When delivering an API to the pulmonary tract of the human body, the droplet size of the formulation exiting the actuator must be the correct size to travel to the deep lung and enter the alveoli for absorption. When the droplet size is correct, the API will be delectable in the systemic blood circulation within about 5 to 8 seconds at 75% of total dose administered. The other 25% will enter the systemic blood circulation within 5 to 8 minutes.
In order to ensure this 5 to 8 second onset, each formula MUST be tested with equipment and instruments that can measure this very fine particle size. In fact this is how we determine which actuator needs to be used with each formula. There are three different parts inside the actuator that have a direct effect on the droplet size of the formula as the aerosol exits the mouthpiece of the actuator. Stem size, jet length and the orifice all play a huge role in droplet size and here is the kicker, with 3 different size stems, 12 different jet lengths and 22 different orifices, the combinations of actuators are endless. You can not just guess which one will deliver the correct droplet size, it has to be developed.