Kompella's stuff Flashcards
What are some agents that are administered by inhalation?
Localized effects:
-Antiasthma agents:
Bronchodilators: Terbulatine sulfate (Brethaire)
Anti-inflammatory: Beclomethasone Dipropionate (Beclovent, Vanceril, Vancenase)
-Mucoinetics: rhDNAse (Pulmozyme)
-Antimicrobials: Tobramycin (Tobix)
Systemic Effects:
- General Anesthetics: Isoflurane (Forane)
- Peptide/Protein drugs: Insulin (Exubera- discontinued; Afrezza), rhDNAse
Describe the respiratory tract
Divided into conducting (zone 0-16; trachea to terminal bronchi) portion and respiratory (zone 17 - 23; respiratory bronchioles to alveolar sacs) portion (where gases get exchanged)
Tracheobronchial region lined with ciliated pseudostratified columnar epithelial cells
Alveoli consists of type I and type II epithelial cells
What are barriers to respiratory delivery?
- Particle clearance: Cilia (in upper airway) clear material toward throat
Mucus layer
goblet cells between columnar cells produce mucus - drug clearance through enzymes: proteases and nucleases
macrophage engulfment & degradation
has to cross membrane barriers (tight junctions)
Why respiratory delivery for systemic effects?
large surface area (140 m2) thin alveolar epithelium high blood supply no hepatic first pass metabolism rapid onset of action in contrast: oral route - high metabolism of some drugs, parenteral route - expensive, painful, poor acceptance, pulmonary route: even proteins are absorbed. can be used for local or systemic effects
How are drugs absorbed through lung epithelium?
passive diffusion through membrane or aqueous pores (useful for most drugs)
carrier mediated transport (useful for small, nutrient-light molecules)
endocytosis (good for large molecules like peptides & proteins)
also openings in capillaries which can allow movement of drugs across barriers (tight junctions in epithelium & fenestrae in capillary endothelium)
What is proper aerosol administration technique?
remove dust cap shake exhale mouth piece into mouth & close lips inhale slowly and deeply while pressing actuator remove the aerosol & hold breath allow 5 minutes between doses
What are some factors influencing particle deposition in lungs?
-Physical properties of the aerosol:
particle size, density, shape, size distribution, charge, and hygroscopicity (readily absorbing moisture - comes into humidified airways, picks up moisture & changes dimension)
propellants used and pressure (dictates droplet size, aerosol velocity, breakup of aerosol jet - important to control this)
solution vs suspension (if in solution, don’t have to deal with hygroscopicity: spread of drug better with solution than suspension, suspension has to dissolve before it spreads, suspension has localized islets of drug)
excipients such as surfactants
temperature of spray
-Device
design of pressurized metered-dose inhalers (pMDIs), dry powder inhalers (DPIs) and nebulizers
use of a spacer device with the above (spacer can take away larger particles - finer particles can go deeper into the lungs)
-Patient related factors
lung geometry & breathing pattern
What are patient related factors influencing particle deposition in lungs?
Lung geometry:
adults vs infants (highest fraction deposition in infants)
Healthy vs disease state (asthma & COPD, small airway resistance to flow increases)
angle of patient’s neck
Breathing pattern:
oral vs nasal inhalation (deep lung deposition not as good with nasal)
respiratory flow rate
tidal volume (amount of air inspired during normal, relaxed breathing)
time for breath hold
Slow, large volume breathing & control of cough improves deposition
what are the mechanisms of particle deposition in lungs?
Impaction (due to inertia): occurs in upper & large conducting airways, favored by high velocities & rapid changes in flow directions, significant for particles > 2 micrometer, increases with particle size
sedimentation (due to gravitational forces): occurs primarily in small conducting airways & in the alveolar region of the lung, favored by deep, slow breathing, becomes negligible for particles < 0.5 micrometer, rate is proportional to the square of the diameter of the particle & the density difference between the particle and air, main mechanism of deposition of respiratory aerosols
diffusion: occurs in the lung periphery w/small airway dimensions, favored by breath-holding, becomes effective for particles < 0.5 micrometer, increases with decreasing particle size, such particles may be exhaled before deposition (e.g., components of cigarette smoke)
areas of respiratory drug delivery and what mechanisms reach them
extrathoracic (nasal/oral passages, pharynx, and larynx) deposition: mainly inertial impaction tracheobronchial deposition: inertial impaction sedimentation (increasing importance as airway get smaller) alveolar deposition: primarily sedimentation diffusion for very small particles
how are drugs removed from respiratory tract?
mucociliary clearance
coughing
permeation across alveolar epithelium into the systemic circulation
metabolism in the lung
What are the kinds of inhalation delivery devices?
Aerosol: a drug delivery system which depends on the power of a compressed or liquefied gas to expel the active ingredients from the container (e.g., pressurized metered-dose inhaler or pMDI)
Inhaler: a drug delivery device from which the drug is inhaled when the patient inhales. That is, it is activated only when the patient breathes in (e.g., dry powder inhaler or DPI)
Nebulizer: generally a mechanical device which generates a very fine mist which is inhaled by the patient using a mask over a period of 10-15 min.
Aerosols (what is dispensed by inhalation devices) are very finely subdivided liquid or solid particles dispersed in and surrounded by air
What are some pMDIs?
Brethaire (terbutaline sulfate)
Vaceril (beclomethasone dipropionate)
both for asthma
What are some DPIs?
Turbohaler DPI for budesonide (Pulmicort)
Rotahaler DPI for albuterol (ventolin)
Classification of aerosol products
based on size of particles:
space sprays: high pressure aerosols which contain approximately 85% propellant and dispense a finely divided spray with particles no larger than 50 microns
surface sprays: contain 30-70% propellant and produce wet or coarse sprays with larger particles: dermatological sprays
foam sprays: contain 6-10% propellant and produce emulsions of propellants with the product concentrate. Medicated foams, vaginals foams, and shaving cream.
