8.12 : Nonlinear Pharmacokinetics: Role of Transporters

A drug's nonlinear kinetics can be influenced by a diverse range of transporter proteins that serve as crucial players in drug distribution. These transporters, found within cells, can enhance or reduce local drug concentrations by facilitating the influx or efflux of drugs. For instance, the expression of xenobiotic transporters can be influenced by factors such as age and gender, potentially impacting the linearity of drug response.

Polymorphisms occurring in drug transporters can alter pharmacokinetics, affecting drug toxicity and efficacy. The interplay between drug transporters and enzymes in the liver is significant in determining the systemic linearity of drug response. Similarly, in the intestine, ATP-binding cassette and bile acid transporters influence drug absorption, bioavailability, and the linearity of absorption.

Various organic anion and cation drug transporters in the kidney can significantly alter the linearity of systemic drug elimination. Additionally, breast cancer resistance proteins are instrumental in drug linearity and require careful consideration when establishing dosing strategies in cancer therapy.

Moreover, drug-drug interactions involving transporters can potentially disrupt clinical relevance, pharmacokinetics, pharmacodynamics, and toxicity, shifting from linear to nonlinear kinetics. The abundant presence of organic anion and cation drug transporters in the kidney also contributes to alterations in the linearity of systemic drug elimination.

Furthermore, P-glycoprotein, a multidrug resistance protein, plays a pivotal role in determining drug concentration within cells, exerting a considerable influence on pharmacokinetic linearity. Mammalian oligopeptide transporters also contribute significantly to drug absorption and distribution, impacting drug linearity.

Overall, understanding the impact of transporters on pharmacokinetics is essential for optimizing drug dosing, improving safety, and enhancing efficacy. By understanding the intricate mechanisms through which transporters modulate drug kinetics, healthcare professionals can make informed decisions to maximize therapeutic outcomes.