Biology of drug use

• USA is number one drug-producing & drug-consuming country
• -Many of the drugs are legal, though several are not
• -led to a "war on drugs"

"Drug" can have a few different meaning depending on the context.

• Biological: any chemical substance that alters the function of a living organism.
• -other than by supplying energy or nutrients

Medical: any agent used to treat or prevent diease

Psychoactive drugs: any chemical substance that alters consciousness, mood, or perception

Pharmacology: study of drugs and their properties & effects

Dose: amount given at one time

Effective dose: amount "effective" in producing desired change

Toxic dose: amount in which drug produces harmful effects

• Lethal dose: amount that kills the organism
• -comonly termed "overdose"

• Some drugs have a wide margin of safety
• -great difference between effective and lethal dose

• Amount that is effective, toxic or lethal differs...
• -with the chemical structure of the drug
• -from one individual to the next

• Swallowed
• -must be able to withstand acidic stomach and be easily absorbed

• Inhalation
• in gaseous form: like anesthetics
• -high density of blood capillaries in lungs
• -drug moves into bloodstream by diffusion
• in particulate form: all types of smoke
• -particles adhere to lung tissue

• Injection
• into muscle, under the skin, or into a vein
• -ex: insulin administered intramuscularly
• -intravenous faster than other routes

Example: Cocaine

• -product of coca plant
• -native south americans chew leaves (gut absorption) low concentrations enter bloodstream (ionized)
• -purified into powder: sniffing, increases amount absorbed
• -further purification (free-based cocaine and crack) are unionized, rapidly absorb, smoking increases rate of absorption

• Intially concentrated in site of entry
• -then blood vessels distrubute throughout body

• Some organs have more capillaries than others
• -therefore, receive more drug faster
• -examples: liver, kidney, heart
• -skin, muscle, fat: not as many capillaries

In order to act on nerve cells of the central nervous system (CNS), drugs must pass through blood-brain barrier

• If can't pass, remains in bloodstream while in brain
• -whereas would enterthe tissue of other organs
• -Ex: most antibiotics do not cross, hard to treat bacterial infections of brain
• -alcohol easily crosses barrier

• Drug activity dependent on molecular structure & dosage...
• -but also on existence of specific receptors in the body

• Receptors can be on cell surface or within cytoplasm of cell
• -not all cell types have all receptors

drug activity in certain tissue depends on drug's ability to reach tissue and presence of receptors for that drug in tissue's cells

• drugs taken by whole organism, not isolated cells
• -likely to produce several effects
• -even given with intent to produce a specific effect
• -side effect: not the main effect of the reason for which the drug was taken
• -can be positive or negative

When 2+ drugs taken together, may interact in various ways

additive effect: 2 drugs elicit same response, and when taken together, total response equal to sum of response each produces individually

Synergistic effect: one drug potentiates action of the other, total response is greater than sum of responses individually

antagonistic effect: one drug inhibits action of another so total response is less than response of the drugs individually

• One mechanism: a drug changes the threshold for response of the other
• -value below which no effect detected
• -Raising threshold: antagonistic
• -Lowering threshold: synergistic
• -often by increasing or decreasing # of receptors

• increasingly important to understand
• -Many people taking medications for chronic conditions
• -potential for interactions between street drugs, medications, alcohol, etc.

• most broken down and/or removed as soon as they enter
• -unlike food, which may be stored
• -drug metabolism: breaking down into an inactive form

• Some drugs alter metabolism of others:
• -ex: Barbiturates eliminated via liver enzymes, so body makes more of those enzymes
• (same enzymes also eliminate several medications, including steroid hormones (like birth control pills)

• elimination via normal pathways of excretion:
• -mostly in urine
• -but also in saliva, sweat, and exhaled air
• -In breast milk too

• Drug half lives
• length of time required for concentration to decrease by half
• -alcohol & cocaine: short (hrs/mins)
• -marijuana: long (days/wks)

depends on complexity of inactivation process

• implications for interactions
• -long half life: potential to interact with drugs long after use

• if rate of intakes exceeds rate of metabolism
• -most forms of alcohol easily exceeds this

act directly on the brain (CNS)

