Pharmacology-Antibiotics Classifications

Questions and Answers

Describe the mechanism for Class 1 antibiotics.

Antibiotics which block specific metabolic steps that are essential to the microorganism (Trimethoprim, Sulfonamides). Agents that affect the nucleic acid metabolism (rifampin and quinolones).

Describe the mechanism for Class 2 antibiotics.

Agents that inhibit synthesis of microbial cell walls. Includes Penicillins and Cephalosporins which are structurally similar (Beta-lactams).

Describe the mechanism for Class 3 antibiotics.

Bacteriocidal agents that bind to the 30 S ribosomal subunit and alter protein synthesis, which eventually leads to cell death. Includes aminoglycosides.

Describe the mechanism for Class 4 antibiotics.

Bacteriostatic agents that affect the 30S or 50S ribosomal subunit function to cause a reversible inhibition of protein synthesis. Includes Chloramphenicol, Tetracyclines, Macrolides, and Clindamycin. Signup and view all the answers

Give examples of Class 1 antibiotics.

Trimethoprim, Sulfonamides, Rifampin, and Quinolones. Signup and view all the answers

Give examples of Class 2 antibiotics.

Penicillins and Cephalosporins. Signup and view all the answers

Give examples of Class 3 antibiotics.

Aminoglycosides. Signup and view all the answers

Give examples of Class 4 antibiotics.

Chloramphenicol, Tetracyclines, Macrolides, and Clindamycin. Signup and view all the answers

Give examples of Class 5 antibiotics.

Isoniazid, Rifampin, Ethambutol, Streptomycin, Pyrazinamide, Dapsone, Clofazimine. Signup and view all the answers

Describe the purpose of Class 5 antibiotics.

Antibiotics for mycobacterial disease such as tuberculosis, Mycobacterium avium, and leprosy. Signup and view all the answers

What is the structure and function of Sulfonamides?

Bacteriostatic in function and in structure they are similar to PABA (p-aminobenzoic acid). Signup and view all the answers

What is the inhibitory mechanism of Sulfonamides?

Susceptible bacteria need PABA for an essential step in the formation of purines and nucleic acid. Since sulfonamides are structural analogs of PABA, they competitively inhibit dihydropteroate synthesis. Signup and view all the answers

What works synergistically with Sulfonamides?

Trimethoprim. Signup and view all the answers

What range of antimicrobial activity do Sulfonamides possess?

Wide range of activity against gram-positive and gram-negative bacteria - Streptococcus pneumoniae, S. pyogenes, N. actinomyces. Signup and view all the answers

What antimicrobial(s) is/are used in Nocardiosis (Nocardia spp.)?

Sulfonamides are very effective. Signup and view all the answers

What antimicrobial(s) are/is used in Toxoplasmosis?

Combination of pyrimethamine and sulfadiazine. Signup and view all the answers

What is co-trimoxazole and what is it commonly used to treat?

Sulfamethoxazole in combination with trimethoprim is used for urinary tract infections, GI infections, prophylaxis in neutropenic patients. Signup and view all the answers

What are some of the adverse reactions associated with Sulfonamides?

Disturbances in the urinary tract, acute hemolytic anemia, granulocytosis, aplastic anemia, sulfa allergies, hyporexia, nausea, and vomiting. Signup and view all the answers

What specific drug interactions are associated with Sulfonamides?

Oral anticoagulants, sulfonylurea, hypoglycemic drugs, and hydantoin anticonvulsants. Signup and view all the answers

What is the structure and function of fluoroquinolones?

They are DNA gyrase inhibitors. Synthetic fluorinated analogs of nalidixic acid have broad antimicrobial activity with very few side effects. Signup and view all the answers

Describe the mechanism of action of fluoroquinolones.

Quinolones block bacterial DNA synthesis by inhibiting topoisomerase II (gyrase - primary target) and inhibiting topoisomerase IV (secondary target). Signup and view all the answers

What is the significance of inhibition of gyrase?

It prevents the relaxation of positively supercoiled DNA that is required for normal transcription and replication. Signup and view all the answers

What is the significance of topoisomerase IV inhibition?

It interferes with separation of replicated chromosomal DNA into respective daughter cells during cell division. Signup and view all the answers

Describe and list the newer fluoroquinolones and their bacterial spectrum.

Ciprofloxacin, Enoxacin, Lomefloxacin, Levofloxacin, Ofloxacin, and Pefloxacin. All possess good broad spectrum activity. Signup and view all the answers

Study Notes

Class 1 Antibiotics

Block specific metabolic steps essential to microorganisms.
Include Trimethoprim, Sulfonamides, Rifampin, and Quinolones.
Affect nucleic acid metabolism.

Class 2 Antibiotics

Inhibit synthesis of microbial cell walls.
Include Penicillins and Cephalosporins (structurally similar Beta-lactams).

Class 3 Antibiotics

Bactericidal agents targeting the 30S ribosomal subunit.
Alter protein synthesis leading to cell death.
Include Aminoglycosides.

Class 4 Antibiotics

Bacteriostatic agents affecting the 30S or 50S ribosomal subunit.
Cause reversible inhibition of protein synthesis.
Include Chloramphenicol, Tetracyclines, Macrolides, and Clindamycin.

Class 5 Antibiotics

Target Mycobacterial diseases such as tuberculosis and leprosy.
Include Isoniazid, Rifampin, Ethambutol, Streptomycin, Pyrazinamide, Dapsone, and Clofazimine.

Sulfonamides

Bacteriostatic and structurally similar to PABA (p-aminobenzoic acid).
Inhibit dihydropteroate synthesis, blocking folic acid production.
Wide antimicrobial activity against gram-positive and gram-negative bacteria.

Synergistic Agents for Sulfonamides

Trimethoprim works synergistically with Sulfonamides to enhance efficacy.

Clinical Uses of Sulfonamides

Effective against Nocardiosis (Nocardia spp.).
Used in combination with pyrethamine and sulfadiazine for Toxoplasmosis.

Co-trimoxazole

Combination of sulfamethoxazole and trimethoprim.
Commonly used to treat urinary tract infections and GI infections.

Adverse Reactions of Sulfonamides

Urinary tract disturbances, acute hemolytic anemia, granulocytosis, aplastic anemia.
Sulfa allergies and gastrointestinal issues such as nausea and vomiting.

Drug Interactions for Sulfonamides

Interact with oral anticoagulants, sulfonylureas, hypoglycemic drugs, and hydantoin anticonvulsants.

Fluoroquinolones

Synthetic fluoroquinolones are DNA gyrase inhibitors.
Broad antimicrobial activity with minimal side effects.

Mechanism of Action of Fluoroquinolones

Block bacterial DNA synthesis by inhibiting topoisomerase II (gyrase) primarily and topoisomerase IV secondarily.

Importance of Inhibition of Gyrase

Prevents relaxation of supercoiled DNA necessary for transcription and replication.

Significance of Topoisomerase IV Inhibition

Interferes with separation of replicated DNA during cell division.

Newer Fluoroquinolones

Include Ciprofloxacin, Enoxacin, Lomefloxacin, Levofloxacin, Ofloxacin, and Pefloxacin.
Exhibit broad-spectrum activity particularly against gram-negative bacteria.

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Description

Explore the mechanisms and classifications of antibiotics in pharmacology. This quiz covers Class 1 and Class 2 antibiotics, detailing their actions on microbial metabolism and cellular structures. Perfect for students studying pharmacology or medicine.