Glad I could enlighten. The therapeutic index is a very subjective measurement that makes some drugs sound safer (or more dangerous) than they really are. Both

Glad I could enlighten. The therapeutic index is a very subjective measurement that makes some drugs sound safer (or more dangerous) than they really are. Both the numerator and denominator in the ratio are very situation dependent. For example, trazadone is a hypnotic at doses in the tens of milligram but an anti-depressant at doses in the hundreds of milligrams so depending on what you're using it for, its therapeutic index could be different by up to 100x. Likewise, in a clinical setting (i.e, with a trained anesthesiologist in fentanyl's case), the dose at which 50% of patients die from a given drug is usually much higher because trained professionals can quickly receive feedback by monitoring the patient's symptoms and apply drugs or medical devices to keep them alive well beyond what could kill someone on the street.