Sulfonamides Cotrimoxazole And Quinolones Question And Answers

Sulfonamides Cotrimoxazole And Quinolones Important Notes

1. Sulfonamides

• hey have a structural resemblance to PABA
• They compete with PABA for incorporation into folic acid
• They act by inhibiting the enzyme folic acid synthetase which is essential for bacterial growth

Sulfonamides, Cotrimoxazole And Quinolones Uses:

• Nocardial infection
• Leprosy
• Toxoplasmosis
• Ulcerative colitis

Read And Learn More: Pharmacology Question and Answers

Sulfonamides, Cotrimoxazole And Quinolones Adverse Effects:

• Crystalluria
• Haematuria, anuria
• Kernicterus in newborns
• Fixed drug eruption by sulfadiazine
• Steven Johnson syndrome

2. Cotrimoxazole

• It is a combination of Sulfamethoxazole and trimethoprim
• It has a synergistic bacteriocidal effect
• Dose: trimethoprim 80 mg + Sulfamethoxazole 400 mg
• Uses:
• Uncomplicated UTI
  • Respiratory infections
  • Gonorrhoea
  • Otitis media

3. Fluoroquinolones

• Ciprofloxacin, ofloxacin, norfloxacin are fluoroquinolones
• They are contraindicated in children as they cause Arthropathy and damage to developing cartilage
• They are effective against facultative anaerobes
• They inhibit the bacterial enzyme DNA gyrase

Sulfonamides Cotrimoxazole And Quinolones Long Essays

Question 1. Classify sulphonamides. Discuss the mechanism of action, adverse effects, And uses of cotrimoxazole.
Answer:

Sulfonamides Classification:

1. Short-acting – sulfadiazine.
2. Intermediate-acting – sulfamethoxazole.
3. Long-acting – sulfadoxine.
4. Special purpose sulphonamide – Sulfasalazine, Silver sulfadiazine.

Cotrimoxazole:

• A combination of trimethoprim And sulfamethoxazole is called cotrimoxazole.

Cotrimoxazole Mechanism of action:

• Cotrimoxazole causes sequential blockage of folic acid synthesis.

Cotrimoxazole Uses:

• Respiratory tract infections – tonsillitis, pharyngitis, sinusitis, bronchitis.
• Urinary tract infections – acute And chronic.
• Diarrhea And dysentery.
• Typhoid, chancroid, granuloma inguinale.
• Pneumocystis jiroveci pneumonia in AIDS patients.
• Orodental infections.

Cotrimoxazole Adverse effects:

• Nausea, vomiting, headache, stomatitis, rashes.
• Precipitate megaloblastic anemia.
• Blood disorders – anemia, granulocytopenia.
• Uremia in patients with renal diseases.
• Neonatal hemolysis And methemoglobinemia. When administered to pregnant women.

Question 2. Enumerate fluoroquinolones. Mention their antimicrobial spectrum, uses, And adverse effects.
Answer:

Fluoroquinolones:

• These are quinolones antimicrobials having one or more fluorine substitutes.

Fluoroquinolones Classification:

Antimicrobial spectrum:

1. Gram-positive organisms like

• Staphylococci, chlamydiae, mycoplasma, And mycobacterium.

2. Gram-negative organisms like

• Gonococci, meningococci, E-coli, salmonella, shigella, H. Pylori.

3. Some anaerobic organisms.

Antimicrobial spectrum Uses:

Antimicrobial spectrum Adverse effects:

• Nausea, vomiting, abdominal discomfort, diarrhea, rashes.
• Tendinitis.
• Damage to growing cartilage
• Headache, dizziness.
• Precipitate seizures in epileptic patients.

Question 3. Classify drugs used in the treatment of infections caused by gram-negative organisms. Mention the mechanism of action of fluoroquinolones.
Answer:

Fluoroquinolones Classification:

• Drugs used in the treatment of infections caused by gram-negative organisms are:

1. B-lactam antibiotics

• Penicillin, cephalosporin.

