AbsorptionDrug moves from site of administration into the blood, crossing at least one membrane (except if administered IV)To cross membranes, drugs must be in solution and lipid solubleInfluenced by..oRoute of administrationoDosage form – solution, tablet, suppository, etc.oSolubility of the drug – if lipid soluble, drugs cross membranes more easilyoOther factors – food in stomach, type of food in stomach; movement of drug through stomach and small intestine, pH of stomach/intestinal fluids, etc.First-pass effect – influences bioavailability of the drugBioavailability of the drug - “portion of a [drug] dose that reaches systemic circulation and is available to act on body cells

Absorption is the process by which a drug moves from the site of administration into the bloodstream. This typically involves crossing at least one membrane, except when the drug is administered intravenously. In order to cross membranes, drugs must be in solution and lipid soluble.

The absorption of a drug can be influenced by several factors. Firstly, the route of administration plays a role. Different routes, such as oral, topical, or intravenous, can affect the absorption process. Additionally, the dosage form of the drug, whether it is in the form of a solution, tablet, suppository, etc., can also impact absorption.

The solubility of the drug is another important factor. If a drug is lipid soluble, it can cross membranes more easily compared to drugs that are not lipid soluble. Other factors that can influence absorption include the presence of food in the stomach, the type of food in the stomach, the movement of the drug through the stomach and small intestine, and the pH of the stomach and intestinal fluids.

The first-pass effect is a phenomenon that affects the bioavailability of a drug. It refers to the metabolism of a drug that occurs in the liver before it reaches systemic circulation. This can significantly reduce the amount of the drug that ultimately reaches the target cells and affects its overall bioavailability.

Bioavailability is defined as the portion of a drug dose that reaches systemic circulation and is available to act on body cells. It is an important measure of the effectiveness of a drug and can be influenced by various factors, including absorption, distribution, metabolism, and excretion.