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Testing useful in choosing, comparing drugs
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MAUI, Hawaii — The effectiveness of antibiotics can be determined by measuring the drugs’ minimal inhibitory concentrations value, studying the pharmacokinetics and determining the speed of bacterial killing, according to Richard J. O’Callaghan, PhD.
Dr. O’Callaghan discussed his testing of fluoroquinolones as a means of choosing an antibiotic appropriate for a particular infection and evaluating antibiotics relative to one another.
To determine which antibiotic is appropriate in certain cases, not only is a drug’s ability to inhibit enzyme activity important, but it is also important to evaluate the penetrability of a drug and its ability to resist being secreted, he said.
The bacterial strain’s susceptibility to inhibition by an antibiotic is determined by measuring the minimal inhibitory concentrations (MIC) value.
“The determinations of susceptibility by the MIC method provide ophthalmologists with data descriptive of the interaction of the drug with the bacterium isolated from a specific infection,” he saidn here during Hawaii 2003: the Royal Hawaiian Eye Meeting.
Dr. O’Callaghan said comparing antibiotics with each other is also important in treating bacterial strains resistant to multiple antibiotics.
Another important parameter in evaluating a drug’s effectiveness is its availability in the ocular tissues. In one study, drugs were applied to corneas of patients undergoing corneal transplantation and the concentration of three fluoroquinolones was compared.
According to Dr. O’Callaghan, “This method should be applied to additional antibiotics because the comparisons are performed on normal human corneas and avoids any possibility of subject-to-subject variation.”
He added, “Effectiveness is the best measurement of what works best.”