Explore the system
Follow a drug through the body
Choose an entry route and trace absorption, circulation, tissue distribution, metabolism, and excretion.
Sources and model limits
Original schematic. Positions show relationships; structures and concentrations are not to scale.
- Julien's Primer of Drug Action · 15 · 1 · Follow a drug through the body · PDF 8, 10, 11, 12, 13 · 1.1, 1.3, 1.4
Course notes and existing practice
Learning objective
Separate transdermal delivery, local topical action, IV entry and absorption from tissue depots.
Local action or systemic delivery
Topical products act at or near an application site; transdermal delivery moves drug across skin into systemic circulation. The lecture uses patches to illustrate sustained input over hours or days. Slow input changes the concentration-time profile, but does not by itself establish safety or eliminate adverse effects.
Different destinations for an injection
IV delivery introduces drug into a vein. Intramuscular delivery places it in muscle, and subcutaneous delivery places it beneath the skin. IM and subcutaneous drug must still move from that tissue into circulation. The deck contrasts aqueous IM formulations with longer-release depot formulations. A depot is a release source, not a claim that the drug has an intrinsically long elimination half-life. Page 20 illustrates tissue layers; procedural injection instructions are outside this lesson.
- Depot formulation
- A formulation that serves as a reservoir from which drug is released over time.
- Transdermal
- Delivery across skin into systemic circulation.
Professor deck 04, PDF pages 15, 16, 17, 18, 19, 20. Course material is paraphrased. Qualifications and excluded clinical generalizations are documented in the Pharmacokinetics editorial record. Source review does not establish clinical validation.
Examples and practice explanations are original study aids, not professor quotations, exam requirements or medication instructions.