What does poor aqueous solubility directly translate to regarding the administered dose of an oral drug?
Low bioavailability, meaning a smaller percentage reaches circulation.
Bioavailability is the fraction (percentage) of an administered drug dose that successfully reaches the systemic circulation unchanged. For orally administered medications, the very first mandatory step toward achieving bioavailability is dissolution in the gastrointestinal fluids. If a drug possesses very low aqueous solubility, it cannot dissolve efficiently in the stomach or intestinal fluids. This failure to dissolve means the active ingredient cannot be absorbed through the gut lining. Therefore, poor solubility directly correlates with poor bioavailability, resulting in a substantial amount of the intended dose being eliminated from the body without ever exerting a therapeutic effect.
