Pharmacology in the PICU

Abstract

Rational drug therapy requires the application of pharmacologic principles to maximize efficacy while minimizing adverse reactions. In the setting of the Pediatric Intensive Care Unit (PICU), drug therapy is predicated on an understanding of the pathophysiology of the disease being treated, the pharmacology of the drug(s) selected and the expected effects (therapeutic and toxic) of the chosen agents. An understanding of how disease processes, genetics and other concurrent treatments affect the pharmacologic properties of drugs is also paramount to a rational approach to drug therapy. Two therapeutic strategies, target effect and target concentration are commonly employed when administering medications to treat specific diseases. Pharmacokinetics describe the processes of drug absorption, distribution, biotransformation, and excretion; what the body does to a drug. Pharmacodynamics describe the relationship between a drug’s concentration at its site of action and its effect; what a drug does to the body. Pharmacokinetics and Pharmacodynamics may be influenced by developmental changes, interactions with other drugs or nutrients, disease states, and genetic influences such as polymorphisms. Drug interactions can be classified as drug-drug, drug-disease, or drug-food interactions. The mechanism can be divided into pharmaceutical, pharmacokinetic or pharmacodynamic interactions. The most serious drug interactions involve drugs with severe toxicities and a narrow therapeutic index. Medication errors are a common cause of adverse drug reactions and have unfortunately been associated with fatalities in too many cases. This chapter reviews basic pharmacologic principles and their bedside application to provide a guide for safe and rational drug therapy in caring for the critically ill child.