Coughing immediately after using an inhaler is common for people managing respiratory conditions like asthma or chronic obstructive pulmonary disease (COPD). An inhaler delivers aerosolized or powdered medication directly into the lungs. This cough is often an uncomfortable reflex response, signaling that the airways have encountered an unexpected or irritating stimulus. Understanding the physical and chemical factors that trigger this reaction helps users mitigate discomfort and ensure effective medication delivery.
Mechanical Factors of Delivery
The physical process of medication delivery can initiate a cough reflex. Metered-dose inhalers (MDIs) release a high-velocity aerosol spray that can hit the sensitive tissue at the back of the throat and upper airway. This sudden, forceful impact acts as a mechanical stimulant, activating nerve fibers that trigger an immediate cough.
For MDIs, the temperature of the propellant is another factor causing irritation. Propellants, such as hydrofluoroalkanes (HFAs), rapidly expand and cool upon release. The inhalation of this cold burst of air and medication can irritate the airways. In sensitive individuals, this may cause a temporary tightening of the bronchial tubes, leading to a cough.
Dry powder inhalers (DPIs), which lack a propellant, can also cause mechanical irritation. The physical sensation of inhaling fine, dry powder may stimulate cough receptors in the throat. Furthermore, DPIs require a fast and deep inhalation to properly disperse the powder, and this strong inspiratory effort can irritate the airways, resulting in a cough.
Irritants in the Formulation
Beyond device mechanics, the specific components of the inhaled substance can chemically irritate the airways. The formulation contains the active drug plus inactive ingredients called excipients, necessary for stability and delivery. These excipients can stimulate cough receptors by changing the local acidity or osmolality (salt concentration) of the airway lining.
In dry powder formulations, the carrier substance, often lactose, is present in a much larger quantity than the active drug. This fine powder can cause a tickling sensation or irritation in the throat, leading to coughing. This irritation often results from the powder depositing in the mouth and throat rather than reaching the lower airways.
The active drug itself can also be an irritant. Inhaled corticosteroids, for example, occasionally cause throat irritation or hoarseness as a local side effect. Certain bronchodilators, such as ipratropium bromide, also list cough as a common side effect.
Correcting Inhaler Technique
Improper inhaler technique is a major reason medication fails to reach the lungs and instead irritates the throat, leading to a cough. With MDIs, a common mistake is not coordinating the actuation (pressing the canister) with the start of inhalation. This results in the medicine plume hitting the back of the throat at high velocity, which causes the cough reflex.
Using a spacer, also known as a holding chamber, is recommended to correct this issue, particularly for MDIs. A spacer is a tube that attaches to the inhaler, holding the medicine cloud temporarily after release. This accessory slows down the aerosol velocity and allows the propellant to evaporate, warming the spray.
The spacer ensures the medication is inhaled more slowly and smoothly, allowing a greater concentration to reach the lungs while reducing throat deposition. When using an MDI with a spacer, a slow, deep breath is more effective than a quick gasp. For DPIs, technique focuses on a fast, forceful inhalation, and rinsing the mouth after using any corticosteroid inhaler prevents local irritation and fungal infections.
When to Consult a Healthcare Provider
While a mild, transient cough immediately following inhaler use is often a simple reaction to the delivery method, certain signs suggest the need for professional consultation. If the cough becomes excessive, persistent, or causes significant discomfort, a healthcare provider should evaluate the situation. A worsening cough may indicate the medication is not reaching the lungs effectively, meaning the underlying respiratory condition is not being treated adequately.
It is important to discuss any signs of a potential allergic reaction, such as a rash, swelling, or difficulty breathing, which may require an immediate change in medication. The provider can check the user’s technique, recommend a spacer, or suggest switching to a different type of inhaler that may contain less irritating excipients or propellants. They can also determine if the persistent cough is a sign that the dosage needs adjustment or if it indicates a separate, untreated medical condition.