Intoxicology, themedian toxic dose (TD₅₀) of a drug or toxin is the dose at whichtoxicity occurs in 50% of cases.^[1]: 73 Thetype of toxicity should be specified for this value to have meaning for practical purposes. Themedian toxic dose encompasses the category of toxicity that is greater thanhalf maximum effective concentration (ED₅₀) but less than the median lethal dose (LD₅₀). However, for some highly potent toxins (ex.lofentanil,botulinum toxin) the difference between the ED₅₀ and TD₅₀ is so minute that the values assigned to them may be approximated to equal doses. Since toxicity need not be lethal, the TD₅₀ is generally lower than themedian lethal dose (LD₅₀), and the latter can be considered anupper bound for the former. However, since the toxicity is above the effective limit, the TD₅₀ is generally greater than the ED₅₀. If the result of a study is a toxic effect that does not result in death, it is classified as this form of toxicity.^[2] Toxic effects can be defined differently, sometimes considering the therapeutic effect of a substance to be toxic (such as withchemotherapeutics) which can lead to confusion and contention regarding a substance's TD₅₀. Examples of these toxic endpoints include cancer, blindness, anemia, and birth defects.^[2]