Chapter 25: Therapeutic Drug Monitoring and Poisoning

Therapeutic Drug Monitoring and Poisoning details the necessity of monitoring substances with a narrow therapeutic window, such as digoxin, lithium, and aminoglycoside antibiotics like gentamicin, where precise blood concentration assays help prevent severe ototoxicity and nephrotoxicity while ensuring therapeutic success. The text explores complex factors influencing plasma drug levels, including patient compliance, volume of distribution variations in obese or edematous patients, protein binding competition with albumin, and the saturable metabolism kinetics characteristic of phenytoin. Furthermore, it highlights the significance of pharmacogenetics, such as thiopurine methyltransferase (TPMT) variants affecting azathioprine metabolism and cytochrome P450 phenotypes, in personalizing medication dosages to avoid adverse reactions. In the realm of emergency medicine, the material covers the biochemical diagnosis and management of acute overdoses, specifically the hepatotoxicity of paracetamol triggered by glutathione depletion and its reversal via N-acetylcysteine, alongside the unique respiratory alkalosis and subsequent metabolic acidosis caused by salicylate poisoning. By integrating clinical laboratory findings with physiological responses, this study guide provides a comprehensive overview of how biochemical markers assist in identifying toxic exposures to substances like ethylene glycol, carbon monoxide, and organophosphates, while guiding supportive care and targeted antidote administration.