The Effectiveness Of Chemotherapeutic Agents

Drug Resistance

Resistance may be due to enzymatic destruction of a drug, prevention of penetration of the drug to its target site, or cellular or metabolic changes(alteration of the drug's target sites, rapid efflux or pumping drug out of cell before it becomes effective) of target site.

Hereditary drug resistance (R) factors are carried by plasmids and transposons.

Resistance can be minimized by the discriminating use of drugs in appropriate concentrations and dosages.

Abuse of Antibiotics

Antibiotics can be abused by:

• Prescribing them for problems when they will not be effective such as for any uncomplicated viral infection. However, they can and should be prescribed for viral infections that have complications of bacterial infections such as bacterial pneumonia imposed on influenza.
• Not taking all of the prescribed amount of antibiotic. This may leave the infection at low levels leading to reoccurrence of the problem and/or the bacteria exposed may develop resistance (antibiotic resistant strains). This strain can be harbored by the patient and shed leading to infection in others.

Antibiotic Safety

The risk (e.g., side-effects) verses the benefit (e.g. curing an infection) must be evaluated prior to use of antibiotics.

Effects of Combinations of Drugs

Some combinations of drugs are synergistic; they are more effective when taken together.

Some of the combinations of drugs are antagonistic; when taken together, both drugs become less effective than when taken alone.

The Future of Chemotherapeutic Agents

Many bacterial diseases, previously treatable with antibiotics, have become resistant to antibiotics.

Chemicals produced by plants and animals are providing new antimicrobial agents, including peptides.

New antimicrobial drugs include DNA that is complementary to specific genes in a pathogen; the DNA will bind to the pathogen’s DNA or mRNA and inhibit protein synthesis.