Drug Absorption Factors - Summary Chart

Vocabulary-style flashcards covering key factors that influence drug absorption.

Lipid-soluble drugs

Absorb more easily and cross membranes (including the blood-brain barrier) due to high lipid solubility.

Water-soluble drugs

May require transporters and have limited CNS access.

Blood flow to absorption site

Increased blood flow enhances absorption; decreased flow slows it.

Important for IM, SC, and transdermal routes

Temperature

Heat increases absorption via vasodilation; cold reduces absorption.

Can be manipulated in localized drug delivery

Food effects on absorption

Food may enhance or inhibit absorption; fasting may speed or slow absorption.

Food, hunger, fasting

Can speed or slow absorption depending on the drug and gastric motility.

Depends on drug properties and gastric motility

Stress

Reduces GI blood flow and GI activity; may delay absorption.

Chronic stress may affect metabolism

Pain

Activates sympathetic response; reduces blood flow and GI activity; can delay onset of action.

pH

Affects drug ionization; non-ionized forms of acids absorb better. Acidic drugs absorb in stomach. Basic drugs in intestines

Route of administration

Determine speed and extent of absorption

Method of delivering a drug (e.g., IV, oral, sublingual); affects onset and bioavailability (IV = rapid, oral = variable, sublingual = fast, bypasses liver).

First-pass effect

Liver metabolizes drug before it reaches systemic circulation, reduces bioavailability for oral drug

Bioavailability

Percentage of the administered drug that reaches systemic circulation unchanged; IV is 100%, oral varies.

Ionization

The ionization state of a drug (influenced by pH); non-ionized forms cross membranes more readily, affecting absorption.