12.2: Dosage Regimens: Partial Pharmacokinetic Parameters

It is not uncommon for complete drug pharmacokinetic profiles to remain elusive in pharmacokinetics. This necessitates certain educated assumptions by pharmacokineticists to determine appropriate dosage regimens without comprehensive pharmacokinetic data from animal or human studies. One prevalent assumption is setting the bioavailability factor, denoted as F, to 1 or 100%. This assumption caters to the scenario where a drug doesn't achieve full systemic absorption, resulting in the patient being under-medicated rather than over-medicated. Such assumptions are selected based on the drug's safety, efficacy, and therapeutic range.

An increasingly favored approach in these circumstances is population pharmacokinetics. This method capitalizes on the average characteristics of a patient population, coupled with a limited number of serum drug concentration samples from patients. This approach has seen a surge in application within therapeutic drug monitoring (TDM), largely owing to the burgeoning availability of computerized databases and the evolution of statistical tools designed for observational data analysis.

So, despite incomplete pharmacokinetic profiles, informed assumptions and innovative methodologies like population pharmacokinetics facilitate effective dosage regimen calculations, ensuring patient safety and therapeutic effectiveness.