How can medicine work so quickly if the digestion process takes a long time?


Bit of context, I didn’t sleep very well because of allergies. I went to take some allergy medicine but realized my stomach is still heavy from the meal I ate last night, so it may not be the relief I am searching for. To my surprise, the allergy medicine started kicking in rather quickly (I can breathe again).
Does oral medicine bypass food in your stomach? Or does it dissolve and is more dense than the stomach acid and sinks to your liver more quickly? How can allergy medicine/anti-inflammatories/anything work as advertised on full stomachs?

In: Biology

Some drugs are absorbed into the blood stream through the stomach lining while others are absorbed into the blood stream in the intestines. I believe that if it’s an acidic drug it absorbs in the stomach and alkaline absorbs in the intestine. The liver receives the drug through the blood stream so the quicker it gets to the blood, the quicker the liver gets it.

The contents of the stomach are constantly churning and fast acting drugs are designed to dissolve fast. I would venture to guess that your drugs are acidic and absorbed through the stomach lining. Since stomach contents are always moving, it doesnt have to fight your food to get where its going.

Different routes of administration result in different timelines for therapeutic effects. Medications swallowed will be absorbed by your GI lining (not necessarily “digested” which is why it doesn’t take as long as digestion) and then it has to go through the liver where part of it is broken down (first pass effect) before it returns to your heart via the inferior vena cava and it pumped to the rest of your body. Your stomach is the site of absorption here so it doesn’t have to make its way through your GI system for it to fully work.

Medications absorbed through the mouth mucosa (like under the tongue) get brought back to your heart via the superior vena cava and do not go through the liver. Therefore effects are much faster and typically requires a lower dosage.

Some medicines are absorbed into the bloodstream and that is a very fast process. Think about drinking alcohol and how quickly that gets you tipsy.

My two cents – you have membranes in your mouth called buccal ones (I believe buccal means cheek) – drugs can pass into the bloodstream this way

I have severe anxiety and in the case of a panic attack, I dissolve the pill under my tongue so I feel better in 15 minutes instead of 30-45

We were taught that carbs will empty in 20 minutes. If you add fats, you are looking at an hour because the bile needs to be a part of the process. So basically if you take a pill with crackers and water it’ll get out of your stomach faster than if you had a glass of milk. The absorption occurs in the intestine. The blood stream that collects off the intestine then carries all the nutrients, meds, molecules to the liver. That is the portal vein. Then everything passes thru the liver and gets changed if need be. That is why when you are really sick and need antibiotics we give them right into say an arm vein because that vessel returns first to the vena cava (not the liver) and gets sent out to the body more or less full strength. And yes there are a few other places where absorption such as under the tongue i.e. instant glucose, nitroglycerin and some of the instant dissolving meds, also the nose had a bunch of fibers and the lungs have a mucous membrane that can sop stuff up. But most occurs from the intestinal villi not the stomach where the acid and bile mostly break everything into molecular pieces.