(NewsUSA) - People take medications expecting fast relief. If you're swallowing pills, however, you might have a longer wait.

Medications designed to work immediately don't come in pill form. Take the epipen. Epipens are meant to stem severe allergic reactions, which can progress rapidly. The medication comes in the form of an injection, so someone entering anaphylactic shock can shoot the drug epinephrine directly into their bloodstream, leading to the fastest possible relief.

On the other hand, when you take a pill, the medication has to go through your esophagus and stomach, dissolve somewhere in your intestines, move through your intestinal wall into the bloodstream, get processed by the liver, and them move to the area where it's needed. The process can take up to 20 minutes -- and then you have to wait for the medication to actually start working.

It's not an easy trip. The pill's active ingredients have to survive the hostile conditions of the gastrointestinal tract before they can enter the bloodstream and get to work. In addition, organs like the liver and kidneys may filter some of the medication out of your body. The liver may also break down or change some of the compounds in the pill in a process called "first pass metabolism."

Injections skip all those steps, but not everyone wants to give themselves shots. This is where sublingual medications, which are delivered under the tongue, come in. The membranes under the tongue readily absorb medications, which then enter the bloodstream without traveling through the gastrointestinal tract.