As I’m using my asthma inhaler this morning, I realize, why don’t we use inhalation for other medications?
Obviously wouldn’t be needed for everything, but things that need to act fast I feel like it would be effective.
The alveoli in your lungs are a direct connection to your blood supply, and seem pretty effective for the nicotine while smoking.
I’ve even seen it a few times in fiction like Dread or Cyberpunk.
So why not?
In: Biology
It’s not necessary. The things that *need* to act fast we already have fast ways of administering it (possibly via an inhaler). What’s an example of a drug you need administered more quickly than we already do?
A cloud of tiny particles can cause the patient to cough, tossing the medication onto the floor. It’s difficult work to build inhalers that don’t cause this effect.
The lungs are really best at letting gasses into the body, and very few drugs are gasses for manufacturing and distribution reasons. It’s just a lot easier (=cheaper) to make a compressed pill or powder filled capsule that the user can just swallow.
Inhalers are risky in multiple ways that all other delivery methods aren’t. You can breathe wrong and miss the dose or lose part of it. It can deposit the medicine elsewhere and thus not deliver correctly. Dosage may be irregular or variable, perhaps due to buildup inside the inhaler itself. Etc. Further, the propellant is a possible irritant.
More or less, it’s an unnecessary risk of loss, waste, or inefficiency when we already have perfectly good alternatives. The vast majority of inhaler delivered medicines need to go to the lungs specifically and are for breathing related stuff because it’s useful to deliver it straight to the destination.
You see stuff like this in cyberpunk stories because in the 80s this was the bleeding edge of medicine and we didn’t really know whether it was beneficial or not to deliver other meds this way. In general, it’s not an improvement worth the risks.
The lungs are designed to process air and only air. Anything that isn’t air could cause damage to the lungs and this includes many medicines. Even getting the medicine to the lungs can be difficult as the throat is designed to filter out impurities like powders and aerosolized liquids. Your asthma inhaler is even an example of this since most of the medicine ends up right in your throat, treating the inflamed airways.
Most Inhaled drugs work on the lungs, or need a quick route to circulatory system like narcan. It would not help Inhaling a drug that gets processed by you liver or kidneys.
On a side note oral medications usually have poor absorption rates vs IV drugs. but I doubt people would want to shoot up their heart burn medication.
Asthma inhalers allow us to put the medication right where it’s needed as fast as possible. Most other medications that we need to act fast but don’t act on the lungs, have to be put in your blood as fast as possible. So we either put them under the tongue (many veins there), or better, inject them. It’s faster and/or more practical. For example, trinitrin is a medication that dilates your blood vessels and is sometimes used as a symptomatic treatment for some types of cardiac chest pains. It’s a spray that you use under the tongue and is usually effective in less than 2 minutes.
(Also, the lining in your lungs is more fragile/sensitive than you’d think. It’s really easy to provoke a coughing reaction when trying to put anything in there)
This has been investigated, but there are a couple of limiting factors. Primarily, a lot of medications would require a lot of material going into the lungs which isn’t feasible. A low dose medication into the lungs is easy, but getting a lot of medication into the lungs doesn’t work very well.
Some medications, such as insulin, are available and inhaled forms. Or at least inhaled forms exist, not sure if they are still being commercially produced. But since the dose of insulin is very critical, it’s very dependent on inhaler technique and it was determined that there was too much user variability to make it viable.
In emergency situations lots of needs can be given through breathing tubes such as epinephrine or anti seizure medications if IV access isn’t available.
Most inhaler distributed drug are delivered that way because they’re supposed to act on the respiratory track (Drugs for Asthma for example).
Nicotine is well absorbed because it’s vaporized by the heat of the cigarette but vaporizing drug isn’t a solution either because the heat might destroy the drug or make it have unintended effects.
Drugs packaging is well studied to make sure it is absorbed in the ideal part of the digestive track, for example a drug might no resist the stomach acid so you put it in a capsule that will slowly get dissolved by the acid to release the drug in the intestine.
Edit : Removed some incorrect section of my answer, see comment below for clarification.
Interesting thought experiment, and I think your line of thinking is valid. I’m going to approach it a different way. In the past, there were very few methods of administering drugs. Most were eaten, if somebody could not eat, they could give it rectally (like enemas). For the few medications that were volatile, they could administer it through inhalation (like chloroform, which essentially was used as anaesthesia). The invention of IV greatly improved things because now you can give a lot of medication, have it work very quickly, and have it work even if someone is unconscious or has difficulty breathing. Inhalation only really addresses the 2nd of those 3 because the lungs don’t absorb a lot of medications and inhaling the medication usually requires conscious effort and technique.
This is a bit of conjecture, but it is possible that the lungs will not like to absorb so many of these “large” (relative to gas like O2 and CO2) molecules. I haven’t looked at the literature on excessive overuse of inhaled medications and the potential damage to the membranes it could cause, but that’s something that could be an issue if a lot of medications go that route.
Nowadays, we still have other inhaled medications apart from asthma drugs such as inhaled anaesthesia drugs like sevoflurane. But a lot of these inhaled medications used in high volumes are also bad for the environment. Some anaesthetists are proposing moving to only using IV medications.
Furthermore, inhaled medications aren’t perfect. Inhalers are very technique dependent and can be very difficult to learn for some. Gas that isn’t absorbed immediately can be exhaled or leaked into the surrounding environment. If done in a closed room to a large enough extent (like in some operating theatres), everybody in the room ends up absorbing some of the medication. Not good if you have people allergic to medications potentially getting exposed.
Finally, of course, there is cost and business. You don’t just develop the medication, but also the delivery system. Or at least have to manufacture it. Storage of the medication and shelf life will also likely be reduced compared to individually sealed pills so the supply chain is impacted.
Getting the correct particle size is a big technical challenge. The drug needs to itself be or complexed with something that exists in a particle that gets into whatever you’re targeting (upper airway, conducting channels, alveoli). An inhaler specifically also requires some engineering.
That being said, we do administer many medications via the respiratory tract. You can nebulize many drugs, including antimicrobials, topical pain relief like lidocaine, furosemide, epinephrine, corticosteroids, and just plain saline to provide relief of clinical signs, and some of these see at least systemic absorption, although that is not always the intend.
Intranasal medications (aerosolized), like fentanyl or ketamine, for relief of pain or respiratory distress, or sedation, and take advantage of the rich vascular bed of the nasal passages.
I’m a veterinarian and we use these frequently, and from human literature and speaking to physician colleagues these also have a role in humans. Typically for specific conditions and under the supervision of a medical professional.
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