Guidance for Metered-Dose Inhalers is Finalized


Erik Swain

FDA has finalized its guidance for industry on dose-counting mechanisms for metered-dose inhalers (MDIs). 

The document, "Integration of Dose-Counting Mechanisms into MDI Drug Products," published March 12, 2003, can be viewed at www.fda. gov/cder/guidance/5308FNL.pdf. It contains only minor editorial changes from the draft version published December 11, 2001.

The guidance is geared to manufacturers that are developing or plan to develop metered-dose oral-inhalation products. It is not specifically intended for those that already have such products on the market, or those making dose-counters for products using other routes of administration. Nor is it intended for those making multidose dry-powder inhalers. But its contents should be considered by any manufacturer of any MDI product. 

Many current MDIs contain more formulation than is needed strictly for the labeled number of doses, because there is no practical way for patients to track the remaining number of doses or the amount of medication.

Thus, the guidance recommends integrating a dose-counting device into the MDI drug product. It must provide a clear indication of when the MDI is approaching its recommended number of actuations, and when it has reached and exceeded that number. If numeric counts are used, the device should count downward to zero. 

If the dose counter cannot be guaranteed to be 100% reliable, it must be designed to avoid undercounting, a potentially dangerous situation in which patients assume they have medication left when they may not. Reliability should be tested in vitro as well as during clinical trials. 

Lockout mechanisms to prevent doses beyond the labeled number of actuations are an optional feature but should not be used for treatments of acute bronchospasm. 

For further information, contact Sandy Barnes, Center for Drug Evaluation and Research (HFD-570), Food and Drug Administration, 5600 Fishers Lane, Rm. 8B-45, Rockville, MD 20857; 301/827-1055.

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