Pharmacology General Considerations Question And Answers

General Considerations Important Notes

1. Antibiotics

• Antibiotics are biological substances elaborated by microorganisms that suppress the growth of other microorganisms or destroy them in high dilution

2. Classification of antibiotics

• Based on the mechanism of action

General pharmacology questions and answers

• Based on antibacterial activity

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• Based on the spectrum of activity

3. Superinfection

• It refers to the appearance of a new infection as a result of antimicrobial therapy
• Drugs that cause superinfection are
  • Tetracyclines
  • Chloramphenicol
  • Ampicillin
  • Amoxycillin

4. Methods to prevent drug resistance

• Indiscriminate, inadequate, and prolonged use of antibiotics should be avoided
• The drug should be given after a culture sensitivity test
• If antibiotics are to be given for a prolonged period, combination therapy should be instituted

5. Uses of a combination of drugs

• To achieve synergism
• To reduce the severity or incidence of adverse effects
• To prevent the emergence of resistance
• To broaden the spectrum of antimicrobial action

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6. Examples of a combination of drugs

• A combination of two bacteriostatic drugs that are often additive and rarely synergistic
  • Tetracycline + chloramphenicol/ erythromycin
  • Sulfonamide + trimethoprim
  • Clavulanic acid + amoxicillin
• A combination of two bacteriocidal drugs that are frequently additive and sometimes synergistic
  • Penicillin/ ampicillin + streptomycin/ gentamycin
  • Carbenicillin + gentamycin
  • Ceftazidine + ciprofloxacin
  • Rifampicin + tuberculosis
• Combination of bacteriostatic and bacteriocidal drugs
  • Penicillin + erythromycin
  • Penicillin + tetracycline/ chloramphenicol
  • Penicillin + sulfonamide
  • Streptomycin + tetracycline
  • Rifampicin + dapsone

General Considerations Long Essays

Question 1. Mention some examples of antibodies and describe the mechanism of action and side effects of two commonly used antibiotics.
Answer:

Antibiotics:

• Antibiotics are produced by microorganisms that selectively suppress the growth or kill other microorganisms at very low concentrations.

Antibiotics Classification:

1. Based on chemical structure.

• Sulfonamides – sulfones, dapsone.
• Diaminopyrimidines – trimethoprim.
• Quinolones – nalidixic acid, norfloxacin.
• β-lactam antibiotics – penicillin, cephalosporin.
• Tetracyclines – Oxytetracyclines.
• Aminoglycosides – streptomycin, gentamicin.
• Macrolide – erythromycin, Azithromycin.
• Polyene antibiotics – Nystatin.
• Azole derivatives – clotrimazole, ketoconazole.

2. Based on the mechanism of action.

• Inhibit cell wall synthesis.
  • Penicillin, cephalosporins.
• Causes leakage from the cell membrane.
  • Polypeptides – polymyxins, colistin.
• Inhibit protein synthesis.
  • Tetracyclines, chloramphenicol.
• Causes misreading of mRNA
  • Aminoglycosides.
• Inhibit DNA gyrase – fluoroquinolones.
• Interfere with DNA function – Rifampicin.
• Interfere with DNA synthase – Acyclovir.
• Interfere with intermediary metabolism.
  • Sulfonamides, trimethoprim.

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3. Based on the type of organisms against which it acts.

• Antibacterial – Penicillin, aminoglycosides.
• Antifungal – Griseofulvin, Amphotericin B.
• Antiviral – Acyclovir, Amantadine.
• Antiprotozoal – Chloroquine, metronidazole, chloroquine.
• Anti-helmintic – Mebendazole.

4. Based on the spectrum of activity.

• Narrow spectrum – Penicillin G, streptomycin.
• Broad spectrum – Tetracyclines.

5. Based on the type of action.

• Bacteriostatic – sulphonamides, tetracyclines.
• Bacteriocidal – Penicillins, Aminoglycosides.

Antibiotics Penicillins:

Penicillins Mechanism of action:

Penicillins Adverse effects:

1. Hypersensitivity reactions.

• Skin rashes, urticaria, fever, bronchospasm, serum sickness, and anaphylaxis.

2. Paint the site of injection.

3. CNS effects.

• Confusion, muscle twitching, convulsions, coma.

4. Suprainfection.

5. Jarisch-Herxheimer reaction.

• Occurs when penicillin is injected into the syphilitic patient
• It is characterized by the sudden destruction of spirochete chapters and the release of its lytic products.

Antibiotics Sulfonamides:

Sulfonamides Mechanism of action:

• Many bacteria synthesize their own folic acid from p-aminobenzoic acid (PABA) by the enzyme folic acid synthetase.
• Sulfonamides are structurally similar to PABA.

• Thus, sulphonamide is bacteriostatic in action.

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Sulfonamides Adverse effects:

• Nausea, vomiting, epigastric pain.
• Renal Irritation, hematuria, albuminuria, and crystalluria.
• Hypersensitivity reactions.
• Kernicterus.
• Hemolysis in G-6 PD deficiency patients.
• Hepatitis.
• Stomatitis, conjunctivitis, And Arthritis

Question 2. Explain four advantages of the combined use of antimicrobials with examples.
Answer:

Advantages of a combination of antimicrobials:

1. To achieve synergism.

• The same drugs may be synergistic for one organism but antagonistic for another.

2. To reduce adverse effects.

• Combining two antimicrobials may reduce the dose of each agent.
• This may thereby reduce the toxicity of drugs.
• Example: Streptomycin + penicillin G for subacute bacterial endocarditis.

3. To prevent the emergence of resistance.

• It is used primarily for chronic infections needing prolonged therapy, like tuberculosis and leprosy.
• Rifampin + ciprofloxacin – prevents S.aureus resistance.

4. To broaden the spectrum of antimicrobial action.

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General Considerations Short Essays

Question 1. What is superinfection? Give two examples.
Answer:

Superinfection:

• It refers to the appearance of a new infection as a result of antimicrobial therapy.

Superinfection Reason:

• Antimicrobial agents cause alterations in the normal flora of the intestine, respiratory, and genitourinary tracts.
• Normal microbial flora contributes to host defense.
• In it, the pathogen has to compete with the normal commensals for nutrition.
• But by the use of antimicrobial agents, there is a lack of competition.
• As a result, infection is caused easily.
• The broader the antimicrobial spectrum, the greater the chances of superinfection.

Conditions Predisposing to Superinfection:

• Corticosteroid therapy.
• Leukemia.
• AIDS.
• Agranulocytosis.
• Diabetes.
• Disseminated lupus erythematosus.

Superinfection Examples: