Page 179 - MNU-PM502- Pharmaeutical Microbiology Theoritical Book

Pharm D- Clinical Pharmacy Program Third Level Pharmaceutical Microbiology& Antimicrobials (PM 502)

Additive

• The result observed with more than one drug should be the sum of the
separate effects of the drug being tested if those drugs do not interact with

one another (1+1=2).

• e.g. combination of two B-lactam antibiotics

Synergism

• The positive interaction of two or more agents

• The combined effect is significantly greater than the expected
sum of their individual effects (1 + 1 = 3).

• .g. ᵦ- lactams + Aminoglycosides (Ampicillin+gentamicin in entercoccal

infection)

Jawetz Law:

Classifies antibiotics according to whether they are bactericidal or bacteriostatic
➢ Bactericidal + bactericidal = Synergistic

(Penicillin + Gentamicin)
➢ Bacteristatic + bacteristatic = additive

(Tetracycline + Chloramphenicol)
➢ Bactericidal + bacteristatic = antagonistic

(Gentamicin + Chloramphenicol)

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