Inhalers are drug delivery systems designed to manage respiratory conditions like asthma and Chronic Obstructive Pulmonary Disease (COPD). These devices ensure that medication reaches the lungs precisely and effectively. The integrity of the medication depends on how it is handled and stored after the protective packaging is opened. Once an inhaler is put into use, its effectiveness is governed by a separate, shorter timeframe than the one printed on the box.
Distinguishing Shelf Life from In-Use Life
The expiration date printed on the inhaler box or canister is the “shelf life,” which guarantees the medication’s potency and stability while the device remains sealed in its original packaging. This date assumes the product is stored under specified, controlled conditions. The moment the protective seal is broken or the first dose is administered, the product shifts to its “in-use” life, which is significantly shorter.
This change occurs because the medication is newly exposed to the external environment, primarily air and humidity. This exposure can compromise the drug’s stability and delivery mechanism, leading to reduced efficacy. Patients must adhere to the in-use expiration date, which is determined by the manufacturer based on stability testing. It is helpful to write the date the package was opened directly on the inhaler device to track this shorter limit accurately.
Time Limits and Management for Metered-Dose Inhalers (MDI)
Pressurized Metered-Dose Inhalers (MDIs) deliver medication suspended in a propellant, such as hydrofluoroalkane (HFA), releasing a measured dose as an aerosol spray. The in-use life for an MDI is determined by a fixed time limit or when the dose counter reaches zero, whichever comes first. Time limits after removal from the foil pouch typically range from one month (30 days) to three months (90 days), depending on the specific drug formulation.
Most modern MDIs are equipped with a dose counter, which is the most reliable way to monitor remaining medication. The inhaler must be discarded immediately once this counter displays zero, even if the fixed time limit has not been reached. MDIs require “priming” before initial use or after non-use, involving releasing sprays into the air to ensure the correct amount of medication fills the dosing chamber. These priming sprays count toward the total number of available doses on the counter.
Time Limits and Management for Dry Powder Inhalers (DPI)
Dry Powder Inhalers (DPIs) deliver medication as a fine, non-propellant powder, relying on the patient’s forceful inhalation to aerosolize the dose. These devices are sensitive to moisture, which is the primary factor limiting their in-use life. When moisture is absorbed, the fine powder particles can aggregate, leading to agglomeration. This prevents the drug from dispersing correctly and reduces the amount of medication reaching the lungs.
The in-use life for DPIs is typically a short, fixed period after opening the protective foil pouch, regardless of doses used. This fixed period is often six weeks (42 days) or two months (60 days), though some products may extend longer. Some DPIs utilize capsules that must be kept in their blister strip until immediately before use to protect the powder from moisture exposure. Strict adherence to this short time window is necessary because moisture degradation may not be visually apparent.
Recognizing Device Degradation and Proper Storage
Recognizing Device Degradation
Beyond the established time limits, patients should watch for physical signs that indicate the inhaler may no longer be functioning properly. For MDIs, a noticeable change in the force or feel of the spray, a weak puff, or a lack of the familiar sound upon actuation can suggest a problem with the propellant or a blockage. For DPIs, the powder may appear clumped or sticky, or there may be an unusual taste, although visual degradation is not always present.
Proper Storage and Disposal
Proper storage is essential for maintaining device integrity and efficacy. Both MDI and DPI devices should be stored at room temperature, generally between 59 and 77 degrees Fahrenheit, and kept away from extreme heat, cold, and direct sunlight. High humidity, such as that found in bathrooms, is damaging to DPIs and should be avoided.
When an inhaler is finished or has reached its in-use expiration date, it requires safe disposal. Pressurized MDI canisters contain HFA propellants and can pose a safety hazard if crushed or exposed to high temperatures. The safest method is usually returning expired or used inhalers to a local pharmacy through a take-back program.