Final answer:
The blood level showing the highest drug concentration during TDM is the peak concentration, which occurs shortly after administration for IV drugs and takes longer for oral or intramuscular drugs.
Step-by-step explanation:
During therapeutic drug monitoring (TDM), the blood level that will show the highest concentration of drug is known as the peak concentration. This level is drawn after the drug is assumed to have reached the highest concentration in the bloodstream, following its administration. For intravenous drugs, this peak occurs very quickly after administration, whereas for oral or intramuscular drugs, the peak takes a longer time to reach. The peak concentration is significant in TDM as it helps to avoid drug toxicity and ensure that drug levels stay within the optimal therapeutic range. This balancing act helps to maximize drug efficacy and minimize therapeutic costs, while also taking into account factors like individual patient differences in age, weight, genetic polymorphism, co-morbid diseases and drug-drug interactions (DDI).