The document discusses the concept of prodrugs. It defines a prodrug as a pharmacologically inactive compound that is metabolized into an active drug. The goals of prodrug design include overcoming problems like instability, poor solubility, toxicity and inadequate absorption. Ideal prodrugs are metabolized into active drugs at the target site and have non-toxic carrier molecules. Prodrugs can improve properties like solubility, lipophilicity, targeting, and duration of action to optimize drug delivery. Examples provided are valacyclovir, famciclovir and capecitabine.