Dose Counter May Not Work

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An asthma patient called his pharmacist to ask how long his inhaler was supposed to last. He stated that he had been using the product for months, yet the window showed that 182 puffs remained of ASMANEX TWISTHALER (mometasone furoate), a steroid inhalation powder available in 14, 30, 60, or 120 metereddose sizes. When the patient brought the Twisthaler in for inspection, the pharmacist verified that the dosage counter, indeed, read 182 puffs of medication. The Asmanex Twisthaler is designed to work by “cap activation technology.” To prepare a dose, the white cap is twisted in a counter-clockwise direction and removed. When the cap is removed, the dosage counter decreases by one and the medication powder is loaded in the device and ready to be inhaled. After the dose is inhaled, the cap is replaced by turning it clockwise until hearing a clicking noise to confirm that it is fully closed and ready for loading the next dose. When the dosage counter reaches “00,” the Twisthaler should automatically lock shut to prevent patients from using an empty device. The pharmacist who reported this error attempted to recreate the situation using an Asmanex Twisthaler placebo demonstration inhaler. She found that when she set the dosage counter to “00” and applied enough force while twisting the inhaler cap, the counter reset to 199.

We have alerted Schering-Plough, the manufacturer, to this problem. They were aware that if a patient “forcefully” attempts to remove the cap once the dosage counter reaches “00,” the counter could reset. The company agreed to investigate this safety issue further. If you prescribe, dispense, or administer this product, educate patients about proper use and call attention to the indented arrow located on the white portion of the Twisthaler, directly above the pink base, which points to the dosage counter (see photo). Remind patients to discard the Twisthaler 45 days after the pouch has been opened or if the dosage counter reaches “00” before then, and to refill the prescription when the dosage counter reaches “10” or less.

An online educational tutorial on proper use of this medication delivery device is available here.