BSCI 424 Pathogenic Microbiology -- Ideal Drug

BSCI 424 — PATHOGENIC MICROBIOLOGY — Fall 2000

Characteristics of an Ideal Chemotherapeutic Drug

(There are No Perfect Drugs)

Selective Toxicity Against Target Pathogen But Not Against Host

Would like LD₅₀to be high and Minimal Inhibitory Concentration (MIC) and/or Minimal Bactericidal Concentration (MBC) to be low

LD₅₀= Lethal Dose 50%; Measure of drug toxicity/lethality against host

MIC; Measure of the concentration of the antibiotic necessary to inhibit growth of the target pathogen

MBC; Measure of the concentration of the antibiotic necessary to kill the target pathogen

Favorable Pharmacokinetics: Survive in high concentration and reach the target site (site of infection)

Pharmacokinetics: Action of drugs in the body over a period of time including:

Absorption
Distribution
Localization in tissues

Biotransformation (biochem. alterations)
Excretion

Would Like the Drug to be:

Bactericidal (Microbicidal): Kills microbes (-cidal = death or killing)

vs.

Bacteriostatic: Stops growth of microorganisms without killing them (-static = stationary; at rest; stasis)

Spectrum of Activity (Broad vs. Narrow) Coordinated with Diagnosis

For example:

a broad-spectrum antibiotic would be indicated against a polymicrobial infection, e.g., an intrabdominal anaerobic infection

a narrow spectrum antibiotic would be ideal for an infection caused by a single pathogen, e.g., a staphylococcal skin infection.

Lack of "Side Effects"

Able to Cross Outer and Cytoplasmic Membranes

No or Low Level of Antibiotic Resistance in Target Pathogen and Lack of Cross-Resistance in Closely Related Strains

Resistant to Inactivation by Microbial Enzymes

Go to Chemotherapy of Bacterial Infections

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