• Produce changes in consciousness, mood or perception
• -sensation: receipt of stimuli
• -perception: higher-order brain function processing & interprentation of environmental stimuli
• -both can be altered, sometimes permanently

• Some psychoactive drugs work through specific receptors due to structural similarity to a neurotransmitter
• -drugs that don't work via receptors (e.g. caffeine & alcohol) have more generalized effect

• Narcotics
• -Drugs that cause drowsiness or sleep

most also cause some degree of euphoria & are effective pain killers

most are highly addictive

high doses may result in coma & death

• common: heroin, morphine, codeine
• -derived from the opium poppy

• Act on specific receptors on membranes of many cell types in addition to neurons
• -relax various muscles, including those in colon
• *some antidiarrheal medications include morphine
• *severe constipation an effect of long-term opiate use

• Receptors normally bind endorphins & enkephalins
• -peptides of simliar structure to opiates
• -decrease activity of neurons that normally signal pain and distress

• Several psychoactive drugs in marijuana
• -THC (tetrahydrocannabinol) is most active

• THC causes release of norepinephrine, producing euphoric effects
• -also effects area of brin that regulates steriod sex hormones
• *long-term use decreases testosterone levels & # of sperm in males
• *Alters femal menstruaal/ovulation cycle

• binding to THC to specific receptors produces altered sense of time & intensity of sensory stimuli among other side effects
• -not sure role of endogenous substances that bind to these receptors

• Cigarette smoke contains over 100 drugs
• several are carcinogens
• nicotine =primary psychoactive drug
• -stimulates release of several neurotransmitters to produce a variety of physiological effects
• *increased heart rate and blood pressure
• *constriction of blood vessels
• *changes in carbohydratess & fat metabolism

• CNS stimulants
• -considered quite dangerous: apx. 50%
• -all derivatives of ephedrine
• *drug that incrase activity of the reticular formation.

• mimic effects of norepinephrine, bind to its receptors
• -blocks reuptake of norepinephrien

Prolonged use: agression, delusions, hallucinations

• Controversial example: Ritalin
• -differnet effect on children w/ ADHD: reduces hyperactivity

part of brain maintaining baseline level of neuronal brain activity, keeping organism at baseline level of wakefulness & awareness

lower function in reticular formation, need to move around to stimulate the area

structually similar to the neurotransmitter serotonin (aka the happiness hormone)

• Causes heightened sensory perception & halluncinations
• -altered perception: change in awareness of stimuli that actually exist
• -hallucination: no outside stimulus received
• -can be visual, auditory, olfactory, or cognitive

• Heavy use leads to permanent brain damage
• -from memory impairment, attention span & abstract thinking
• -to severe long-lasting psychotic reactions

• In various plant structures: seeds, leaves, fruit
• -acts as a natural pesticide

World's most widely consumed psychoactive drug

• Not only targets CNS neurotransmitters
• -produces effects within cells throughout body too
• -increases rate of cellular metabolism for a general stimulatory effect
• -inhibits the messenger cyclic AMP
• -In CNS: binds to adenosine receptors, influencing sleep-wake cycles

Increases heart rate & rate of excretion from kidney

Some are highly sensitive: insomia, anxiety, irritability

• Depress function of CNS by inhibiting signal transimission in reticular formation
• -also includes barbiturates & tranquilizers

• Easily crosses blood-brain barrier
• -high alcohol cnt.: further penetrates brain

• Drug abuse: excessive or harmful (social) use
• -Major problem in U.S.
• -Most drugs abused socially are psychoactives
• -most abused drugs are addictive (but not all)

• compulsive physiological & psychological need for substance
• -both biological & mental in nature

• Some, such as LSD, not known to be addictive
• Addictive drugs cause physiological dependence: person can no longer function normally w/o drug
• -stopping drug use produces biological symptoms of withdrawal
• -how long it takes to become dependent depends on drug

morphine= 48hrs but very sick, not fatal

alcohol = more severe, can be fatal

• person can no longer behave "normally" w/o drug
• -withdrawal symptoms concerned w/ physiology of the brain rather than entire body

• Sensation felt during withdrawal generally opposite produced by drug
• -antideprs. withdrawal: person is anxious/agitated
• -pain killer wtdrwl: person feels pain (though biological source of pain is gone)

