Symbicort Rapihaler 100/3 is a metered dose inhaler, indicated for management of asthma or chronic obstructive pulmonary disease. The National Asthma Council recommends using a spacer with Symbicort Rabihaler.

1. Discuss how the use of the spacer with the inhaler may reduce the side effect of throat thrush. Your answer should use the relevant equation of deposition. (3 marks)

2. Controlling the particle size range (within 2-5 micron) of drugs used in Symbicort Rapihaler is critical to their successful deposition in the respiratory tissues. Discuss this statement using the relevant equation of deposition. (3 marks)

3. Outline the formulation components of Symbicort Rapihaler 100/3 and the purpose of each component included in this formulation. Your answer should explain how ingredients can overcome the main physical instability of the formulation. (4 marks)

4. If the formulation was prepared using two propellants HFA-134a and HFA-227 (in a ratio of 0.25 moles of HFA-134a to 0.75 moles of HFA-227), calculate the total vapour pressure achieved in the inhaler in kPa at 20 C. You need to show your calculations. [4 marks]

Note: you may refer to the vapour pressure of each propellent (at 20 C) from the lecture notes or Table 37.1 in chapter 37 (Pulmonary drug delivery) in Aultons pharmaceutics (2018).