Microsoft word - 1 anti microbial therapy
a) Microbial diseases (anti microbial) b) Parasitic infestation (anti parasites) c) Neoplastic diseases (anti cancer)
a) Pituitary hormones b) Thyroid hormones c) Insulin and oral hypoglycemics d) Estrogens and androgens e) Suprarenal hormones
Anti Microbial therapy
These are drugs used for treatment of microbial diseases
These drugs include:
1. Antibiotics 2. Sulfonamides 3. Anti mycrobacterials 4. Anti fungal 5. Anti viral 6. Anti protozoal 7. Anti helmintics
SELEction of antimicrobial drug may be according to :
1. Culture and sensitivity . 2.empiric :In which we administer broad spectrum antibiotic until appearance of the result of culture and sensitivity and this empiric treatment is done in cases of severe illness as in meningitis and encephalitis to safe life of the patient . .
Factors that determine the choice of anti microbial drug
depend on :
1:MICROBIAL FACTORS :
a. Identification of the organisms : by
Microorganisms may be sensitive to bactericidal antibiotics which kill the organisms directly or to bacteriostatic antibiotics which inactivate the organisms and facilitate its killing by phagocytosis.
i. MIC:Is the minimum inhibitory concentration of antibiotic which produce
area of inhibition in culture of organisms.
ii. MBC: Is the minimum bactericidal concentration of antibiotic that results
2: Patient factors:
Adequate amount of antibiotic must reach the site of infection b.
Capillaries carry drugs to the body tissues through openings act as windows c.
Barriers of the body:
i. Blood Brain Barrier. physiological barrier between
ii. Placental Barrier….anatomical barrier between maternal
d. Drugs can pass B.B.B : should be :
Renal dysfunction delay execretion lead to accumulation of drugs with serious
Hepatic dysfunction: antibiotics which are
eliminated by liver (e.g. tetracycline + erythromycin) should be avoided in patients with advanced liver diseases
Bad local circulation at site of infection decrease antibiotic levels locally h.
Age: extremes of age there are decreased renal and hepatic elimination of
Pregnancy and lactation
i. All antibiotics can pass placental barrier
ii. Tetracycline have bone + dental effects) .
F.D.A. categories of antibiotics:
¾ B: No studies, no human risk, but animals show potential risk
¾ C: Animal foetal risk developed, but undefined human risk
¾ D: Human foetal risk present, but benefits from the drug are more
3 : FACTORS RELATED TO DRUG :
a. Drug safety
:most antibiotics are among the least toxic drugs as penicillins.
b.Drug cost :always we prefer less coasty antibiotic if it is effective as others
Routes of administration of anti biotics :
usually antibiotics are given orally.But in some cases we need to give antibiotics by :
1. I.V. therapy to give rapid high conc. In blood but this should be followed by oral
2. Parental administration : in the following cases….
Determination of Dose and frequency of administration :
Persistant suppression of microbe after the level of antibiotic become less
Antimicrobials used in bacterial infections
Spectra of antimicrobial
1. Narrow spectrum antibiotic:
these are effective against one type of organism or limited
2. extended spectrum antibiotic:
which are effective against gram +ve organism and some
3. Broad spectrum antibiotic:
which are effective against many types of microorganism
e.g. Tetracyclines and chloramphenicol but lead to super infection by candida albicans.
Combination of antibiotics:
• Broader spectrum of antibacterial action
• Bacteriostatics inactivate microorganism
• Bactericidal act effectively on active organisms only,
So don’t combine Bacteriostatics drug whith Bactericidal agent.
1. Bacterial mutation due to genetic alterations of mutation of DNA which may be:
b. DNA transfer from cell to another cell
Complications of Antibiotic:
1. Hypersensitivity and idiosyncrasy which may lead to anaphylactic shock.
2. Super infection by fungus infection in intestine (candida albicans) after broad spectrum
3. Blood dyscrasia like aplastic anemia after chloramphenicol .
5. Crainial nerve injury like aminoglycosides which lead to auditory vestibular (8th crainial)
nerve damage lead to deafness and vertigo .
Sites and mechanisms of action of antibiotics
1. Inhibit metabolic pathways in organism: like (a) sulfonamides b. trimethoprim
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