Mucous membranes, which are present in many places in the body (nose, mouth, trachea, lungs, stomach, eyelids, and rectum) often have slightly different structures, but they all feature a layer of epithelial cells that connect to layer of connective tissue that lies beneath. These epithelial cells are quite tough, being able to withstand abrasion and other sources of wear that come through exposure to external forces. Most importantly for drug delivery, they also contain cells suitable to absorption.
When a drug is prepared for insufflation, it is usually chopped into a fine powder. Therapeutic drugs designed for intranasal dosing are often suspended in a liquid, which is sprayed into the nose (like many forms of allergy medications), or they are turned into an aerosol, as with a nebulizer, which is often used in asthma treatment.
Many drugs of abuse are prepared for use in this way. Cocaine is almost always snorted (though some users inject it), but many prescription drugs like oxycodone, Percocet, and fentanyl are also ingested via insufflation. Users crush the pills and snort them for two key reasons: to amplify the effects of the drug and to speed the onset of effects.
Swallowing a pill means it must be broken down in the stomach before it can be absorbed by the stomach lining or intestines in order to make its way into the bloodstream and on to the brain. This takes time. When these medications are crushed and snorted, the full effect of the entire pill is felt within minutes.
In addition to opioid pills, users of methamphetamine, ketamine, heroin, and MDMA also use insufflation as a delivery system for their drug of choice.