Therapeutic drug monitoring (TDM) is the clinical practice of measuring specific drug levels in a patient’s blood at designated intervals to maintain a constant concentration within a therapeutic range. This practice is crucial for medications with narrow therapeutic windows, where small changes in drug concentration can lead to subtherapeutic effects or toxic side effects. TDM aims to optimize individual dosing regimens, ensuring maximum efficacy while minimizing adverse effects. Common drugs monitored include anticonvulsants, antibiotics, immunosuppressants, and certain psychotropic medications. 

TDM also plays a vital role in personalized medicine, as it considers the patient's unique characteristics such as age, weight, organ function, genetic factors, and concurrent health conditions. This approach helps in managing chronic conditions, preventing drug resistance, and improving overall treatment outcomes. Overall, TDM is an essential tool in clinical pharmacology, enhancing the safety and effectiveness of drug therapies through tailored and precise medication management.