Pharmacodynamics and pharmacokinetics of digoxin in the presence of lithium

Differential pharmacokinetics of digoxin in elderly patients

Digoxin remains one of the most commonly prescribed of all cardiac medications. The main indications for digoxin usage include atrial fibrillation and heart failure; both these conditions are more prevalent in older patients. Given the aging population and the increasing incidence of heart failure we would expect prescribing of digoxin to remain as frequent or to even increase in older patients. Older patients are also more likely to develop toxicity and diagnosis of digoxin toxicity can be difficult in this group. Numerous components contribute to the development of toxicity in older patients, ranging from aging-related changes in renal function or body mass to polypharmacy and possible interactions with digoxin. It is therefore important to understand how the pharmacokinetics of digoxin may be altered in the older population. Application of basic pharmacological principles may be helpful in anticipating these problems. This review describes the pharmacokinetics of digoxin, the changes in pharmacokinetics with increasing age and how concomitant disease states or drug interactions may affect the pharmacokinetics of digoxin. Greater knowledge about the causes and prevention of digoxin toxicity should further reduce the morbidity and mortality arising from digoxin toxicity, especially in the elderly population.

The use of lithium in the medically ill

Many patients taking lithium for the treatment of mood disorders suffer from concomitant medical illnesses. Because of its effects on multiple organ systems, extra caution is required when lithium is used in the presence of medical illness. Available data regarding the use of lithium in the presence of thyroid, renal, cardiovascular, dermatologic, and respiratory disease as well as in the presence of disorders of glucose and calcium metabolism are reviewed. In addition, recommendations regarding safe use, serum monitoring, and potential drug interactions are discussed.