The Difference Between One-step Filling And Two-step Filling Of Medicinal Aerosol

In the field of medicinal aerosol, a relatively special one is inhalation aerosol. Inhalation medication has a long history in my country. As early as more than a thousand years ago, ancient China, ancient Egypt, ancient Greece and ancient India used inhalation medication to prevent and treat diseases. Since the development of inhalation medication, it has been increasingly valued due to its small dosage, rapid onset and few adverse reactions. Its filling process has always been our vigorously research and development. The following introduces the differences between its different filling methods.
There are cold filling and pressure filling methods for the preparation of aerosols. The pressure filling method is divided into one-step and two-step methods. In European and American production, cold filling and one-step pressure filling methods are mainly used. Due to the large initial investment of the cold filling method and the large production plant area required, the pressure filling method has gradually begun to be used.
The first alternative to the cold filling method was the two-step pressure filling method. The production of this method is to prepare the concentrated solution or suspension of the drug, low-volatile liquid and other excipients and fill them into the empty cans first, install the valve and seal the mouth. The propellant is then pressed into the can through the valve. The two-step pressure filling method uses relatively simple equipment and has lower requirements for the drug solution. It is more commonly used when the propellant is CFC.
The disadvantage of the two-step pressure filling method is that the evaporation of the solvent during the filling of the concentrate can cause an increase in the drug concentration; the change in the filling weight of the concentrate and the propellant will have a significant impact on the drug concentration in the MDIs product, so that each can of aerosol can be considered as a separate batch. Therefore, accurate filling equipment is the key to the two-step pressure filling method.
When CFC is replaced by HFA, the one-step pressure filling method is more commonly used in industry. The one-step method is to first install the valve on the can, tighten it, and then prepare the drug solution and propellant into a solution or suspension at room temperature and high pressure, and press it into a closed container through the valve. Before filling the drug solution using this method, the air in the container must be removed to reduce the filling resistance, and it can also reduce the oxidative degradation of the drug during the storage period.