repeat-action tablet

A repeat-action tablet packs two doses into one pill, taken with a built-in pause between them. The first dose is released right away to start working, and a second, hidden dose is held back and released a few hours later — as if you had swallowed one tablet now and remembered to take another later, except the tablet does the remembering for you.

The classic construction is a coated inner core inside an outer immediate-release shell. The outer shell disintegrates and gives the first dose; the inner core, protected by an enteric or otherwise delayed coating, stays sealed until conditions further down the gut dissolve it, releasing the second dose. The effect is two immediate-release pulses spaced in time.

Repeat-action tablets are essentially the simplest form of pulsatile release, and they lengthen the dosing interval without holding the drug at a steady level. They have largely been overtaken by sustained- and extended-release designs, which give smoother profiles, but they remain a clear teaching example of building timing into a single dosage form.