Pharmacology General Considerations Question And Answers

General Considerations Important Notes

1. Antibiotics

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

2. Classification of antibiotics

• Based on the mechanism of action

• Based on antibacterial activity

• 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 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 combination of drugs

• Combination of two bacteriostatic drugs that are often additive and rarely synergetic
  • Tetracycline + chloramphenicol/ erythromycin
  • Sulfonamide + trimethoprim
  • Clavulanic acid + amoxicillin
• Combination of two bacteriocidal drugs that are frequently additive and sometimes synergetic
  • Penicillin/ ampicillin + streptomycin/ gentamycin
  • Carbenicillin + gentamycin
  • Ceftazidine + ciprofloxacin
  • Rifampicin + tuberculosis
• Combination of bacteriostatic and bacteriocidal drug
  • 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 suppresses the growth or kill other microorganisms at very low concentration.

Antibiotics Classification:

1. Based on chemical structure.

• Sulfonamides – sulfones, dapsone.
• Diaminopyrimidies – trimethoprim.
• Quinolones – nalidixic acid, norfloxacin.
• p-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.
• Cause leakage from the cell membrane.
  • Polypeptides – polymyxins, colistin.
• Inhibit protein synthesis.
  • Tetracyclines, chloramphenicol.
• Cause misreading of m-RNA
  • Aminoglycosides.
• Inhibit DNA gyrase – fluoroquinolones.
• Interfere with DNA function – Rifampicin.
• Interfere with DNA synthase – Acyclovir.
• Interfere with intermediary metabolism.
  • Sulfonamides, trimethoprim.

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

• Antibacterial – Penicillin, aminoglycosides.
• Antifungal – Griseofulvin, Amphotericin B.
• Antiviral – Acyclovir, Amantadine.
• Antiprotozoal – Cloroquine 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, 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 spiro chapters And the release of its lytic products.

Antibiotics Sulfonamides:

Sulfonamides Mechanism of action:

• Many bacteria synthesize their own folic acid from p- amino benzoic acid (PABA) by enzyme folic acid synthetase.
• Sulfonamides is structurally similar to PABA.

• Thus sulphonamide is bacteriostatic in action.

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.

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 alteration in the normal flora of the intestine respiratory And genitor-urinary 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.
• Broader the antimicrobial spectrum, the more the chances of superinfection.

Conditions Predisposing to Superinfection:

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

Superinfection Examples: