Drug products are bioequivalent when they not only contain the same active ingredient but also produce virtually the same blood levels over time. Bioequivalence thereby ensures therapeutic equivalence, and bioequivalent products are interchangeable. These controlled-release dosage forms slow or delay the rate at which a drug is dissolved. These dosage forms are coated with a material that doesn't begin to dissolve until it comes in contact with the less acidic environment or digestive enzymes of the small intestine. Such protective coatings don't always dissolve properly though, and many people, especially the elderly, pass such products intact in their feces.
Capsules consist of drugs and other substances within a gelatin shell.
The gelatin swells and releases its contents when it becomes wet. The shell usually erodes quickly. The size of the drug particles and other substances affects how fast the drug dissolves and is absorbed. Drugs from capsules filled with liquids tend to be absorbed more quickly than those from capsules filled with solids. After a drug is absorbed into the bloodstream, it rapidly circulates through the body, as blood has an average circulation time of 1 minute.