Drugs and Our Society
How Drugs Work in the
Body and the Mind
Pharmacology of Drugs
1. Pharmacology relates to the way
drugs are:
- administered to the body
- how they are absorbed
- how distributed through the body
- how metabolized by the body
- and how excreted from the body
2. There are 4 primary routes through
which drugs are administered
- oral / inhalation / injection /
absorption
Administration of Drugs
3. Ingesting drugs (oral) produces different
effects from inhaling
- smoking marijuana has a different
effect from ingesting it
- chewed tobacco is absorbed
differently from smoked tobacco
- the effects of injected narcotics
are
more intense than other forms
4. Not all drugs can be injected, such as
marijuana
- resin and water don’t mix
Admin of Drugs, cont
- it is less likely to be abused than
narcotics and opiates
- which can be injected
5. Cocaine is more likely to be abused
than caffeine
- the effects of cocaine are much
more powerful
- it takes effect more quickly.
Depending on administration
- injected more powerful than
snorting
Admin of Drugs, cont
6. Alcohol is metabolized in the liver
- primary absorption site is the
small intestine
- removed through exhaling / sweat /
urination
- rate of 3/4th ounce per hour
7. Snort cocaine
- mucous membranes in nose
absorb drug quickly
- effects are felt within minutes
Admin of Drugs, cont
8. Amphetamines taken orally
- produce peak effects in 2 to 3
hours
- eliminated in 2 to 3 days
- effect of injected amphetamines is
5 minutes
9. Caffeine effects is between 15 to 45
minutes
- metabolized in the liver
- removed by the kidneys
Admin of Drugs, cont
10.Marijuana smoked allows half of the
THC to be absorbed through lungs
- before entering the bloodstream
- the liver initially detoxifies the THC
- it is removed primarily through
feces
Oral Administration
1. Ingesting by mouth is the oldest and
easiest way
- digesting / then absorbing into the
bloodstream
2. Absorption time is longer after ingestion
- between 5 and 30 minutes
- not complete until after 6 to 8 hours
3. Gastrointestinal system consists of the
esophagus, stomach / intestines
- enables body to absorb nutrients
- and remove waste
Oral Administration, cont
4. Interior of stomach is highly acidic
- drugs can be impacted by acidity
- this can weaken effect of morphine
/ heroin / cocaine
- which are highly alkaline drugs
5. From small intestine to bloodstream
- drugs then processed by the liver
- liver “metabolizes” the drug
- enzymes break the drug down
Oral Administration, cont
6. A larger dosage is needed when
taken orally
7. 200 drugs show increase in enzyme
activity
- Phenobarbital has effect and
duration decreased
- valium and marijuana the active
metabolites produce similar effects
to the parent drug and prolongs the
effect considerably
Oral Administration, cont
8. Ingesting drugs on a full
stomach or an empty
stomach
- does make a difference in the
effect drugs will have on the
body
Injection
1. Parenteral drug use refers to the
injection of drugs
- injected drugs reach the brain
quickly
- the fastest means of injection is
intravenous (IV): within a vein
- it is called “mainlining”
- with prolonged use, the vein wall
loses strength and elasticity
- and the vein can collapse
Injection
2. Heroin injected into the forearm
- 10 to 15 seconds to the heart / lung /
and brain
- blood vessel walls are relatively
insensitivity
- irritating material can also be
injected
- it is possible to deliver high
concentrations of a drug
3. Another method is intramuscular
- which is injection into a muscle
4. Muscle tissue serves as a filter, so the
absorption time is slower
Injection, cont
5. Example:
- onset of euphoria after injecting
heroin intravenously is 7 to 8
seconds
- intramuscular the euphoric onset is
5 to 8 minutes
- the more blood vessels the muscle
has, the faster the absorption
- deltoid muscle injections are faster
than the buttocks
Injection, cont
6. Subcutaneous injection
- injecting just below the layers of
the skin
- the drug is absorbed less evenly
and slowly
- it is also referred to as a “skin pop”
or “skin popping”
Inhalation
1. This is where drugs are absorbed
into the bloodstream via the lungs
2. Speed and efficiency are quite high
- due to the accessibility of capillary
walls
- from the lungs, drugs go directly to
the brain in 5 to 8 seconds
- effects usually are brief
3. Smoking tobacco / marijuana / crack
- ‘huffing’ glue, paint, other inhalants
Absorption Through Skin
or Membranes
1. Quick absorption - 15 to 20 seconds
2. Mucous membranes
- found in the nose / mouth / rectal /
and vaginal areas
- drug adheres to membrane
- dissolves into bloodstream
3. Intranasal
- sniff / snort a drug such as cocaine
- in dust or powder form
Absorption Through Skin
or Membranes
4. Transdermal application
- ointment applied to skin
- patch placed directly on the
skin
How Drugs Exit the Body
1. The body has a fairly efficient
system to rid itself of unwanted
substances
- gases and solvent vapors can be
eliminated in exhaled breath
- small amounts can be eliminated
through sweat / saliva / or feces
- but primarily through urine
2. The major job of elimination is the
liver and kidneys
- the “dynamic duo” of excretion
Kidneys
1. Two organs about the size of a fist
- located on either side of the spine
2. Primary functions:
- maintain balance between water
and salt in body fluids
- and the excretion of excess water
in the form of urine
3. It functions as a complex filtering
system
- the kidneys physically remove
certain substances from the blood
Kidneys, cont
4. - it filters everything out
- then selectively reabsorbs what is
required
5. The kidney can make urine acidic or
basic
- the pH value can be manipulated
- pH value refers to the acidity of a
solution
Liver
1. A large organ located high in the
stomach under the diaphragm
2. Function
- compare it to a chemical factory
- molecules are modified to form new
useful substances
- toxic molecules are changed into
less harmful substances
3. Changes made by molecules are
called ENZYMES
- depending on the drug / liver can
create additional enzymes
Liver, cont
- metabolizes (breaks down) the
molecules
- the product of metabolism is
metabolites, which are more
useful and less toxic
- they breakdown drugs into less
active forms, called detoxification
4. Metabolites of certain drugs can be
more active than the original (active
metabolites)
- good examples are THC and
psilocybin
Rate of Excretion
1. Kidneys operate most efficiently
with high concentrations of the drug
in the blood
2. Concentration falls
- kidneys cannot filter out the drug at
the same rate
3. Rate of excretion can be described
in terms of ‘half-life’
- time for the body to eliminate half
- of a given blood level of drug
Rate of Excretion, cont
4. Half the original blood level is
eliminated in 30 minutes
- 30 minutes later, level is 25%
- 30 minutes later, level is 12.5%
5. Every 30 minutes the body gets rid of
half the drug circulating in the blood
- so the half-life of the drug is 30
minutes
6. Half-life equals 1 hour
- 50% / 25% / 12.5% / 6.25% / etc.