General

How do inhalers work?

If you're one of the 235 million people on Earth with asthma, you're no doubt familiar with inhalers — the plastic, push-button cylinders that deliver medicine straight to the lungs. Depending on which type of medicine is inside, this convenient device can quickly relieve symptoms like shortness of breath and wheezing, as well as control asthma over time. Here's what you need to know about inhalers.

What people used before inhalers

Person holding up a blue inhaler with background out of focus
Credit: Stephane Bureau du Colombier/ iStock

By the turn of the 20th century, doctors had figured out that certain allergens caused asthma, and that removing the allergens from a patient's environment could ease their asthma symptoms. But the best way to treat the symptoms with medications was still in development. Before inhalers were invented, physicians in the early 1900s prescribed cigarettes containing the dried leaves and flowers of Datura stramonium, the thorn-apple or jimsonweed plant. The active ingredient, called belladonna alkaloids, blocked the signals from certain nerves in the lungs and prevented airway constriction.

In the 1940s, doctors began treating asthma patients with theophylline, a compound that seemed to help the immune system function better. It also opened up constricted airways and allowed patients to breathe more easily. Other remedies included adrenaline injections and inhaled epinephrine, both to treat acute asthma symptoms.

How did early inhalers work?

The first inhalers looked nothing like the small plastic vials used today. In 1778, British physician John Mudge created a device out of a beer tankard to cure coughs. He drilled a hole in the tankard's lid and attached a flexible breathing tube. Holes in the handle and a valve in the lid allowed fresh air to mix with steam from boiling water and herbs in the tankard. Users inhaled the therapeutic vapor (or opium, as was often the case) through the tube — Mudge coined the term inhaler when he presented this new apparatus.

A French physician invented a portable nebulizer in 1858 that used a pump to bring liquid medication from a reservoir through an atomizer, similar to a perfume bottle's mechanism. Further development of this concept occurred in the following decades: Inhalers of the 1940s and early 1950s took the form of a glass vial and mouthpiece attached to a rubber bulb. Users added medicine to the vial, squeezed the bulb to atomize the liquid, and breathed in through the mouthpiece.

Modern inhaler makes dosing easier

A big problem with the early inhalers was the difficulty in delivering exact doses of medicine. They were also hard for children to use. In 1955, after his young daughter asked why her asthma medication couldn't be put in a spray can like her hairspray, Riker Laboratories president George Maison began to design a simpler inhaler. With a chemist who had formerly worked at Coca-Cola, he built a prototype from empty Coke bottles, a bottle capper, and CFC refrigerant. His final iteration held medicine in a pressurized canister fitted inside a plastic mouthpiece with a push-button mechanism. When a patient held the inhaler in her mouth and pushed the button, an exact dose of aerosolized medicine would be expelled. Maison's metered-dose inhaler was approved by the FDA in 1956, and soon became the medical standard for rescue inhalers. Today, some inhalers provide medicine in dry powder form as well (which may be prescribed for shorter-term treatments, such as for bronchitis, emphysema, or walking pneumonia).

How today's inhalers treat asthma

Two blue inhalers with refill sitting on a counter
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Asthma is a chronic condition characterized by episodic inflammation of the smooth muscles around the airways. (Smooth muscles are controlled by the autonomic nervous system, which also regulates your body's involuntary actions like pupil dilation and breathing rate.) The inflammation often results from the immune system's overreaction to an environmental trigger.

Most inhaled medications for asthma relax the smooth muscles around the airways and allow the patient's breathing to return to normal. The treatments fall into two basic categories: short-term and long-term. Short-term medications are used once or twice a week in rescue inhalers to relieve acute symptoms of asthma attacks. Long-term medications are used daily to control and prevent asthma symptoms.

Common short-term medications for asthma attacks include inhaled corticosteroids, like fluticasone and mometasone, which reduce mucus in the airways and inflammation of the smooth muscles constricting the airways. Short-acting beta agonists, like albuterol sulfate, activate the beta-2 receptors on the cells of the smooth muscles and relieve constriction. Short-acting beta agonists treat asthma as well as chronic pulmonary obstructive disorder (COPD).

Long-term medications are meant to control asthma or COPD symptoms and prevent asthma attacks from happening in the first place. Long-acting beta agonists are always combined with an inhaled corticosteroid to suppress both chronic inflammation and the nerve signals that might trigger inflammation. These combos include the brand names Advair (fluticasone and salmeterol), Dulera (mometasone and formoterol), and Symbicort (budesonide and formoterol). Another type of inhaled long-acting medication, ipratropium, blocks the activity of certain nerves that cause the airways to contract and is mostly used to treat COPD.

When not to use inhalers

Long-acting inhalers are not meant to be used for sudden asthma attacks, since the long-term medications have actually been linked to severe asthma attacks. Overuse of rescue inhalers can also cause scarring or mucus buildup in the airways, so it's important to follow dosing and usage instructions and talk to your doctor if you feel your symptoms aren't well controlled. And, you should always consult your healthcare provider before starting, changing, or ending any medical treatment.