2. Tetracyclines – Doxycycline.

3. Aminoglycosides – Gentamicin, streptomycin.

4. Macrolides – erythromycin, Azithromycin.

5. Nitroimidazoles – Metronidazole.

6. Quinolones – Norfloxacin, Ciprofloxacin.

Fluorozuinolones (FQ):

Fluoroquinolones Mechanism of action:

• DNA gyrase enzyme is required for DNA replication.
• This enzyme has subunits A And B

2. At low doses.

Sulfonamides Cotrimoxazole And Quinolones Short Essays

Question 1. Write important side effects of sulphonamides.
Answer:

Sulphonamides:

• Sulfonamides were the first effective antibacterial agents to be used systemically in man.
• It contains a sulphonamide group.

Sulphonamides Adverse Effects:

1. GIT effects.

• Nausea, vomiting, anorexia, abdominal pain.

2. Renal effects.

• Renal irritation, hematuria, albuminuria. Crystalluria.
• It occurs due to the precipitation of the drug in acidic urine.
• Avoided by:
  • Intake of plenty of fluids.
  • Alkalinizing the urine with sodium bicarbonate.

3. Hypersensitivity reactions.

• Fever, rashes, anaphylaxis, urticaria, and photosensitivity – occur rarely.
• Stevens-Johnson syndrome And exfoliative dermatitis – occurs commonly.

4. Contact sensitization on topical application.

5. Hemolysis.

• Occurs in patients with G6PD deficiency.

6. Kernicterus.

• Occurs in newborns.
• Sulfonamides displace bilirubin from binding sites.
• This then crosses BBB And causes kernicterus.

Question 2. Sulfonamides are not very effective in the presence of pus. Explain.
Answer:

Some bacteria synthesize their own folic acid which consists of p-amino benzoic acid (PABA).

• Sulfonamide is structurally similar to PABA.
• Thus it competitively inhibits the formation of folic acid.
• Pus contains.
  • Purines And thymidine – which decreases the bacterial requirement for folic acid.
  • Antagonizes sulphonamide action.
  • It is rich in PABA.
  • Thus, sulphonamides are not very effective in the presence of pus.

Question 3. Explain the mechanism of action of co-trimoxazole.
Answer:

The combination of trimethoprim And sulfamethoxazole is cotrimoxazole.

Co-trimoxazole Mechanism of action:

• Individual drugs are bacteriostatic.
• While combination causes bacteriocidal action.
• Through their combined effect sequential blockade of folic acid synthesis occurs.

Sulfonamides Cotrimoxazole And Quinolones Short Question And Answers

Question 1. Long-acting sulphonamides.
Answer:

Long-acting sulphonamides are sulfadoxine And sul- famethopyrazine.

• The action lasts for more than 1 week because of
  • High plasma protein binding.
  • Slow renal excretion.
• They attain low plasma concentration so they are not suitable for the treatment of acute pyogenic infectious.

Long-acting sulphonamide Uses:

• In malaria in combination with pyrimethamine.
• Pneumocystis jiroveci pneumonia in AIDS patients.
• Toxoplasmosis.

Long-acting sulphonamide Adverse Reaction:

• Serious cutaneous reactions.

Question 2. The rationale of a combination of sulfamethoxazole with trimethoprim.
Answer:

Sulfamethoxazole And trimethoprim are individually bacteriostatic

• Sulfamethoxazole inhibits the conversion of PABA to dishy-dro folic acid while trimethoprim inhibits and prevents the reduction of dihydrofolate to tetrahydrofolate.
• Thus, combining sulfamethoxazole And trimethoprim causes sequential blockade of folic acid synthesis And has bacteriocidal action.

Question 3. Ciprofloxacin.
Answer:

Ciprofloxacin is first generation fluroquinolones.

• It has a wide spectrum of activity
• Has rapid bacteriocidal activity And high potency.
• It is less active at acidic pH
• It is rapidly absorbed orally.

Ciprofloxacin Uses:

• Systemic infections.
• Typhoid
• Gonorrhoea.
• Gastroenteritis.

Ciprofloxacin Adverse Reactions:

• GIT effects – nausea, vomiting, anorexia.
• CNS effects – Dizziness, headache, anxiety, insomnia, tremors.
• Hypersensitivity reactions – rash, pruritis, photosensitivity, urticaria.
• Tendonitis.

Question 4. Ciprofloxacin is contraindicated in children. Why?
Answer:

Ciprofloxacin is fluoroquinolone.

• It causes damage to the growing cartilage of weight-bearing joints.
• This results in arthropathy.
• Thus, it is contraindicated in children.