroquinolones may prolong the QT interval, contraindicated in patients predisposed to arrhythmias
Ciprofloxacin may increase serum levels of theophylline, warfarin, caffeine, and cyclosporine

Pharmacology of Select Quinolones

Norfloxacin: effective against gram-negative and gram-positive organisms, used for treating UTIs, prostatitis, and traveler's diarrhea
Ciprofloxacin: effective against gram-negative bacilli, used for treating infections caused by Enterobacteriaceae, Pseudomonas aeruginosa, and in respiratory tract infections
Levofloxacin: effective against gram-positive bacteria, used for treating respiratory tract infections, bone and joint infections, and soft tissue infections

Folate Antagonists

Inhibitors of folate synthesis: sulfonamides, sulfasalazine, and silver sulfadiazine
Inhibitors of folate reduction: pyrimethamine, trimethoprim, and cotrimoxazole
Combination of inhibitors: sulfamethoxazole plus trimethoprim

Sulfonamides

Analogues of para-aminobenzoic acid
Broad spectrum of coverage: both gram-positive and gram-negative
Mechanism of action: inhibits dihydropteroate synthase, preventing folic acid synthesis

Therapeutic Uses

Urinary tract infections
Nocardiosis
Toxoplasmosis

Toxicity/Contraindications

Urinary tract: crystalluria, urinary obstructions
Hematopoietic system: acute hemolytic anemia, agranulocytosis, and aplastic anemia
Hypersensitivity reactions: skin and mucous membrane manifestations, Stevens-Johnson syndrome, and toxic epidermal necrolysis
Miscellaneous reactions: nausea, anorexia, and vomiting

Methenamine

Mechanism of action: decomposes at acidic pH in the urine, producing formaldehyde, which is toxic to most bacteria
Antibacterial spectrum: primarily used for chronic suppressive therapy, effective against lower UTIs
Pharmacokinetics: administered orally, distributed throughout the body fluids, eliminated in the urine
Adverse effects: gastrointestinal distress, albuminuria, hematuria, and rashes

Nitrofurantoin

Narrow antimicrobial spectrum and toxicity
Less commonly employed for treating UTIs

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Description

This quiz covers the basics of quinolones, folic acid antagonists, and urinary tract antiseptics, including their generations and types.