Medicine is absorbed through the stomach and intestine walls into the blood in the same way as any food. Contact has time release capsules which are coated with a material that is resistant to stomach acid and takes a long time to dissolve so the drug is released in the middle into the body. The dozens of different little granules in a contact capsule are coated with different thicknesses of this stuff so the drug inside is released at different times from different nodules. This way your body receives a continuous dose of the drug over a long period of time - about 8-12 hours depending on the formulation.