toxic dose/therapeutic dose

LD₅₀/ED₅₀

• the higher the index, the better the chemotherapeutic agent

lethal dose 50

the dose at which 50% of the test subjects die

effective dose

dose at which 50% of the test subjects produce a therapeutic response

a bacterial enzyme that crosslinks peptidoglycan in bacterial cell walls.

common target of antibiotics

is more resistant to b-lactamase than some other antibiotics and is used for treating penicillin-resistant
bacteria such as Neiserria gonorrhoeae

binds to bacterial membranes which forms a pore in the membrane. 

Depolarizes the membrane = no energy = cell death

• Drug discovery: synthesis, isolation from natural sources, initial testing in laboratory
  setting
• Phase I trials – evaluation of drug safety and side effects on small groups of 20-100 individuals
• Phase II trials – test for efficacy; randomized and “blind” placebo/drug trials
• Phase III trials – larger scale tests on up to several thousand patients
• FDA approval – typically takes a year or more
• Post-marketing/Phase IV – continued monitoring of drug safety and efficacy;
  comparison of results with other drugs

synthetic growth factor analogs that inhibits a necessary step in a microbial metabolic pathway

Mode of action: Inhibits incorporation of para-aminobenzoic acid into the vitamin folic acid
•Bacteria synthesize their own folic acid – higher

animals get folic acid only from their diet

Sulfanilamide is an analog of p-aminobenzoic acid

inhibits DNA/RNA synthesis

1. nalidixic acid
2. Ciprofloxacin
3. Novobiocin

1&2 are Quinolone antibiotics

inhibits bacterial cell wall synthesis (prevent transpeptidase reaction by binding to the enzyme)

contain a β-lactam ring

• Penicillin

produced by the fungus cephalosporium

has activity similar to penicillin

mode of action: Binds to the 30S subunit of bacterial ribosomes and inhibits protien synthesis

mode of bacterial resistance:  Some bacteria have acetyltransferase which modifies the drug into an inactive form