Which factor is considered to determine the dosage of drugs once a regimen is assigned?

Determining the dosage of drugs in a tuberculosis treatment regimen is primarily based on the patient's weight. This is because the efficacy and safety of many medications are closely related to the body mass of the individual receiving treatment. Weight helps to ensure that the patient receives an adequate amount of medication that is proportional to their body size, allowing for effective treatment while minimizing the risks of toxicity or suboptimal dosing that may lead to treatment failure.

In tuberculosis treatment, appropriate dosing is critical for achieving the right concentration of the drug in the bloodstream and within the infected sites of the body. If the dosage is too low due to an underestimation of weight, it may not effectively kill the bacteria, leading to drug resistance. Conversely, a dosage that is too high may increase the risk of adverse effects. Thus, calculating the dosage based on weight is a standard practice in pharmacotherapy, particularly in tuberculosis management where precise dosing is crucial for successful outcomes.