ABSORPTION

Absorption is the transmission of medications from the location of administration (gastrointestinal [GI] tract, muscle, skin, mucous membranes, or subcutaneous tissue) to the bloodstream. The most common routes of administration are enteral (through the GI tract) and parenteral (by injection). Each of these routes has a unique pattern of absorption.

● The rate of medication absorption determines how soon the medication will take effect.

● The amount of medication the body absorbs determines the intensity of its effects.

● The route of administration affects the rate and amount of absorption.

Oral

BARRIERS TO ABSORPTION: Medications must pass through the layer of epithelial cells that line the GI tract.

ABSORPTION PATTERN: Varies greatly due to ● Stability and solubility of the medication ● GI pH and emptying time ● Presence of food in the stomach or intestines ● Other concurrent medications ● Forms of medications (enteric-coated pills, liquids)

Sublingual, buccal

BARRIERS TO ABSORPTION: Swallowing before dissolution allows gastric pH to inactivate the medication.

ABSORPTION PATTERN: Quick absorption systemically through highly vascular mucous membranes

Other mucous membranes (rectal, vaginal)

BARRIERS TO ABSORPTION: Presence of stool in the rectum or infectious material in the vagina limits tissue contact.

ABSORPTION PATTERN: Easy absorption with both local and systemic effects

Inhalation via mouth, nose