CHARACTERISTICS OF THERAPEUTIC AEROSOLS Mohammad Yadak, MHPE,RRT June 29, 2020 Mohammad Yadak, MHPE,RRT_Aerosol Characteristics 1 Introduction • The aim of aerosol therapy is to deliver a therapeutic dose of the selected drug to the desired site of action (nose, throat, airways, or deep lung). • The indication for any specific aerosol is based on the need for the specific drug. • Administration of drugs by aerosol offers higher local drug concentrations in the lung with lower systemic levels compared with other forms of administration. • Improved therapeutic action with fewer systemic side effects provides a higher therapeutic index June 29, 2020 Mohammad Yadak, MHPE,RRT_Aerosol Characteristics 2 CHAPTER OBJECTIVES After reading this chapter you will be able to: Define the term aerosol. Describe and name factors affect aerosol deposition. Describe how aerosols are generated. List the indications associated with aerosol drug therapy. List the hazards associated with aerosol drug therapy. June 29, 2020 Mohammad Yadak, MHPE,RRT_Aerosol Characteristics 3 Definition of an aerosol June 29, 2020 Mohammad Yadak, MHPE,RRT_Aerosol Characteristics 4 History of Inhalers June 29, 2020 Mohammad Yadak, MHPE,RRT_Aerosol Characteristics 5 Advantages of Aerosol Therapy Aerosol dosage smaller . Onset of effect is faster . Minimal systemic exposure.(side effects) less painful and is relatively comfortable June 29, 2020 Mohammad Yadak, MHPE,RRT_Aerosol Characteristics 6 Disadvantages of Aerosol Therapy Lung deposition is low A number of factors can affect lung deposition Coordination problems Lack of knowledge of use of aerosol devices Variability of devices type confuses patient June 29, 2020 Mohammad Yadak, MHPE,RRT_Aerosol Characteristics 7 Hazards of Aerosol Therapy Adverse Reaction: Bronchospasm Drug Concentration: Infection Eye Irritation: June 29, 2020 Mohammad Yadak, MHPE,RRT_Aerosol Characteristics 8 Pharmacokinetics of Inhaled Drugs June 29, 2020 Mohammad Yadak, MHPE,RRT_Aerosol Characteristics 9 The effectiveness of an aerosol is largely dependent on how much of the medication actually reaches the smapp peripheral airways of the lungs June 29, 2020 Mohammad Yadak, MHPE,RRT_Aerosol Characteristics 10 Factors affect Aerosol Deposition June 29, 2020 Mohammad Yadak, MHPE,RRT_Aerosol Characteristics 11 June 29, 2020 Mohammad Yadak, MHPE,RRT_Aerosol Characteristics 12 June 29, 2020 Mohammad Yadak, MHPE,RRT_Aerosol Characteristics 13 Commonly Used Terms in Aerosol Delivery Labeled dose (LD)* or nominal dose The mass of d rug per actuation that is available from the aerosol generator- the dose that is mete red and specified on the inhaler package Emitted dose (ED) or delivered dose The mass of d rug emitted per actuation that is actual y available for inhalation at the mouth Fine particle dose (FPD) The mass of particles <5 ~tm in diameter per actuation with in the emitted dose Fine particle fraction (FPF) The fine particle dose per actuation divided by the emitted dose per actuation Mass median aerodynamic diameter (MMAD) Divides the aerosol size distribution in half: the diameter at which 50% of the particles of an aerosol by mass are larger and 50% are smaller than the median diameter Geometric standard deviation (GSD), Gg Measures the dispersion of particle diameters; defined as the ratio of the median diameter to the diameter at ±1 standard deviation (from the median diameter Aerosols with GSD ≥1.22 are considered polydisperse; most therapeutic aerosols are polydisperse and have GSDs in the range of 2-3 June 29, 2020 Mohammad Yadak, MHPE,RRT_Aerosol Characteristics 14 Airway anatomy (tree) Weibel June 29, 2020 Mohammad Yadak, MHPE,RRT_Aerosol Characteristics 15 Particle dynamics in respiratory tract June 29, 2020 Mohammad Yadak, MHPE,RRT_Aerosol Characteristics 16 Particle deposition • Inertial impaction occurs at bifurcation of main branches of the bronchial tree, • It occurs mainly with large particles or high velocity particles where they are unable to follow the airstream • when It changes direction, thus Impacting on the airway wall. • Gravitational sedimentation occurs for smaller particles that are able to follow the airstream and penetrate the more peripheral bronchioles June 29, 2020 •Particles to settle on to the airway surfaces either during the course of low steady breathing or during breath-holding. Mohammad Yadak, MHPE,RRT_Aerosol Characteristics 17 Particle deposition • Breath-holding Is Important for smaller particle sizes owing to the increased chance of exhalation of the drug, because they can remain airborne for a considerable time • Particle size is important , those that too small may be exhaled , those that are too large experience inertial impaction in the oropharynx and large conducting airways. • Increased aerosol particle Increases the probability of deposition by Impaction in the oropharynx and large conducting airways • Slow aerosol particles allows more particles penetrate the peripheral bronchial tree. • Breath-holding increase gravitational sedimentation. June 29, 2020 Mohammad Yadak, MHPE,RRT_Aerosol Characteristics 18 June 29, 2020 Mohammad Yadak, MHPE,RRT_Aerosol Characteristics 19
