Drug dosing in acute kidney injury (AKI) is one of the broadest topics in human medicine. It requires an understanding of markedly altered and constantly changing physiology under many disease situations, the use of the drugs to treat those variety of diseases, and the concept of drug removal during blood cleansing therapies. Early in AKI kidney function may be supraphysiologic, while later in the course there may be no kidney function. As function deteriorates other metabolic pathways are altered in unpredictable ways. Furthermore, the underlying disorders that lead to AKI alter metabolic pathways. Heart failure is accompanied by vasoconstriction in the muscle, skin and splanchnic beds, while brain and cardiac blood flow proportionally increase. Third spacing occurs and lungs can become congested. As either kidney or liver function deteriorates, there may be increased or decreased drug sensitivity at the receptor level. Acidosis accompanies several failing organs. Protein synthesis is qualitatively and quantitatively altered. Sepsis affects tissue permeability. All these abnormalities influence drug pharmacokinetics and dynamics. AKI is accompanied by therapeutic interventions that alter intrinsic metabolism which is in turn complicated by kidney replacement therapy (KRT). So metabolism and removal are both altered and constantly changing. Drug management in AKI is exceedingly complex and is only beginning to be understood. Thus, we approach this discussion in a physiological manner. Critically ill patients pass through phases of illness, sometimes rapidly, other times slowly. The recognition of the phases and the need to adjust medication administration strategies is crucial to improving outcomes. An early phase involving supraphysiologic kidney function may be contributory to therapeutic failures that result in the complication of later AKI and kidney function failure.