how drugs enter the body (1) oral administration - substance is ingested through the mouth -...
TRANSCRIPT
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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
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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
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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
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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
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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
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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.
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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.
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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
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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
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Nervous System (1)
• Central Nervous System
– Brain and spinal cord– Central mass of nerve tissue– Integrates information, learning, memory,
coordination
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Nervous System (2)
• Somatic Nervous System– Sensory nerves - information to CNS– Motor nerves - impulses to muscles
• Autonomic Nervous System– Regulates body functions– Involuntary functions
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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
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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
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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.
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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
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Neurotransmitters (1)
• Gamma-aminobutyric acid (GABA)– sedation, relaxation, drowsiness, depression
• Acetycholine - mild euphoria, excitation, insomnia
• Serotonin - sleep, relaxation, sedation
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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
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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.
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Specific Actions of Drugs
• Dopamine: activated by stimulants
• Serotonin: activated by LSD
• GABA: activated by alcohol and other depressants
• Endorphins: activated by narcotics