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