Storage instructions for inhalation capsules: consequences of incorrect storage and adherence in daily practice

The objective was to study the influence of storage conditions on the quality of inhalation capsules and to investigate patients' knowledge and adherence to storage instructions. Inhalation capsules marketed in the Netherlands were stored at normal (20°C/60% relative humidity) and dry (20°C/25% relative humidity) conditions during 34 days and checked for brittleness. After 1 day of storage at normal conditions, no brittleness was perceived. Longer periods and dry conditions increased the risk of brittleness. Only tiotropium capsules resisted all test situations. Subsequently, patients using inhalation capsules were sent a questionnaire in order to investigate their knowledge and actual behavior regarding storage of the capsules. Adherence to the required storage instructions was achieved by only 31.8% of all patients. Inferior storage locations turned out to be the main problem, 58.7% of the patients applied an incorrect place. Knowledge of the required storage instructions was lacking in 83.6% of all patients. It is concluded that the majority of patients store their inhalation capsules incorrectly and have insufficient knowledge of the appropriate storage conditions. Incorrectly stored capsules may become brittle and cause splintering during inhalation. The feeling of splinters in the mouth/throat may reduce the patient's confidence in the product's quality and affect compliance.