Therapeutic Index (TI)

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A ratio that compares the blood concentration at which a drug becomes toxic and the concentration at which the drug is effective. The larger the therapeutic index (TI), the safer the drug is. If the TI is small (the difference between the two concentrations is very small), the drug must be dosed carefully and the person receiving the drug should be monitored closely for any signs of drug toxicity.
Related Term(s)
Therapeutic Drug Monitoring (TDM)
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Space between the concentrations at which a drug becomes effective and toxic.

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