Bioavailability refers to the extent and rate at which a drug enters the systemic circulation, becoming available at the site of action.
Absorption: Bioavailability is significantly influenced by how well a drug is absorbed from the site of administration.
First-Pass Metabolism: Oral drugs may undergo significant metabolism in the liver before reaching systemic circulation, reducing their bioavailability.
Drug Formulation: The way a drug is formulated (e.g., tablet, liquid, controlled-release) can impact its bioavailability.
Route of Administration: Bioavailability can vary based on the route of administration. Intravenous (IV) administration typically results in 100% bioavailability.
Physiological Factors: Patient-specific factors like age, sex, disease state, and genetic factors can also affect drug bioavailability.
Food and Drug Interactions: Food or other drugs can interact with the drug, affecting its absorption and hence bioavailability
Measurement: Bioavailability is typically assessed as a part of the drug development process through clinical pharmacokinetic studies.
Dosage Adjustments: Understanding a drug's bioavailability helps in determining the correct dosage for achieving the desired therapeutic effect.
Drug Efficacy: Low bioavailability can lead to decreased drug efficacy, as less of the drug reaches the target site to exert its effects.