Can Drugs Be Absorbed Through the Mouth?

Over 18% of people report having difficulty swallowing pills, but for certain medications, this is not even required for absorption. This is because drugs can be absorbed through the mouth, utilizing the highly vascularized oral mucosa for rapid entry into the bloodstream while bypassing the digestive tract.

Quick Summary

This article explores how medications are absorbed through the mouth via the sublingual and buccal routes. It details the mechanisms, benefits such as rapid onset and increased bioavailability, key influencing factors, and provides a comparison of the different methods of oral mucosal delivery.

Key Points

• Oral absorption is possible: Certain medications can be absorbed through the oral mucosa, bypassing the gastrointestinal tract and liver.

• Two primary routes: Sublingual (under the tongue) and buccal (between the cheek and gum) are the main methods for oral mucosal absorption.

• Faster onset of action: The rich blood supply under the tongue allows for very rapid absorption, which is vital for emergencies like angina.

• Bypasses first-pass metabolism: This route delivers drugs directly to the bloodstream, increasing their bioavailability and therapeutic effect.

• Ideal for certain patients: Oral mucosal absorption is a convenient alternative for those with difficulty swallowing, nausea, or who are unconscious.

• Sustained release possible: The buccal route, with its thicker lining and mucoadhesive formulations, can provide slower, more sustained drug release.

• Limited dosage capacity: The oral mucosa can only absorb small doses effectively, which limits its use for certain drugs.

• Factors influence absorption: A drug's properties, formulation, and physiological factors like saliva flow and oral health all affect how well it is absorbed.

The oral cavity, lined by a mucous membrane called the oral mucosa, serves as a pathway for administering certain medications. This absorption, often categorized as transmucosal, allows the drug to enter the bloodstream directly through the mucosal tissues. This method offers advantages over traditional oral ingestion by bypassing the digestive system and the liver's first-pass metabolism. The two main routes for absorption through the mouth are sublingual (under the tongue) and buccal (between the cheek and gum).

Sublingual Administration

This method involves placing medication under the tongue, where a rich network of capillaries facilitates rapid absorption into the systemic circulation. Examples include nitroglycerin for angina, buprenorphine for opioid dependence, and some vitamin B12 formulations.

Advantages:

• Rapid onset of action
• Avoids first-pass metabolism
• Convenient for patients with swallowing difficulties

Buccal Administration

Medication placed between the gums and inner cheek uses the buccal mucosa for absorption. While generally slower than sublingual, this route can provide a more sustained release. Examples include fentanyl for breakthrough cancer pain, prochlorperazine for nausea and vomiting, and some testosterone treatments.

Advantages:

• Potential for sustained release
• Bypasses first-pass metabolism
• Can be easily removed if needed

The Science Behind Oral Mucosal Absorption

Drug absorption through the oral mucosa primarily relies on passive diffusion. The oral cavity's vascular supply, particularly in the sublingual area, provides an efficient route to the bloodstream. For more detailed information on the factors influencing this process, benefits, limitations, and a comparison of sublingual vs. buccal administration, please refer to {Link: ScienceDirect https://www.sciencedirect.com/science/article/abs/pii/S0168365909005422}.

Conclusion

Yes, drugs can be absorbed through the mouth using sublingual and buccal methods. These routes utilize the oral mucosa's characteristics to provide rapid onset and high bioavailability for specific medications while bypassing the liver. While there are limitations on the dose size, this method is a valuable alternative, especially for patients who cannot swallow and when immediate effects are needed. Ongoing developments in drug formulation are expanding the use of oral transmucosal delivery.

Frequently Asked Questions

What is the difference between sublingual and buccal administration?

Sublingual administration involves placing medication under the tongue for rapid absorption, whereas buccal administration places it between the gum and inner cheek, typically for a slower, more sustained release.

Why are some drugs absorbed through the mouth instead of being swallowed?

Some drugs are absorbed through the mouth to achieve a faster onset of action or to increase their bioavailability by bypassing the digestive system and the liver's first-pass metabolism, which can otherwise reduce their effectiveness.

Can you swallow a sublingual or buccal tablet?

No, swallowing these tablets is not recommended. It would send the drug to the gastrointestinal tract, where it would be absorbed differently, potentially altering its effects or rendering it ineffective.

What is first-pass metabolism and why is bypassing it important?

First-pass metabolism is the process where a drug's concentration is reduced by the liver before it reaches the rest of the body. Bypassing it, as with oral mucosal absorption, ensures a higher and more predictable dose reaches the systemic circulation.

How does the drug get from the mouth into the bloodstream?

The drug, after dissolving in saliva, diffuses directly through the thin, highly vascular oral mucosal membranes into the underlying blood vessels. This rich blood supply facilitates direct entry into the systemic circulation.

Does food or drink affect oral mucosal absorption?

Yes, eating, drinking, or smoking while a sublingual or buccal tablet is dissolving can wash away the medication or interfere with absorption, affecting its effectiveness.

What are some common medications absorbed through the mouth?

Examples include nitroglycerin (sublingual) for chest pain, fentanyl (buccal) for cancer pain, and certain forms of vitamin B12 and opioid dependence medication.