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In Reply.
—We appreciate the interest and concern of Dr Pulido et al regarding the determination of aminoglycoside toxicity following intravitreal administration. Basic toxicity studies are performed for safety assessment so we can predict the likely adverse effects of a drug in humans. Two objectives of toxicity studies include defining a nontoxic (no observable effect) dose level and a toxic dose level. The characterization of the dose-response relationship for toxic effects observed at doses above the no-effect level is vital. Two approaches can be undertaken to achieve the objectives: incremental increases in the drug-dose level, and a log-dose interval, as suggested by Dr Pulido et al.An experimental data set with a dose-response relationship over several log units of drug dose may allow reliable interpretation of the results and perhaps extrapolation of the results to humans, as stated by Dr Pulido et al. The log doseresponse relationship is critically important