Pharmacokinetic studies are crucial for designing drug dosage regimens. Typical pharmacokinetic (PK) sample analysis includes several steps, including acquiring funding, approval from the ethics committee, thorough study design, and sample analysis and strategies. Pharmacokinetic services form a crucial component of drug development studies. A candidate drug molecule can only be converted into a potential drug compound after an in-depth understanding of pharmacokinetic and pharmacodynamic drug properties. However, discovering these pharmacokinetic properties can be challenging.
PK analysis in clinical trials and preclinical assessments faces several challenges, including the complex relationship between physiological processes, regulatory feedback mechanisms, structural similarity to biomolecules, molecule characteristics, and many more. Hence, the current article discusses the challenges PK labs and mass spec services encounter while conducting a pharmacokinetic study.
Challenges in pharmacokinetic studies
Whether it’s PK ADA assessment or DMPK studies, evaluating absorption, distribution, metabolism, and excretion profile is crucial. Let us dive deep into these unique processes and understand the challenges.
The digestive enzymes in the GI tract, along with individual physical properties of a drug product, affect its absorption through the GI membrane. Hence, multiple therapeutic compounds are usually delivered through intravenous, intramuscular, or subcutaneous administration. However, these routes of administration may have several limitations. Although intravenous administration directly delivers compounds into the systemic circulation, it is highly inconvenient and may not necessarily provide the required concentration-time profile. Besides, intramuscular and subcutaneous injections may potentially have decreased bioavailability due to injection trauma or local blood flow.
Drug compounds must extravasate via the vascular capillaries and pass the interstitial to reach the target site and exert pharmacological effects. However, this process may involve transcytosis and convection. Besides, this process is largely determined by molecular weight, size, physicochemical properties, and protein binding factors. On the other hand, biological factors such as disease state, blood flow rate, and differences in capillary makeup may also affect the distribution of a drug product. These challenges make evaluating distribution kinetics difficult for a drug product.
Similar challenges occur while evaluating metabolism and excretion characteristics. Generally, post-biliary excretion drugs metabolize in the GI tract. As the drug size increases, the metabolic rate decreases. Besides, the degradation rate also depends on other elements such as charge, functional group, and lipophilicity. The kidneys are the primary organ for metabolizing a drug product. The size of a particular drug dictates the rate of glomerular filtration.
Besides, pharmacokinetic testing in individuals, such as neonatal and elderly populations, may face additional challenges. For example, taking blood samples from this population is often difficult. Hence, pharmacokinetic testing requiring blood samples must consider testing a small proportion of existing blood samples taken for other assessments. This precaution ensures that neonatal and elderly patients do not undergo unnecessary blood sampling.
In Conclusion
pharmacokinetic studies have multiple challenges. These challenges require multi-factor solutions that can help streamline the governance and execution of large-scale pharmacokinetic studies. Moreover, continuous efforts in advancing pharmacokinetic modeling and technology will remain critical in accelerating drug development programs.