Caffeine, nicotine, and marijuana all produce psychological dependence

• if consider addiction as degree of difficulty of getting through withdrawal w/o returning to the drug
• -nicotine considered one of most addictive drugs

Psychological drug dependence - context is very important

• -places & people
• -conditional withdrawal syndrome: visual cues associated with drug use can bring on physiological withdrawal symptoms

• *suggested that addicts try to avoid such triggers
• *important to consider in drug recovery programs

• Affect brain's ability to respond to normal positive signals
• -EX: appreciateing a good meal, enjoying friends' company, general feelings of well being

• By decreasing number of receptors on nerve cells
• -only effectively triggered by taking drugs

• Homeostatic compensation (body adjusting to new conditions)
• -same dose exerts decreased effect
• -Greater amounts needed to get same effect
• *higher doses affect other body systems, begin to produce negative mental states: paranonia, hostility
• *increased doses can reach toxic or lethal levels

Metabolic: body makes excess enzyme to break down drug

Cellular: changes in receptors, decrease # or increase their response threshold

• Most harmful with consider frequency of use
• -rare for a CNS depressant to be legal

Most effects are acute: reversible in hours or days

• Some are chronic: permently damaged tissue in brain, liver, heart, muscles
• -Resulting in dementia, cirrhosis, and CVD
• -tissue damage may result in altered uptake of and sensitivity to medications
• (can interfere with vitamin absoption)

Depresses the immune system

increased risk for cancer

Carcinogenic in any form

work synergistically with alcohol to increase risk of cancer

Particulate matter in smoke remains in lungs

Builds up to formm more tar per weight of plant material than tobacco

Inhibits immune cells

Alters reproductive hormones

Therapeutic effects: reduces eye pressure in glaucoma patients, suppresses nausea in chemo patients, stimulates appetite in chemo and AIDS patients


there are still a lot of unknowns

• Prescription and OTC drugs generally considered "safe" when used as directed
• -due to heavy regulations that assure standarized quantities of every ingredient
• -Know harmful impurities are not present

• No such assurance with street drugs
• -especially those that are synthesized
• -strychnine: deliberately added to LSD to sensitize nerves to drug
• *also sometimes added to marijuana
• *can cause abnormal muscle contractions
• *sometimes used as rat poison

Some drugs can damage gametes, but most affect embryo in utero

• Placenta is very capillary-rich
• -resulting in effective delivery of molecules from mother to baby's blood
• -drugs with small effect on mother can be toxic or lethal for fetus

• Some drugs stay present in child after birth
• -Interferes with brain & immune system development

Damages/weakens placenta

increases likelihood of miscarriage, premature birth, and damage to fetus

• quickly crosses placent
• -remains in fetal circulation longer than mother's

causes oxygen depletion: need oxygen to continue to make & develop new cells

present in fetus in same concentration as mother's blood

Quickly distributed to fetus

can cause fetal alcohol syndrome

embryo most effected during first month

toxic to sperm: decrease # produced

• One concept views drug addiction as crime & drug abuse as a law enforement problem
• - Common in U.S.

• Another approach based on harm reduction:
• view addiction as a disease, treated as public health problem.

• Common in some European countries
• -Lower drug-abuse rates than U.S.

• harm to addict minimized by legally prescribing drugs
• -Minimizes incentive to commit crimes or prostitution
• -reduces incentive to recuit other addicts
• -illegal trade minimized (lack of profits) so decreases new cases of addiction

• People from various political backgrounds have considered legalizing various drugs, taxing them, & treating as public health problems
• -Similar to way we treat alcohol & tobacco
• *Heavy reliance on education & prevention programs

-Could be dangerous: addiction easy to establish & difficult to break

• Drug need not be illegal to be socially harmful
• -nicotine addiction causes far more deaths than all other drugs combined
• -Alcohol abuse causes more fatal accident & family/carreer problems than illegeal drugs
• -Caffeine not regarded aas a drug by most, readily avaible even to children, yet is clearly addictive

These inconsistencies are example of policy decisions on societal issues influenced by science, but not always made on scientific criteria.