Antimicrobial drugs

1. General chemotherapy and
Cotrimoxazole

2. Antimicrobial Drugs
• Antibiotics
• Chemotherapy
• Antimicrobial agents

3. Problems with use of AMA
• Toxicity: Local and systemic
• Hypersensitivity reactions
• Drug resistance

4. Unresponsiveness of a microbe to an AMA
• It refers to tolerance of microorganism to
inhibitory actions of AMA
• Natural resistance
• Acquired resistance
It is the development of resistance by an
organism due to the use of AMA over a period
of time
• Can happen with any microbe
• Depends upon microbes and drugs

5. Prevention of drug resistance
• Using AMA for appropriate period
• Prefer selective AMA (narrow)
• In prolonged therapy use combination of
AMA, Eg. Tuberculosis
• Intensive therapy for the organism known to
develop resistance, Eg: Tuberculosis

6. Super infection (Supra infection)
• Appearance of new infection as a result of
antimicrobial therapy
Commonly seen in
• Compromised host defence
– AIDS, diabetes, corticosteroid therapy,
anticancer drug therapy
• Use of broad spectrum antibiotics

7. Patient Factors
• Age:
– Chloramphenicol → gray baby syndrome
– Sulfonamide → kernicterus
• Renal function
– Tetracycline, cephalothin
• Hepatic function
– Erythromycin, Tetracycline
• Local factors:
– Pus, hematoma, anaerobic abscess
• Drug allergy
• Pregnancy
– Penicillins, cephalosporins, erythromycin
• Genetic factors

8. Combination of AMA
• To achieve synergism
• To ↓ adverse effects
• To prevent resistance development
• To broaden spectrum of AMA

9. Chemoprophylaxis
• This refers to the use of AMA for
preventing the setting in of an infection or
suppressing contacted infection before it
becomes clinically manifest
– Rheumatic fever – Benzathine penicillin
– Tuberculosis – Isoniazid
– M. meningitis – Rifampicin
– Malaria - Chloroquine

10. Cotrimoxazole
• A fixed dose combination of
sulfamethaxazole and trimethaprim
• Causes sequential block of folate
metabolism
• Individually bacteriostatic
• Together – Bacteriocidal
• Synergestic effect

11. MECHANISM
PABA
Sulfonamide  Folate Synthase
DIHYDROFOLATE
Trimothoprim x Dihydrofolate reductase
TETRAHYDROFOLATE

12. Uses
• Urinary tract infection
• Respiratory tract infection
• Typhoid fever
• Pneumocystic carini infections in AIDS
• Infective diarrhea
• Chancroid
• Granuloma inguinale

13. ADVERSE EFFECTS
1. GIT disturbances:-
2. Folate deficiency:
3. Fever ,rashes, bone marrow hypoplasia
-in AIDS.
4. Haemolysis and Methaemoglobinemia -
neonate.