Name the processes and barriers for drug delivery to occur
- Administration - Distribution - Molecular Targeting - Drug Action
- Anatomical Barriers - Physiological barriers - Immunological barriers - Metabolic barriers
Molecular/cellular permeation of external protective barriers of the body
- Anatomical barriers demarcate the interior system from its surroundings
- Blood-tissue barriers (such as blood-brain barrier)
Potential difficulties with efficient drug transportation and molecular targeting
- Delivery via GI-tract: extremely acidic environment in stomach
- Delivery via pharynx/trachea/bronchioli: mucociliary movement of trapped drug aerosols from pharynx to larynx
- Limitations of plasma protein transportation
- Hydrophobic interactions (fatty tissue, membranes)
Production of drug derivatives and/or swift elimination via biotransformation
- Biotransformation Phase 1 & Phase 2 reactions
- Liver: major organ of drug biotransformation
- Kidney: excretory function of drug or metabolite elimination
Potential Problems due to immune response.
- Natural protection against infectious agents; auto-immune complications
- Potential allergic reactions, hypersensitivity, anaphylactic shock
Name the 3 types of drug administration
- Enteral administration
- Parental administration
- Topical Administration
Enteral (enteron = intestine) administration
- Oral administration (swallowed or topically) - via GI tract to systemic circulation
- Buccal administration (between gums and cheek) - fast absorption via buccal mucosa
- Sublingual administration (under the tongue) - fast absorption via sublingual mucosa
- Rectal administration - slow absorption through rectal mucosa
Parenteral (system route) administration
Parenteral injection or infusion (needle or catheter)
(anything susceptible to the pH in the stomach should be given this way)
- Intravenous - achieves high drug concentration in circulatory system
- ** Intra-arterial ** - rarely used form of drug administration
- Intramuscular - uniform drug absorption with rapid onset of drug action
- Subcutaneuous - slow drug absorption under the skin with prolonged drug action
- ** Intra-articular** - direct drug administration into inflamed joined cavities
- **Intrathecal ** - delivery into space between spinal cord and its protective sheath
- Intradermal - drug administration within skin layers.
- Systemic route: inhalation - absorption through lungs
Topical administration
Administration to surface mucous membranes
Examples of oral administration
- tablets, capsules, solutions
- coated or matrix tablets
Inhalational administration
- aerosols, nebulizer
Dermatological agents
- Powders, (greasy) ointments, creams
- Transdermal delivery systems
Injection or infusion
- Intravenous
- intrea-arterial
- subcutaneous
- intramuscular
- sublingual
- rectal
Where does drug absoption occur?
Solid dose (disintegration) - dissolution - (liquid dose) absorption
Drug absorption occurs through gastrointestinal mucosal lining.
Due to the slow processes involved in the disintegration of tablets and the dissolution of must drugs, absorption occurs mostly in the mucosal lining of the Intestine.
Solutions/mixtures permit direct absorption already in stomach region.
What is the function of the shell on Coated tablets?
Coated tablets consist of a drug-containing core and a covering shell to:
- facilitate passing of drug on swallowing
- mask a disagreeable taste
- protect a perishable drug
Enteric-coated tablets:
Coating as barrier function to protect acid labile drugs
Capsules
With oblong casing usually contains drug in powder form
Matrix tablet
contains the drug embedded in an enert meshwork:
Upon contact with water, drugs are slowly released by diffusion.
Inhalational Drugs
- Drug delivery in the form of an aerosol
- Conversion of drug solution or micronized powder to gas form
- Drug distribution as a gas or mist by nebulizer or spray dispenser * Delivery mostly to bronchial mucosa
What does the Effectiveness of Delivery Process of Inhalational Drugs depend on ?
- Size of aerosol particles
- Position of inhaler device
- Coordination between spray release and inspiration
Depth of drug penetration
- Particles: > 100μm Trapped in oropharyngeal cavity
- Particles: : 0-60μm Trachea (bronchi)
- Particles: < 2μm Bronchioli (alveoli) Very little; mostly exhaled
What determines the speed of drug absoption ?
The route and method of application determines the speed of drug absorption
Fastest to slowest methods of drug absorption
- Intravenous injection
- Intramuscular injection
- Subcutaneous injection
- Oral application
Factors that play a role in the delay of pain killer action
Do capsules work faster than dissolved agents?
- Large amounts of undigested food in GI-tract may slow down the passage of some pharmacological agents
- Dissolved agents usually act faster than substances in stomach acid-resistant capsules
- Drug-drug interactions can have a major effect on the pharmacological effects of pain killers
Aspirin
- fast acting , water-soluble, already absorption in stomach, with lower levels of bioavailability.
