Transcript How Drugs Enter The Body (1)

How Drugs Enter The Body (1)
Oral Administration - substance is ingested
through the mouth - digested and absorbed in
gastrointestinal tract - passes through liver carried to the brain through the circulatory
system.
-Most absorption occurs in 5 to 30 minutes, but is
not completed for up to 6 to 8 hours
-Slowest method
How Drugs Enter The Body (2)
Injection - bypasses the digestive tract.
Intravenous -injected directly into a vein drug arrives in
the brain within 15 seconds; effect are irreversible
Intramuscular - injected into a large muscle group,
slower absorption
Subcutaneous - injected under under the skin, slowest
absorption
How Drugs Enter The Body (3)
Inhalation - smoke or vapors of a substance are
drawn into the lungs.
- Simplest way to receive a drug
- Passes from alveoli in the lungs to blood stream
and then to the brain
- Fastest pathway for a drug to enter the body
- Risk permanent damage to lungs
How Drugs Enter The Body (4)
Absorption Through Membranes
Intranasal-absorption through mucous
membranes in the nose
Sublingual - absorption occurs under the tongue
Transdermal - absorption occurs through the
skin
How Drugs Leave The Body
All substance are excreted through urination or
defecation.
Water Soluble substances pass through the body
more quickly.
Factors Effecting the Process of Biodegradation
- Quantity - larger the amount, more quickly
metabolized (except for alcohol)
- Type of drug
Timing
Timing effects the physiological impact of a substance.
Latency Period - The amount of time from ingesting a
substance till you begin to feel its effect.
The larger amount of a substance in blood stream the
stronger the effects.
An individual can reach the maximum positive effect
dose but their level still continue rise resulting negative
side effects.
Drug Interactions
Additive - Occurs when two or more drugs combine to
produce an effect greater than effect of either drug
taken alone.
Additive: 1 + 1 = 2
Synergistic (hyperadditive): 1 + 1=6
Potentiation - a drug with no effect is combined with
another drug to cause a toxic effect.
Antagonistic - one drug weakens or cancels out the effect
of another drug.
Homeostasis
• Maintenance of internal stability of the body.
• Body continually adjusts and adapts to internal and
external changes in the environment.
• Self-Regulating Mechanisms
– Organ function
– Temperature, blood pressure
– Metabolism
Homeostasis
• Two Major body systems
• Nervous System
– Regulated by the release of neurotransmitters
– Responsible for sending chemical messages
• Endrocine System
– Regulated by release of hormones
– Functioning of many vital organs
Nervous System (1)
• Central Nervous System
– Brain and spinal cord
– Central mass of nerve tissue
– Integrates information, learning, memory,
coordination
Nervous System (2)
• Somatic Nervous System
– Sensory nerves - information to CNS
– Motor nerves - impulses to muscles
• Autonomic Nervous System
– Regulates body functions
– Involuntary functions
Neurons
• Specialized nerve cells
• Receive and send information
• Parts of neurons
– Cell body: nucleus, dendrites with receptors
– Axon: long wire like extensions
– Synapse: space between neurons
How CNS Works (1)
• Neurotransmitters: signaling chemicals released
by neurons
• Have brief localized effects
• Enables communication between neurons
• Released into synapse (1/10,000 inch)
• Receptors: specialized to receive chemical signals
How CNS Works (2)
• Neurotransmitter and receptor are like “lock and
key”
• Response is specific depending on which receptor
is activated
• Receptor will either “excite” or “inhibit”
electrical impulse.
Neurotransmitters (1)
• Enable brain to receive, process, and respond to
information by carrying impulse from one
neuron to the next.
• Dopamine - mild euphoria, excitation, insomnia
• Endorphins - euphoria, blocks pain, slows
respiration
Neurotransmitters (1)
• Gamma-aminobutyric acid (GABA)
– sedation, relaxation, drowsiness, depression
• Acetycholine - mild euphoria, excitation,
insomnia
• Serotonin - sleep, relaxation, sedation
How Drugs Work (1)
• Drugs enter the body; carried through the
circulatory system to cells
• Molecular structure is similar to
neurotransmitters
• Cross the blood brain barrier
How Drugs Work (2)
• Drug actions
– May act on synthesis, storage, release, re-uptake, or
metabolism of transmitter
– Alter the availability of neurotransmitter
– Mimic action of a neurotransmitter and activate or
occupy receptor to prevent neurotransmitter from
activating it.
Specific Actions of Drugs
• Dopamine: activated by stimulants
• Serotonin: activated by LSD
• GABA: activated by alcohol and other
depressants
• Endorphins: activated by narcotics