What is a narrow therapeutic index?
The narrow therapeutic index is a very small dose range in which the drug provides benefits without causing serious and potentially fatal complications. This means that very small dosage changes can have a serious impact on patient results. Care providers have caution when working with drugs that have a narrow therapeutic index to reduce risks to patients. It is important to carefully manage the instructions administered with such medicines, because a small mistake could be fatal. It is expressed as a range between medium effective dose known as ED50, and medium toxic dose, TD50. Patients taking low doses may not have benefits, while patients taking drugs at higher doses could be threatened by serious complications or death. The range between ED50 and TD50 can be considerable depending on the physician.
If the difference between these two extremes is double or less, the drug has a narrow therapeutic index. Patients who accidentally use two tablets instead of one could be in the range of deadly doses. This does not mean that they necessarily die, because the TD50 is an expression of a median, not every single member of the study. In addition, because killing people in clinical evaluations to find out how fatal the drugs are, it is not ethically acceptable, pharmaceutical companies calculate the therapeutic index using factors such as the development of serious complications in the experiment. The TD50 is based on animal studies and on the evaluation of clinical trials on humans to create a reasonable estimate, erring on the side of caution.
Patients about drugs with a narrow therapeutic index must be careful because overdose may endanger them. Must make the sustain to follow the dosing schedule and carefully read the instructions. This may include exploring tablets or suspensions before using them to check symptoms of abnormalities, such as designations that do not look familiar. Some examples of drugs with narrow therapeutic index include liThium, digoxin and warfarin.
Care providers must also be careful about drugs and facilities such as clinics and hospitals, may have special rules for their management. This may include the requirement for doctors to fully write recipes to eliminate the confusion of dosing, ask nurses to check each other before the administration of narrow therapeutic index drugs, and using special marking for such medicines. For example, a nurse preparing a salt drip infused with a dangerous drug could use a special color -marked label to warn other content providers.