Pharmacology L3 Flashcards
Barriers to drug delivery
- molecular/ cellular permeation of external protective barriers of the body
- potential difficulties with efficient drug transportation and molecular targeting
- production of drug derivatives and/or swift elimination via biotransformation
- potential problems due to immune response
Molecular/ cellular permeation of external protective barriers of the body
- anatomical barriers demarcate the interior system from its surrounding
- blood-tissue barriers (eg blood brain barrier)
Potential difficulties with efficienct drug transportation and molecular targeting
- delivery via GI-tract: extremely acidic environment in stomach
- delivery via pharynx/ trachea/ bronchioli: mucociloary movement of trapped drug aerosols from pharynx to larynx
- limitations of plasma proteins transportation
- hydrophobic interactions (fatty tissue, membranes)
What is biotransformation
Natural mechanisms that protects the body from ingested molecules
Production of drug derivatives and/or swift elimination via biotransformation
- 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
Drug administration is carried out by?
- enteral administration
- parental administration
- topical administration
Enteral administration involves
- oral administration (swallowed or topically)
- buccal administration (between gums and cheek)
- sublingual administration (under the tongue)
- rectal administration
How does oral administration occur
Via GI-tract to systemic circulation
How does buccal administration occur
Through fast absorption via buccal mucosa
How does sublingual administration occur
Fast absorption via sublingual mucosa
How does rectal administration occur
Slow absorption through rectal mucosa
Parenteral administration occurs through what?
Through injection or infusion (needle or catheter). Susceptible to high pH of stomach
Types of parenteral administration
- intravenous
- intra- arterial
- intramuscular
- subcutaneous
- intra- articular
- intrathecal
- intradermal
Intravenous
Achieves high drug concentration in circulatory system
Intramuscular
Uniform drug absorption with rapid onset of drug action. If drug is to be given slowly at high conc eg opium overdose
Subcutaneous
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
Topical administration (skin)
Administration to surface mucous membrane
Oral administration
- tablets, capsules, solutions
- coated or matrix tablets so drug can get to the right place
Inhalational administration
- aerosols, nebulizers
Dermatological agents
- powders, (greasy) ointments, cream
- transdermal delivery systems
Injection Or infusion
- intravenous
- intra-arterial (rare)
- subcutaneous
- intramuscular
- sublingual
- rectal
Drug absorption following oral administration occurs through
The gastrointestinal mucosal lining
Absorption occurs through mucosal lining of?
The intestine
Why does absorption occur through the intestine mucosal lining?
Due to slow processes involved in the disintegration of tablets and the dissolution of most drugs
Where do solutions/ mixtures get absorbed
In the stomach region
Mechanism of drug liberation
Disintegration (solid dose)
Dissolution
Absorption (liquid dose)
What does modification of drug liberation mechanism do?
Protects sensitive agents and to alter time-course and site- specific absorption
What do time-course and site-specific absorption do
Leads to retardation of drug release
Oral dosage delivery forms
- drops
-mixtures - effervescent solutions
- matrix tablets
- capsules
- tablets
- Coates tablets (with delayed release)
What is the importance of different drug packages and methods of application
Difference drug packages deliver drugs to different targets
Method of application affects drug release and absorption
What do coated tablets have?
A drug-containing core and a covering shell to:
- facilitate passing of drug on swallowing
- mask a disagreeable taste
- protect a perishable drug
What do capsules have?
An oblong casing which contains drug in powder form
What does a matrix tablet contain
The drug embedded in an inert meshwork which upon contact with water, is slowly released by diffusion
What are inhalational drugs?
They involve drug delivery in the form of an aerosol by converting drug solution or micronized powder to gas form.
How does drug delivery of inhalational drugs occur?
As a gas or mist by a nebulizer or spray dispenser. Delivery is mostly to bronchial mucosa
Effectiveness of delivery process of inhalational drugs depends on
- size of aerosol particles
- position of inhaler device
- coordination between spray release and inspiration
Depth of drug penetration of particles >100micro(m)
Trapped in oropharyngeal cavity
Depth of drug penetration of particles: 0-60micro(m)
Trachea (bronchi)
Depth of drug penetration of particles <2micro(m)
Bronchioli(alveoli). Very little, mostly exhaled
Rank the methods of drug application using injection/infusion from fastest to slowest
- Intravenous injection
- Intramuscular injection
- Subcutaneous injection
- Oral application: slowest, biggest chance of being derivatized
Factors that play a role in the delay of pain killer action
- large amounts of undigested food in GI-tract may slow down passage of some pharmacological agents
- dissolved agents usually act faster than substances in stomach acid-resistant capsules
- drug- drug interactions can have major effects on the pharmacological effects of pain killers
What is bioavailability
Bioavailability refers to the extent and rate at which the drug enters systemic circulation, thereby accessing the site of action.
Bioavailability of an active substance depends on?
- patient specifics
- drug preparation
Bioavailability of Aspirin
Fast-acting, water-soluble, already absorption in the stomach, with lower levels of bioavailability
Bioavailability of Paracetamol
Slower-acting, but higher levels of bioavailability after approximately an hour
Bioavailability of Ibuprofen
Fast acting and high bioavailability, but may be negatively affected by large amounts of i digested food in GI-tract
