THERAPEUTIC INDEX.pptx

Drug

1. THERAPEUTIC INDEX PHM 301

2. Therapeutic Index Therapeutic index (TI) refers to any of the several indices that are used for measuring a drug’s safety . A safer drug has a higher therapeutic index   A more dangerous drug has a lower therapeutic index may require regular monitoring of drug levels examples include: Warfarin Lithium Digoxin Phenytoin Gentamicin Amphotericin 5-fluoro-uracil Zidovudine It is generally considered that a drug has a good safety profile if its TI exceeds the value of 10

3. Definition of terms LD 50  stands for median lethal dose, and ED 50  stands for median effective dose. LD 50  refers to the dose that would produce a lethal effect in 50% of the population, whereas ED 50  refers to the dose that will produce the desired therapeutic effect in 50% of the population. TD 50  refers to the minimum drug dose that would produce a toxic effect in 50% of the population

4. TI CURVES

5. SIGNIFICANCE The larger value of TI indicates that there is a wide margin between the toxic and effective dose . S maller value indicates that there is a narrow margin between the effective and toxic dose . D rugs that have a low TI, even a small increase in the dosage can produce toxic effects. Additional care must be taken while prescribing a drug with a narrow TI.

6. Limitations Initially , the ratio of the LD 50  and ED 50  was determined through animal studies . It must be noted that the ratio measured by animal studies might not be very accurate when it comes to humans. H uman subjects cannot be used for determining a median lethal dose, for obvious reasons. Using animals for determining a lethal dose raises ethical issues.